That's why some care was used in choosing the recommended code points in the various RFCs. If you use the default values, a router set up for precedence will behave reasonably.
But indeed, an IPv4 network where some routers have legacy TOS behaviour and others have diffserv behaviour will not deliver perfect diffserv. We shouldn't have this problem for IPv6, where TOS behaviour was never defined. Brian - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Brian E Carpenter Distinguished Engineer, Internet Standards & Technology, IBM NEW ADDRESS <[EMAIL PROTECTED]> PLEASE UPDATE ADDRESS BOOK Christian Huitema wrote: > > > >Does anyone know is use of DiffServ field supported in some equipment > and > > >networks? > > > > It is supported in some equipment. I wouldn't be able to tell you how > > networks configure their equipment; they generally view this as NDA > > information. > > We have found some issues when trying to use the diffserv field in > practical deployments. There are a number of routers in the network that > were built and deployed before diffserv was widely accepted as a > standard. Understandably, these routers implement the previous standard, > i.e. the RFC 791 definition of the TOS bit. Specifically, the old > routers look at the three precedence bits and treat it as a priority > level. In practice, this restricts the number of diffserv code points > that can be safely used. You don't want for example to define a code > point for "less than best effort" in which the three precedence bits > happen to mean "high priority" in the old routers... > > -- Christian Huitema > > -------------------------------------------------------------------- > IETF IPng Working Group Mailing List > IPng Home Page: http://playground.sun.com/ipng > FTP archive: ftp://playground.sun.com/pub/ipng > Direct all administrative requests to [EMAIL PROTECTED] > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
