[plug] Source-routed? (OT)

[Bernard Blackham]

Hi Derek

> In network parlance, what does the term "source-routed" mean?

There's at least two contexts I'm aware of...

   1) On a client machine: being able to specify what route your
   packets should take to reach out to the internet - ie, the path
   of gateway machines that your packet will hop through. Back when
   the internet was much less paranoid, it seemed to be a feasible
   practice, but nowadays most routers ignore source routing
   information.
 
   If you feel like trying it, look at traceroute's -g option, and
   /proc/sys/net/ipv4/conf/{interface}/accept_source_route on a
   linux router.

   2) On a router: most often, routing decisions are made based on
   their destination IP. (eg, if packet comes in destined for xxxx
   send it out this network interface, etc). On occasions, you want
   to be able to say "if the packet came from this address or from
   this interface, route it out that interface". iproute2 can do
   this (be warned, it's not for the faint hearted!).

   eg, at LCA, we were using source routing to say "any traffic
   coming from UWA (or WAIX which never quite happened) should be
   sent through a different interface from regular traffic", so we
   could count how much real chargable traffic we were generating.

Does this help at all? :)

Regards,

Bernard.

-- 
 Bernard Blackham 
 bernard at blackham dot com dot au