Return-Path: william@bourbon.usc.edu Delivery-Date: Thu May 3 22:39:33 2007 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on merlot.usc.edu X-Spam-Level: X-Spam-Status: No, score=-3.3 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00, NO_REAL_NAME autolearn=ham version=3.1.3 Received: from bourbon.usc.edu (bourbon.usc.edu [128.125.9.75]) by merlot.usc.edu (8.13.5/8.13.5) with ESMTP id l445dX6S008149 for ; Thu, 3 May 2007 22:39:33 -0700 Received: from bourbon.usc.edu (localhost.localdomain [127.0.0.1]) by bourbon.usc.edu (8.13.5/8.13.5) with ESMTP id l445cbAT025486 for ; Thu, 3 May 2007 22:38:37 -0700 Message-Id: <200705040538.l445cbAT025486@bourbon.usc.edu> To: cs551@merlot.usc.edu Subject: Re: about two-bit diff-serv Date: Thu, 03 May 2007 22:38:37 -0700 From: william@bourbon.usc.edu Someone wrote: > 1.the two-bit diff-serv means Premium and Assured service, > setting the P bit and A bit? Correct. > 2.and in silde 13 lecture 22, "wait for token"&"Test if token" is > to check the profile is P or A? The top picture is for Premium traffic and the bottom picture is for Assured traffic. > but what's the difference for "wait for token"&"Test if token"? In the case of "test if token", the a packet is never delayed. When a packet arrives, if there is a token, the A bit is set; if there isn't, it's unmarked. In the case of "wait for token", if there is no token, the packet is held until a token arrives. -- Bill Cheng // bill.cheng@usc.edu