Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!MIRSA.INRIA.FR!Christian.Huitema From: Christian.Huitema@MIRSA.INRIA.FR (Christian Huitema) Newsgroups: comp.protocols.iso Subject: Re: CONS question Message-ID: <8912011020.AA12134@jerry.inria.fr> Date: 1 Dec 89 10:04:40 GMT References: <8912010056.AA05147@cmcvax> Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 32 Two solutions are currently used for providing CONS over Ethernets and other LANS. One is orthodox (OIS wise) and the other one is popular. The orthodox line is to stack the X.25 PLP (ie. iso 8208) over IEEE 802 LLC-2, and use NSAP addressing, considering that the Ethernet address is somehow a SNPA. It is quite a piece of code, not so easy to optimize. Five years ago, we experimented with the CNET in France a lighter version of it (using LLC-1), but although the performances were good, it failed to reach a general agreement in the community. A full implementation of that has been done at Edinburgh University. It is used in JANET, and can in principle be ordered from your favorite manufacturer. The popular line is to stack a small convergence protocol over TCP-IP, e.g. in order to provide packet delimitation within a byte stream. Here again, one can use NSAP addressing, and consider the TCP-IP as a 48 bits SNPA. This is implemented in ISODE, and also in the EAN X.400 service, as well as by CISCO. Problem here is the lack of an agreed convergence protocol (RFC?). In both cases, a fully working solution need to use a CONS "ARP" for converting between NSAP and SNPAs. It is called a Connection Oriented ES/IS protocol in the lingo, and is not completely formalized within ISO (DP stage, as far as I remember). A secundary problem is that it is tailored for passing X.25 addresses, which are 15 digits, and that you need an agreement for the representation of 48 bits over 15 digits. Christian Huitema PS. A full implementation of X.25 over LLC-2 has been done at Edinburgh University. It is used in JANET, and can in principle be ordered from your favorite manufacturer. Brought to you by Super Global Mega Corp .com