At 12:36 PM +0000 10/16/02, bergenpeak wrote: >Sorry for the OT post. Figured I'd float this here and see if >any one might be able to help. > >Does anyone really know where the 50 ms SONET detect/fail-over time >comes from? >I've heard many answers, but none seem to be verifiable. I'm looking >for pointers to docs which explain where or what drove the 50 ms number. > >I've heard that: > >* 50 ms was a requirement to support voice. The way this one is told >is that > more than 50 ms of noise/nothingness seriously impacts MOS. Not sure > I buy that. > > >* Old telco switches would go bonkers if many T1's started to flap > a the same time. 50ms at the SONET level prevented the T1s from > flapping. > >* others, etc. > >Again, looking for docs / pointers which details the answer. > >Thanks
I won't call this gospel, but the SONET developers I know told me the requirement came from SS7, not SONET itself or user traffic. There were circumstances under which loss of SS7 signal for >50 ms could cause a significant number of call drops. Unfortunately, this somehow became a user rather than a control plane requirement. It's been necessary to have 50 msec failover mechanisms in MPLS to get significant telco buy-in. The irony is that many telcos are moving their SS7 networks off separate facilities and onto their IP-based Operations Support Services (OSS) networks. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=55702&t=55700 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
