Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!nbires!hao!hplabs!ucbvax!ANDREW.CMU.EDU!leong From: leong@ANDREW.CMU.EDU (John Leong) Newsgroups: mod.protocols.tcp-ip Subject: Re: RING vs. ETHER - Theory and practice Message-ID: Date: Mon, 21-Jul-86 14:44:56 EDT Article-I.D.: andrew.MS.leong.0.leong.139.5 Posted: Mon Jul 21 14:44:56 1986 Date-Received: Tue, 22-Jul-86 03:44:23 EDT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 23 Approved: tcp-ip@sri-nic.arpa Mark, Re : 802.2 Type 2 operation 802.2 offers you Type 1 or Type 2 operation. Type 1 is pure datagram stuff with the ARPANET's "take your chance" approach while Type 2 goes the other extreme and do both flow control and error recovery. The general idea is that if you are going for a heavy weight Tranpsort Layer already such as TCP or TP-4, you should leave every thing to that layer and chose Type 1. If you are going to use light weight Tranpsort layer such as TP-0, then Type 2 is for you. (Interestingly, IBM is using Type 2 since under SNA, the link layer is the only level that will do error recovery). Hence unless we can get IEEE802.2 to create a Type 1.5, we don't think it is worth our while to spend the cycles required for Type 2. (Actually, having a Type 1.5 that will do low level acknowlegement but without flow control and error recovery procedure may be quite useful - particularly for network level gateway machines). Leong