ELINSKY@YKTVMX.BITNET (Jay Elinsky) (07/30/87)
This is from Jay Elinsky at IBM Yorktown, originally sent on the Bitnet- based IBM TCP/IP For VM Mailing list. He asked that it be forwarded to the TCP/IP mailing list. - Mark Bodenstein, Cornell University ----------------------------Original message---------------------------- I'm one of the developers of the VM code at Yorktown, and I want to clarify some possible misconceptions on this subject: 1) We use source routing only on Token Ring. Even on Token Ring, we can certainly also route through a router, if the destination host is on a different net or subnet. If the destination host is on a different ring with the same net or subnet number, we do indeed use source routing. I believe that this is consistent with the architecture of the Token Ring. Is it inconsistent with any existing implementation of TCP/IP over Token Ring? If so, I'd certainly like to know about it. 2) Re "No RIF field, no function": If a host is on the same ring, the ARP code will recognize it, and subsequent packets between the hosts have no routing field at all. 3) Our TCP/IP certainly is inter-operable with other TCP/IP implement- ations. That is our reason for supporting TCP/IP. To repeat what I said in (1), the source routing issue is only on Token Ring, and to the best of my knowledge our implementation is consistent with other TCP/IP Token Ring implementations, and with Token Ring architecture. 4) In the VM code, the Token Ring routing information is kept as part of the address translation cache. I think that's logical. Jay Elinsky IBM T.J. Watson Research Center Yorktown Heights, NY
ELINSKY@IBM.COM (Jay Elinsky) (08/01/87)
Here's a copy of a note I sent to IBMTCP-L, on the subject of source routing in the IBM TCP/IP code. My apologies in advance if it shows up twice -- someone else may have also sent it, but it hasn't shown up on our database at Yorktown. I want to make sure it shows up on this mailing list, since the note that started it all appeared here. Date: Wednesday, 29 Jul 1987 17:54:27 EDT From: Jay Elinsky <ELINSKY@YKTVMX> To: <IBMTCP-L@CUNYVM> Subject: Source routing I'm one of the developers of the VM code at Yorktown, and I want to clarify some possible misconceptions on this subject: 1) We use source routing only on Token Ring. Even on Token Ring, we can certainly also route through a router, if the destination host is on a different net or subnet. If the destination host is on a different ring with the same net or subnet number, we do indeed use source routing. I believe that this is consistent with the architecture of the Token Ring. Is it inconsistent with any existing implementation of TCP/IP over Token Ring? If so, I'd certainly like to know about it. 2) Re "No RIF field, no function": If a host is on the same ring, the ARP code will recognize it, and subsequent packets between the hosts have no routing field at all. 3) Our TCP/IP certainly is inter-operable with other TCP/IP implement- ations. That is our reason for supporting TCP/IP. To repeat what I said in (1), the source routing issue is only on Token Ring, and to the best of my knowledge our implementation is consistent with other TCP/IP Token Ring implementations, and with Token Ring architecture. 4) In the VM code, the Token Ring routing information is kept as part of the address translation cache. I think that's logical. Jay Elinsky IBM T.J. Watson Research Center Yorktown Heights, NY