mskuhn@faui09.informatik.uni-erlangen.de (Markus Kuhn) (02/04/91)
Some days ago, I asked here about possibitilies for OSI connections on asynchronous/start-stop RS-232 lines. There seems to be some interest in this topic. I got some suggestions: 1. H.T.Alvestrand suggested me to check X.32 in the CCITT Blue Book. I did this. Unfortunately this recommendation says only something about synchronous modes on the V.24 (= RS-232) interface. The other modes are "for further study" (section 4.3.1). Perhaps they intend to use the new HDLC start-stop mode as a further option in the '92 version. 2. Tim Clark reported that in the UK acedemic community, a protocol called ATS is used to convert LAP-B in an asynch protocol. 3. Micheal Roe reported that there is a standard in the TCP/IP world called 'Serial Line IP' that does exactly what I want. So I could run X.25 over TCP/IP. He also suggested to modify LLC-1 (also a HDLC subset) for asynchronous lines in the same way, HDLC does this in the start-stop-mode addendum (1990). This would be the connectionless alternative to my own suggestion of an asynch LAP-B. As I personally prefer X.25, I think, I will implement LAP-B. But the idea of using LLC-1 sounds also quite interesting to me. Unfortunately, ATS and Serial Line IP aren't pure OSI so I don't like them so much. Thank you for your answers. Any further suggestions? Has anyone detailed information about the HDLC start-stop mode (frame format, transparency, etc.)? Is anyone planning to implement something like this? Especially in ISODE (would be great)? Markus Kuhn CS student
enag@ifi.uio.no (Erik Naggum) (02/05/91)
In article <mskuhn.665668137@faui09> mskuhn@faui09.informatik.uni-erlangen.de (Markus Kuhn) writes: > Some days ago, I asked here about possibitilies for > OSI connections on asynchronous/start-stop RS-232 lines. > There seems to be some interest in this topic. I got > some suggestions: > 1. H.T.Alvestrand suggested me to check X.32 in the CCITT > Blue Book. I did this. Unfortunately this recommendation > says only something about synchronous modes on the > V.24 (= RS-232) interface. The other modes are "for further > study" (section 4.3.1). Perhaps they intend to use the > new HDLC start-stop mode as a further option in the '92 version. The start-stop mode lower layer of X.25 was issued as an "expedited procedure" recommendation or somesuch. I believe it's X.32 bis. CCITT has opted for a speedy procedure for most of the interesting things. [FX].435, for instance. You don't have to wait until 1992 for all the neat things they decide to recommend. -- [Erik Naggum] <enag@ifi.uio.no> Naggum Software, Oslo, Norway <erik@naggum.uu.no>
goldstein@delni.enet.dec.com (Fred R. Goldstein) (02/05/91)
In article <mskuhn.665668137@faui09>, mskuhn@faui09.informatik.uni-erlangen.de (Markus Kuhn) writes... >Some days ago, I asked here about possibitilies for >OSI connections on asynchronous/start-stop RS-232 lines. Check the addendum to ISO3309 (HDLC Frame Format). It specifies a new asynchronous flavor of HDLC. (It's also spec'd for PPP.) Async HDLC uses a flag value, byte stuffing for transparency, and also frogs one bit of "control" values (preceded by an escape) as required by some devices. I don't know if it is IS yet or still DIS. --- Fred R. Goldstein Digital Equipment Corp., Littleton MA goldstein@delni.enet.dec.com voice: +1 508 486 7388 Do you think anyone else on the planet would share my opinions, let alone a multi-billion dollar corporation?