Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!ames!zodiac!joyce!hercules!cslb.csl.sri.com!cire From: cire@dustbin.cisco.com (Eric B. Decker) Newsgroups: comp.os.minix Subject: Re: Amoeba on Token Ring Message-ID: Date: 29 May 89 03:56:46 GMT References: <16240@louie.udel.EDU> <760@scaup.cl.cam.ac.uk> Sender: usenet@CSL.SRI.COM Distribution: comp Organization: cisco Systems Lines: 69 In article <760@scaup.cl.cam.ac.uk> scc@cl.cam.ac.uk (Stephen Crawley) writes: Path: hercules!joyce!ames!hc!lll-winken!uunet!mcvax!ukc!cam-cl!scc From: scc@cl.cam.ac.uk (Stephen Crawley) Newsgroups: comp.os.minix Date: 26 May 89 21:21:25 GMT References: <16240@louie.udel.EDU> Sender: news@cl.cam.ac.uk Organization: U of Cambridge Comp Lab, UK Lines: 11 Posted: Fri May 26 22:21:25 1989 Amoeba on a token ring would be difficult. Amoeba transaction protocol (TP) relies on (bletch) broadcast to locate an Amoeba service (actually a port) on the network. On an ethernet this will work, though you get problems you have lots of amoeba nodes chattering away. Token rings (and slotted rings) do not support physical broadcasts. This is ONE of the reasons that Amoeba TP is unpopular around here. A few months ago I was talking to CWI people about a broadcast-less version of TP, but that project got put to one side. -- Steve How do you figure that? Token Rings at least the IBM and IEEE 802.5 versions sure do support broadcast. Not that I agree with server rendezvous using broadcasts in general. But saying Token Rings don't support physical broadcasts must therefore be an over-generalization. I figure you must be talking about some other implementation of Token Ring. The IBM/IEEE 802.5 Token Ring supports various flavors of group/multicast addresses. The first is broadcast. A Token Ring interface is required to recognize either 0xC000FFFFFFFF or 0xFFFFFFFFFFFF as the broadcast address and accept the packet. The former is for backward compatibility with early IBM implementations (so I figure) and the later to simplify some of the problems with Token Ring and Ethernets coexisting and inter-operating. Another class of group address is the Group. This is analogous to multicast addresses on Ethernets. This allows an arbritrary address within limits to be assigned to the interface. My big bitch with this one is the chipset I happen to be using only gives you one. Drag city. Group addresses are in the range 0xC00080000000 to 0xC000FFFFFFFE. The last class and certainly an interesting one is the Functional address. This is a bit significant address. That is you can set you address to say 0xC000 0088 4000 and you will nab packets with the destination addresses of 0xC00000800000, 0xC00000080000, or 0xC00000084000. You get the packet if any of the bits in the destination address are also turned on in your functional address. The Group or Functional address would be real great for server type rendezvous. The Functional would allow defining groups of servers. Hope that clears some of the fog. -c -- cire|eric Eric B. Decker Token Ring Development cisco Systems - engineering Menlo Park, California email: cire@cisco.com uSnail: 1360 Willow Rd., Menlo Park, CA 94025 Phone : (415) 326-1941