MPLS QoS no longer experimental
By stretch | Monday, March 2, 2009 at 12:00 a.m. UTC
Okay, so quality of service enforcement under MPLS isn't quite cutting-edge technology. However, until recently, MPLS QoS markings have always made use of a field in the MPLS label header designated "Experimental" (Exp) as defined in RFC 3032.
Recently released RFC 5462, a proposed standard, renames the Experimental field to the Traffic Class (TC) field. This is a change in name only; everything you know and love about 3-bit QoS markings remains the same. So why the update? From RFC 5462:
The EXP field, from the start, was intended to carry "Class of Service" (CoS) information. The field was actually called the "Class of Service field" in early versions of the working group document that was published as RFC 3032. However, at the time that RFC 3032 was published, the exact usage of this "Class of Service" field was not agreed upon and the field was designated as "experimental use"; hence, the name has since been the "EXP field".
The designation "for experimental use" has led other Standards Development Organizations (SDOs) and implementors to assume that it is possible to use the field for other purposes. This document changes the name of the field to clearly indicate its use as a traffic classification field.
(Why do I know this? I subscribe to the IETF's New RFCs RSS feed.)
About the Author
Jeremy Stretch is a network engineer living in the Raleigh-Durham, North Carolina area. He is known for his blog and cheat sheets here at Packet Life. You can reach him by email or follow him on Twitter.
March 2, 2009 at 5:33 p.m. UTC
I was just reviewing the mpls... the name will be intuitive for cisco use since cisco used the experimental bit for CoS... thanks for the information. im sure it will be of great use for new leaners, since the new name is what it is used for.
March 2, 2009 at 7:32 p.m. UTC
Why do I know this? I subscribe to....
It's tidbits of info like this that make your website a goldmine of info. I really appreciate the sharing of knowledge, but I find the sharing of 'sources of knowledge' to be the most valuable!
Thanks for posting!
March 3, 2009 at 12:34 a.m. UTC
March 3, 2009 at 3:31 a.m. UTC
I second JohnG! The "sources of knowledge" are invaluable. Any further updates on your job stretch? Just curious :)
March 7, 2009 at 6:53 p.m. UTC
Old news, but still something worth mentioning.
December 9, 2009 at 11:52 a.m. UTC
Is there any MPLS QoS Mode - pipe mode, short pipe mode ... cheatsheet can help me to know the difference in a nutshell ?
February 13, 2011 at 11:05 a.m. UTC
Hadn't considered subscribing to the RFC RSS feed until now, thanks for the link!!