[c-nsp] WCCPv2 - what happens to existing connections when redirect-list is modified?

Dale Shaw dale.shaw+cisco-nsp at gmail.com
Fri May 22 18:42:30 EDT 2009

Hi Geoff,

On Sat, May 23, 2009 at 12:25 AM, Geoffrey Pendery <geoff at pendery.net> wrote:
> If I'm "core WAAS", and I see a new TCP conn
> come in, I need to know just by looking at this conn whether it's
> coming from another WAAS or just an end host.  So if I'm taking a new
> conn from an end host, when I pass it on I need to modify it so that
> other WAASes (WAASi?  WAASen?  ouch.) know that I'm out there.

Discovery of other WAAS devices is performed using TCP options. I
haven't captured a SYN as it travels from an end host, through a WAAS,
towards the destination, but I imagine that within the TCP option
'payload', the WAAS embeds its ID which is known to the far-end WAAS
by virtue of their common link with the Central Manager.

Pure speculation, but anyway, discovery IS performed using TCP
options. It is possible for a WAAS device to pass-through a connection
without modifying the packet (TCP header) contents at all.


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