Many thx all for the comprehensive answers :)
-----Original Message----- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] Sent: 30 December 2002 18:50 To: [EMAIL PROTECTED] Subject: RE: STP and CDP Ethernet Frames use 802.3 format - Why [7:59956] [EMAIL PROTECTED] wrote: > > Can anyone explain the above and why they do not use the Ethernet_II > format? STP comes from IEEE as does 802.3. It would have been politically messy for IEEE to ask the DIX consortium for an EtherType when they were busy obsoleteing the DEC/Intel/Xerox (DIX) Ethernet standard, with help, of course, from DEC, Intel, and Xerox. Also, the industry thought Ethernet II would go away, just like we thought TCP/IP would be replaced by OSI. We were wrong, of course. It refused to die because IP uses it. Newer protocols don't use it though. 802.3 is considered somewhat superior because it has a length field, which Ethernet II does not have. With Ethernet, the chipset doesn't know it's hit the end of the frame until it hears silence. CDP actually uses 802.3 with 802.2 and SNAP. By the time CDP came out, the IEEE was no longer assigning 802.2 Service Access Points (SAPs). It's a one-byte field, so they were worried about running out. So newer protocol use a SNAP SAP (0xAA) and withing the SNAP header include a two-byte type field. Priscilla > > > Many thx > > > ________________________________________________________________ > Ken Farrington > Global Networks, Barclays Capital, 5 The North Colonnade, Canary > Wharf, London, E14 4BB > * Tel : 020 7773 3550 > * Mob : 07768-866655 > * [EMAIL PROTECTED] > > > > > ---------------------------------------------------------------------- > -- > For more information about Barclays Capital, please > visit our web site at http://www.barcap.com. > > > Internet communications are not secure and therefore the Barclays > Group does not accept legal responsibility for the contents of > this > message. Although the Barclays Group operates anti-virus > programmes, > it does not accept responsibility for any damage whatsoever > that is > caused by viruses being passed. Any views or opinions > presented are > solely those of the author and do not necessarily represent > those of the > Barclays Group. Replies to this email may be monitored by the > Barclays > Group for operational or business reasons. > > ---------------------------------------------------------------------- > -- Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=60008&t=60008 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
