Distributed remote monitoring (dRMON) for networks

Distributed remote monitoring (dRMON) for networks
US006108782A
United States Patent [19]
[11] Patent Number:
Fletcher et al.
[45]
[54]
DISTRIBUTED REMOTE MONITORING
(DRMON) FOR NETWORKS
[75]
Inventors: Rick Fletcher, San Jose; Prakash
Banthia, Santa Clara, both of Calif,
Date of Patent:
6,108,782
Aug. 22, 2000
J ander, “Midlevel Managers Ease SNMP Information Over
load,” Data Communications, vol. 22, No. 17, Nov. 1993,
pp. 53, 54, 56, 58.
Jander, “Lightening the Load on Management Stations,”
Data Communications, vol. 23, No. 9, Jun. 1994, pp. 45, 46.
Johnson, “A three—Layered Solution for Managing the
Enterprise,” Data Communications, vol. 24, No. 8, Jun.
[73] Assignee; 3COM Corporation, Santa Clara,
Calif.
[60]
Continuation-in-part of application No. 08/766,274, Dec.
13, 1996, abandoned.
Provisional application No. 60/040,876, Mar. 21, 1997,
abandoned-
1995, pp. 41, 42.
Larsen, “Mastering Distributed Domains via the Web,” Data
Communications, vol. 25, No. 7, May 1996, pp. 36, 38.
Lee, “A Distributed Network Management System,” Pro
ceedings of the Global Telecommunications Conference,
San Francisco, CA, Nov. 28—Dec. 2, 2994, vol. 1, Nov. 1994,
Institute of Electronics Engineers, pp. 548—552.
Roberts, “RMON Adapters Shed Light on LAN’s,” Data
Communications, V01- 25, NO~ 6, May, 1996, PP~ 43, 44~
Schwager, “Remote Network Monitoring MIB,” Annual
Review of Communications, National Engineering Consor
tium, Chicago, IL, vol. 46, Jan. 1992, pp. 752—754.
[51]
[52]
Int. c1.7 ............................. .. H04L 9/00- G06F 11/30
US. Cl. ........................ .. 713/153; 713/201; 713/202;
Sta11ing$> “Patching the Cracks in SNMP? BYE VOL 21> No
8’ Aug' 1996’ PP' 5556'
[58]
Field of Search ................................... .. 709/224, 235,
[21] Appl' NO” 08/882’207
[22] Filed;
Jun, 24, 1997
Related US, Application Data
[63]
709/224; 709/235; 370/245; 370/252
709/227, 230, 248; 370/252, 241, 245;
713/201, 202, 151, 153, 160, 162
[56]
References Cited
Primary Examiner—Gilberto Barron, Jr.
Attorney) Agent» Or Firm—[email protected] Murabito & Hao LLP
[57]
ABSTRACT
Distributed remote monitoring (dRMON) of network traffic
and performance uses distributed nodes to collect traffic
statistics at distributed points in the network. These statistics
U_S_ PATENT DOCUMENTS
are forwarded to collectors which compile the statistics to
create combined views of network performance. A collector
4,817,080
3/1989 Soha ...................................... .. 370/252
may mimic a prior art, nomdistributed, network probe and
572517152 10/1993 Notess
709/224
may interact with network management software as though
5’45O’6O1
709/224
it were a stand alone network probe thereby simplifying a
9/1995 Okudf‘ """ "
Desai Ct 8.1. ............................. ..
5,961,596
10/1999
Takubo et al.
........................ ..
userzs interaction
709/224
network management protocols including SNMP, RMON,
FOREIGN PATENT DOCUMENTS
0 573 248 A1 12/1993 European Pat. Off. .
0 726 664 A2 8/1996 European Pat Off- WO 96/38955 12/1996 WIPO -
and RMON2 but is not limited to those environments. The
invention has applications in a variety of communication
system environments including local area networks, cable
television distribution systems, ATM systems, and advanced
OTHER PUBLICATIONS
Green?eld, “Network Management Filters Down to the
Desktop,” Data Communications, vol. 20, No. 13, Sep.
1991, pp. 39, 40, 42.
telephony systems. A speci?c embodiment of the invention
solves is particularly optimized to work in LAN environ
ments with end systems running under Windows-compatible
network operating systems.
26 Claims, 6 Drawing Sheets
INPUT PASSWORD FOR USE IN COLLECTOR AND AGENT
ENCRYPT PASSWORD AT COLLECTOR AND EMBED
ENCRYPTED PASSWORD IN COLLECTOR EXECUTABLE FILE
SEPARATELY ENCRYPT PASSWORD AT AGENT USING
DIFFERENT ALGORITHM FROM COLLECTOR AND EMBED
DIFFERENT ENCRVF'TED PASSWORD IN AGENT EXECUTABLE
AT RUN'TIME, DECRYPT EMBEDDED PAS$WORD AT AGENT
AND AT COLLECTOR AND PRODUCE IDENTICAL ORIGINAL
PASSWORD AT BOTH, ORIGINAL PASSWORD ONLY STORED IN
RUN-TIME MEMORYv
AT COLLECTOR] PLACE PASSWORD IN AUTHENTICATION FIELD
OF POLL PACKET AND SUBSEQUENT PACKETS. ENCRYPT
PACKETS To BE TRANSMIT'I'ED USING PRIOR ART NETWORK
(MD5) ENCRYPTION ALGORITHM
AT AGENT, DECRYPT PACKET AND COMPARE PASSWORD IN
AUTHENTICATION FIELD OF POLL PACKET TO PASSWORD.
DO PASSWORDS MATCH’?
RESPOND TO
POLL PACKET
the distributed System‘ Tihe invention
is
designed
to work in
accordance with
a variety
of standard
IGNORE POLL
PACKET
U.S. Patent
Aug. 22, 2000
Sheet 1 0f 6
6,108,782
52a
E Agent
62
52b
72a
E
/
, I
FEE-2E
Agent
.0
52c
IS / dRMON Collector
529
52f
Agent
Agent
72d
Agent
526
52d
Agent
Agent
518
El 50b
/70e
_
Non-Agent
50c
IS / dRMON
Agent
Collector w/proxy
50d
Q" Non-Agent
54
Management
Console
U
COLLECTOR
42
73b
4
/
dRMON
DOMAIN
SERVER/ROUTER
FIG. 1
COLLECTOR
U.S. Patent
Aug. 22, 2000
Sheet 2 0f 6
ETHERNET HEADER
AMP HEADER
ETHERNET
AMP
ADDR(48)
ID
DATA
6,108,782
ETHERNET
TRAILER
(24 BITS)
FIG. 2
HIGH
LAYER NAME (NUMBER)
QILSLCK
DATA
PROTOCOLS
HIGHER LAYER PROTOCOLS
APPL'CAT'ON (7)
Protocol
Manager APP Packets/MlBs
PRESENTATION (6)
SESSION (5)
SESSIONS
PACKET
TRANSPORT (4)
NETWORK (3)
LOW
DATA LINK (2)
PHYSICAL (0,1)
STREAM
ROUTING
DTA DRIVER
PACKETS
MC
PACKETS
ADAPTOR
BITS
(DTA DRIVER)
FIG. 3
SNMP, FTP,
HTTP
Data Encryption/
Compression
FULL/HALF
DUPLEX
TCP, UDP
IP
ETHERNET
ETHERNET
U.S. Patent
Aug. 22, 2000
6,108,782
Sheet 3 0f 6
dRMON Agent
Windows 95 or NT
User Mode
DTA DLL
DTA TDI Driver
Kernel Mode
NIC Driver
FIG. 4
RMON
RMON
Engine
Data
112
Structures
110
114
dRMON
Data
Structures
DLM
Mgr.
1L
115
dRMON interface Module
SNMP
118
/
dRMON
Protocol
116
System
/
FIG. 5
Windows 95 or NT
dRMON Collector
User Mode
SNMP Extensions
Kernel Mode
MS SNMP Agent
DTA TDl Driver
NIC Driver
FIG.6
DTA DLL
U.S. Patent
Aug. 22,2000
Sheet 4 0f6
6,108,782
146
SSN61
dMRE
MM45
2PCNaM
DMLgMr.
P
—————
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m
ts
R81dDl OeNMdeO
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o
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wNm
m
mmmw
a. M0wmN l
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w8O
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b
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.Wmo
mNlo
SNMP
Management
Stations
80/
81\
Ddmmmmnm
C
80
Work Group
Collectors
> x of 9
dRMON
U.S. Patent
Aug. 22,2000
Sheet 5 0f6
6,108,782
INPUT PASSWORD FOR USE IN COLLECTOR AND AGENT
I
ENCRYPT PASSWORD AT COLLECTOR AND EMBED
ENCRYPTED PASSWORD IN COLLECTOR EXECUTABLE FILE
I
SEPARATELY ENCRYPT PASSWORD AT AGENT USING
DIFFERENT ALGORITHM FROM COLLECTOR AND EMBED
DIFFERENT ENCRYPTED PASSWORD IN AGENT EXECUTABLE
FILE
I
AT RUN-TIME, DECRYPT EMBEDDED PASSWORD AT AGENT
AND AT COLLECTOR AND PRODUCE IDENTICAL ORIGINAL
PASSWORD AT BOTH, ORIGINAL PASSWORD ONLY STORED IN
RUN-TIME MEMORY.
I
AT COLLECTOR, PLACE PASSWORD IN AUTHENTICATION FIELD
OF POLL PACKET AND SUBSEQUENT PACKETS. ENCRYPT
PACKETS TO BE TRANSMITTED USING PRIOR ART NETWORK
(MD5) ENCRYPTION ALGORITHM
I
AT AGENT, DECRYPT PACKET AND COMPARE PASSWORD IN
AUTHENTICATION FIELD OF POLL PACKET TO PASSWORD.
DO PASSWORDS MATCH?
RESPOND TO
POLL PACKET
IGNORE POLL
PACKET
FIG. 9
6,108,782
1
2
DISTRIBUTED REMOTE MONITORING
computers, Workstations, and printers and additionally may
(DRMON) FOR NETWORKS
be digital devices such as digital telephones or real-time
video displays. Different types of ESs can operate together
This application claims priority from provisional patent
on the same LAN. In one type of LAN, LAN intermediate
systems (IS) 60—63 are referred to as bridges or sWitches or
hubs and WAN ISs 64 and 66 are referred to as routers,
application 60/040,876, ?led Mar. 21, 1997 noW expired
abandoned. This application is a continuation-in-part of Ser.
No. 08/766,274LE A1EU ( )757 Pk2-D15 306-3101, ?led
Dec. 13, 1996 noW abandoned.
MICROFICHE APPENDIX
10
This application has been ?led With a micro?che appendix
containing a user manual relating to one speci?c embodi
ment of a system incorporating aspects of the invention. A
portion of the disclosure of this patent document contains
material Which is subject to copyright protection. The copy
containing a header having at least a destination address
specifying an ultimate destination and generally also having
15 a source address and other transmission information such as
transmission priority. Packets are generally formatted
according to a particular protocol and contain a protocol
identi?er of that protocol. Packets may be encased in other
packets. FIG. 2 illustrates a packet.
right oWner has no objection to the facsimile reproduction
by anyone of the patent document or the patent disclosure,
as it appears in the Patent and Trademark Of?ce patent ?le
or records, but otherWise reserves all copyright rights What
20
soever.
layers, data is vieWed and organiZed differently, different
25
protocols are folloWed, different packets are de?ned and
different physical devices and softWare modules handle the
data traffic. FIG. 3 illustrates one example of a layered
netWork standard having a number of layers, Which We Will
refer to herein as: the Physical Layer, the Data Link Layer,
30
the Routing Layer, the Transport Layer, the Session Layer,
the Presentation Layer and the Application Layer. These
for monitoring and analysis of netWork traf?c using a
distributed remote traf?c monitoring (DRMON) technology.
Related technology is discussed in co-assigned
co-pending US. patent applications Ser. Nos. 08/506,533,
Layers
Modern communication standards, such as the TCP/IP
Suite and the IEEE 802 standards, organiZe the tasks nec
essary for data communication into layers. At different
BACKGROUND OF THE INVENTION
This invention relates to transmission of information
betWeen multiple digital devices on a netWork. More
particularly, this invention relates to a method and apparatus
hoWever many different LAN con?gurations are possible,
and the invention is not limited in application to the netWork
shoWn in FIG. 1.
Packets
In a LAN such as 40, data is generally transmitted
betWeen ESs as independent packets, With each packet
entitled METHOD AND APPARATUS FOR ASYNCHRO
NOUS PPP AND SYNCHRONOUS PPP CONVERSION,
layers correspond roughly to the layers as de?ned Within the
TCP/IP Suite. (The 802 standard and other standards have
different organiZational structures for the layers.)
?led Jul. 25, 1995 now US. Pat. No. 5,666,362; and
08/542,157, entitled METHOD AND APPARATUS FOR
TRANSPARENT INTERMEDIATE SYSTEM BASED
FILTERING ONA LAN OF MULTICAST PACKETS, ?led
Oct. 12, 1995 now US. Pat. No. 5,818,838 and incorporated
herein by reference to the extent necessary to understand the
invention.
35
Generally, When an ES is communicating over a netWork
Networking Devices Standards
This speci?cation presumes familiarity With the general
concepts, protocols, and devices currently used in LAN
40
using a layered protocol, a different softWare module may be
running on the ES at each of the different layers in order to
handle netWork functions at that layer. Examples of softWare
modules existing Within an ES at different layers are shoWn
in FIG. 3.
Drivers and Adapters
Each of the ISs and ESs in FIG. 1 includes one or more
netWorking applications and in WAN internetWorking appli
cations. These standards are publicly available and dis
cussed in more detail in the above referenced and other
adapters and a set of drivers. An adaptor generally includes
circuitry and connectors for communication over a segment
45
co-assigned patent applications.
This speci?cation also presumes some familiarity With the
speci?c netWork and operating system components dis
cussed brie?y in the folloWing paragraphs, such as the
simple netWork management protocol (SNMP) for manage
and translates data from the digital form used by the com
puter circuitry in the IS or ES into a form that may be
transmitted over the segment, Which may be electrical
signals, optical signals, radio Waves, etc. A driver is a set of
instructions resident on a device that alloWs the device to
ment of LAN and WAN netWorks, and the RMON MIBs
accomplish various tasks as de?ned by different netWork
protocols. Drivers are generally softWare programs stored on
de?ned for remote netWork monitoring and management.
the ISs or ESs in a manner that alloWs the drivers to be
General NetWork Topology
modi?ed Without modifying the IS or ES hardWare.
NIC Driver
FIG. 1 illustrates a local area netWork
50
40 of a type
that might be used today in a moderate siZed enterprise as an
example of a netWork in Which the present invention may be
deployed. LANs are arrangements of various hardWare and
softWare elements that operate together to alloW a number of
digital devices to exchange data Within the LAN and also
55
may include internet connections to external Wide area
60
The loWest layer adaptor softWare operating in one type of
netWork ES is generally referred to as a NIC (NetWork
Interface Card) driver. A NIC driver is layer 2 softWare
designed to be tightly coupled to and integrated With the
adaptor hardWare at the adaptor interface (layer 1) and is
netWorks (WANs) such as WANs 42 and 44. Typical modern
also designed to provide a standardiZed interface betWeen
layer 2 and 3. Ideally, NIC drivers are small and are designed
LANs such as 40 are comprised of one to many LAN
so that even in an ES With a large amount of installed
intermediate systems such as 60—63 that are responsible for
data transmission throughout the LAN and a number of end
netWork softWare, neW adaptor hardWare can be substituted
systems (ESs) such as ESs 50a—d, 51a—c, and 52a—g, that
65
With a neW NIC driver, and all other ES softWare can
continue to access the netWork Without modi?cation.
represent the end user equipment. The ESs may be familiar
NIC drivers communicate through one of several avail
end-user data processing equipment such as personal
able NIC driver interfaces to higher layer netWork protocols.
6,108,782
4
3
Examples of NIC driver interface speci?cations are NDIS
Prior Art RMON Overview
(Network Driver Interface Speci?cation developed by
Prior art Remote Monitoring (RMON) technology is a set
of software and hardware speci?cations designed to facili
tate the monitoring and reporting of data traf?c statistics in
Microsoft and 3Com) and ODI (Open Data-Link Interface
developed by Apple Computer and Novell).
Generally, when an ES is booting up and begins building
its stack of network protocol software, the NIC driver loads
RMON
a local area
was network
originally(LAN)
de?ned
or by
wide
thearea
IETFnetwork
(Internet Engi
neering Task Force) in 1991. RMON de?ned an independent
?rst and tends to be more robust than other network software
modules because of its limited functions and because it is
tightly designed to work with a particular hardware adaptor.
Management and Monitoring of Individual ESs in a Net
work Environment
A network such as that shown in FIG. 1 is generally
managed and monitored within an enterprise by a central
10
machines provided the various functions described by the
de?ning IETF RFC documents, RFC-1271, RFC-1513 and
RFC-1757.
According to the original standards, a special application
Information Services department (ISD), which is respon
sible for handling all the interconnections and devices
shown. The same ISD is generally responsible for managing
the applications and system components on each of the
network probe, which was generally implemented as a
separate CPU-based system residing on the monitored net
work. Software running on the probe and associated
program, sometimes referred to as an RMON Manager,
15
individual ESs in the network.
Many prior art systems have been proposed to allow an IS
staff person to manage and partially monitor network infra
structure remotely over a network. Such systems include
IBM’s NetView, HP’s OpenView or Novell’s Network Man
controlled the operation of the probe and collected the
statistics and data captured by the probe. In order to track
network traf?c and perform commands issued to it by the
RMON Manager, a prior art probe operated in a promiscu
ous mode, where it read every packet transmitted on network
segments to which it was connected. The probe performed
analyses or stored packets as requested by the RMON
Manager.
agement System (NMS). However, these systems generally
Prior art RMON builds upon the earlier Simple Network
rely on a full network protocol stack to be correctly running
effectively on the remote ES in order to accomplish any
remote ?le management operations.
Management Protocol (SNMP) technology while offering
25
four advantages over SNMP agent-based solutions:
(1) RMON provides autonomous Network Management/
Monitoring, unlike SNMP which required periodic polling
Simple Network Management Protocol (SNMP)
A common protocol used for managing network infra
structure over the network is the Simple Network Manage
ment Protocol (SNMP). SNMP is a layer 7 network and
cation when a user wishes to access information kept at the
system management protocol that handles network and
probe.
of ESs. RMON stand-alone probes are constantly on duty
and only require communication with a management appli
system management functions and can be implemented as a
(2) RMON’s alarm capability and user-programmable
driver (or SNMP agent) interfacing through UDP or some
other layer 4 protocol. Prior art SNMP installations largely
event triggers furnish a user with asynchronous noti?cation
of network events without polling ESs. This reduces the
network bandwidth used and allows across-WAN links
without concern for performance costs.
were not placed in ESs because SNMP did not handle ES 35
management or monitoring functions and because SNMP
(3) RMON automatically tracks network traf?c volume
agents are processor and memory intensive.
SNMP is designed to provide a simple but powerful cross
and errors for each ES MAC address seen on a segment and
platform protocol for communicating complex data struc
maintains a Host Matrix table of MAC address pairs that
have exchanged packets and the traf?c volume and errors
associated with those address pairs.
tures important to network infrastructure management.
However, its power and platform-independent design makes
it computationally intensive to implement, and for that
(4) RMON permits the collection and maintenance of
reason it has limited applications in end system management
or monitoring. It is primarily used in network infrastructure
management, such as management of network routers and
45
bridges.
capture capabilities which allowed a user to collect impor
SNMP is designed to support the exchange of Manage
tant network packet exchanges and analyZe them at the
management console.
The new capabilities of RMON were quickly appreciated
and RMON probes soon became the preferred choice for
remote monitoring. It has become common place for ISs,
particularly hubs and switch/bridges to embed RMON probe
ment Information Base (MIB) objects through use of two
simple verbs, get and set. MIB objects can be control
structures, such as a retry counter in an adaptor. Get can get
the current value of the MIB and set can change it. While the
SNMP protocol is simple, the MIB de?nitions can be
dif?cult to implement because MIB ids use complex data
structures which create cross-platform complexities. SNMP
has to translate these complex MIB de?nitions into ASN.1
which is a cross-platform language.
historical network performance metrics thereby facilitating
trend analysis and proactive performance monitoring.
(5) RMON includes fairly sophisticated packet ?lter and
55
functions.
RMON2
Shortly after adoption of RMON, users wanted more
which will often be the case when the network connection is
management information than the layer 2 statistics RMON
provided. In particular, network managers wanted to track
higher layer protocols and the sessions based upon those
protocols to learn which applications were using which
protocols at what expense in available network bandwidth.
failing. When working, SNMP provides a protocol interface
Therefore, a new version of RMON, RMONZ was devel
Even if installed in an ES, an SNMP agent cannot be used
to manage or diagnose an ES or update system components
where the UDP protocol stack is not working properly,
for higher layer prior art management applications.
oped to provide more advanced capabilities. RMON2 pro
vides network header layer (layer 3) through application
SNMP is described in detail in a number of standard
reference works. The wide adoption of SNMP throughout
the networking industry has made compatibility with SNMP
an important aspect of new management and monitoring
tools.
65
layer (layer 7) monitoring for a number of commonly used
protocols and applications, including the Internet protocol
suite (IP and UDP) and Internet applications (FTP, Telnet,
TCP and SNMP).
6,108,782
5
6
Limitations of IS-Based (Hub-Based/SWitch-Based RMON
(telephone, television) on any such communication system
A traditional stand-alone RMON probe, connected to a
sWitch like any other host device, only sees network traf?c
?owing on the segments to Which it is connected, greatly
limiting its usefulness in modern, more complicated netWork
or to encompass distributed points in the netWork interme
diate of an end systems. It is also intended that the Word
“packet” as used in the speci?cation and claims be read to
cover any unit of transmitted data, Whether an ethernet
topologies. One solution is to place the RMON probe Within
the sWitch itself and have it monitor all ports simultaneously.
unless the context requires otherWise.
packet, a cell, or any other data unit transmitted on a netWork
HoWever, this requires considerable processing capability in
order to handle the large bandWidth made possible by
modern sWitching architectures.
SUMMARY OF THE INVENTION
10
In a conventional 10 Mb Ethernet or 4/16 Mb Token Ring
environment, a stand-alone RMON probe on a single net
Work segment could usually be implemented on a 486-class
processor. HoWever, Where multiple netWork interfaces must
be monitored or Where netWork bandWidths are higher, (such
as With 100Base-T LANs or sWitching hubs/ATM), it is
considerably more costly to build a probe With suf?cient
processing poWer to capture all, or even most, of the netWork
components, are placed Within each (or a subset) of the ESs
15
RMON functional groups but only capture and analyZe
embodiments captures packets that the ES communicates
that RMON products claiming to keep up With higher
bandWidth netWork traf?c generally cannot, in fact, keep up
With an ES that does not have an dRMON agents installed;
as a result, the processing requirements of the dRMON
agents are kept Well Within the range of the ES (or host)
CPU’s capabilities and generally do not result in a notice
25
some of the previously referenced applications because it
can act as a proxy for, or mimic, the behavior of a prior art
dRMON probe), existing someWhere on the WAN/LAN.
The collector combines received agent data thereby creating
called a copy port) Where all packets are repeated to the
35
at the collector the vieW that a prior-art stand-alone RMON
probe Would have if all the ESs Were on the same LAN
segment With the probe. According to the invention, the
collector may be a stand-alone device connected to the LAN,
such as 61b or 65a, or may be implemented Within a sWitch
In general, What is needed is an ef?cient and Workable
mechanism for the distributed collection of performance
statistics in a communication system. Within the speci?c
environment just described, What is needed is an RMON
in the LAN such as 62 or Within a server, such as 64.
According to one embodiment of the invention, a
dRMON collector can mimic the SNMP responses of a prior
technology Whereby RMON functionality can be imple
mented in a LAN/WAN Without unduly harming netWork
performance and not requiring additional expensive netWork
hardWare to support. Ideally, this technology Would be
compatible With standard RMON and RMON2 technology
able loss of performance.
According to the invention, on a periodic basis, initiated
by a polling packet from the collector in one embodiment,
the dRMON agents forWard their statistics and/or captured
packets to a dRMON collector (referred to as a proxy in
sWitch vendor has provided a monitor port (sometimes
external RMON probe. HoWever, this approach decreases
data traffic performance in the sWitch, and does nothing to
reduce the processing overhead required of the probe.
such as 50a—c, 51a—c, and 521-g, connected to the LAN or
Within server machines. These agents implement prior art
packets that their native ES sends or receives, or in some
packets being exchanged. Independent laboratory tests shoW
With all data How during peak netWork rates. The situation
Worsens considerably When attempting to do RMON2 analy
sis of netWork packets in high bandWidth environments.
Processing poWer required can be easily ?ve times greater
than needed to simply capture packets, and data storage
requirements can easily increase ten fold.
Use of ?ltering sWitches and hubs (discussed in the above
referenced patent applications) in netWorks further limits the
usefulness of probes because, unlike repeaters, not all the
packets appear at every output port of the sWitch. This makes
the use of external stand-alone probes infeasible unless the
The present invention is a method and apparatus for
distributed remote netWork monitor (dRMON) in a LAN.
According to an embodiment of the invention, dRMON
agents, Which are softWare or softWare plus hardWare
45
so it could operate effectively With existing netWork man
agement softWare.
For purposes of clarity, the present discussion refers to
netWork devices and concepts in terms of speci?c examples.
HoWever, the method and apparatus of the present invention
art non-distributed RMON probe so that existing netWork
management or monitoring softWare can interact With the
collector as though the collector Were a prior art probe.
Therefore prior art netWork management softWare need not
be aWare of the existence of the dRMON agents.
According to a further embodiment, multicast domains
are handled specially. In a default mode, ESs in the same
multicast domain are treated by a collector as though they
are on one LAN segment. This approach alloWs other
vendor’s RMON netWork management applications to inter
may operate With a Wide variety of types of netWork devices
act With the collector as though it Were a prior art probe;
including netWorks and communication systems dramati
cally different from the speci?c examples illustrated in FIG.
hoWever, When used With enhanced dRMON Managers, a
user is provided the ability to combine ports and hosts in
order to create Virtual LAN (VLAN) de?nitions Which
Would cause the monitoring function to behave as though all
1 and described beloW. It should be understood that While
the invention is described in terms of a computer netWork,
the invention has applications in a variety of communication
systems, such as advanced cable television systems,
advanced telephone netWorks, ATM, or any other commu
55
selected hosts Were on the same LAN segment being served
by the same RMON probe. A dRMON collector in this
embodiment could create and maintain several such vieWs
nication system that Would bene?t from distributed perfor
mance monitoring and centraliZed collection and compila
With each appearing as one interface to conventional RMON
tion. It is therefore not intended that invention be limited,
except as indicated by the appended claims. It is intended
According to a further embodiment, agent proxies are
provided to be placed in IS systems such as bridges to handle
the dRMON agent functions for ESs that do not have agents.
Management applications.
that the Word “netWor ” as used in the speci?cation and
claims be read to cover any communication system unless 65 These proxies can be used in environments Where some ESs
the context requires otherWise and likeWise “end system”
and “node” be read to encompass any suitable end system
are running operating systems for Which dRMON agents are
not yet available. According to the invention, using a proxy
6,108,782
7
8
agent in an IS for just some of the ESs can allow that IS to
FIG. 5 is a more detailed diagram of a particular embodi
ment of an agent according to the invention and other
collect just those statistics needed for agent-less ESs and
therefore does not overburden the IS processing capabilities.
There are several key advantages to various embodiments
of the invention When compared to other solutions. among
these advantages are scalability, affordability, true end-to
components upon Which it depends.
FIG. 6 is a block diagram of an embodiment of a dRMON
Collector according to the invention.
FIG. 7 is a more detailed internal vieW a of an embodi
end response time monitoring, redundancy, visibility into
client node, distributed architecture, and Web support.
ment of a dRMON Collector according to the invention.
FIG. 8 is a diagram illustrating hierarchical collectors
Because each agent is analyZing only its oWn directed
according to an embodiment of the invention.
FIG. 9 is a How chart illustrating a security mechanism
according to an embodiment of the invention.
FIG. 10 shoWs a particular embodiment of a simpli?ed ?le
that may be used to communicate netWork statistics data to
traf?c, or possibly its oWn traf?c and the traf?c of a limited
number of other ESs, dRMON can handle extremely high
bandWidth environments With relative ease. Compared to
stand-alone probes, dRMON is more affordable as a remote
monitoring tool, particularly in sWitched environments. Very
inexpensive PC technology can be used to host the Collector
softWare resulting in loW equipment costs.
15 a remote terminal.
FIG. 11 is a diagram of a computer system as an example
of a system used to deploy the invention.
RMON2, for all its poWer, still does not afford the
netWork manager one of the most asked for features, that
being continual response time monitoring. RMON2 appli
DESCRIPTION OF SPECIFIC EMBODIMENTS
cations can only do this if packet capture is used to forWard
the protocol streams to the management station, at a price in
netWork utiliZation and performance. dRMON Agents rou
FIG. 1 is a block diagram illustrating the deployment of
the invention in an example netWork according to a speci?c
embodiment of the invention. The invention includes tWo
tinely perform this analysis and forWard the results (not the
types of primary components, the agents that reside in ESs
entire packets) to the Collector.
The fact that dRMON agents in the ESs themselves are
collecting the data additionally creates a more precise vieW
of the LAN since any LAN ’s characteristics vary based upon
Where in the Wire a node is connected; furthermore, because
of their cost, probes are often located close to the backbone
25
dRMON Agent
In one embodiment, the dRMON agent is implemented in
the C programming language. The agent executable code is
Where feWer probes can see more of the traf?c. This
approach prevents the netWork manager from spotting infra
structure problems and delays occurring betWeen the probe’s
location and the desktop. Only dRMON can perform true,
accurate, end-to-end response time analysis.
Since data collection is done by the managed nodes and
and the collector or collectors that collect and compile the
netWork statistics and interacts With netWork management
applications (such as an application running on console 54)
to provide a management/monitoring picture to the netWork.
launched each time an ES is started or rebooted and the
agent may be tightly bound to ES adaptor driver softWare.
Because the dRMON agent has no visible ES user interface,
the ES user is unaWare of the agent’s presence, and can do
35
RMON Collectors can substitute for each other, there is no
single point-of-failure and dRMON therefore inherently
nothing With regards to recon?guring the ES that Would
inadvertently disable the agent.
FIG. 4 shoWs one particular embodiment of an agent and
provides monitoring redundancy. In the case of monolithic
probes or management add-in cards, unless multiple probes
other components upon Which it depends. An NDIS Desk
Top Agent type module (DTA) is used to bind to the netWork
adapter driver, thus establishing a source of directed packets
are deployed on each LAN segment, a probe’s failure can be
disastrous When attempting remote monitoring.
to analyZe as Well as a means to communicate With the
Because the dRMON agent softWare of the invention
resides in ESs, it can capitaliZe upon native operating system
interface mechanisms (for example OS APIs such as
Microsoft’s WIN32) to gather information about the ES that
could never be ascertained from the Wire via packet capture
dRMON collector via the netWork. Multiple NIC bindings
may be supported by the agent and may alloW the agent to
monitoring traf?c on different segments having different
45
Among the important functions that can be performed by
and analysis. Examples of the kinds of information avail
able: (1) NetWork protocol stack con?gurations and NIC
agents according to various embodiments of the invention
are: (1) receiving and responding to messages from the
collector and con?guring its operation to conform to col
con?gurations including problematic situations; (2) Appli
cation information such as What protocols an application is
lector instructions; (2) performing RMON analysis and
compiling statistics regarding netWork traf?c for forWarding
to the collector; (3) performing packet capture at the agent
for forWarding packet streams to the collector, and (4)
bound to, the application’s manufacturer, version, ?le date
and time, DLLs used and their versions, etc.; (3) ES system
information such as memory, CPU, disk space, current
resource utiliZations, etc.; and (4) System performance met
rics.
The invention Will be further understood upon revieW of
providing a mechanism for receiving and executing doWn
55
the folloWing detailed description in conjunction With the
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a local area netWork of one type in
tures and tables are built and maintained Within the section
Which the invention may be effectively employed.
FIG. 2 is a diagram of a packet.
FIG. 3 is a diagram shoWing a layered netWork protocol.
FIG. 4 is a diagram of a particular embodiment of an agent
Which it depends.
loadable modules.
FIG. 5 provides an exploded vieW of the dRMON Agent’s
internal components. Central to the agent’s functionality is
RMON Engine 110. This module takes the packet stream
received from the netWork via the DTA and subjects it to
RMON analyses as con?gured via the collector. Data struc
draWings.
according to the invention and other components upon
layer 1 protocols.
65
labeled RMON Data Structures 112 in order to accomplish
and store the results of this RMON analysis. The agent
compares packets to ?lters in effect that have been set by the
collector and, upon a match, an event is generated for
analysis and/or the packet is retained and added to a capture
channel. The invention may include support for DoWn
6,108,782
10
Loadable-Modules (DLMs) through DLM manager 111.
protocol traf?c With its Agents. The DTA is also used as a
packet interface to alloW the Collector to monitor its oWn
This allows the user to download executables such as
diagnostics from the RMON management console that can
directed traf?c as Well as the broadcast and multicast traf?c
perform system analysis, network analysis or both. dRMON
?oWing Within its sphere of management. To prevent dupli
data structures 114 are used to store information necessary
cation of statistics, only the Collector maintains RMON
for agent-to-collector functioning according to the
information on broadcast and multicast traffic.
Since, in one embodiment, the Collector must communi
invention, such as, in one embodiment, a list at the agent of
the layer 2 (MAC) addresses of all other ES that include
cate With RMON Manager applications using SNMP, a full
functioning dRMON agents.
set of SNMP interfaces and services 142 exists in the
Collector Which is not found in the dRMON Agent. In the
The dRMON Interface Module 115 is intended to isolate
the Agent core from ES platform and netWork protocol
dependencies to maximiZe the portability of the agent
executable code and therefore to facilitate the porting of the
WindoWs95(TM) and WindoWsNT(TM) environments,
Microsoft(TM) offers an extensible SNMP agent. This agent
provides the UDP/IP protocol stack, PDU parser and basic
agent softWare to other operating system (OS) platforms.
BeloW dRMON Interface Module 115 are the loWer layer
components used to communicate With the dRMON
15
MIB-II support, but alloWs a user-provided extension to
register MIB objects that are to be maintained by the
user-provided extension. When the extensible agent receives
collector, the DTA and the operating system. dRMON
protocol box 116 is Where the dRMON protocol and DTA
registered objects, it passes the request to a user-provided
interfaces are realiZed. While dRMON protocol is used for
callback function for processing. In one embodiment, a
communication With the Collector, many requests coming
collector according to the invention registers the full RMON
MIB With the Extensible Agent. In embedded applications
an SNMP PDU referencing one or more of the user
from the Collector, such as requests to set ?ltering or packet
capture parameters, are essentially SNMP protocol data
units (i.e. PDUs or packets) encapsulated in dRMON pro
tocol; hence, the presence of the SNMP interface and
decoder module 118, Which decodes the necessary subset of
(e.g., sWitches), the Microsoft Extensible Agent may be
replaced With customiZed SNMP services.
FIG. 7 gives a more detailed internal vieW of the Collector
25
SNMP.
In an alternate embodiment, the invention could use a
different (possibly routable) protocol instead of dRMON
protocol for Agent-to-Collector exchanges. The dRMON
Interface Module provides for this by isolating the protocol
dRMON Mapper 144 performs the task of mapping betWeen
details from the Agent’s core.
dRMON Collector
The dRMON Collector receives RMON analysis and
capture data from the agents and sorts, collates, and aggre
gates that information into a cohesive database that recreates
the vieW a prior art RMON probe Would have if the ESs Were
all on the same LAN segment With the prior art probe. The
executable. Again, the architecture is very similar to that of
the dRMON Agent and may use a third-party RMON2
engine as RMON2 engine 140. The SNMP Services com
ponent 142 provides the RMON extensions that are regis
tered With the Microsoft Extensible SNMP Agent. The
35
RMON MIB objects and their internal representations con
tained Within the module labeled RMON Data Structures
146.
The Integrator 148 merges RMON statistics, tables and
capture streams coming from the remote dRMON agents
With the equivalent output from the Collector’s analysis of
its oWn directed traf?c combined With the broadcast and
multicast traffic present at its interface. The ?nal result is an
collector can then makes this information available to man
agement applications, either using SNMP and the MIB-II
and RMON MIBs or optionally, to WEB broWsers via HTTP
or other Web interface language. Different instances of the
Collector, like the Agent, can be developed to support a
integrated vieW of all of the monitored traf?c just like one
Would get from a conventional RMON probe.
The other loWer-layer components such as the dRMON
Interface Module 150 provide the same platform isolation
number of different operating systems.
function that they do for the dRMON Agent thus permitting
Any SNMP operation on the netWork Which Would affect
the con?guration or operation of a stand-alone RMON probe
is captured by the collector and forWarded, as appropriate, to
the agents so that the agents can modify their behavior
the other modules to be implemented in a Way Which
45
maximiZes their portability.
Protocol for Communications BetWeen Adaptor and Collec
tor
accordingly. An example Would be an SNMP packet setting
According to the invention, a protocol is de?ned for
?lter de?nitions for Which packets ?oWing on the netWork
are captured for later analysis. Such a packet Would be
received by the collector and then passed along to dRMON
agents Which Would each individually compare received
packets to the ?lter de?nitions.
communications betWeen a collector and its agents. The
speci?c details of the protocol are not necessary for an
understanding of the invention, and the protocol may be a
prior art netWork management protocol, such as SNMP or a
subset of standards-based SNMP.
HoWever, the invention is also able to Work With a simple
While the invention may be most easily described as a
netWork having a single collector, because the actual data
55
gathering and monitoring is being performed at the managed
and more ef?cient protocol for speci?cally communicating
certain kinds of netWork management information and this
ESs, it is possible to have another collector on the LAN/
represents a preferred embodiment. A preferred protocol
WAN assume the data collection duties of a defective or
tors on a LAN, in Which case in this embodiment an
Would encompass both an application level protocol that
handles MIB objects and a netWorking protocol that is
poWerful for the particular purposes for Which it Was
identi?er is used so that an agent communicates With only
designed. A preferred protocol does not require and is not
one collector. In one embodiment, this identi?er also acts as
susceptible to con?guration by an ES user, so that it is not
as easily inadvertently disabled by a user as many other
off-line collector. It is also possible to have multiple collec
a security passWord as described beloW.
netWork protocols are. A preferred protocol Would bind
FIG. 6 is a block diagram of an embodiment of a dRMON
Collector according to the invention. Like the Agent, the
Collector loads automatically When the system starts and
depends upon the same DTA services to exchange dRMON
65
more directly to a NIC driver so that the protocol Will load
and be functional even if other netWork protocol stacks do
not load or are not operating properly. A preferred protocol
6,108,782
11
12
Will generally require no acknowledgement by default, but
discovery request is broadcast. In one embodiment, this
delay is set by each agent based on a random number. In
other embodiments, as described beloW, response delay is
Will include the ability to establish acknowledgements for
reliability and also to include encryption features for secu
rity.
based on some characteristic attached to each speci?c ES,
such as MAC address. Discovery requests are repeated
periodically to detect nodes Which have been added or
Apreferred protocol may be restricted to communication
betWeen intermediate system collectors and end system
poWered-up since the last discovery operation.
Time Synchronization and Polling
To facilitate proper time-based ordering of captured pack
agents, an area Where users do not otherWise need to
interface. The collector, in one embodiment, is designed to
interface With other netWork management softWare through
a standards based protocol, like SNMP, to facilitate interop
erability With netWork management softWare.
A preferred protocol Will result in loWer netWork traf?c,
10
be very reliable and require a small installation on the
agent maintains a clock, derived from its system clock. To
end-systems. A preferred protocol Will be designed With an
aWareness of the reliability of modern netWork infrastruc
be meaningful, the clocks in each Agent must be kept fairly
15
tures realiZing that many prior art protocols are designed
they are transmitted. In modern netWorks, in fact, packets
rarely get dropped once they are sent by the transmitter. A
sends out a time synchroniZation message periodically.
These messages may also be used to trigger the return of
statistics from the Agents. As elseWhere described herein,
each Agent sets a random delay interval before sending its
data to prevent ?ooding the collector.
preferred protocol, therefore, eliminates much of the
acknoWledgement and redundant traffic generated by other
netWork protocols that unnecessary for reliable netWork
operation.
25
In a speci?c embodiment, agents and Collectors keep time
in 100-nanosecond increments, each individual agent and
collector ultimately deriving its count from the CPU clock of
its oWn host. The Collector includes in each poll, sent out
every 5 seconds, its current uptime counter Which is the
number of 100-nanosecond increments that have occurred
since the collector Was started. Agents compare this value
With their oWn count, computed from their oWn system
clock, and compute any corrections that need to be made to
account for variations in system hardWare at each node.
agents communicate over the netWork as the dRMON pro
tocol. Unless the context otherWise requires, the dRMON
protocol should be understood to represent any possible
protocol betWeen collectors and agents for the eXchange of
management/monitoring information, generally in the form
of MIBs, including prior art SNMP-type protocols or includ
ing a preferred specialized protocol as just described.
Collector and Agent Functions
From the perspective of the user, the primary functions of
the agents and the collector are to collectively implement the
close to those of its peers and their Collector, although
precise alignment is generally not possible and is not
required by the invention.
In order to keep agent time-stamps aligned, the Collector
With the assumption that netWork traf?c Will be very unre
liable and that packets Will often get dropped or lost after
For the purposes of this description of the invention, We
Will refer to the protocol by Which dRMON collectors and
ets at the Collector and to ensure that statistics are placed
into the proper time period buckets, statistics and packets
coming from the Agents to the collector are time-stamped by
the agents. In order to accomplish this time-stamp, each
Agents use their oWn corrected counters to provide a relative
35
time stamp on the statistics and captured packets that they
return. In a speci?c embodiment, the agent and collector
monitoring, management, and packet capture capabilities
counters are each roll-over counters.
de?ned from RMON2, SNMP, and related netWorking stan
dards With enhancements resulting from the distributed
In one embodiment, average latencies in the path betWeen
the agent and the collector are ignored, because in most
real-World local area netWorks, the transmission delay Will
be effectively Zero. Other embodiments are possible Where
nature of the invention as herein described. As these primary
functions are described in publicly available standards and
documents and are Well-knoW to practitioners in the art,
the agents compute average latencies and adjust their time
stamps accordingly.
details of the netWork statistics gathering, packet capture, or
standards-based con?guration of those function are not
described here. What folloWs is a description of the func
tions according to the invention that alloWs the invention to
During packet capture, the collector time-sorts captured
45
ordered correctly in the capture channels. The timestamps
added by the agents Will normally be sufficient to do this, but
perform netWork monitoring, in a distributed fashion.
Some collector functions Will noW be described. In addi
tion to performing RMON2 analysis on its oWn directed
traf?c as Well as all multicast and broadcast traffic the
at times, because of corrections made at the agents, some
captured packets may get returned With nearly identical
time-stamps. In that case, the collector uses some protocol
Collector performs several other functions pertain to the
management or con?guration of its remote agents. dRMON
embodiments may be designed to interoperate With a variety
of RMON Management applications and all major SNMP
Management Platforms (e.g., HP OpenVieW) that support
packets returned to it to ensure that protocol eXchanges are
interpretation (such as sequence numbers, or request/
response indications) to correctly order the captured packets.
Agent Management by Collector
55
Agent Management can be roughly divided into tWo
areas: agent con?guration and RMON con?guration.
the original RMON MIBs. Doing so requires only that the
collector be programmed to communicate With the particular
Agent con?guration refers to such issues as hoW much
memory/storage for the agent to reserve for RMON data
management application and that ?ltering functions required
by the management application be translatable by the col
space, version management, etc. These actions are not
lector to directives to the agent.
dRMON protocol management frames.
RMON con?guration consists of ?lter settings, historical
de?ned in prior art RMON and are accomplished using
Agent Discovery by Collector
The collector is responsible for automatically discovering
all of the dRMON Agents Within its management sphere.
According to one speci?c embodiment, a special multicast
discovery frame is used to solicit identifying responses from
the agents. Each agent sets a different response delay so as
not to ?ood the Collector With discovery responses When a
sampling intervals and other RMON MIB-de?ned user
settable options as Well as the neWly accepted Aspen MIB
for standards-based probe con?guration. dRMON protocol
65
frames are used to carry these exchanges but Within them are
SNMP-formatted PDUs carrying the actual management
information.
6,108,782
13
14
Optimization of Network Traf?c by Agents and Collectors
is used by the Collector, as needed, to supplement the use of
the timestamps in recreating correct time order of the
According to the invention, network traf?c betWeen
agents and Collector is designed to be “?nite”, i.e., in as
captured packets.
many cases as possible, agents and collectors communicate
In one embodiment, captured packets Within a poll
using a minimum number of packets. The folloWing steps
are taken by the invention to help optimiZe and minimiZe
interval are grouped and sent to the Collector on the sub
netWork traf?c betWeen the collector and the agent:
resources at the agent for more packet-captures ahead.
sequent multicast request. This frees up memory and system
1. For discovery, reporting of statistics, and time
synchronization, the collector generates a multicast poll to
Which each of the agents replies. If a multicast poll is
dropped at any agent, no retransmission or acknoWledge
ment is attempted. This is possible because according to the
In one embodiment, the invention does not protect against
loss of captured packets once those packets are transmitted
10
at a node, the captured packets it contains Will be lost.
HoWever, other elements of the invention as described
herein, reduce the dangers that a collector Will not receive a
packet once it has been transmitted by a node. In an
invention, traf?c information reported by the agents to the
collector is in the form of cumulative counters; if a report
packet from an agent is dropped or is missed by the
from an ES. If, for some reason, a packet cannot be received
15
collector, a subsequent report packet from the agent Will
correct the statistics at the Collector.
alternative embodiment, an acknoWledgement based proto
col connection is established When captured packets are to
be transmitted.
Coverage of End-Systems Without dRMON Agents and
2. Conversation traf?c information sent by the agents is
time-?ltered, i.e., only the conversation entries that Were
updated since the last retrieval by this collector are sent by
the agent.
3. Traffic information sent by the agents to the Collector
gather statistics or capture packets pertaining to other ES
in the response is complete Within one packet; no response
depends on the availability or arrival of a second packet
from the agent, so responses can be processed immediately.
Which do not have active dRMON agents. In this Way, the
invention may be effectively employed in a netWork even
Where all ES are not equipped With dRMON agents. In this
Duplicate Data Filtering
According to one embodiment of the invention, provi
sions are made for ESs With dRMON agents installed to
25
Even if certain response packets get lost, impact to overall
embodiment, the collector and agents Work together to
eliminate duplicate statistics information reported to the
accuracy of collector statistics is minimal.
4. Agents generate a statistics response packet only in
collector by various agents and to reduce unnecessary net
Work traf?c overhead. To avoid both of these problems,
according to this embodiment, the collector maintains a list
response to a request by a collector. In general, there is no
other traffic generated by agents unless speci?cally
requested by the collector in a multicast packet.
of identi?ers of ESs With active dRMON agents. In one
Distribution of Packet-Capture Among dRMON Agents
embodiment, this list consists of the MAC (layer 2)
According to the invention, the agent and collector can
also perform capture of speci?c packet streams, as de?ned
by RMON for stand alone RMON probes. To accomplish
packet-capture, an RMON-management application sets up
addresses of the ESs With agents. This list is communicated
to every dRMON agent controlled by the collector piece
by-piece, With a certain number (N) of ES indications
noti?ed to all agents in each multicast request. Agents
35
the proper ?lters, channel and buffer control parameters at
capture and use this information to reduce unnecessary
traffic as described herein. The information may be con
the Collector, as described in standard RMON MIBs, and as
Would be done in a standard RMON probe. All neW ?lter
tained Within the agent ES in any type of table structure and
de?nitions, channel de?nitions, and buffer control de?ni
in one embodiment the information is stored in a binary tree
tions are then forWarded by the collector to all dRMON
Agents using multicast packets, as soon as these de?nitions
are set up at the Collector. In addition, the collector may
received ES addresses to determine Whether or not this agent
communicate existing de?nitions periodically to all
dRMON agents.
Based on these de?nitions, dRMON agents capture pack
table in order to facilitate quick look-up at the agent of
45
Will capture that received traffic.
Agents and the collector folloW certain rules to reduce
netWork traf?c overhead. In general, agents report statistics
captured packets only in non-multicast conversations in
regarding only conversations that are (1) directed (i.e. not
multicast), and are (2) to them (i.e. received (RX) traffic). For
transmitted traf?c, the agent reports statistics for directed
Which it is an active member. If the conversation is With a
traffic only When the receiving ES does not have an active
non-agent ES, then the agent node is responsible for the
capture. If the conversation is With another dRMON agent,
dRMON agent according to the reporting agent’s list. Other
rules are possible that eliminate duplicate reporting.
ets and forWard them to the collector. Each dRMON agent
then in one embodiment to maintain the time order of
In cases Where for some reason an agent incorrectly
captured packets (i.e., the response is after the request, etc.),
reports transmitted traffic to another active agent, the col
lector can eliminate duplicate reports by giving higher
only one of the tWo agents in a conversation captures the
packets and is responsible for sending these packets to the
In general, if only one side of a conversation has an active
priority to reports from the agent at Which the traffic Was
received.
Therefore, if agents A and B both report traffic betWeen
them, a collector Will use part of the traf?c information from
A in Which traf?c is directed to A and part of the traf?c
information from B in Which traf?c is directed to B. Another
eXample, in Which A is an agent ES and Z is not, conver
agent, that side captures packets for both sides.
sation betWeen them Will be reported by A only, and there is
55
Collector. In one embodiment, if both sides of a conversa
tion contain an active agent, a simple comparison of MAC
Addresses is made and a MAC Address Which is lexico
graphically bigger becomes responsible for capture. Other
rules for determining priority for packet capture are possible.
no duplication to be avoided.
In some embodiments, in some situations, both sides of a
conversation Will be reporting captured packets. Where
necessary, the periodic synchroniZing timebase messages
from the Collector are used to keep the dRMON Agent’s
According to speci?c embodiments of the invention, a
number of other strategies may be used to prevent transmit
ting duplicate data to the collector or, When duplicate data is
packet timestamps in close alignment and protocol analysis
transmitted, to prevent that duplicated data from being
65
6,108,782
15
16
counted twice at the collector. These strategies can vary
based on Whether the data is captured packet data streams
forWarded to the collector or is RMON statistics only sent
from the agent to the collector.
the interoperability design issues to the module (agent or
collector) necessary for interface With that system.
Speci?c Adapter/NetWork Operating System (NOS) Support
by Agent
The ?rst release of one speci?c embodiment of the
invention includes support for NDIS 3.X Which encom
Furthermore, to prevent duplication of multicast and
broadcast statistics, in one embodiment only the Collector
itself tracks multicast and broadcast packets and ES agent
passes WindoWs for Workgroups 3.11, WindoWs 95 and
tracking is disabled for those packets. Agents do not report
WindoWs NT 3.51 or later. Novell’s Client 32 Will be
supported in these same environments via the NDIS 3
any traffic statistics based on broadcasts. Currently, multi
cast traf?c is also handled by Collector only. In some
alternative embodiments, it may be desirable to have agents
Wrapper Which Will still be present. Any vendor’s NIC Which
offers an NDIS 3.X compliant driver can and Will be
participate in reporting of multicast traffic.
Preventing Flooding of Collector
According to the invention, the collector sends out a
multicast request to all its agents every polling interval. If all
the agents respond to this request immediately, or With a
similar delay, there is a chance of ?ooding the Collector With
supported, although NIC drivers designed for use With the
invention may be enhanced to provide additional features.
All Microsoft-de?ned Physical Media Management OIDs
15
more packets than it can receive and process. The collector
in turn may have to drop some packets depending on the
buffer-resources available. To avoid that, each agent uses a
A special Transmit Callback from the dRMON Agent is
supported in drivers designed for use With the invention.
This transmit callback alloWs outbound traf?c from the host
to be monitored by dRMON Without the performance pen
delay algorithm, Which calculates amount of time to Wait
before sending the response. Ideally, this delay algorithm is
such to spread responses from the agents as evenly as
possible over a poll response period so that the collector can
more easily handle all response packets. In one embodiment,
an agent derives a delay value from its unique MAC address
of the ES to distribute response packets across the desired
alty resulting from putting the adapter in promiscuous mode,
25
systems there is no Way for a higher layer protocol (such as
the dRMON agent) to signal to the driver that it Wants to see
copies of data that is being transmitted on the netWork.
random number generator, seeded With the unique MAC
According to the invention, the dRMON agent performs
a set operation against the NIC driver using the transmit
callback OID, indicating a 32-bit pointer to the dRMON
agent’s call-back routine. If that operation succeeds, then the
35
agent responses, including deterministic algorithms based
on the number of agents responding to a given collector.
Aging out of Agents and Collector
Agents age-out collectors When the agent no longer
receives any multicast requests for a prolonged period.
45
order to check for the presence of a neW or reaWakened
collector on the netWork.
The collector also times-out an agent if it does not receive
a response to a series of multicast polls for a prolonged
This alternative aspect of the invention is necessary
because in Microsoft’s original NDIS architecture, an adap
tor NIC driver communicating through the NDIS Wrapper
does not have the ability to pass transmitted packets back up
to a different higher layer protocol than the protocol that
originated the packets. Therefore, in a prior art NDIS NIC,
the agent cannot get access to packets transmitted by other
higher layer protocol.
period. In addition to freeing up resources in the collector
that are no longer needed, this information (i.e., that this
particular ES is no longer a dRMON agent) is communi
cated to other agents. Other agents can then start reporting
for this neW non-agent, as explained elseWhere in the
application.
dRMON agent knoWs that the NIC driver includes code to
support the transmit callback. The agent then can instruct the
NIC driver, using set operations, to set NIC driver ?lters to
monitor directed transmit traf?c. If the callback set operation
fails, then the agent sets the adaptor ?lters to promiscuous
mode, in Which case the adaptor reads all packets that appear
on the Wire, including packets it transmits, and those packets
are available to higher layer protocols.
When an agent ages out all collectors, the agent can free up
the ES resources no longer needed, and also it no longer
needs to process every single packet because there is no one
to Whom it can send packet statistics. Only the dRMON
protocol packets need to be processed by dormant agents in
as is currently required in many prior art drivers in order to
see transmit traf?c. In some current netWork operating
response time. In another embodiment, an agent uses a
address of the ES, to distribute response packets across the
desired response time. In other embodiments, agents seed a
random number generator With tWo numbers, one based on
a changing value such as a system clock. This redistributes
responses from ESs during each response time. Other
response distribution algorithms are possible that distribute
(object ID.) will be implemented including those catego
riZed as optional. This alloWs dRMON agents to detect all
media-based error events When running on adapters and
drivers designed for use With dRMON.
Transmit Callback
The NDIS Wrapper does, hoWever, give a driver the
ability to hold a packet in buffer memory until the driver has
determined from the adaptor card that the packet has been
copied to the card and sent. According to this aspect of the
55
According to one embodiment, there is very little memory
invention, a driver takes advantage of this mechanism to
communicate directly With an dRMON agent DTA TDI that
a transmitted packet in the buffer and can Wait until the TDI
a collector packet, at Which time the RMON engine is
has read and analyZed the packet before signalling to the
NDIS Wrapper that processing on the packet is complete.
initialiZed and a number of buffers are allocated.
Security
requirement (less than 10K bytes) for the agent until it sees
Compatibility and Interoperability
Communication betWeen a dRMON agent and Collector
According to the present invention, collectors and agents
may be designed to operate effectively With a number of
different netWork interface cards (NICs) and NOS architec
tures and a number of different management applications.
The separability of the agent and collectors alloW the
management system according to the invention to be
adapted to different operating environments While localiZing
is secure. Before either an agent or a Collector is installed,
the user sets a passWord that one collector and all agents
With Which it is communicating use to encrypt all messages
betWeen them. The passWord is separately encrypted by each
65
agent and by the collector and an embedded key is stored in
each image (executable) ?le of the dRMON Agents and the
Collector. According to the invention, the agent and the
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18
collector each use a slightly different algorithm that produce
The present invention in one embodiment reduces this
traffic by having a collector continuously update one or a
group of simple ?les at the collector that contained data
different embedded keys from the password, though the tWo
algorithms are guaranteed to alWays be able to reproduce the
representing the compiled statistics of netWork operation.
same passWord at When they are run. This mechanism is
employed so that a “hacker” can not simply do a comparison
of a dRMON collector and agent executable ?les in order to
derive the embedded key. The invention protects against a
hacker from simply dif?ng the eXecutable ?les to locate the
passWord and then inserting that in a “rogue” Collector
executable.
These ?le may be stored as simple teXt ?le. A management
station or a display terminal enabled to receive and display
this data can then make one request for a compiled ?le then
and use the data in the ?le to display a representation of
netWork operations. A dRMON collector, according to an
10
In some types of netWorks, those con?gured to be one
done is prior art interfaces. One application for this embodi
large LAN, several collectors may be deployed to handle all
the agents in the LAN and each collector Will collect
ment Would be to make the data available over an internet
type netWork, and displayable by a Web broWser.
statistics from one group of ESs on the LAN. Communica
FIG. 10 shoWs a representation of an eXample of one
tion betWeen the ES and its collector is controlled by the
shared passWord because agents Will not correctly be able to
decode and Will simply ignore poll packets that do not use
the passWord set for themselves and their collector.
In one embodiment, the dRMON agents have tWo
passWords, one a dRMON-and-auto-update passWord, the
other an auto-update-only passWord (also referred to as a
back door key). Both of these are stored Within the dRMON
agent in an intermediate, encrypted form.
At run time, the dRMON agent and the Collector, using
15
slightly different algorithms, calculate a ?nal passWord key
25
simpli?ed data ?le that may be used to report statistics
according to the invention. The ?rst line, “ipcount”, identi
?es Whether the data has changed. “Pktdist,” “pktrate,”
“stats,” are keyWords that preceed data lines for a particular
class of data. In this example, data in quotes is treated as
labels and ?oating point numbers are treated as values.
Hierarchical Collectors
Multiple alternative deployments of dRMON collectors
from their stored intermediate passWord. This derived value
Will be the same at both ends (both the collector and the
agent) and Will be kept in run-time memory only and never
stored anyWhere the user might hack. This Collector’s
calculated key is carried in the Authentication ?eld (also 16
are possible according to the invention, With different
embodiments including different sets of the features
described herein.
In addition to distributing the data collection process, the
data archiving and retrieval process may also be distributed.
Today’s management systems traditionally have focused on
a centraliZed management console model Where all the data
ultimately lives at one management station such as 54 after
having been retrieved from its remote sources. The obvious
bytes long) of the dRMON protocol Common Header. Once
and signi?cant disadvantage to this is that the information is
unavailable to a netWork manager Who is physically located
elseWhere.
the key is placed on the netWork, some type of netWork
encrypting, such as MDS, is used to protect the security of
the packets on the netWork.
If the Collector’s ?nal calculated key does not match
embodiment of the invention, may also include an SNMP
interface alloWing it to report individual counter values as is
35
either of the dRMON agents’ keys (normal or backdoor
keys), the dRMON agents Will reject its request. If this key
matches the back-door-key, then auto-update Will be
alloWed. If this key matches With dRMON agent’s key, then
Most larger netWorks already have various information
sources already deployed at some locations such as RMON
probes, embedded RMON implementations (often partial
of a security feature according to the invention.
group support) or embedded SNMP Agents. It is advanta
geous to incorporate their input into the dRMON vieW,
supplementing it When possible With more complete man
agement data.
An enhanced collector provides sophisticated manage
In one embodiment, once an agent has validated a col
lector it stores an indication for an address of the collector
include in the standard collector, especially When the Col
auto-update as Well as other dRMON information is pro
vided to it. FIG. 9 provides a How chart of one embodiment
and does not have to validate subsequent packets received
from the collector.
Other embodiments are possible that use security features
ment capabilities that are too dif?cult or costly to routinely
45
provided by the netWork operation system and that therefore
do not require a user to set a passWord. In such
embodiments, a different, but possibly related mechanism
may be used to alloW multiple collectors to be heard by only
a subset of agents.
Thus, the invention provides a number of alternative
security measures that together provide secure communica
tion betWeen agents and collectors.
lector is embedded in a hub, sWitch, or router. Such
enhanced capabilities might include WEB support With
55
JAVA server capability, the ability to feed management data
into standard databases or intelligent analysis of manage
ment data to spot problems before those problems become
critical.
FIG. 8 illustrates hoW this concept may be implemented
according to an embodiment of the invention and hoW it may
be distributed Within the netWorking environment. TWo
classes of Collectors are depicted: Workgroup Collectors 81
and Domain Collectors 80. All collectors are addressable by
Ef?cient Reporting of dRMON Data over a NetWork
Management stations 84, but often only Domain Collectors
Prior art RMON probes typically communicate informa
tion about the netWork’s operation With a management
are in fact addressed by a management application.
Workgroup Collectors oversee smaller regions of the
station using RMON de?ned MIBs and ?lters that are
netWork such as a single ?oor in a multilevel building.
individually reported to the management station upon
Because their sphere of management is smaller, a Workgroup
request of individual MIB data. Prior art RMON de?nes a
number of different counters, each of Which an RMON
probe can report to a management station upon query by that
etc.) are also smaller; as a result, they can often be embedded
in sWitch or hub. In smaller netWorks, these Collectors
station through SNMP or another generic netWork manage
ment protocol. This can potentially lead to a large amount of
traf?c ?oWing betWeen a prior art probe and a management
station in order to display an overall picture of the network.
collectors’ physical requirements (CPU poWer, memory,
Would probably be adequate for their management needs and
65
a second tier of Domain Collectors Would not be required.
Domain Collectors (DCs) are used in larger netWorks to
collect and archive management data from Workgroup Col
6,108,782
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20
lectors Within their sphere of management. DCs typically
represent larger regions Within the enterprise network such
Domain Collectors
as a remote of?ce or a Whole building on a large campus.
on the front-end (i.e. at the ES level), it is Domain Collectors
80 Which distribute it on the back-end (i.e. at the manage
ment terminal level). DCs are generally implemented on
While dRMON Agents distribute RMON’s functionality
Each one can support multiple management stations 84, thus
permitting any manager to monitor that domain from any
Where in the enterprise. Because of their greater scope of
poWerful hardWare, possibly based upon Pentium/Pentium
responsibility and the need to provide considerable long
Pro systems running WindoWs NT. DCs are concentrators
for large amounts of netWork management data. In one
term and nonvolatile data storage, DCs are generally much
more poWerful devices than Workgroup Collectors and as
such, are generally implemented as stand alone stackable
embodiment, DCs alloW capturing more netWork monitoring
data Without overly burdening distributed collectors by
periodically off-loading statistics from the 15s, freeing up
devices generally located With the sWitches and hubs they
oversee.
those IS resources to continue to capture neW data. This data
A more detailed description of these Collector types and
various alternative embodiments folloW.
is gathered from a variety of possible sources, such as:
dRMON Workgroup Collectors, Embedded RMON (full or
Workqroup Collectors
AWorkgroup class dRMON Collector is located in a prior
15
and organiZes this various information to create a seemingly
cated device. There are advantages and disadvantages to
each of these hardWare implementations as discussed beloW.
(1) Probe Based. RMON probes often have more
resources available than do management cards embedded in
sWitches and hubs and are often strategically located
throughout the netWork in a Way that makes them prime
candidates for collection points for dRMON. Combined
homogenous vieW of its management domain. The manage
ment domain may include different LANs that communicate
across routers and domain collectors generally are able to
communicate via a routed netWork protocol, such as IP. The
merged vieW is then made accessible in any variety of
possibly Ways, including to compliant SNMP-based man
With a desire to monitor devices Which do not have a
dRMON agent installed, locating a Collector in the probe
has further advantages. For example, a dual-interface
agement applications, published using WEB protocols, via
25
RMON probe could be connected to tWo sWitch ports Which
are shared With a number of older PCs, Mackintoshes and
station anyWhere in the enterprise.
Other features that may be included in alternative embodi
ments of DCs or in higher performance collectors include:
the other sWitch ports. Ideally, the probe Would be con?g
urable to provide a choice of vieWs such that the user could
Data sourcing for popular database products. ODBC in
select to have the probe combine the Collector’s data With its
this embodiment are used to cull important management
data from the domain vieW and feed it to databases created
oWn to create one interface vieW or to present them as
separate interfaces.
35
in manageable versions including management functions, so
it is a natural option to place a dRMON Collector Within
them. The primary disadvantages to this approach are that
management cards are often resource constrained both in
available CPU poWer as Well as in RAM capacity, With the
and maintained by the user. This capability alloWs users to
use the database query and reporting tools they use every
day to also access and analyZe their netWork management
data.
WEB-based device management. The Domain Collector
may provide a WEB front-end to the SNMP device man
RAM limitations often enough to preclude doing much in
agement thus making any broWser-equipped station a device
management station.
Expert Analysis. One of RMON’s greatest strengths is its
the Way of packet capture and store, and that to one degree
or another, the inclusion of RMON analysis in the sWitch
usually negatively affects overall sWitch performance.
Nevertheless, many users may prefer this approach and it
dial-up, etc. Because of the large and extensible storage
capabilities that may be included With DCs, considerable
historical data and many large captured packet streams could
be maintained and archived and offered to any management
UNIX Workstations Which do not have dRMON Agents. All
other dRMON-equipped nodes Would be distributed across
(2) Hub/Switch Based. Most Hubs or SWitches are offered
partial) in sWitches/hubs, RMON probes and/or Embedded
SNMP Management Agents in sWitches/hubs. A DC merges
art type RMON probe, a hub/sWitch, or a stackable dedi
45
?lter and capture capabilities. HoWever, unless the user is a
protocol expert, most of the poWer of this feature is lost to
dedicated dRMON Collector Whose packaging may be iden
them. Expert systems tools, like those noW appearing for
WindoWs NT, may be used in this embodiment to provide
ongoing analysis of the management data and alert the user
to problems before they become critical and can suggest
tical to that of the stackable hubs Which it Would manage. It
may be based upon proprietary hardWare or possibly a PC
possible resolutions.
Systems Management Integration. At present, manage
Without monitor or keyboard. This Collector has a more
ment tools vendors have lined up on opposite sides of the
fence: there are those Who focus on systems management
tools and those Who have concentrated efforts on netWork
enables an RMON solution for products that do not have the
resources to support full embedded RMON.
(3) Stackable/Stand alone. The Stackable Collector is a
poWerful CPU than most embedded management cards and
is capable of holding considerable RAM and, optionally,
hard disk storage; as a result, it can hold much more RMON 55 management. Unfortunately, many of the real World prob
lems users face are not cleanly isolated to one side or the
data such as large amounts of historical data or captured
packets. It may also provide additional services such as
other. There are numerous systems management tools such
WEB-based RMON management and even WEB-based
device management of the rest of the stack. The inclusion of
as LANDesk and Microsoft’s SMS Which could be coupled
into a DC via interfacing softWare. In combination With
many of these enhanced capabilities into this Collector’s
speci?cations are facilitated by basing it upon the PC
expert analysis, DCs could then provide problem detection
and resolution of many common problems regardless of
Whether they Were system problems, netWork problems or a
combination of the tWo.
architecture and using an OS such as WindoWs NT to
support various add-ons. The development tools for the PC
platform are also far ahead of those for embedded
processors, thus shortening substantially the time-to-market
and maximiZing the availability of experienced program
mers.
65
The invention may be embodied in a set of executable
computer program code Which may be stored into a ?xed
computer medium such as a disk, diskette, volatile memory
or non-volatile memory, or any other medium for storing
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22
5. The method according to claim 1 further comprising:
capturing netWork data streams at said nodes; and
forWarding said captured data streams to said collector.
computer code. In such a case When such instructions are
loaded and executed in an appropriately con?gured netWork
intermediate system, the intermediate system Will perform
as described herein. A representation of such a system 700
in shoWn in FIG. 11, containing CPU 707, optional input
6. The method according to claim 4 Wherein said com
piled statistics are as de?ned by published RMON or
devices 709 and 711, disk drives 715 and optional monitor
RMON2 monitoring protocols.
705. Fixed media 717 may be used to program such a system
and could represent a disk-type optical or magnetic media or
a memory. A system such as 700 may be used in conjunction
7. The method according to claim 1 Wherein a plurality of
said nodes are end systems that provide netWork commu
With the invention as embodied on a ?xed media to generate
executable ?les that can be distributed throughout a netWork
to various netWork components as described herein.
The invention has noW been explained With reference to
nications to a user.
10
speci?c embodiments. Other embodiments Will be apparent
to those of skill in the art. In particular, method steps have
been grouped and labelled as being part of various sub
methods in order to increase clarity of the disclosure,
protocol, said ?rst protocol being a higher layer protocol
15
de?ned for the monitoring and management of netWorks and
Wherein said node communicates With said collector using a
second protocol, said second protocol being a loWer layer
protocol that in unacknoWledged and is speci?cally designed
hoWever, these steps could be differently grouped Without
changing the essential operation of the invention.
for loWer layer netWork management communication.
Furthermore, it should be understood that While the inven
tion has been described in terms of a computer netWork, the
invention has applications in a variety of communication
10. The method according to claim 1 Wherein said col
lector and said nodes communicate via a protocol in Which:
statistics data from nodes to the collector is generated
only in response to a poll packet received from a
systems, such as advanced cable television or telephone
netWorks, or any other communication system including
collector;
system performance monitoring at distributed points in the
system and reported back to a centraliZed collector. It is
therefore not intended that this invention be limited, except
as indicated by the appended claims. It is also intended that
8. The method according to claim 1 Wherein a plurality of
said nodes communicate using an ethernet protocol.
9. The method according to claim 1 Wherein said collector
communicates With said netWork manager using a ?rst
25
poll and response packets are not acknoWledged or
retransmitted;
nodes report all netWork statistics in terms of cumulative
the Word “netWor ” as used in the speci?cation and claims
be read to cover any communication system unless the
counters so that any failure of any poll or response
packet does not result in erroneous data at the collector
context requires otherWise and likeWise “end system” be
read to encompass any suitable end system (telephone,
but merely results in a delay in the collector receiving
the data.
11. The method according to claim 10 Wherein said
television) on any such communication system or to encom
pass distributed points in the netWork intermediate of an end
systems. It is also intended that the Word “packet” as used
in the speci?cation and claims be read to cover any unit of
protocol further provides that node responses to a poll from
a collector are complete in one data unit so that a received
35
transmitted data, Whether an ethernet packet, a cell, or any
other data unit transmitted on a netWork unless the context
tiple nodes each respond to said multicast poll data unit from
said collector and ?ooding of the collector is prevented by
having each node delay its response by said random value,
requires otherWise.
What is claimed is:
1. Amethod for distributed collecting of netWork statistics
Wherein said random value determined at each node and
derived from an address of said node.
13. The method according to claim 1 Wherein said mul
comprising:
gathering netWork statistics at a plurality of nodes dis
tributed in a netWork;
transmitting data containing said statistics to a collector;
tiple nodes each repeatedly respond to repeated multicast
poll data units from said collector and ?ooding of the
combining said statistics from said plurality of nodes into
group netWork statistics to form complied statistics;
collector is prevented by having each node delay its
response by said random value, Wherein said random value
reporting netWork performance data based on said com
piled statistics, from said collector, to a netWork man
ager; and
determined at each node and derived from an address of said
node and a changing value such that responses to a multicast
poll data unit are redistributed With each poll.
14. The method according to claim 1 Wherein a node and
Wherein multiple nodes each respond to a multicast poll
data unit from a collector and ?ooding of the collector
a collector each have embedded Within them an identical
is prevented by having each node delay its response by
passWord that is separately encrypted by different reversible
a random value.
2. The method according to claim 1 further comprising:
setting values at said collector to con?gure said collecting
of netWork statistics; and
forWarding con?guration data by said collector to said
nodes to con?gure said gathering by said nodes.
3. The method according to claim 1 further comprising:
launching an agent in nodes participating in said distrib
uting collecting, said agent being an executable module
for gathering netWork statistics and communicating
With said collector.
4. The method according to claim 1 Wherein said com
piled statistics are as de?ned in a standard de?ned for the
gathering of netWork-Wide performance statistics.
response from a node can be processed Without depending
that any other data unit be received.
12. The method according to claim 1 Wherein said mul
algorithms and Wherein said collector and said node unen
55
crypt their identical passWords at run-time only said Wherein
said collector places said identical passWord in an initial poll
data unit and Wherein said node responds to that collector
only if a passWord in a poll data unit matches its passWord.
15. The method according to claim 9 Wherein said ?rst
protocol is a standard-based SNMP protocol alloWing said
collector to communicate With standard netWork manage
ment applications and said second protocol is a non-routed
layer 2 protocol optimiZed for unacknoWledged communi
cation betWeen a collector and a node.
65
16. The method according to claim 1 Wherein said col
lector is a set of functions embedded Within a netWork
intermediate system.
6,108,782
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23
17. The method according to claim 3 wherein said agent
at said node, establishing capture channels resident on
is a set of functions incorporated in other driver or system
softWare installed in a node.
said node for storing said captured data units prior to
encapsulating and transmitting said units to said col
18. The method according to claim 1 further comprising:
lector.
21. The method according to claim 19 further comprising:
launching an agent in nodes participating in said distrib
uted capture, said agent being an executable module for
transmitting data containing compiled statistics from said
collector to a domain collector;
compiling statistics from a plurality of collectors at said
domain collector; and
providing reports based on said compiled statistics, from
establishing capture channels, capturing packets, and
10
said domain collector, to a netWork manager.
19. A method for distributed capture of data unit streams
22. The method according to claim 19 Wherein a plurality
of said nodes are end systems that provide netWork com
comprising:
munications to a user.
capturing data units at a plurality of nodes distributed in
a netWork;
15
encapsulating said captured units and transmitting said
de?ned for the monitoring and management of netWorks and
combining said captured units from said nodes into group
Wherein said node communicates With said collector using a
capture channels;
second protocol, said second protocol being a loWer layer
protocol that is ?exibly either unacknowledged or
acknowledged, has loW overhead, and is speci?cally
designed for loWer layer netWork management communica
reporting said group capture channels, from said collector,
to a netWork manager; and
collector;
using said synchroniZation data at said nodes to maintain
a time at said nodes that is in synchroniZation With the
time at said collector;
and time-stamping captured data at said nodes When said
data is transmitted from said nodes; said time-stamp
representing an elapsed time at said node from When
said data is received at said and When said encapsulated
data is transmitted to said collector;
examining said time-stamp at said collector to determine
and order said captured data units.
20. The method according to claim 19 further comprising:
setting values at said collector to con?gure capture chan
nels for said data;
forWarding con?guration data by said collector to said
nodes to establish capture channels and ?ltering de?
nitions; and
23. The method according to claim 19 Wherein said
collector communicates With said netWork manager using a
?rst protocol, said ?rst protocol being a higher layer protocol
encapsulated data to a collector;
transmitting at periodic intervals from said collector to
said nodes a synchronization data unit, said synchro
niZation data unit representing an elapsed time at said
communicating With said collector.
25
tion.
24. The method according to claim 19 Wherein said
collector furthers examines a time stamp for captured data
units and, Where necessary, examines other protocol infor
mation in said data units to determine a correct order for said
data units.
25. The method according to claim 19 Wherein a node
records the identity of all other nodes capable of performing
distributed capture and only captures data if:
35
the data traf?c is directed data traf?c either to or from that
one node; and if the other node is either not capable of
performing data capture or if the address of the other
node indicates that said node is designated to perform
packet capture.
26. The method according to claim 19 Wherein a node
transmits encapsulated data only in response to a poll signal
from a collector.
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