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srr-queue bandwidth share on 3750

 

 

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vuillaumes at gmail

Aug 31, 2009, 1:33 PM

Post #1 of 2 (4096 views)
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srr-queue bandwidth share on 3750

Guys,

i was wondering and because i can;t test, in that case below

interface GigabitEthernet1/0/1

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 607

switchport mode trunk

srr-queue bandwidth share 1 59 30 10

srr-queue bandwidth shape 30 0 0 0

mls qos trust dscp

In case of congestion, let's say my queue 2 is free of use (empty) .... How
are my queues 3 and 4 gonna to use the free queue bandwidth queue 2? i mean,

with this configuration my queue 2,3 and 4 get the remaining bandwidth after
the queue 1:

queue 2, 59/99*66Mps = 39 Mbps

queue 3, 20Mbps

queue 4, 6Mps

so it means 39 Mpbs available to allocate to queue 3 and Queue 4... how ths
traffic will be shared between 3 and 4? ( i suppose it's related to the
priority of the queue)

Can you confirm?

tks
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peter at rathlev

Sep 4, 2009, 7:56 AM

Post #2 of 2 (4016 views)
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Re: srr-queue bandwidth share on 3750 [In reply to]

On Mon, 2009-08-31 at 16:33 -0400, samuel vuillaume wrote:
...
> srr-queue bandwidth share 1 59 30 10
...
> In case of congestion, let's say my queue 2 is free of use
> (empty) .... How are my queues 3 and 4 gonna to use the free queue
> bandwidth queue 2? i mean, with this configuration my queue 2,3 and 4
> get the remaining bandwidth after the queue 1:
>
> queue 2, 59/99*66Mps = 39 Mbps
> queue 3, 20Mbps
> queue 4, 6Mps
>
> so it means 39 Mpbs available to allocate to queue 3 and Queue 4...
> how ths traffic will be shared between 3 and 4? ( i suppose it's
> related to the priority of the queue)

They will share, but not equally. Queue 3 will take 75% of the remaining
bandwidth, queue 4 will take 25%. If any queue does not use it's
allocated amount (either because it uses a shaping SRR instead or
because there are no packets) the allocation is simple disregarded.

You can view the SRR sharing algo as:

1) take W1 packets from queue 1 (=> 0, shaping)
2) take W2 packets from queue 2 (=> 0, queue empty)
3) take W3 packets from queue 3 (=> 30 if they're there)
4) take W4 packets from queue 4 (=> 10 if they're there)
5) repeat from step 1)

So each round of 40 packets takes 30 from Q3 and 10 from Q4.

--
Peter


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