simple network management protocol

simple network management protocol
Technical Bulletin 2/14
SATELLAR 2DS/20DS
SIMPLE NETWORK MANAGEMENT PROTOCOL
SATELLAR MANAGEMENT WITH SNMP GET AND SET
THE SNMP PROTOCOL
The SIMPLE NETWORK MANAGEMENT
PROTOCOL, SNMP is a widely used
management protocol that operates on top of
IP and UDP protocols. In the basic mode of
operation the SNMP is a Request / Response
protocol. The requesting, controlling process is
called the Manager and the process
responsible for providing the responses is
called the Agent. In the SATELLAR use case,
the SATELLAR modem will act as a SNMP
Agent and the monitoring PC or SCADA would
be the SNMP Manager.
RSSI too low!
THE SNMP REQUEST
SNMP requests can be either Get or Set type.
The Get request queries for a value of the
parameter from the managed device and the
Set writes a new value for the parameter.
The requested parameters are identified with
OID (Object Identifier). For example, the value
for the device temperature would be identified
by the OID: 1.3.6.1.4.1.30306.1.1.1.4.2.1.1.0 .
MIB
Mappings between OID numbers and
parameters are stored in a tree formatted
hierarchical database called Management
Information Base, MIB. To enable SNMP query
of a certain parameter, both the Manager and
the Agent must have respective OID available
in their MIB. For SATELLAR-2DS/20DS modem,
the MIB database contents for SATELLAR related
parameters are available for download at
SATEL web pages. After download, they can be
installed or imported to the Manager MIB.
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1
SMART
RADIO
SNMP GET OPERATION
The following drawing illustrates the SNMP Get
operation in more detail. The SCADA system has
been configured to periodically monitor the
temperature of the SATELLAR modems in the
network. The SCADA system has a MIB entry
stored for the SATELLAR specific parameter, so the
SCADA will be able to map the temperature
parameter to the correct OID. This OID is then
included in the request. When the request is
received by the SATELLAR, it will map the OID to
the requested parameter of temperature. The
internal logic in the SATELLAR reads the
temperature value and sends it in the SNMP
response back to SCADA. Again, in the response SMART
RADIO
the identifier for the requested parameter is the
OID. The monitored SATELLAR device can be
either locally connected or remote modem behind
the IP radio interface. The SATELLAR network must
be configured to operate in the Packet Mode.
However, if it is sufficient to monitor only locally
connected modem, radio protocol mode can be
selected freely.
SCADA
45°C
For local monitoring,
the radio protocol mode can be selected
SATELLAR Packet Mode
(IP operation) required.
Monitored device
can be any SNMP
enabled device with
Agent functionality.
SCADA SUPPORT
In this case, the MIB
resides at the OPC
Gateway, instead of
SCADA.
Many SCADA solutions have a built-in support
for the SNMP. Also, many SCADA providers
recommend SNMP usage by adding a protocol
gateway to the system. The protocol gateway
will convert the SCADA supported protocol to
SNMP queries and vice versa. For example ABB
Microscada supports the SNMP operation via
the SNMP-OPC (Open Connectivity via Open
Standards) gateway. See the following drawing
for the illustration for the gateway operation.
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2
The OPC gateway
mediates and
translates the OPCSNMP communication.
SNMP SET OPERATION
The following drawing illustrates the SNMP Set
operation in more detail. The user wants to enable
the Serial IP functionality of the remote SATELLAR
by setting the Serial IP to Server mode. The
management PC has the MIB configured and thus
it is able to map the correct parameter to the OID,
together with the desired value. In the following
example, this is the step 1.): Serial IP mode is
identified by the OID
1.3.6.1.4.1.30306.1.1.1.4.2.1.1.15 and the
“Server mode” is represented by the value 1. The
manager sends this information to the SNMP
Agent running in the remote SATELLAR, and issues
the parameter value change with SNMP SET
request, as illustrated in the step 2.). In the step
3.), the SNMP Agent receives the Set request and SMART
RADIO
again, maps the OID to the correct parameter,
together with the received value 1. In this
example, MIB query was successful, as well as
setting the parameter in the step 4.). Therefore,
the SNMP Agent at the remote SATELLAR replies to
the Manager by sending the SNMP SET Response,
together with the status indication (no errors), the
changed OID, and the value. Remote
configuration with SNMP Set protocol was
successful.
1. SNMP GET Request
SNMP TIMEOUT
When the SNMP Get or Set Request has been
sent by the Manager application, the Manager
expects the Response to arrive within a specified
time, SNMP Timeout. If there is no response
received, the SNMP Manager application stops
the communication with the agent. Therefore,
in SATELLAR networks with radio links, it is
recommended to increase the timeout value set
in the Manager. How this is done, depends on
the application.
2. Timeout
3. Retry: SNMP Get
4. Delayed response
5. No response:
operation halted.
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3
ENABLING SNMP OPERATION
SNMP PARAMETERS IN THE SATELLAR
First step to enable SNMP operation in
SATELLAR is to download the MIB files from the
SATEL web pages, from Support, Downloads,
Firmware section (April 7, 2014:
http://www.satel.com/support/downloads/
firmware). Import all the MIB files to the
Manager application. The details on how this is
done fully depend on the selected manager
application. Files needed are:
Services
SNMPD State:
Turns the SNMP functionality on or off.
SNMP
SNMP RO Community:
Password to query values from this device with
SNMP Get commands. The Manager side
configuration must be set to match with this
string.
SNMP RW Community:
Password to set values to this device with SNMP
Set commands. The Manager side configuration
must be set to match with this string.
SNMP RW Community IP:
IP address range that is allowed to send Set
commands to this device.
SNMP Notification IP:
The IP address of the destination that his device
sends the SNMP notifications to, when such a
notification is available.
Next, configure the SNMP parameters with a
web browser connection to SATELLAR IP–
address. Required parameters are in Modem
Settings tab, on the Services page as well as
on the SNMP configuration page.
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4
3RD PARTY MANAGER APPLICATIONS
SATEL does not currently provide any SNMP
Manager applications. One reason for this is that
many systems already have an operational SNMP
Manager. However, if the 3rd party SNMP
manager is required, several options can be
found from the Internet. Available software varies
a lot. Many of them are complex and heavy
solutions with full of features and functionality that
would not be needed in the SATELLAR network
management. This makes the usage of the
application clumsy and slow. Some applications
also often lack of the visual presentation of the
network and the monitoring state. Another issue
with many applications is that they are sending
extensive amount of SNMP Get queries for values
that one might not be interested about. And in
many cases there is no way to suppress these
messages or control which SNMP requests to send
and how often.
According to the SATEL testing of SNMP
Managers, currently the most interesting ones
seem to be applications called “LAN State Pro”
and “The Dude.”
FEW SNMP MONITORING SOFTWARE EXAMPLES
LAN State Pro

Commercial monitoring tool

Designed for large IP networks

Restricted set of SNMP functionality

Controllable set: no extra messaging

Visual monitoring available

Viewing normal values requires mouse over

Working and extensive alarm functionality

Free 30-day trial
The Dude

Free and open monitoring tool

Extensive set of SNMP functionality

Some functionalities generate additional
messaging and cannot be turned off

Configurable and extensive visual
monitoring

Working and extensive alarm functionality

Scripting functiolality
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