[cisco-voip] RTP arriving early generating ICMP unreachable

[Dale Shaw]

[ probably should've marked this thread 'OT' ]

Thanks to Nick and Wes for their replies.

Keeping the original scenario in mind, I'm curious what the audience
thinks of the behaviour described in this Juniper KB article:

http://kb.juniper.net/index?page=content&id=KB16823

..what would you expect the impact of this behaviour to be in your networks?

I guess what I'm trying to gauge is, how common is the 'early RTP'
situation in real, properly tuned networks (Nick and Wes's replies
indicate it can be 'normal'), and how much sense does it make for the
Juniper SRX routers to respond the way described in the article linked
above?

cheers,
Dale
(bitten! ;-))

On Tue, May 18, 2010 at 7:49 AM, Dale Shaw
<dale.shaw+cisco-voip at gmail.com> wrote:
> Hi,
>
> Disclaimer: The scenario I describe below is not present in a Cisco
> deployment -- at the moment I'm just trying to get a feel from this
> audience for how normal (or not) this behaviour is in other voice over
> IP environments.
>
> I'm investigating a situation at the moment where IP phones are
> generating an ICMP unreachable (destination port unreachable) packet
> on receipt of the first RTP packet during voice mail access.
>
> To me, it indicates a signalling timing/sequencing problem -- the
> phone is indicating it wasn't yet ready to process RTP and effectively
> wasn't listening. A very short time later, RTP begins flowing
> bi-directionally and everything is OK.
>
> Is there a generic explanation for this behaviour? Is it 'normal'? If
> you saw this in your network, would you investigate and tune?
>
> cheers,
> Dale