Re: [armd] RtgDir review: draft-ietf-armd-problem-statement-03

"Bhatia, Manav (Manav)" <> Fri, 31 August 2012 00:52 UTC

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From: "Bhatia, Manav (Manav)" <>
To: Thomas Narten <>
Date: Fri, 31 Aug 2012 06:22:50 +0530
Thread-Topic: RtgDir review: draft-ietf-armd-problem-statement-03
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Subject: Re: [armd] RtgDir review: draft-ietf-armd-problem-statement-03
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> > 
> > What exactly do you object to in that sentence?
> My concern with the opening sentence of Sec 7.1 is that it 
> generalizes large L2 domains and makes a sweeping statement 
> that seems to suggest that all routers in large L2 domains 
> need to process "a lot of " ARP traffic. This is patently 
> incorrect. As I have said earlier, this issue is specific to 
> L2 domains that see a lot of ARP/ND traffic and is not true 
> in general for all large L2 domains. 

Some more clarification.

There are large L2 domains that might see lot of ARP/ND traffic but will NOT process them. Such domains will treat all such traffic as regular bcast/mcast traffic and will flood it appropriately. The draft seems to suggest that large L2 domains have an issue because they need to process all such traffic which could lead the reader to believe that all such traffic is punted to the CPU where its processed. However in reality, most large L2 domains are oblivious to whether the bcast traffic is ARP or something else. Handling this traffic is not an issue at all. Its dealing with the unlearnt traffic that's an issue in such domains as the source MACs need to be learnt. If the L2 table is hash based then dealing with collisions, etc is another problem. If its CAM based then the size is often a limitation on the number of MACs that can be learnt.

Cheers, Manav