Evaluation of 3COM NJ100 Network Jack - Berk-Tek

Evaluation of 3COM NJ100 Network Jack - Berk-Tek
Evaluation of 3COM® NJ100 Network Jack
Data Communications Competence Center
July 11, 2007
Test Summary
Outlined in this report are the results of a performance assessment of the 3Com NJ100
network jack. Testing was performed to determine the strengths and weaknesses of the
The 3Com NJ100 network jack is a 4-port, unmanaged Ethernet switch
that fits into any standard data port opening. It is connected to the LAN
by one UTP network connection. The concept of the product is to bring
switching capability into a single port, while allowing the connection of up
to four networking devices such as several computers or peripherals.
Figure 1 depicts the 3Com NJ100.
The network jack features 10/100 Mbps auto-negotiation that configures
Figure 1: 3Com Network Jack
the jack for 10 Mbps or 100 Mbps operation. The NJ100 operates in
either full or half-duplex operating modes. It contains a switch that
toggles between the ports to deliver the network traffic to the appropriate connection.
The network jack requires a source of power to operate and is supplied by either a single
or multi-port Ethernet power supply that provides IEEE 802.3af compatible power over
Ethernet. Power over Ethernet supplies voltage over the UTP network cable allowing
the device to receive both power and data from the same network cable. The
components may also be powered locally by an independent supply located at the unit.
Test Setup
Active network testing was performed using the Spirent SmartBits® 200 and 2000
mainframe units that contained Fast Ethernet modules. SmartBits is a multi-port traffic
generation and performance analysis system. It provides scrutiny of the Ethernet frame
traffic that occurs between active network elements.
In addition to SmartBits testing, Chariot®, a Net IQ software product, was used to
evaluate the performance of the switch that is imbedded in the NJ100. Chariot allows
the analysis of switch while using different types of network traffic such as streaming
video or Internet traffic to demonstrate data transfer while under congestion control.
Test Equipment
o Spirent SmartBits® Models 200 and 2000 Multi-Performance Analysis
System with SX-7410B Fast Ethernet modules.
Other Equipment
o 3Com 3C16468 10/100/1000 Ethernet Switch
o 3Com Ethernet Power Supply
o NetIQ Chariot®
132 White Oak Road New Holland, PA 17557
Phone: 717-354-6200 Fax717-354-7933
Evaluation of 3COM NJ100 Network Jack
July 11, 2007
o Cable
ƒ Berk-Tek LANmark-350
o Connectivity
ƒ Patch Panel: Ortronics GigaMo CAT5e
ƒ Jacks: Ortronics GigaMo CAT5e
ƒ Patch Cables: Ortronics GigaMo CAT5e
SmartBits 2000 with
Gigabit Ethernet Cards
3Com NJ100 Network Jack
3Com Power Source
Category 5e Patch Cords
Figure 2: Utilizing the NJ100 for a local connection
SmartBits 2000 with Fast
Ethernet Cards
3Com NJ100 Network Jack
90 Meters Category 5e Cable
Category 5e Patch Panel
Category 5e Patch Cords
3Com Power Source
Figure 3: Utilization of the NJ100 in a network configuration with SmartBits
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SmartBits 200 with Fast
Ethernet Cards
Evaluation of 3COM NJ100 Network Jack
3Com NJ100 Network Jack
3Com Switch
Category 5e Patch Cords
Chariot Running
July 11, 2007
3Com NJ100 Network Jack
90 Meters Category 5e Cable
3Com Power Source
Chariot Endpoints
Figure 4: NJ100 in a real-world network configuration measured by Chariot
Test Results
SmartBits Testing
The local setup shown in Figure 2 tests the performance of the network jack as an
independent switch. This would simulate multiple computers being connected to the
ports of the NJ100 and transmitting locally across the internal network jack switch.
Performance between each local port was analyzed.
In this mode of operation, three of the four network jacks performed their function as
expected with no frames lost. One of the four NJ100 switches dropped frames. The
overall throughput of this NJ100 switch was reduced due to the need to resend data.
This port had a frame loss of 4.1x10-6 as compared to the specified Ethernet frame loss
of 10-7. Other ports performed better, but still lost some frames. The typical frame error
rates for these ports were 8.1x10-9 – well within the required maximum.
Figure 3 shows a setup that emulates a complete network configuration. Ninety meters
of horizontal cable connected the NJ100 to the patch panel. The total length of the
cabling channel was 100 meters.
Four channels of the SmartBits unit were set to transmit 64-byte frames with 0.96microsecond gaps between the frames. Signals were sent from the network jack to the
single connection. The purpose of this test was to evaluate if there was any preference
between the ports of the NJ100 when it was transmitting to the network. Ports on three
of the four switches showed little preference from port-to-port. The NJ100 that showed
poor performance in other tests also exhibited it in this test. Of the frames transmitted to
the network, 41 percent were from port 1, 35 percent were from port 2, 15 percent were
from port 3 and 9 percent were from port 4.
A second full network test was configured so that the SmartBits 2000 was sending Fast
Ethernet signals into each port of the NJ100 simultaneously (uplink). At the other end of
the cabling channel, the SmartBits 200 unit was transmitting to the NJ100 (uplink) at the
same time. Three of the NJ100s performed without any lost frames. The fourth jack, the
same unit that showed performance problems in the other tests, had a downlink frame
loss of 1.8x10-1 and an uplink loss of 6.7x10-6.
Chariot Testing
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Evaluation of 3COM NJ100 Network Jack
July 11, 2007
For all of the Chariot testing, data was sent at 100 Mbps and the resulting receiver
speed was measured for different configurations and file types. Table 1 shows the
Table 1: Chariot Test Results
Transaction Type
Data Rate
Ethernet frames
Ethernet frames and MPEG video file
incoming from local PC
Ethernet frames
Ethernet frames and MPEG video across
the network
FTP transfer simulation
Ethernet frames from 2 PCs sharing the
Entire Network
(Figure 4)
Entire Network
Entire Network
Data Rate
Wall Jack Data
Local is defined as between devices connected to the NJ100
Connecting through the NJ100 showed a substantial degradation in received data rate
no matter what type of data was being sent.
3Com claims that the NJ100 will save companies from “pricey” new cable installations,
but the equipment manufacturer neglects to mention that there is a subsequent cost that
manifests itself in performance degradation and network security issues.
Advantages and disadvantages of the NJ100 are summarized in Table 2.
Table 2: NJ100 Advantages and Disadvantages
Enables local connections of peripherals
Poses potential security issues because
for a work group
devices can be connected to the network
that are not approved by network
Potential to reduce cabling connections for Throughput decreased to each port by as
work groups
much as 75 percent if all four ports are
being used.
Unmanaged – may not auto-negotiate to
the best solution-set.
Not upgradeable to Gigabit speeds
Other results also showed that there may be another problem with the NJ100 as far as
manufacturing consistency goes. Three of the four NJ100s investigated performed as
expected in Smartbits testing, but the fourth executed very poorly in comparison. This
part had difficulty transferring frames between the ports of the unit both downstream and
upstream to the LAN. This particular network jack also showed preference to certain
ports. The other three NJ100s did not exhibit this anomaly.
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Evaluation of 3COM NJ100 Network Jack
July 11, 2007
Nexans maintains that using a NJ100 may be an easy interim solution for companies
that are growing and would like to add personnel onto existing network connections, but
to use them for long-term system links will prove to be detrimental to both productivity
and security.
Data Communications Competence Center
Nexans’ Data Communications Competence Center, located at the BerkTek Headquarters in New Holland, Pennsylvania, focuses on advanced
product design, applications and materials development for networking
and data communication cabling solutions. The Advanced Design and
Applications team uses state-of-the-art, proprietary testing and modeling
tools to translate emerging network requirements into new cabling
solutions. The Advanced Materials Development and Advanced
Manufacturing Processes teams utilize sophisticated analytical
capabilities that facilitate the design of superior materials and processes.
The Standardization and Technology group analyzes leading edge and
emerging technologies and coordinates data communication
standardization efforts to continuously refine Nexans’ Technology
Roadmap. An international team of experts in the fields of cable,
connectors, materials, networking, standards, communications and
testing supports the competence center. The competence center
laboratories are a part of an extensive global R&D network that includes
eight competence centers, four application centers and two research
centers dedicated to advanced technologies and materials research.
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