Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!cbatt!ucbvax!SIERRA.STANFORD.EDU!GROSSMAN From: GROSSMAN@SIERRA.STANFORD.EDU.UUCP Newsgroups: mod.protocols.tcp-ip Subject: Re: danger of bridges Message-ID: <12290893946.25.GROSSMAN@Sierra.Stanford.EDU> Date: Tue, 31-Mar-87 19:56:55 EST Article-I.D.: Sierra.12290893946.25.GROSSMAN Posted: Tue Mar 31 19:56:55 1987 Date-Received: Fri, 3-Apr-87 04:15:53 EST References: Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 20 Approved: tcp-ip@sri-nic.arpa Good guesswork! Endnodes do indeed listen to a special multicast address. A breif explanation: When a DECnet endnode wants to send a datagram, it sends it to a DECnet node known as the 'Designated Router'. The designated router is known by the endnode because he periodically emits a special hello message to say who he is. Now, theres a little bit more glue and filler to deal with getting the endnode to use a more direct route if possible (such as if the dest node is on the same ethernet), and cacheing of the next hop (ie: best gateway) to get to a specified node. Just to throw another monkey into the wrenchworks, there is the added feature that the designated router can move around! There's a little bit of protocol and stuff that arbitrates who gets the honor, but theres no special setup needed to establish the DR. Oh yeah, just one more thing, just in case there is NO DR at all, the endnode can still talk to other systems on the same wire, it just computes the Ethernet address from the DECnet address, and sends the datagram! Stu Grossman -------