<bold>My humble opinion</bold> SLAs are more for accountants and lawyers. Get the right tech support on the phone and you can solve most issues without all the hassle. SLAs really are minimal if you can contact the right people and work through the problem. +1 to Level3 and Cogent as I have had some of the best trouble shooting for even minimal problems... ---------------------------------------- From: "david peahi" <davidpeahi@gmail.com> Sent: Thursday, November 15, 2012 3:31 PM To: nanog@nanog.org Subject: Fwd: MPLS acceptable latency? ---------- Forwarded message ---------- From: david peahi <davidpeahi@gmail.com> Date: Thu, Nov 15, 2012 at 12:15 PM Subject: Re: MPLS acceptable latency? To: Mikeal Clark <mikeal.clark@gmail.com> Assuming no configuration errors, this underscores the need to negotiate SLAs, and serious SLA penalties, with the telcos, and to always request a telco network map, with the telco path that data will be transitting end-to-end.. My rule of thumb in network design is that data over copper or fiber takes 10 ms per 1000 miles, which is governed by the speed of light. Network devices along the path add serialization/de-serialization delay, but with modern network devices this delay is negligible. So according to this rule of thumb 85 ms is almost enough time for data to traverse the USA 3 times. I have found that telcos have been setting round trip SLAs so high that they are meaningless (e.g. 50 ms for a GigE MEF ELAN service, 20 ms for "Gold" MEF EVPL service), and border on being fraudulent. In one case I also noted 100 ms round trip times between sites less than 1 mile away, and discovered that every packet was being sent back to east Texas from Southern California, almost a 5000 mile detour.