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- Path: sparky!uunet!sun-barr!ames!agate!ucbvax!CAYMAN.COM!josh
- From: josh@CAYMAN.COM (Josh Littlefield)
- Newsgroups: comp.protocols.appletalk
- Subject: Re: Proteon AppleTalk Router problem
- Message-ID: <9207302032.AA03168@saba.Cayman.COM>
- Date: 30 Jul 92 20:32:19 GMT
- References: <josh@saba> <9207301521.AA03050@saba.Cayman.COM>
- Sender: daemon@ucbvax.BERKELEY.EDU
- Distribution: world
- Organization: The Internet
- Lines: 38
-
- ....
- >> : "IF the router generates an NBP LkUp packet with a DDP source
- >> : address set to the address of the originating node (A), and a
- ....
- >> : Huh? The incorrect behavior in this case is the router putting
- >> : something other than its own address in the DDP source address field.
- >> : The originating node's address goes in the NBP tuple.
- >> :
- >>
- >> The router is behaving correctly in this case. Because, router are not
- >> suppose to change DDP source address, it only pass packets to different
- >> network interfaces and thus change only the Ethernet address in this
- >> case.
-
- Bzzzzzzz! Sorry, but no. Good try, though! You would, of course, be
- correct if the router was routing a packet. But the router is performing a
- service. In response to an NBP BridgeRequest packet it received, the router
- is generating its own NBP LkUp packet, indicating that node A is looking for
- a service. The router should set the DDP src addr to itself, and the hop
- count to 0.
-
- >> The problem is, if (using the same example mentioned) node A and node B are
- >> truely in the same network, shouldn't NBP lookup be a link layer broadcast
- >> to the local network rather than querying it from the router?
-
- Bzzzzzzz! Unfotunately, no. Because an NBP Lookup is a ZONE-WIDE thing,
- and the end node knows nothing about which networks are part of which zones,
- in the presence of any router the end nodes must NOT broadcast their own
- NBP Lookups, but instead send an NBP Broadcast Reqeust to a router.
-
- -josh
-
- /--------------------------------------*--------------------------------------\
- | Josh Littlefield Cayman Systems, Inc. |
- | josh@cayman.com University Park at MIT |
- | (617) 494-1999 26 Landsdowne Street |
- | fax: (617) 494-5167 Cambridge, MA 02139 |
- \--------------------------------------*--------------------------------------/
-