[c-nsp] 12.2(33)SRA is finally out!

[Rodney Dunn]

We actually do the tcp adjust MSS in the CEF path on software
forwarding platforms.

Rodney

On Sun, Jul 02, 2006 at 09:11:29AM -0700, Tim Stevenson wrote:
> Yes, that is my understanding, the initial SYN is handled in the 
> process path, while the remaining packets are CEF switched in 
> software based platforms.
> 
> Tim
> 
> At 11:09 AM 7/2/2006 -0400,  uttered:
> >Tim,
> >
> >My apologies for straying off topic, but can you explain how central 
> >forwarding platforms (7200, ISR, etc) handle mss-adjust ? The SYN 
> >packets get handled in the process path, and the rest of the flow hits CEF ?
> >
> >On 6/27/06, Tim Stevenson 
> ><<mailto:tstevens at cisco.com>tstevens at cisco.com> wrote:
> >The model is that the ACL TCAM is programmed to punt just initial TCP
> >SYN packets to the RP CPU so the MSS can be modified as it transits 
> >the router.
> >
> >Yes, this has implications for the CPU utilization in the face of
> >heavy SYN traffic - you can configure the ACL bridge input rate
> >limiter on PFC3 to rate limit traffic punted due to an ACL bridge
> >result (mls rate-limit unicast acl input <rate>), but doing so could
> >be a tradeoff between CPU & session establishment time.
> >
> >Thanks,
> >Tim
> >
> >At 04:27 AM 6/27/2006, Ian Henderson submitted:
> > >On Sun, 25 Jun 2006, Asbjorn Hojmark - Lists wrote:
> > >
> > > > I don't know for sure, but I don't see how it could be. The MSS is a TCP
> > > > option, and when it's changed, you have to recalculate headers checksums
> > > > etc.
> > >
> > >That's why I posted the question - it sounded an odd thing to add.
> > >
> > >Since posting, our Cisco SE has told us that a number of the features in
> > >SRA were crossported from the 7200, possibly including CEF based Adjust
> > >MSS.
> > >
> > >--
> > >Ian Henderson, CCIE #14721
> > >Senior Network Engineer, iiNet Limited
> > >_______________________________________________
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> >
> >
> >Tim Stevenson, <mailto:tstevens at cisco.com>tstevens at cisco.com
> >Routing & Switching CCIE #5561
> >Technical Marketing Engineer, Catalyst 6500
> >Cisco Systems, <http://www.cisco.com>http://www.cisco.com
> >IP Phone: 408-526-6759
> >********************************************************
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> 
> 
> 
> Tim Stevenson, tstevens at cisco.com
> Routing & Switching CCIE #5561
> Technical Marketing Engineer, Catalyst 6500
> Cisco Systems, http://www.cisco.com
> IP Phone: 408-526-6759
> ********************************************************
> The contents of this message may be *Cisco Confidential*
> and are intended for the specified recipients only.
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