Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/17/84; site ittvax.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!ittvax!hagouel From: hagouel@ittvax.UUCP (Jack Hagouel) Newsgroups: net.mail Subject: Line costs used in pathalias Message-ID: <1605@ittvax.UUCP> Date: Fri, 18-Jan-85 11:12:06 EST Article-I.D.: ittvax.1605 Posted: Fri Jan 18 11:12:06 1985 Date-Received: Mon, 21-Jan-85 03:03:19 EST Distribution: net Organization: ITT-ATC, Stratford Ct. Lines: 84 Given the interest in the meaning of the DAILY, HOURLY, ... designations I thought that this excerpt of a message I sent to Mark Horton may be of interest to this newsgroup. I believe that a more rigorous approach to defining the line costs used by pathalias is possible if the optimization objectives are more clearly defined. The syntax of expressing these costs is not addressed here, although it is also important. ----- start of excerpt ----- The cost values allocated to connections appear to be arbitrary. If there was a formula that was used to compute them I would be interested to learn it. The rest of this letter deals with thoughts and sketchy suggestions on computing the cost. I think that a good definition of cost will be appreciated by both the users and the providers of Usenet service. Current cost trend appears to be that frequent connections have lower cost (but not proportionally so). Telephone charges may also be relevant. I couldn't guess any more factors. The issue to be resolved is how to achieve least cost routing (using the pathalias program). The problem arises in that the user perceives a different cost (delay) from the cost of the service provider (mostly dollars and fairness). To top it all, the "network manager" is concerned with efficient utilization of the resources, i.e. throughput. With the advent of domains the problem becomes more manageable. At least for some domains (like ATT) the domain manager and the service providers are the same; possibly even many of the users (internal traffic). Since the whole concept of Usenet is based on voluntary, non-abused, contribution of resources for the collective good, fairness appears to be the driving force. For Usenet to become useable low delay could work wonders. Throughput may have to be left in the background. Currently pathalias is not very dynamic (path computations occur infrequently). In the future that may change, I hope. It is desirable to preserve the same cost definition in both cases. Focus on fairness: I think that the best way to define it is that a site will not be asked to handle more mail than it commited to when it joined the network. Question: do sites declare their capacity constraints? If not maybe some semi-formal definition is necessary (beyond the frequency of calls). I've often seen new sites mentioning a vague "as long as we do not get a lot of transient traffic". Based on these capacity constraints pathalias should be able to do some load splitting, i.e. the optimal path is not always used since that would overutilize the "good" connections and ignore the "bad" ones. The following algorithm could be used: each node is initially allocated bandwidth through other nodes in the network. The amount allocated would depend on the topological distance of the two nodes and the total bandwidth available. Each node may allocate its own bandwidth. The allocation would last for a predetermined amount of time (say a month). Pathalias will execute based on these values. The source of traffic will monitor its bandwidth consumption. When it exceeds a limit on a node then it generates a new path based on the remaining allocation. Intermediate nodes may monitor for adherence to their limits and inhibit excess traffic. Allocations that are underutilized may be either redistributed or negotiated periodically. Bids for additional bandwidth may be automatically processed at allocation time. This becomes an organic algorithm where node bandwidth becomes a commodity and it is fairly allocated to demand. The penalty is increased bookeeping and control traffic. The advantage is that nodes can budget their Usenet contribution in some predictable and consistent fashion. Jack Hagouel ...!ittvax!hagouel (203) 929-7341 x244