The MPLS WG Archive

[Badri Devalla <Badri.Devalla@metera.com>]

Title: RE: QoS in Shared Media

|| -----Original Message-----
|| From: Fred Baker [mailto:fred@cisco.com]
|| Sent: Friday, May 04, 2001 12:48 PM
|| To: Naidu, Venkata
|| Cc: 'mpls@uu.net'; 'te-wg@ops.ietf.org'
|| Subject: Re: QoS in Shared Media
||
||
|| At 10:58 AM 5/4/2001 -0400, Naidu, Venkata wrote:
|| >I have a doubt regarding "QoS in Shared Media".
||
|| many have doubts in this area.
||
|| Fundamentally, if I can talk with a switch, I am in control
|| of my end of
|| the line and it is in control of its end, and we can make
|| promises about
|| what we will each do in our direction. On shared media,
|| anything resembling
|| QoS assertions or guarantees requires making promises on
|| behalf of other
|| systems one does not control. The nearest solutions I see to
|| that have been
|| in 802.5 and FDDI LANs, and I wouldn't describe those as having been
|| "wildly successful."
||

Just a nit-pick.
I agree with your thoughts on inability to guarantee QoS without control in multi-access shared media.
However, 802.5 and FDDI LANs are multiple access and can be run in modes where you can provide guaranteed deadlines (and not shared media). I am referring to Synchronous Bandwith allocation and Timed token protocol. You cannot do this is shared Ethernet.

Token ring and FDDI are like Baby Boomers - they had their time ;)

badri