Path: utzoo!utgpu!BITNIC!FUTURE-L Date: Wed, 28 Feb 90 12:36:00 EST Reply-To: BITNET Futures List Sender: BITNET Futures List Comments: Warning -- original Sender: tag was news@MATH.LSA.UMICH.EDU From: Edward Vielmetti Subject: Re: The fall of Bitnet Comments: To: bit-listserv-future-l@cs.psu.edu To: UofToronto LAN redistribution References: MAINTCMS@PUCC.BITNET's message of 28 Feb 90 14:43:56 GMT Message-ID: <90Feb28.124943est.57387@ugw.utcs.utoronto.ca> Newsgroups: list.future-l Distribution: ut Approved: devnull@gpu.utcs.toronto.edu (interactive messaging vs. Internet services to do same) It's my understanding that BITNET uses a type-of-service (TOS) queueing approach to speed "interactive" messages along their way while ordinary mail traffic gets a slower store-and-forward approach. There is a TOS queuing facility that discriminates between interactive traffic (telnet, rlogin) and bulk traffic (NNTP, SMTP, FTP data) in Van Jacobsen's "compressed SLIP" package for running IP links over slow dial-up type lines on the order of 9600 bits/second -- it improves perceived performance considerably for normal use. Any site that's converting over to IP that uses data links in this range should specify the availability of such priority queueing to make sure that they can cope sensibly with a mix of bulk and interactive traffic. I'm not sure what the state-of-the-art type of service markings are, but here's an indication of how they are specified in IP (RFC 791) as an example of the sorts of factors to be balanced. Type of Service: 8 bits The Type of Service provides an indication of the abstract parameters of the quality of service desired. These parameters are to be used to guide the selection of the actual service parameters when transmitting a datagram through a particular network. Several networks offer service precedence, which somehow treats high precedence traffic as more important than other traffic (generally by accepting only traffic above a certain precedence at time of high load). The major choice is a three way tradeoff between low-delay, high-reliability, and high-throughput. Bits 0-2: Precedence. Bit 3: 0 = Normal Delay, 1 = Low Delay. Bits 4: 0 = Normal Throughput, 1 = High Throughput. Bits 5: 0 = Normal Relibility, 1 = High Relibility. Bit 6-7: Reserved for Future Use. 0 1 2 3 4 5 6 7 +-----+-----+-----+-----+-----+-----+-----+-----+ | | | | | | | | PRECEDENCE | D | T | R | 0 | 0 | | | | | | | | +-----+-----+-----+-----+-----+-----+-----+-----+ Precedence 111 - Network Control 110 - Internetwork Control 101 - CRITIC/ECP 100 - Flash Override 011 - Flash 010 - Immediate 001 - Priority 000 - Routine The use of the Delay, Throughput, and Reliability indications may increase the cost (in some sense) of the service. In many networks better performance for one of these parameters is coupled with worse performance on another. Except for very unusual cases at most two of these three indications should be set. Type of Service The type of service (TOS) is for internet service quality selection. The type of service is specified along the abstract parameters precedence, delay, throughput, and reliability. These abstract parameters are to be mapped into the actual service parameters of the particular networks the datagram traverses. Precedence. An independent measure of the importance of this datagram. Delay. Prompt delivery is important for datagrams with this indication. Throughput. High data rate is important for datagrams with this indication. Reliability. A higher level of effort to ensure delivery is important for datagrams with this indication.