Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!munnari.oz.au!mel.dit.csiro.au!latcs1!wcc!tom From: tom@wcc.oz (Tom Evans) Newsgroups: comp.protocols.appletalk Subject: Re: tcp/ip Message-ID: <1087@wcc.oz> Date: 10 Oct 90 09:09:37 GMT References: <5A0A0406200600BE-MTABOGECNVE*MUCM000@BOGECNVE> Organization: Webster Computer, Melbourne, Australia Lines: 64 In article <5A0A0406200600BE-MTABOGECNVE*MUCM000@BOGECNVE>, MUCM000@BOGECNVE.BITNET writes: > a few questions on tcp/ip: > > 1) For macs on a localtalk, there are only two possibilities for accessing > an IP network: > > a) A router that will take IP packerts from another network > (like an ethernet) and ship them over to the localtalk in IP format. > ... > I believe that pure IP formatted packets > wouldn't get across any appletalk routers in the localtalk since > it's only looking for appletalk packets, correct? Correct. It is not done this way. > b) A bridge that will encapsulate IP packets into AppleTalk packets > and ship them over to the Localtalk network. Correct, but "bridge" isn't the correct term. My favourite name for the protocol involved is "MacIP", and the devices that do it as "MacIP Gateways". There are more complexities than just the encap/decap too. Because Macs move around, it isn't "safe" to hard-configure an IP address into them. The MacIP gateways advertise themselves as an "IPGATEWAY" on NBP. The Macs, either running MacTCP-based or standalone (like NCSA Telnet) applications first find the IPGATEWAY and ask it for an IP address. The MacIP gateway supplies one that is appropriate to that network/port/whatever. When the Mac is told to connect to IP host "a.b.c.d" it then looks for "a.b.c.d:IPADDRESS", which the gateway then proxies for. Note we're trying to change this - the Mac should send it straight to the gateway. The IP packet is sent in a DDP packet to the responding device (gateway) which then forwards it to the IP host. For packets from the IP host to the Mac the same encapsulation is used. > Also, > Encapsulated IP packets, though they would solve the appletalk > router problem, would need to be treated differently at the Macs > since telnet software is looking for IP packets, not > encapsulated packets. is this right? No. If you run NCSA Telnet Classic, you manually configure it to connect to "AppleTalk" or "Ethernet". If you run the MacTCP version, then it is MacTCP's problem - you configure MacTCP for the appropriate interface, and if it is LocalTalk then it does the search/encap/decap. > A friend of mine > just got AUX up and I was wanted to login to it from my Mac over localtalk > using telnet. Is this possible with only localtalk? You need one of the MacIP gateways you mentioned, or log into it serially. ======================== Tom Evans tom@wcc.oz.au Webster Computer Corp P/L, 1270 Ferntree Gully Rd Scoresby, Melbourne 3179 Victoria, Australia 61-3-764-1100 FAX ...764-1179 wcc@cup.portal.com 2109 O'Toole Avenue, Suite J SAN JOSE CA 95131 - 1303 CALIFORNIA 1-408-954-8054 FAX 1-408-954-1832 Unit 7, Weltech Centre Ridgeway, Welwyn Garden City Herfordshire AL7 2AA LONDON UK. Ph 44-707-336969 Mobile 44-836-725849 FAX 44-707-373378