newton@einstein.eds.com (Richard E. Newton) (05/02/91)
I am looking for information about Apollo's DDS (Domain Datagram Service) protocols that most of Apollo's native services are built on. In particular, I'm looking for design and planning information for bridging or routing the DDS protocols over wide area network links. I have Apollo's "Planning Domain Networks and Internets" document that contains some "Domain Internet Configuration Rules". In one place the document says that the maximum end-to-end delay of a link must be 100 microseconds, in another 100 milliseconds. Which is correct? (I may have an old version of this document) The document also states "the minimum transmission rate over a single link must be at least one megabit per second". Can these protocols be run over slower links? What is the minimum transmission rate that these protocols can run over? We are only looking at connecting 3 networks together. Does topology and number of network hops effect the minimum transmission rate and maximum delay needed for the protocols to work? Are the apollo protocols able to recognize slow speed or congested links and adjust re-transmission timers and timeouts accordingly? Is there anybody out there running these protocols in a WAN environment? Are there any problems associated with doing so? I have tried get these questions answered by HP/Apollo, but they haven't been able to get me in touch with someone that seems to know what they are taking about. Any assistance would be greatly appreciated. Dick Newton Phone 313-265-7226 Electronic Data Systems ARPA newton@einstein.eds.com 750 Tower Drive, PO BOX 7019 UUCP ...uunet!edsews!einstein!newton Troy, MI 48007-7019
gaz@apollo.HP.COM (Gary Zaidenweber) (05/08/91)
From article <390@einstein.eds.com>, by newton@einstein.eds.com (Richard E. Newton): > I am looking for information about Apollo's DDS (Domain Datagram > Service) protocols that most of Apollo's native services are built on. > In particular, I'm looking for design and planning information for > bridging or routing the DDS protocols over wide area network links. > > I have Apollo's "Planning Domain Networks and Internets" document that > contains some "Domain Internet Configuration Rules". In one place the > document says that the maximum end-to-end delay of a link must be 100 > microseconds, in another 100 milliseconds. Which is correct? (I may > have an old version of this document) 100 Milliseconds is the correct one. > > The document also states "the minimum transmission rate over a single > link must be at least one megabit per second". Can these protocols be > run over slower links? What is the minimum transmission rate that > these protocols can run over? We are only looking at connecting 3 > networks together. Does topology and number of network hops effect the > minimum transmission rate and maximum delay needed for the protocols to > work? Are the apollo protocols able to recognize slow speed or > congested links and adjust re-transmission timers and timeouts > accordingly? I'll take a stab at answering this one. We considered two components of "delay" when specifying the above numbers. 1. Latency: The amount of time between the entry of the first bit of a packet into a router or link and the exit of that first bit from the other end of the link. Over several local interconnections this becomes quite significant. One example of high latency is a satellite link where the uplink-downlink time can exceed 1/2 second (500 milliseconds.) This component is independent of the bitrate of the medium, but dependent on the medium itself. By the way, a link or hop is the only unit of distance that Domain OS knows about; traditional units of distance are not understood. 2. Transmission time: The amount of time between the entry of the first bit of a packet and the entry of the last bit of that packet into the link. This is dependent on the bitrate of the medium and independent of the medium itself. These two numbers must be combined and yield less than 100 milliseconds to be a satisfactory Domain DDS router. Specifically, the time between the entry of the first bit into the local router and the exit of the last bit from the remote router must be less than 100 ms. The protocols cannot recognize congestion, they are a simple best-route (i.e. lowest number of hops) protocol. DDS doesn't provide "class-of- service" routing. So yes, topology and number of hops do affect the routing speed. > > Is there anybody out there running these protocols in a WAN environment? > Are there any problems associated with doing so? We at the Chelmsford MA/Exeter NH sites have a T1 link between our sites and can do all DDS services except diskless booting over the links. > > I have tried get these questions answered by HP/Apollo, but they > haven't been able to get me in touch with someone that seems to know > what they are taking about. > > Any assistance would be greatly appreciated. > > Dick Newton Phone 313-265-7226 > Electronic Data Systems ARPA newton@einstein.eds.com > 750 Tower Drive, PO BOX 7019 UUCP ...uunet!edsews!einstein!newton > Troy, MI 48007-7019 Gary Zaidenweber +1-508-256-6600x4360 | You're only young Apollo Systems Division, Hewlett Packard Company | once, but if you UUCP: {umix|decvax|mit-eddie}!apollo!gaz | do it right, ARPA: gaz@apollo.HP.COM FAX: +1-508-250-9880 | once is enough!