Aucbvax.5236 fa.tcp-ip utzoo!decvax!ucbvax!tcp-ip Wed Nov 18 05:50:19 1981 TCP-IP Digest, Vol 1 #6 >From tcp-ip@brl Wed Nov 18 05:33:31 1981 TCP/IP Digest Wednesday, 11 Nov 1981 Volume 1 : Issue 6 Today's Topics: Administrivia: Long Delay Disabling NCPs -- Directory Service? TOPS-20 TCP Defenses? -- TCP/IP for Cybers? Unix/ArpaNet TCP Problems & Solutions TCP/IP Performance on VAXen Berkeley Enhanced TCP/IP for 4BSD UNIX ---------------------------------------------------------------------- From: Mike Muuss Subject: Administrivia Hello again folks! Sorry about the long delay between this digest and the previous one -- I was in Denver on travel, and could not get to a terminal. I hope to send out future digests as soon as enough material has been accumulated. Cheers, -Mike ------------------------------ From: POSTEL at USC-ISIF Subject: Disabling NCPs There has been some talk of "forcing" the move to TCP by various administrative and policy measures. There was also a claim that there was no technical way to force the abandonment of NCP. It should be pointed out that a quite simple modification to the IMP program would enable the IMPs to filter out and discard all NCP traffic. As far as i know, there has been no decision to do this, but you should be aware that it is technical feasible. --jon. ------------------------------ From: Harris A. Meyers Subject: Request A useful fuction for this list to perform might be to produce a directory of who has IP/TCP available for what machines and operating systems. In particular I am looking for a version to run on IBM's VM/CMS. harris ------------------------------ Subject: Re: TOPS 20 TCP/IP From: mike at RAND-UNIX I have often heard criticisms of TOPS 20 TCP/IP implementation, but never a defense. Does anyone from BBN or ARPA care to defend their implementation or do they agree with the criticisms? ------------------------------ From: roya at UTEXAS-11 Subject: Is there TCP/IP for Cyber machines? Do any of you know any sites that might have or is planning to implement TCP/IP for CDC Cyber machines like 175 with NOS like operating system? Roya [ Tektronix Labs (Clem Cole et.al.) have already implemented TCP and IP in RatFor for their Cyber, running under NOS. -Mike ] ------------------------------ From: greg at NPRDC Subject: Future contributions Now that all the special interest groups have spoken, can we get back to the original subject? In case you've forgotten, it was "Unix/ARPAnet TCP problems and solutions." Although I'm interested in the various problems/ possibilities of using TCP on other operating systems or other ethers, at a minimum, our mutual interest is getting our machines running TCP before the deadline. (Probabally this list goes a little farther than that; to those people, I appologize. But we are the ones with the deadline fast approaching.) Maybe we can discuss theoretical issues later, but I am more interested in the practical issues -- namely, who has TCP up? How is it connected to the ARPAnet (or even another ether, if the problems/ solutions are similar)? What problems were encountered? How fast is it? How does it compare in simplicity/performance/transparancy/completeness/ functionality/limitations/etc. with the other possibilities? So far, we have heard of two real choices (assuming that we're not going to have to buy any additional hardware): BBN and 3COM. Who's got them up? How connected? (I am VDH, so solutions that don't have a VDH driver are uninteresting.) Speak up; now's your chance to brag, and you can do the rest of us a real service. [ Actually, I had hoped that this digest could serve as a forum for technical discussion of networking for ALL systems, but clearly the transition to TCP for current ArpaNet Hosts is the primary motivator. I hope that this list will not restrict itself just to UNIX, though. -Mike] ------------------------------ Subject: TCP/IP Performance on VAX From: CERF at USC-ISI UC Berkeley has been developing a paging UNIX(TM) for the VAX based on V7 UNIX (TM-Western Electric). BBN has been developing a TCP/IP for this VAX UNIX(TM) and UCB recently reported data bandwidths of Mb/sec over a 3 Mb/s Ethernet running TCP/IP to TCP/IP including checksumming. This figure obtained on VAX 11/750 using 1 kilobyte packets. A point of contact for the Berkeley + BBN VAX UNIX(TM) is Prof. Robert Fabry (ARPAVAX.Fabry@Berkeley). A point of contact at BBN is Gurwitz@BBN-RSM(Rob Gurwitz). Vint Cerf (bd) ------------------------------ From: ARPAVAX .wnj at Berkeley Subject: tcp-ip digest contribution Cc: gurwitz@bbn-unix Moderator: Here is a description of the work we are doing a Berkeley with tcp-ip. I hope it is in time for this weeks digest. We have enjoyed the past digests and hope that future digests will be as interesting. Regards, Bill Joy ===== begin ===== The Computer Systems Research Group at Berkeley is enhancing the UNIX operating system with DARPA support. We are improving UNIX memory management facilities, working on extensions to UNIX to support better inter-process communication, and incorporating support for both local and long haul networks. In particular, we expect to try using the INTERNET protocols on a number of different commercially available local network interfaces. The basis for our INTERNET protocols is the TCP/IP implementation done by Rob Gurwitz at BBN. While this TCP has more than adequate performance for use in the ARPANET context, we need extremely good performance to be able to use the protocols as the basis for construction of distributed UNIX applications between machines on a local network. In particular, we wish to insure that data can be transferred rapidly between VAX machines on 10 Megabaud Ethernet cables. Our current file system organization uses 1024 byte records, while a newer, high-performance file system will use 4096 byte records. We are therefore interested in the effective transmission of records of these sizes. We are also interested in low per-packet overhead for distributed applications which exchange many messages. We have just finished about three weeks of tuning of the BBN TCP/IP for our 3 Megabaud prototype Ethernet. We had previously brought TCP/IP up on the Ethernet and were interested in learning more about the internals of TCP and discovering whether the protocol would be a bottleneck when running on a local network. The results we have obtained suggest that this is not the case. As an experiment to investigate the performance of the resulting TCP/IP implementation, we transmitted 4 Megabytes of data between two user processes on different machines. The transfer was partitioned into 1024 byte records and encapsulated in 1068 byte Ethernet packets. Sending the data from our 11/750 to our 11/780 through TCP/IP takes 28 seconds. This includes all the time needed to set up and tear down the connections, for an user-user throughput of 1.2 Megabaud. During this time the 11/750 is CPU saturated, but the 11/780 has about 30% idle time. The time spent in the system processing the data is spread out among handling for the Ethernet (20%), IP packet processing (10%), TCP processing (30%), checksumming (25%), and user system call handling (15%), with no single part of the handling dominating the time in the system. The TCP performance exceeds the throughput of the current VAX/UNIX file system by a factor of 3, due to the small block size of the UNIX file system. It comes within a factor of 2 of our per-spindle performance of a early prototype of a new file system organization we are working on. The relative speed of the TCP/IP protocol and the file system suggests that we will be able to transfer volumes of data regularly between machines without any special protocols. The limited bandwidth of our 3 Megabaud cable may be a bottleneck until we put in one or more 10 Megabaud cables. Higher rates can be expected between VAX-11/780's, but we have no direct measurements yet, as we have only one 780 with easily accessible down time. Improvements are yet possible within the bounds of the TCP/IP protocol and the new Ethernet standard (which limits packets to about 1500 bytes). In particular, we may use IP fragmentation and reassembly on the local network to allow the TCP and higher level system code to process 4096 byte data records (which is a more natural block size for the newer system we are working on, being a basic file system data page size.) This is convenient within the bounds of the Ethernet standards only because IP supports fragmentation and reassembly in a general way. Simple techniques are also available which would reduce the number of ACK's by a significant amount to further speed the TCP. Using information gathered from UNIX kernel profiling we can estimate the speed improvements possible given a 10 Megabaud cable. (All of these projections will be for user-user throughput between 11/750's.) Switching to 4096 byte segments in TCP transfers, while fragmenting at the IP layer (to stay within the packet length restriction of the Ethernet standard) we estimate an increased throughput of 1.9 Megabaud. This is with an interface which is functionality equivalent to our current prototype Ethernets. We plan on changing UNIX soon so that user i/o buffers are naturally page aligned. This would eliminate a copy of the data (when it is read) to raise the throughput to about 2.25 Megabaud. (This speedup only at the receiver gives an end-end speedup because the receiving process otherwise has more work to do.) With checksum calculation support from the interface hardware the user-user bandwidth would rise to about 3.5 Megabaud. At this point the major overhead is the processing of the 4 interrupts for the fragments of the 4k packets; a transmission medium which allowed us to use 4k packets would let the bandwidth rise to about 6.6 Megabaud, user-user. A final improvement would be to implement a variant on the send system call which released the virtual memory when the message was sent. This would be very useful for servers and could also be used by the standard i/o library. This would reduce the transmit overhead (which at this point should be greater than the receive overhead) making the final throughput about 8 Megabaud. On 11/780's, these numbers typically scale up by 1.4 so that we can project the throughput with the improvements described above to be about 11.2 Megabaud, user-user. While factors in the VAX architecture other than the protocol might well dominate before this bandwidth is achieved, this means that high data rates through the protocol can be achieved with a relatively small percentage of the processor. We are working on IPC facilities for UNIX which will interface to the INTERNET protocol family, and allow us to construct distributed applications for UNIX without explicit dependence on the network layer protocols. The measurements reported here suggest that we do not need to look for more efficient local network protocols, but will need to support other protocols only for inter-operability with other networks and systems. We will be working with Rob Gurwitz at BBN in the coming weeks, combining our version of TCP/IP with his current version. We look forward to making a high-performance version of the protocol available to the VAX/UNIX community at an early date. Regards, Bill Joy and Bob Fabry End of TCP-IP Digest ******************** ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.