The 100 Gbit/s problem in your network

Mon Feb 11 13:14:24 UTC 2013

On 11/02/2013 12:16, Aled Morris wrote:
> I don't see why, as an ISP, I should carry multiple, identical, payload
> packets for the same content.  I'm more than happy to replicate them closer
> to my subscribers on behalf of the content publishers.  How we do this is
> the question, i.e. what form the "multi"-"casting" takes.
> 
> It would be nice if we could take advantage of an inherent design of IP and
> the hardware it runs on, to duplicate the actual packets in-flow as near as
> is required to the destination.

Multicast is fine when it works, which is generally only in systems where
the operator has end-to-end control of the entire data path, where the
number of streams isn't too large that the middleboxes have trouble
handling all the state requirements, where the middleboxes all support
multicast adequately without causing collateral problems, and where the end
point talks the same version of multicast as the source, where you don't
run into weird vendor multicast bugs and where you don't have packet loss
on any intermediate systems.

When it stops working, level 3 engineering will usually be able to get it
fixed, given enough time, resources and support from vendors.  If you're ok
about having escalation level engineering dealing with front-line multicast
support issues for customers paying a tenner a month, then I wish you well :-)

Nick