Affects of rate-limiting at the far end of links


Just a quicky. We've got leased line out to a remote site that's pretty much at capacity for remote to local site traffic, and from time to time it appears to lock up for periods of 30 seconds or more.

Investigating it appears we outbound traffic shape, and ingress rate-limit at the 'local' end of the line, but nothing is done at the 'remote' end. The remote end is some 14ms away across a third party MPLS network.

Obviously we need to shape at the remote end, but the current behaviour intrigues me. Rate-limiting, while bad compared to shaping, in my experience doesn't lock out traffic for such long periods of time.

Could it be that buffers and flow-control over the 14ms third party leg are causing the rate-limiting leaky bucket to continue to overflow long after it's full?


Or you are losing line protocol keepalives of some sort (e.g. at L2), or
routing protocol packets. It may also be that your MPLS provider limits
the traffic at X kbps INCLUDING protocol overhead - if so it's going to
police out all sorts of important stuff (assuming you are running FR, ATM
or something rather than some sort of TDM over MPLS).


Hey Alex, thanks for your reply . It's all IP over MPLS AFAIK, and we're using static routes to the site so I can't imagine it's either of these.

We're going to traffic shape at the remote-end, so this should alleviate the problem. Just really wanted to check the line 'outages' could be caused by the nature of rate-limiting (looks like it can) and weren't indicitive of another underlying problem.