CSCO 6000/6500, the test said Not Fast Enough. See extract below.
==================
March 07, 1999, Issue: 2803
Section: Product Leaders
Multilayer switches -- Filling in at Layer 3, But Not Fast
Enough -- Cisco's 6000/6500 Beefs Up Its Layer 3 Line, But
Performance Could Use Some Beefing Up As Well
Marguerite Reardon
Running voice, data, and video over a single network calls for some smart
engineering to make sure top-priority flows get the white-glove treatment.
Cisco Systems Inc. (San Jose, Calif.) says its Catalyst 6000/6500 multilayer
switches have the IQ to get the job done, thanks to advanced QOS that
keeps delay-sensitive traffic in the groove.
And with the industry's highest fast Ethernet/gigabit Ethernet port density, the
6000 series backs its brains with brawn. What's more, since the new gear is
intended to fill the void between the Catalyst 8500 core switch and the
Catalyst 5000, it won't bankrupt Cisco shops.
Still, Cisco's Layer 3 performance is sluggish. "You can't get wire speed when
you run everything at once," says Dennis Walsh, chief technology officer for
General Motors Corp. (GM, Detroit), who is testing the Catalyst 6500 in his
network. Layer 3 switches from Extreme Networks Inc. (Cupertino, Calif.)
don't have this problem.
A Boxing Match
The 6000 series is a campus backbone switch that works standalone or in
conjunction with other networking gear (see the figure). The Catalyst 6000
has a six-slot chassis with a switching backplane that scales to 32 Gbit/s; the
Catalyst 6500 has a nine-slot chassis with a backplane that scales to 256
Gbit/s.
With up to 384 fast Ethernet ports and up to 130 gigabit Ethernet ports, the
6000/6500 can front-end server farms or aggregate lots of subnets.
Its closest competitor, the Corebuilder 9000 from 3Com Corp. (Santa Clara,
Calif.), tops out at 168 10/100-Mbit/s ports and 126 gigabit ports.
But the 6000/6500 isn't just a muscle machine. It can accommodate up to 16
QOS (quality-of-service) queues, a huge improvement over the single-queue
Catalyst 4000 and double-queue 5500. Extreme's Layer 3 gear only supports
four queues. What do corporate networkers do with all these queues? Use
them to set up very fine-grained flow control.
That granularity is a big selling point for companies looking to consolidate
networks. "We're planning to put all our voice, video, and data traffic over
one network," says Walsh. "The Cisco solutions, particularly the Catalyst
6500, will play a major role in our migration."
Layer 3 Laggard
Despite impressive QOS and port counts, the 6000/6500 falls short in Layer
3 performance. What's the holdup? Unlike competitors, the 6000/6500 can't
switch traffic at Layer 2 and Layer 3 on all ports. Instead, a Layer 2 ASIC on
each port forwards Layer 3 packets to a multilayer switch module (MSM) in
the chassis.
Passing packets back and forth this way slows things down. And there's only
one MSM trying to keep up with all ports.
What's more, the MSM is underpowered for the task at hand. It tops out at 6
million packets per second (pps). That barely accommodates four
simultaneous gigabit Ethernet connections. Traffic can flow into each of 130
ports on a fully loaded chassis at 1.5 million pps (the legal limit for gigabit
Ethernet). But each port would only be able to process 46,154 pps, using just
3 percent of its capacity.
It's the same story with fast Ethernet. Only 40 of the 6000/6500's 384 ports
can run at full wire speed when switching Layer 3.
By contrast, Extreme's Summit 48 boasts a Layer 3 throughput of 10.1 million
pps-enough to keep 67 fast Ethernet ports filled to capacity, even though the
box only has 48. |
