first-packet loss without state, case ARP [Re: [RAM] The mapping problem: rendezvous points?]

[Pekka Savola <[e-mail]>]

On Wed, 9 May 2007, David Conrad wrote:
>> First off, all the ARP implementations I know of queue the packet during 
>> the loopkup, i.e., no loss.
>
> That's what I thought, but folks have been saying that routers don't queue 
> anymore.

AFAIK, almost any router an operator would be willing to call a router 
deployed today start ARP (or ND) resolution process when a packet 
arrives that requires resolution.  The packet that initiated ARP/ND 
request is discarded, as are subsequent packets until the resolution 
is complete.

I understand queueing the triggering packets could be a DoS vector for 
networks where the target IP is down.

So, first-hit loss is not completely unheard-of in todays networks.

However, ARP/ND related loss only occurs per destination (and with 
usually long timers -- up to hours), not on (source, destination) 
basis.  That's why you very rarely see ARP-based packet loss even when 
starting communication with a new host.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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