[c-nsp] WAAS

[Brett Looney]

> On Nov 9, 2007 1:39 AM, Brett Looney <brett at looney.id.au> wrote:
> > > AFAIK, no tunnel between WAE boxes? is it correct? how can this work?
> >
> > No tunnel. Only the data segment of the packet is compressed - headers
are
> > left alone. This lets the router still do QoS, etc.
> 
> Regarding following setup:
> Datacenter equiped with WAE
> IP MPLS WAN
> Remote Office A equiped with WAE
> Remote Office B without WAE
> 
> Whitout Tunnel, how the central WAE know that Data to Office A should
> be compressed and data to Office B should not?

The WAE inserts TCP option 33 into the stream. If it sees option 33 come
back from the remote end it knows there is another WAE at the other end and
forms a peer relationship. Because it doesn't see option 33 come back from
office B it will not form a peer relationship and therefore not compress to
that site.

This function also forms part of the failback mechanism - if the remote WAE
goes away compression will stop because option 33 has disappeared.

BTW - this option 33 thing causes an issue when firewalls (particularly ASA
and PIX) are in the mix as they strip all unknown TCP options. You must
configure firewalls to leave option 33 alone.

B.