Re: WCCPv2 support

sön 2006-03-12 klockan 23:04 -0500 skrev Jeremy Hall:

> I'm not sure whether it is a good idea to wait until routers are
> included (until we're 2waying with them, somebody understanding te
> protocol better than I would have great comments I'm sure)

There is multiple negotiations going on.

a) router<->cache negotiation. This is the "HERE_I_AM -> I_SEE_YOU"
handshake. It is completed by the cache getting included the list of
cache servers in I_SEE_YOU messages from the router, which requires a
"HERE_I_AM -> I_SEE_YOU -> HERE_I_AM -> I_SEE_YOU" sequence (first three
to verify connectivity, the last to inform the designated cache you are
available..)

b) Election of the designated cache. Ther is an election algorithm
(outside the protocol) defining which cache is the designated cache. The
recommended algorithm is that the cache with the lowest IP gets elected.
The list of potential designated cache servers is found in the I_SEE_YOU
packets. If you are not there, or not the lowest IP there then you are
not the designated cache..

c) designated cache -> router assignment using REDIRECT_ASSIGNMENT
messages, based on the information it received in the I_SEE_YOU packet
from the router.

In service groups the designated cache election gets a little messy as
each router maintains it's own WCCP state and things can get out of sync
if not all equipment is configured proper or some device is restarted.
Consider for example a potential designated cache only announcing itself
to a subset of the routers in the service group.. but these fine details
can be left to deal with later.. The 1.5 HERE_I_AM_T delay helps a lot
in reducing this.

Regards
Henrik