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diff --git a/doc/rfc/rfc898.txt b/doc/rfc/rfc898.txt new file mode 100644 index 0000000..30d3c67 --- /dev/null +++ b/doc/rfc/rfc898.txt @@ -0,0 +1,1392 @@ + + +Network Working Group R. Hinden (BBN) +Request for Comments: 898 J. Postel (ISI) + M. Muuss (BRL) + J. Reynolds (ISI) + April 1984 + + GATEWAY SPECIAL INTEREST GROUP MEETING NOTES + +STATUS OF THIS MEMO + + This memo is a report on a meeting. No conclusions, decisions, or + policy statements are documented in this note. + +INTRODUCTION + + This memo is a report on the Gateway Special Interest Group Meeting + that was held at ISI in Marina del Rey, California on 28 and 29 + February 1984. Robert Hinden of BBNCC chaired, and Jon Postel of ISI + hosted the conference. Approximately 35 gateway designers and + implementors attended. These notes are based on the recollections of + Jon Postel and Mike Muuss. Under each topic area are Jon Postel's + brief notes, and additional details from Mike Muuss. + + The rest of this memo has three sections: the agenda, notes on the + talks, and the attendees list. + +MEETING AGENDA + + Tuesday, February 28 + + 9:00 Opening Remarks -- BBN - Hinden + 9:15 Opening Remarks -- ISI - Postel + 9:30 The MIT C Gateway -- MIT - Martin + 10:00 The Butterfly Gateway -- BBN - Hinden + 10:30 Break + 11:00 The EGP C Gateway -- ISI - Kirton + 11:20 The BRL Gateway -- BRL - Natalie + 11:40 The CMU Gateway -- CMU - Accetta + 12:00 Lunch + 1:30 The Wisconsin BITNET/CSNET Gateway -- UWisc - Solomon + 2:00 LAN to X.25 Gateway -- Computer Gateways Inc. - Buhr + 2:20 ISI-UCI Gateway -- UCI - Rose + 2:40 FACC Gateway -- FACC - Holkenbrink + 3:00 Break + 3:30 Lincoln IP/ST Gateway -- LL - Forgie/Kantrowitz + 3:50 Minimal Stub Gateways -- MITRE - Nabielsky + 4:10 Discussion + + + + + + + +Hinden, Postel, Muuss, & Reynolds [Page 1] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + Wednesday, February 29 + + 9:00 Opening Remarks -- BBN - Hinden + 9:10 SPF routing -- BBN - Seamonson + 9:35 Multiple Constraint Routing -- SRI - Shacham + 10:00 FACC Multinet Gateway Routing -- FACC - Cook + 10:30 Break + 11:00 Metanet Gateway -- SRI - Denny + 11:20 Address Mapping and Translation -- UCL - Crowcroft + 11:40 Design of the FACC Multinet Gateway -- FACC - Cook + 12:00 Lunch + 1:30 SAC Gateway -- SRI - Su/Lewis + 2:00 EGP -- Linkabit - Mills + 2:30 Congestion Control -- FACC - Nagle + 3:00 Break + 3:30 A Gateway Congestion Control Policy--NW Systems - Niznik + 4:00 Discussion + +NOTES ON THE MEETING + + The MIT C Gateway -- MIT - Martin + + Postel: A description of the gateway implemented at MIT. The + gateway was first developed by Noel Chiappa. It is written in C. + The MIT environment has 32 internal networks which are treated as + subnets of the MITNET on the Internet. The MIT gateways then do + subnet routing in their interior protocol. The subnet routing + scheme is similar to GGP. Liza has added an EGP implementation to + this gateway. + + Muuss: + + Campus network/project Athena + Dynamic routing + Congestion control - grad student + +---------------+---+ + Class A net : | 18|subnet|res|host| + +---------------+---+ + + "Bridges" forward between subnets. + + Campus Network and Project Athena 65 VAX 750s, 200 IBM PCs. + + Hosts: Now = 400, 1986 = 3,000, 1990 = 10,000 + + Subnets: Now = 42, 1985 = 60, 1990 = 200, (4 subnets/building) + + Protocols: Internet, DECnet, Chaosnet + + +Hinden, Postel, Muuss, & Reynolds [Page 2] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + FiberOptic spine between campus buildings. + + MIT gateways: + + 11/03s and 11/23s + 68000 on Abus + 6800 on Multibus (Bridge communications) + + MIT C gateway - + Runs under MOS, bridge OS, homegrown OS. Multiple protocols, + multiple interfaces. + + 11/03 - 100 packets/sec. + 11/23 - 180 packets/sec. + + GGP - Gw/Gw + EGP - Exterior Gw + IGP - Interior Gw + + EGP: Autonomous systems + + EGP: + Neighbor acquisition + Hello/I heard you + Net reachability poll + Net reachability message + + MIT IGP: + + IP header on EGP protocol + Dest: net number, subnet number, 0, 0377 (broadcast address) + + IGP header: + + Autonomous system number + Sequence number + Tasks: + Propagate exterior and subnet routing. + + Packets + Ext route request, and update Routing server + Default gateway + Exceptional gateways + Nets reached + + MIT - Gw broadcasts initial routings when it comes up, and again + on each change, net is flooded on each change several times. Each + bridge can ask for help. + + +Hinden, Postel, Muuss, & Reynolds [Page 3] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + Future: Wideband net gateway from BBN will also sit on net 18, + and an MIT routing server to acquire routing information. Trick - + BBN-Gw will be on an Ethernet, and a modified ARP will be used by + the bridges to "fool" the BBN gateway into acquiring the routes. + + Subnet Routing - inspired by PUP and CHAOS + Neighbor Bridge + Net I/F + Bridge address + Latest seq number + Aging value + Route to subnet + Distance + + Packets + Request + I'm up + + Route update + Distance vector (256 bytes) + 0 - Direct + 1 -127 - hop count + 128-255 - "Interface used for next hop" to subnet + and hop count + 255 - Unreachable + + Problem - + Many neighbors --> too much time and traffic needed for + processing. + + 3 level addressing and routing strategy + Ext Gw: + Routing server + Default Gw + Subnet routing + Small but rich subnet routing updates. + + The Butterfly Gateway -- BBN - Hinden + + Postel: A description of the butterfly hardware and a discussion + of the plans for the new gateway software to be implemented on it. + The butterfly machine is a multiprocessor (MC68000's) + interconnected with a funny switch. The new software will + incorporate the so called "Shortest Path First" or SPF routing + algorithm. + + + + + +Hinden, Postel, Muuss, & Reynolds [Page 4] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + Muuss: + + Replacement for existing 30 PDP-11 "core" gateways. + Problems to be solved. + + o Replace GGP + - Routing updates filling up + - Neighbor probes (N**2) + - Few buffers + + o Present GGP updates only hold 70 net numbers, repacking + data will increase that to approximately 100 nets, but + this is just short term. + + Features of Butterfly - + o 1000's of nets + o Partitioned nets + o Type of service routing, access control + o Flow control + o Large and small gateway configurations + + New functions - + o Routing + o Neighbor discovery + o Reduce neighbor pinging + o Access/departure model + o Connect gateways with point-to-point lines + + Routing - + o SPF - shortest path first + o Gateway based routing (opposed to network routing) + o Routing updates + Gw ID + <nets directly connected> + <neighbor, distance> + o Updates flooded to other gateways + + Next-door - Neighbors + o Neighbor gateways closest to gateway + o Ping next-door-neighbors only + o For up/down acquisition, partition into rings. Reduces + pinging. + + Access/departure model + + First Gw (entrance) picks exit gateway + + + + +Hinden, Postel, Muuss, & Reynolds [Page 5] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + First Gw adds Gw - Gw header + + Butterfly gateway + + Processor nodes and switch nodes + + 4-legged switch nodes, decision is simply UP or DOWN. 2 + inputs + and 2 outputs. + + Processor: MC 68000 + Memory management Unit + Processor node controller - 2901 bit slice + PVC is the memory controller. + + Butterfly - + 32 M bps/path + Bandwith: approximately N - speed + Size: approximately N/2 log N 2 + + Butterfly will support multibus interface; 1822, HDLC, + Ethernet, Ring + + Terminal and load device will be a personal computer + + Small Gw for ARPA is approximately $20K + + New Gw processor structure + + Buffer Management + o Scatter/gather buffers minimum size and extensions + o Buffer pool on processors with I/O + o Primary and secondary collections per device + ==> guaranteed minimum service per device + (implemented w/counts) + + The EGP C Gateway -- ISI - Kirton + + Postel: A user process was installed in Berkeley 4.2 Unix to do + EGP protocol functions leaving the normal router kernel function + in charge of forwarding datagrams. The EGP user process may do + system calls to update the kernel routing data. Based on the work + of Liza Martin. + + + + + + + +Hinden, Postel, Muuss, & Reynolds [Page 6] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + Muuss: + + EGP under 4.2 + + Elimination of nonrouting gateways + + Design - + Forwarding done in kernel + Kernel does not send redirects + EGP user process for route updates + Written in C + EGP based on Liza Martin's code + + Routing Tables + o Kernel + o EGP Process + + EGP Process Table - + o External updates + o Internal information + + Facilities - + + Configuration file- + o Trusted neighbors + o Internal non - routing gateways + + Acquisition - + o Predetermined number of core gateways are EGP'd to + o Only accept from trusted neighbors + o Cannot acquire neighbors indirectly, for now + + Unix Interfaces - + Reuse IP socket (problem with protocol number) + Listening to ICMP for redirects + System calls for - + o Route updates + o I/F config reading + o I/F status check + + Performance - + o 60 ms/packet pair (CPU time) + o Typically 1% of CPU for 1 minute polling + + Protocol function going + Routing updates being implemented + + Should be all going in April. + + +Hinden, Postel, Muuss, & Reynolds [Page 7] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + The BRL Gateway -- BRL - Natalie + + Postel: This was a description of the BRL dumb gateway. More + interesting was the description of the BRL complex and the + inteconnections between machines. The gateway is written in C + (and derived from the MIT C-Gateway) and based on a simple + multiprocess operating system called LOS. + + Muuss: + + BRL history + + LOS design + Message passing + Memory Management + No copying of data, buffer size + + The CMU Gateway -- CMU - Accetta + + Postel: This was a description of the CMU dumb gateway. + + Muuss: + + History - + o "Logical-Host" multiplexor (March 81) + o Gateway (Oct 82) remote debugger and monitor + o Router (Oct 83) + - Modular device and protocol support + - Stub IP dynamic routing + - Local inter-network cable routing. + o Written in "C" + + Uses low memory for buffers (maximum 32K)! + (autoboot of 3M bps Ethernet) + Auto-configuration of devices + Individual stack contents + Round-robin scheduler + Dynamic memory allocation + + Device driver + Network interfaces + Auxiliary support devices + + Does IP, ICMP, UDP + + Splicing through of PUP and CHAOS on chaos net, uses ARP. + + Configuration testing protocol (as in Ethernet Spec). + + +Hinden, Postel, Muuss, & Reynolds [Page 8] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + IP Processing- + + o Consistency checks + o Redirects does not forward misrouted packets + o Fragmentation - ICMP dest unreach If DF Set + o Access list for who can pass through + + No GGP, no EGP, Uses known gateways + + Ordinary devices and PDP-10 and PDP-20 + + The Wisconsin BITNET/CSNET Gateway -- UWisc - Solomon + + Postel: This was a discussion of a mail relay between the + Internet and BITNET to be installed at Wisconsin. + + Muuss: + + WISC-IBM (192.5.2.24) will connect to BITNET + + Mail gateway, BITNET uses RFC 822 headers! + + LAN to X.25 Gateway -- Computer Gateways Inc. - Buhr + + Postel: This was a description of a protocol translation device + between an X.25 world and the DATAPOINT ARCNET world. + + Muuss: + + ARCNET to X.25 Bridge + + ARCNET - from Datapoint, + Baseband coax, 2.5 mbps + Token passing + Reserve/send/wait/ack protocol + RIM chip implements this + + "The OSI models seem less clear than the Internet models, perhaps + because they are less well developed." + + Wraps the subnetwork in an enhanced subnetwork layer. + + Every pair of subnetworks must be connected in this design - hence + a bridge not a gateway. + + Bridge is a network layer RELAY. + + ARCNET address is sent as X.25 data + + +Hinden, Postel, Muuss, & Reynolds [Page 9] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + ISI-UCI Gateway -- UCI - Rose + + Postel: This was a description of the UCI dumb gateway. This one + is made up of two hosts (VAX 750s) 50 miles apart. The VAXs are + connected via a 9.6 Kbs leased line. One is interfaced to the + ISI-NET (an Ethernet) and the other to UCIICS net (also an + Ethernet). The VAXs run Berkeley Unix 4.1. These VAXs run as + regular hosts too. + + Muuss: + + MTU is 512. Effective bandwidth of approximately 6000 baud over + 9600 baud line. + + FACC Gateway -- FACC - Holkenbrink + + Postel: A description of a gateway designed by Ford. The gateway + is based on a MC68000 multiprocessor and a VME bus. An + interesting question that came up during this presentation was + "What is the least information a host (or gateway) must have when + it comes up, and how can it acquire the rest of what it needs to + go into full operation from the environment?" + + Muuss: + + Inter-segment Processor. M68000 CPU with various co-processors. + 68000 IOPS, 1822, IOP Ethernet IOP. 1 cpu does IP, routing. + Multi-cpu version of MOS + + Lincoln IP/ST Gateway -- LL - Forgie/Kantrowitz + + Postel: This was a discussion of the design of the Lincoln + gateways used primarily in the WBCNET for speech transmission + research. This gateway uses special I/O interfaces to promote a + high packet processing rate. The gateway implements both the + regular IP, and the ST protocol which permits resource + reservations to minimize the variation in transmission delay. + These gateways can, of course, act as regular internet gateways, + and have achieved very good performance in terms of datagrams per + second. + + Muuss: + + Packet voice experiments, wideband SATNET. Concentrate traffic + from local nets to trunk net. Needed enough performance to load + WBSATNET. 11/44 and ACC IF11 (Z-80). T1 trunk protocol converter. + (voice T1 <--> datagram) + + + +Hinden, Postel, Muuss, & Reynolds [Page 10] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + IP problems - + o Congestion + o High packet header overhead + o No support for conference call + + ST - + o Virtual circuit + o Know capacity in advance, schedule channel + o Abbreviated header + + 11/44 - 900 to 1000 pkts/sec. + + Port processor: + Sync low speed: 600K bits/sec. + Packet processing: 500 pkts/sec. average + 20-talker LPC voice loop, 28 data + bytes/pkt, 50% duty cycle + Data handling + 4 pcm voice stream loop 64K bps + 184 data bytes/pkt, 100% duty cycle + + Dispatcher Requirements + o Timely do ST + o Utilize rest of circuit for IP + o Performance measurement + + Reservations on the SATNET: Each host makes a reservation for + Nbytes of M messages every INTERVAL. Reservations are absolute. + + ST and IP for each distant run = MPP multipurpose packets. + + 12,000 lines of C code in 11/44 portion. + + Minimal Stub Gateways -- MITRE - Nabielsky + + Postel: This was a more abstract discussion of how stub gateways + could interact and acquire information about the topology of the + Internet. + + Muuss: + + Ethernet stub to Internet + Inexpensive, single-band ISBC 186/51 Intel @ $3000 + High performance. EGP? + + 128K bytes/board + + The Internet forest + + +Hinden, Postel, Muuss, & Reynolds [Page 11] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + Alternative to ARP using Multicast + + SPF routing -- BBN - Seamonson + + Postel: This was a fine presentation of the principles of the + "Shortest Path First" (SPF) routing procedures with some remarks + on how it is tailored to the Internet gateway situation. One + point that was impressed on me was that when using SPF in a set of + gateways (say, the core autonomous system) the procedure will do + routing to an "exit" gateway. Somehow I had not thought about it + in those terms before, but (obviously) just as there is a source + and a destination IMP in the ARPANET there will be an entrance and + an exit gateway in an SPF autonomous system. + + Muuss: + + Features - + Metric, update procedures, path calculation, forwarding + + Current GGP problems - + o Counting to infinity + o Not enough topology information in each Gw + o Updates potentially very large + + SPF in ARPANET + o Single path (not optimal) - no split of flow + o Delay based, to minimize delay + o Global knowledge of connection topology and delays + + Metric used - + o Delay, delay of each packet averaged + (queueing plus transmission plus propagation) + arrival-to-arrival time. + o Average delay on each trunk computed every 9.6 seconds. + Report large changes in delay, fast + + Update procedure - + o Updates report delay to each neighbor + o Update triggered by topology change, significant delay + change, or 1 time/minute. + Decay of threshold to direct to send update + o Sequence numbers + o Flooding on all trunks sent out on all lines + o Receipt of echo is acknowledgement + o Retransmission + o Aging of information + o Updates are 2*n*l packet growth. n = number imps, + l = number lines + + +Hinden, Postel, Muuss, & Reynolds [Page 12] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + - When lines goes up, rather than dumping routing + table,just waits one minute until all updates have + been heard. + + Path calculation + o Dijkstras Algorithm + + 20 + A _______________ F + / \ \ + 3 / \10\15 + / \ \ + B/___5___\D \E + \ / / + \ / / + 1 \ / /5 + \/ / + C / + + 1. A B(A, 3), D(A, 10), E(A, 15). F(A, 20) + + 2. A C(B, 4), D(B, 8), E(A, 15), F(A, 20) + | + B + + 4. A E(C, 9), F(A,20) + | + B + / \ + C D + + 5. A + | + B + | + C + / + E + + Then tree is inverted into a "go here to get to this destination." + + For Internet - + + Similar algorithm, needs special packet header to + indicate "exit" gateway to get to destination network. + + Update procedure - + Neighbor interface, neighbors, and delay to neighbor. + + +Hinden, Postel, Muuss, & Reynolds [Page 13] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + "Next door neighbors" for minimizing traffic. + Ability to package multiple updates in one average + explicit Acks. + + Path calculation - + o Possible to build different trees based on type of + service. + + Forwarding - + o Exit Gw + o Consistent databases are important. + + Multiple Constraint Routing -- SRI - Shacham + + Postel: This was a clear presentation of some of the consequences + of the idea of type of service routing. The level of complexity + of the routing procedure is determined to depend on how many + catagories of service there are and how many selections there are + in each catagory. A few examples were discussed including the + current type of service parameters of IP. + + Muuss: + + Both current and proposed ARPANET algorithms provide "best" path + under single constraint (number of hops, delay). + Internet will have diverse characteristics, it would be nice to + consider more than one constraint. + + o Determine a set of measures. + o Represent each measure as a single number. + o Determine range of values. (complexity 0(c**n) range of n) + o Define path measure as a function of measure of length. + sum (delay, cost) + min/capacity, length, security) + + If just one cost is used, then SPF (or whatever) can be used for + each cost. However, under multiple constraints there is a more + difficult problem. e.g.: minimum delay with packet size of at + least 1000 bytes. + + RUMC has been shown to be in the NP complete family. + + RUMC needs bigger tables, more processing and routing overhead. + Its not awful for 2-choice TOS, like in IP. + + Table size is random, we have to be prepared for the worst case. + + Possible strategies: flood a "search packet," dropped when + + +Hinden, Postel, Muuss, & Reynolds [Page 14] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + constraints are not met, see if it makes it though. Good only for + virtual circuit. Weighted sum (VC only) works only with some + probability. + + TOS is needed for Internet, but the algorithms are costly. + Complexity for providing TOS IP style is not too high. + + FACC Multinet Gateway Routing -- FACC - Cook + + Postel: This approach considered hop count to be an inadequate + metric for routing decsions in a system of different types of + networks (e.g., Ethernets, ARPANETs, 2.4Kb lines). Delay was + selected as the metric to use. There are some interesting issues + in the measurement of delay for some types of networks. Also, the + design considers the use of multiple paths when they are avaiable, + and routing to provide connectivty between the parts of + partitioned networks. + + Muuss: + + Routing with a single constraint. + A network of gateways Access, Transport, or Dual networks. + Some networks are used as backbones between gateways only. + + Routing updates + Variable length + Broadcast routing updates + + Unitary ends - A - Gw - B - Rest + Routing for A is really just routing to B + Neighbor Gws, nets + Lots and lots of tables + + Metanet Gateway -- SRI - Denny + + Postel: This is a project to invent several new addressing + features for gateways. In particular, there is a scheme to use an + option much like the source route option to do multi-addressing of + IP datagrams. It seems as if the gateways that implement this + option will have to know which other gateways do and don't + implement it. Also, there was discussion of a gateway to a + network that is in radio silence, and how to keep TCP connections + going with hosts that can't talk. This project is also concerned + about network reconstitution, security, survivability, congestion + control, and supporting multimedia data (voice, bitmaps, etc.) in + applications. A gateway is being developed in ADA for a MC68000 + machine (SUN), and the initial version of the gateway is to be up + in May 84. + + +Hinden, Postel, Muuss, & Reynolds [Page 15] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + Muuss: + + Navy internet + Multimedia mail and conf. + Radio silence (EMCON) + Security and Survivability. + + EMCON - Causes special problems for EGP and IGP one way nonTCP + mail delivery. No Acks. Uses name screen to redirect mail to + special one-way mail catcher, who then forwards using ordinary + methods. + + Security and survivability + Access control - "capability" - 32/64 bit key which changes + frequently (every hour or so) + + Reconstitution - Partitioning, coalescing, mobile host + Test and monitoring - HMP + + Gateway target - 68000 in ADA. Telesoft compiler + + Address Mapping and Translation -- UCL - Crowcroft + + Postel: This was a discussion of some of the issues in + interconnecting networks of different types including the Internet + and networks in England such as the Universe network. The + Universe network is made up of Cambridge Rings at several sites + linked via a satellite channel. + + Muuss: + + ARPA - SATNET - NULLNET - UCLNET UNIVERSE Satellite, 3 UCL rings + + SAM - + o IP switch to several 1822 hosts + o IP/universe mapper, overlays UCLNET on universe + o Mask and match + 128. 11. code. host + + Three types: + + 1. Direct: code --> subnet + 2. Redirect: 2nd lookup (for multihoming) + 3. Logical: Logical address into a table of universe + names. + Name lookups give addresses and routes. + + IP tunnels through X.25 + + +Hinden, Postel, Muuss, & Reynolds [Page 16] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + BBN Van gateway PSS - IPSS -Telenet - for hosts that can't use + SATNET. + + SAM does access control and multihoming. Clever Multihoming gives + host a second address and sends an ICMP/Redirect to force TCP + connection to go through a different route, but wind up at same + place!!! + + Wrote EGP in ADA. It didn't help at all. + + Design of the FACC Multinet Gateway -- FACC - Cook + + Postel: This is a distributed multiprocessor machine using a + special bus network for the interprocessor communication. The + softaware is written in C. The gateways is in an early test + phase. + + Muuss: + + RADC program + + Started with AUTODIN II, switched to DDN. + Small to large switching devices. + DoD uses of PDNs, and partitioned network problems. + + Distributed processing architecture - + Parallel contention, 90M bps bus, 22 wires. Each node has cpu, + memory, optimal comm line. Wire - OR presentation of address, + contention happens each time bus becomes free, all requestors + put out type of msg, pri, and address. Reads back wire - OR of + result, and highest gwy wins, sorted by (pri, type, higher + addr). + Bus was originally designed for our FAA fail-soft application + Z-800l w/MMU. Not binary addressing, but unitary (base1) + One element resolved per bus transaction. + Boards may be plugged in while running. + Inherent parallelism in layered protocols. + + Interface connector clues board to modem levels and date rate. Up + to 100K bps now, soon up to T1 rate. + + Multiprocessor approach allows routing calculation to take place + out-of-band from the measurement of delay and traffic, and allows + use of more compute power for routing. + + Mostly written in C, with some assembler. Multiprocessor + operating system, designed from scratch. + + + +Hinden, Postel, Muuss, & Reynolds [Page 17] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + SAC Gateway -- SRI - Su/Lewis + + Postel: This was a presentation of the design for the gateways to + be used in the advanced SAC demo experiments on network + partitioning and reconstitution, and communication between + intermingiling mobile networks. Much of these demonstrations will + be done with packet radio units and networks. Some of the ideas + are to use a gateway-centered type of addressing and double + encapsulation (i.e., an extra IP header) to route datagrams. + + Muuss: + + Network dynamics due to component mobility or failure. + Mobile host, reconstitution, partitioning. + H/W: 11/23 + S/W: Some "C" gateway + OS: VMOS (SRI) + + Gateway-centered addressing, rather than network. + Gw host instead of net.host. + Double encapsulation: additional IP header. + TCP uses addr as an ID, IP uses it as an ADDRESS (-> route) + Need to separate these dual uses of this address field. + Incremental Routing (next-hop indication) + + EGP -- Linkabit - Mills + + Postel: A presentation of the EGP design. EGP has three major + aspects, neighbor acquisition, neighbor reachability, and network + reachability. The autonomous system concept was discussed. + + Muuss: + + Background, Implementation, Experience, Disparaging Remarks + + Design goals - + o Established demarcations + o Decouple implementations + o Confine routing loops + o Exchange reachability information + o Provide flow control for connectivity information + o Medium-term lifetime + + Non goals Not trying to do these! + o Flexibility of topology + o Rapid response Very slow update + + + + +Hinden, Postel, Muuss, & Reynolds [Page 18] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + o Adaptive routing + o Common routing metric No agreement at all + o Load sharing or splitting + + "Good news travels fast and bad news travels forever." + Not for routing, but only provides reachability + + RFC827 initial mode, RFC888 stub protocol + + Neighbor acquisition protocol + o 2-way shake + o Flow - rates + o Explicit acquisition/cause + + Neighbor reachability protocol + o Periodic polling + o Parasitic information + o Reachability algorithm Network reachability + protocol + o Periodic pulling + o Remote information + o Direct and indirect neighbors + o Indirect internal and indirect external + neighbors + o Distance information + + EGP neighbors do not need to peer with more than one + CORE gateway, but you may peer with anybody you wish. + + Shortcomings - + o Slow reaction due polling + o Tree-structured routing constraint + - Rigid topology + - Administrative resistance to odering + - Lack of adaptive connectivity + o Neighbor acquisition incomplete. + + Loops between autonomous systems will last a long + time, and are a real no-no. + + System models - + o "Appropriate first hop" criterion + - Not useful for implementation + - Requires global information + - Inadequate for verification + o Graph models + - N-graph shows net connectivity + - T-graph shows system connectivity + + +Hinden, Postel, Muuss, & Reynolds [Page 19] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + - T-acycloc criterion insures loop-free + o Derived features + - Induces spanning tree + + N-graph + + G1 + A_______________B + / \ /\ + G2 / \ G3 G4 / \ G5 + / \ / \ + C------D E-----F G6 + + AS1 = G2, G3, G6 A B + AS2 = G1 + AS3 = G4, G5 AS1 ----- AS2 ----- AS3 + + T-graph + + Test: to ensure that there are no cycles + + Spanning subtree + + Specification effort - Status report State machine designed + + Remaining issues - + o Remove extra hop in core system + o Expand tables + o Test backdoor "GGP" + o Resolve specification issues + o Resolve full gateway configuration + - Back door connectivity guidance + - can only advertise 1 path at a time. + - APF rule guidancee + - Self organization issues + o Implement and distribute for operational systems. + + Congestion Control -- FACC - Nagle + + Postel: This was a discussion of the situation leading to the + ideas presented in RFC 896, and how the policies described there + improved overall performance. + + + + + + + + +Hinden, Postel, Muuss, & Reynolds [Page 20] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + Muuss: + + First principle of congestion control: + + DON'T DROP PACKETS (unless absolutely necessary) + + Second principle: + + Hosts must behave themselves (or else) + + Enemies list - + + 1. TOPS-20 TCP from DEC + 2. VAX/UNIX 4.2 from Berkeley + + Third principle: + + Memory won't help (beyond a certain point). + + The small packet problem: Big packets are good, small are bad + (big = 576). + + Suggested fix: Rule: When the user writes to TCP, initiate a send + only if there are NO outstanding packets on the connection. [good + for TELNET, at least] (or if you fill a segment). No change when + Acks come back. Assumption is that there is a pipe-like buffer + between the user and the TCP. + + The source quench problem Rule: When a TCP gets an ICMP Source + Quench, it must reduce the number of outstanding datagrams on + relevant TCP connections. + + Rule: When a gateway nears overload, before starting to drop + packets, send a Source Quench. + + Node capacity: Each node ought to have one buffer for each TCP + connection, plus some for overload. + + Both fixes really need to be done together, although the first one + is often helpful by itself. Side effect: FTPs start off "slowly," + until the first Ack comes back Dave Mills thinks this will + increase the mean delay for medium-size interactions. This + probably will not work so well for SATNET. + + Problems about propagation time of links biasing the validity of + this result!! + + + + +Hinden, Postel, Muuss, & Reynolds [Page 21] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + A Gateway Congestion Control Policy--NW Systems - Niznik + + Postel: This talk was (for Postel) hard to follow. There were a + number of references to well known results in queuing theory etc, + but I could not follow how they were being used. + + Muuss: + + Replacements for IMP SPF + Topological observations + Nodal congestion control policy + GMD - control application [from German network] + RPN - relational Petri net + DCT - dynamic congestion table + NCCP performance evaluation + Planned GCCP: Gateway congestion control policy + + Lots of diagrams and figures. + + Better throughput than SPF, but somewhat higher delay. + + Cubic structure of table. + + DISCUSSION (Postel's personal comments) + + There was very little organized discussion during the meeting and + not really very much question and answer interaction during the + presentation. There was a lot of discussion during the breaks, + and at lunch time, and at the end of each day. + + Some things that occured to me during the meeting that may have + been triggered by something someone said (or maybe by the view out + the window): + + Don't design a protocol where you expect to get a lot of + messages from a lot of sources at the same time. For example, + don't ask all the hosts on an Ethernet to send you an ack to a + broadcast packet. + + Has anyone worked out in detail the routing traffic costs for + the GGP vs the SPF procedures for the actual case of the + Internet? + + How will the fact that thinking of the routing in the core + autonomous system is cast in terms of an entry and an exit + gateway effect other things? Will there be special + + + + +Hinden, Postel, Muuss, & Reynolds [Page 22] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + + arrangements between the entry and exit gateway? Will an + autonomous system become a circuit switch connecting pairs of + entry/exit gateways? + + Is TOS routing worth the cost? + + Should we allow (as a new type of ICMP message) redirects to + Gateways? + + Does making memory larger ever hurt? If a gateway's memory is + full of inappropriately retransmitted TCP segments would it be + better if there were less memory? + + Is there something reasonable to do with source quench at the + TCP? Re: RFC-896. + + If there are links (or networks) of vastly differing delay and + thruput characteristics what impact would an IP level load + splitting (say by gateways) have on TCP connections (some of + the segments of the connection go one path and others go a + different path)? + + Are any problems avoided (either way) by using double IP + headers vs a "source route like" IP option to separate the IP + level addressing and routing function from the TCP level + end-point naming function of the IP addresses. + + What bad things could happen from the proposed IP + multidestination routing option? + + + + + + + + + + + + + + + + + + + + + +Hinden, Postel, Muuss, & Reynolds [Page 23] + + + +RFC 898 April 1984 +Gateway SIG Meeting Notes + + +MEETING ATTENDEES + + Mike Accetta - CMU + R. Buhr - Canada + J. Noel Chiappa - MIT + Paul Cook - Ford + Jon Crowcroft - UCL + Barbara Denny - SRI + Jim Forgie - LL + Steve Groff - BBN + Phill Gross - Linkabit + Kjell Hermansen - NTA + Robert Hinden - BBN + Patrick Holkenbrink - FACC + Ruth Hough - AIRINC + Willie Kantrowitz - LL + Paul Kirton -ISI + Mark Lewis -SRI + Liza Martin - MIT + Doug Miller - MITRE + Dave Mills - Linkabit + Mike Muuss - BRL + Jose Nabielsky - MITRE + Ron Natalie - BRL + John Nagle - Ford + Carol Niznick NW Systems + Jon Postel - ISI + Joyce Reynolds -ISI + Marshall Rose - UCI + Joe Sciortino - AIRINC + Linda Seamonson - BBN + Nachum Shacham - SRI + Alan Sheltzer - UCLA + Marvin Solomon - WISC + Zaw-Sing Su - SRI + Mitch Tasman - BBN + + + + + + + + + + + + + + +Hinden, Postel, Muuss, & Reynolds [Page 24] + |