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4108 vs 5308: routing performance question

Mark Landin
Valued Contributor

4108 vs 5308: routing performance question

We've got two 4108 switches, one of which is doing VLAN routing. I'd like to replace this switch with a 5308, and I was looking at the comparitive performance of those switches on the Procurve site so I could use the performance boost as a justification. I was confused by this:

4108
====
Latency: < 10.2 microsecs
Throughput: up to 71.4 million pps
Switch fabric speed: 36.6 Gbps


5308
====
Latency: < 6 microsecs
Throughput: up to 48 million pps
Switch fabric speed: 76.8 Gbps

OK ... the 5300 has a higher switch fabric speed, lower latency, but only 2/3 the throughput? Am I reading this wrong? Are any of these statistics considered "routing performance", and if not, where can I find those figures?
3 REPLIES
Ralph Bean_2
Trusted Contributor

Re: 4108 vs 5308: routing performance question

Hi Mark -

The 4108 has a greater pps number because it can support a higher number of ports in a chassis as compared with the 5308, and so can forward more packets (through that greater number of ports).

The densest modules:

4108: J4908A 20-port

5308: J4907A 16-port

Ralph
Mark Landin
Valued Contributor

Re: 4108 vs 5308: routing performance question

I understand that, but that can't be the whole story. The ratio of 16/20 is .8, but the throughput ratio is .67.

And does any of this relate to routing performance? I'm trying to justify this on higher core performance for the 5300, but these are the only measurements I can find and they aren't supporting my argument.
Regnar Bang Lyngsø_2
Frequent Advisor

Re: 4108 vs 5308: routing performance question

It depends on where the bottleneck is. In some cases the switch fabric might be the bottleneck.

My guess is that the switch fabric speed is measured twice (ingoing + outgoing).

In that case (if all traffic is cross module):

5308:
=====
Switch fabric: 76.8 Gbps
Bandwidth per module: 9.6 Gbps
Bandwidth per Gigabit port: 2 Gbps
Number of gigabit ports per module with guaranteed non-blocking: 4

4108:
=====
Switch fabric: 36.6 Gbps
Bandwidth per module: 4.575
Bandwidth per Gigabit port: 2 Gbps
Number of gigabit ports per module with guaranteed non-blocking: 2

A fully saturated Gigabit ethernet link will carry approximately 1.5 Mpps worth of 64 bytes packets (minimum ethernet packet size). This means that the 5308 will be able to serve 32 Gigabit ports. The 4100 will be able to serve approximately 48 Gigabit ports.

To me this indicates that these performance measures are related to the old gigabit modules - the 4108 originally only had the 6 port gigabit module - the 5308 had 4 port gigabit modules.

Whether the switches will be able to deliver full throughput with the new 16 (5308)/20 (4108) ports or if the 5308 has a lower throuhput due to the original design - well - thats for HP know.

Regards
Regnar