Thanks for the comment! I didn't mean to blaim that TCP and IP is not 'clear' ( I should have used the word 'stern', or some other word not so commendatory as 'clear') layered. What I really wanted to say is that I prefer the choice, because I think it is a positive example of fuzzy-layering. Thanks for the comment again! ----- Original Message ----- From: "vinton g. cerf" <vinton.g.cerf@wcom.com> To: "Jason Gao" <jag@kinet.com.cn>; "Fred Baker" <fred@cisco.com> Cc: <ietf@IETF.ORG> Sent: Friday, September 06, 2002 12:30 PM Subject: Re: Fuzzy-layering and its suggestion > this was a choice made long ago to increase by a small amount the efficiency of the representation of the two layers. Keep in mind that IP was split off of TCP in version 3 of the protocol. They were originally combined. > > vint cerf > > At 09:00 AM 9/6/2002 +0800, Jason Gao wrote: > >Well, I should have cited another instance. What the TCP checksum protects includes the pseudu-header which contains the source and the destination IP address. Transport address in TCP (and SCTP) contains IP address. Clearly the IP address is not stored in the transport layer header. IMHO it is not an instance of clear layering. > > Vint Cerf > SVP Architecture & Technology > WorldCom > 22001 Loudoun County Parkway, F2-4115 > Ashburn, VA 20147 > 703 886 1690 (v806 1690) > 703 886 0047 fax > >