JNFORDPB@UIAMVS.BITNET (Jay Ford, U of Iowa) (11/21/87)
This is a request for network configuration suggestions. Any responses should be sent to me rather than to the list. Questions How have other sites approached and/or solved the problems associated with establishing and administering large campus networks? Is the topology outlined below feasible without having static, manually-entered routes for the entire campus? Will an ARP (or any) ethernet-level broadcast from a host on one ethernet make it through a gateway to a host on another ethernet? Will the ARP reply make it back to the broadcaster? Is it necessary to have something along the lines of proxy-ARP to make this work? Does existing software support proxy-ARP? Does anyone have suggestions addressing problems at any level which would alleviate some of the routing complexity? Notes We are new at this, and very well might have incorrect interpretations of the problems we face. By the same reasoning, we certainly are not aware of all the possible solutions to our problems. Any help would be appreciated. Thank you. Background The University of Iowa is in the process of establishing a campus network consisting of departmental LANs hung off of a broadband backbone. The departmental nets use various technologies including Ethernet/IEEE 802.3, proprietary token rings, and fiber. Some departments have multi-level networks (see figure below). Access to the broadband backbone is provided through ethernet bridges (Bridge IB/1 boxes), with each department having one IB/1. The IB/1 is a MAC-level bridge, so that a host on a baseband ethernet connected to an IB/1 in one department appears to be on the same physical cable as a host on a baseband ethernet connected to an IB/1 in another department. We have a mixture of machines and OSs, including VAXes running 4.2 & 4.3 BSD, VAXes running VMS, Encores running UMAX 4.2, Apollos, Suns, PCs, Primes, and IBMs running MVS; we also have a handful of Encore Annex terminal servers. The U of Iowa has been granted a class B Internet number of 128.255. We will soon activate a connection to MIDnet -> NSFnet -> world. Topology The current network topology (with only two departments connected) is: || Annex1 ---| || +------+ | ||---| IB/1 |-----(ethernet1)-----| || +------+ | || Encore1 ---| || |--- Encore2 (broadband) | || |--- Alliant || | +------+ || |-----(ethernet2)-----| IB/1 |---|| | +------+ || |--- VMSVax1 || +---------+ | ||---| Proteon |----> (MIDnet) |--- Apollo1 || +---------+ | --- / \ / \ (Apollo-ring) \ / \ / |--- BSDVax1 --- | | |--- BSDVax2 Apollo2 ----(ethernet3)----| |--- BSDVax3 We would like to assign a subnet number to each physical network. For example: network internet subnet ------- --------------- ethernet1 128.255.32 ethernet2 128.255.22 ethernet3 128.255.20 Apollo ring 128.255.21 Problems The presence of independently administered networks within the campus lends itself to a subnetting scheme, with each department receiving a block of subnet numbers from which to allocate numbers for the networks under the control of the department. We have encountered some routing problems which may be attributable to the coexistence of IP implementations which do support subnetting and those which do not. The broadband bridging makes ethernet1 and ethernet2 appear to be one physical network, so we end up with one network having more than one subnet number. This seems to cause problems with routing for the hosts which understand subnetting. They think the hosts on the other subnet should be on a different physical network and expect to have a gateway to get there. Since there is no gateway, they don't see a path to the other subnet. Disabling subnetting (by changing the netmask to 255.255.0.0 in the subnetting hosts) makes everybody think that the entire campus is one big physical (class B) network. This solves the problem just described, but it defeats the subnet-based routing required to access the networks which are actually subnetted, such as Apollo-ring and ethernet3. One proposed solution is to place a router between the IB/1 and the networks within each department. This has the advantage of making the broadband a separate subnet and providing the gateways (arguably) needed for subnet-based routing as described above. Disadvantages include the decrease in throughput (compared to just the bridge), the added cost of the router (or an additional ethernet interface for a host acting as a router), and the restriction on the protocols which may then cross the broadband. Furthermore, I am not convinced that such a configuration would solve all our problems without introducing new ones. Jay Ford Weeg Computing Center University of Iowa Iowa City, IA 52242 (319) 335-5555
hedrick@ARAMIS.RUTGERS.EDU (Charles Hedrick) (11/22/87)
The author describes a configuration having a mix of vendors, administrators, and network technologies, and asks how to make a level-2 bridge work within it. My recommendation would be: 1) not to do it. I think it is a big mistake to let level 2 technology cross administrative boundaries. Personally I prefer level 3 technology everywhere, but there are good arguments on both sides. But I see nothing in favor of leve 2 technology connecting networks where different people are going to be responsible for diagnosing problems. Since this issue has come up so many times, I now have a canned response which I will mail to the original poster under separate cover (to avoid boring the rest of you). We believe that the next generation of gateways (based on 68020 processors instead of 68000), which should be available in December or January from at least cisco and Proteon, will have throughput close to that of a bridge. The primary performance limitation will then be on long back-to-back strings of packets. That will be resolved by new Ethernet controllers, which should also be available shortly. Even in the current generation, throughput with gateways is enough for most networks. From your description, I believe you would see no performance problems from using routers instead of bridges. 2) if you must do it, I would set the subnet mask to 255.255.255.0 on those machines were you can have multiple subnets on one interface. All BSD-based systems allow this, and I think many others as well. On a BSD system, you say route add x.y.z.0 youraddress 0 for each subnet that you want to add as being local. For systems where this is not possible, I would set the subnet mask to 255.255.0.0. If you have any such systems, then any actual level 3 gateways that may be present in your configuration (Apollo?) will have to be able to do proxy ARP.
RAD@MATH.AMS.COM ("Rich DeJordy, x295") (06/02/89)
I am having a problem with PONY EXPRESS and version 5.1-1 of VMS. The Foreign Protocol Interface keeps dying and killing LOCALSND with it. I have sent separate mail to Peter Karp, but was hoping maybe someone out here might have an answer before he gets a chance to get to it? Anyone else doing this? It doesn't seem to like /PROTOCOL= on th MAIL. It gives me an "Illegal String class" error from the STR facility. (I can only assume that STR is from the STR$ run time library functions.) If anyone can help, I'm in a real desperate situation, so please reply to me directly at RAD@MATH.AMS.COM. Thanks for the help! Rich DeJordy -------
IIIG010@TWNMOE10.BITNET (Cheng-ping Chang) (08/07/89)
Please send me any documents on BSMTP(Batch Simple Mail Transfer Protocol). Thank you.
beach@SERVER.AF.MIL (Darrel Beach) (08/03/90)
For all those reading this: If youanswered some queries I recently posted to TCP/IP, or were continuing a discussion directly with me, please resend anything you sent in the last four days. I was out and lightning took its toll yesterday. Thanks Darrel Beach
ug051@techops.cray.com (Michael Nittman - MERCEDES) (09/26/90)
This message is empty.
ah335@cleveland.Freenet.Edu (Richard Banks) (10/24/90)
I would like to join this list if the moderator sees this please add me, Thanks.
CBAD33@UCVAX.ULSTER.AC.UK (11/05/90)
Could you please help me. I am trying to gather addresses of companies/ academic institutions who are involved with Wide Area Distribution of Geographic Information. This would involve the capture of aerial photographs, digitizing the image, and transferring the resultant material from location to location, based on requirements. Thus, workstations would exist at key sites around the Area, displaying the information to users who access it for particular applications (line maps with data superimposed showing drainage/ telephone cables/elecdtrical ducts), maybe even the location of medical facilities on a town/city map, which would be of interest to planners etc. The obvious problem to the communications engineer, is how to best provide a communications infrastructure to service such a facility at many locations. The problem is compounded by the time scales and class of data being transferred. A user requesting a raster image of a node of a particular line map will want to see the hotel/hospital/golf course that has been highlighted by the mouse, so the amount of information required to satisfy the query is suddenly increased many fold. The time scale is such that one does not want the user to have to wait minutes while this image is transferred from a server located somewhere. What I would like is any clues as to who is involved in this area, that includes companies/universities/real=life commercial/research institutions etc. I can assure you that any information will only be used for research purposes. I would require the e.mail addresses or postal addresses of the places concerned. Please direct your replies to my e.mail address. Thanks for your time Dr Gerard Parr Department of Applied Computing Institute of InformAtics University of Ulster Derry
Sidney_Marshall.WBST128@XEROX.COM (05/25/91)
help