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Network Working Group                                          J. Postel
Request for Comments: 801                                            ISI
                                                           November 1981



                        NCP/TCP TRANSITION PLAN



Introduction
------------

   ARPA sponsored research on computer networks led to the development
   of the ARPANET.  The installation of the ARPANET began in September
   1969, and regular operational use was underway by 1971.  The ARPANET
   has been an operational service for at least 10 years.  Even while it
   has provided a reliable service in support of a variety of computer
   research activities, it has itself been a subject of continuing
   research, and has evolved significantly during that time.

   In the past several years ARPA has sponsored additional research on
   computer networks, principally networks based on different underlying
   communication techniques, in particular, digital packet broadcast
   radio and satellite networks.  Also, in the ARPA community there has
   been significant work on local networks.

   It was clear from the start of this research on other networks that
   the base host-to-host protocol used in the ARPANET was inadequate for
   use in these networks.  In 1973 work was initiated on a host-to-host
   protocol for use across all these networks.  The result of this long
   effort is the Internet Protocol (IP) and the Transmission Control
   Protocol (TCP).

   These protocols allow all hosts in the interconnected set of these
   networks to share a common interprocess communication environment.
   The collection of interconnected networks is called the ARPA Internet
   (sometimes called the "Catenet").

   The Department of Defense has recently adopted the internet concept
   and the IP and TCP protocols in particular as DoD wide standards for
   all DoD packet networks, and will be transitioning to this
   architecture over the next several years.  All new DoD packet
   networks will be using these protocols exclusively.

   The time has come to put these protocols into use in the operational
   ARPANET, and extend the logical connectivity of the ARPANET hosts to
   include hosts in other networks participating in the ARPA Internet.

   As with all new systems, there will be some aspects which are not as
   robust and efficient as we would like (just as with the initial
   ARPANET).  But with your help, these problems can be solved and we


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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   can move into an environment with significantly broader communication
   services.

Discussion
----------

   The implementation of IP/TCP on several hosts has already been
   completed, and the use of some services is underway.  It is urgent
   that the implementation of of IP/TCP be begun on all other ARPANET
   hosts as soon as possible and no later than 1 January 1982 in any
   case.  Any new host connected to the ARPANET should only implement
   IP/TCP and TCP-based services.  Several important implementation
   issues are discussed in the last section of this memo.

   Because all hosts can not be converted to TCP simultaneously, and
   some will implement only IP/TCP, it will be necessary to provide
   temporarily for communication between NCP-only hosts and TCP-only
   hosts.  To do this certain hosts which implement both NCP and IP/TCP
   will be designated as relay hosts.  These relay hosts will support
   Telnet, FTP, and Mail services on both NCP and TCP.  These relay
   services will be provided  beginning in November 1981, and will be
   fully in place in January 1982.

   Initially there will be many NCP-only hosts and a few TCP-only hosts,
   and the load on the relay hosts will be relatively light.  As time
   goes by, and the conversion progresses, there will be more TCP
   capable hosts, and fewer NCP-only hosts, plus new TCP-only hosts.
   But, presumably most hosts that are now NCP-only will implement
   IP/TCP in addition to their NCP and become "dual protocol" hosts.
   So, while the load on the relay hosts will rise, it will not be a
   substantial portion of the total traffic.

   The next section expands on this plan, and the following section
   gives some milestones in the transition process.  The last section
   lists the key documents describing the new protocols and services.
   Appendices present scenarios for use of the relay services.

The General Plan
----------------

   The goal is to make a complete switch over from the NCP to IP/TCP by
   1 January 1983.

      It is the task of each host organization to implement IP/TCP for
      its own hosts.  This implementation task must begin by
      1 January 1982.





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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


      IP:

         This is specified in RFCs 791 and 792.  Implementations exist
         for several machines and operating systems.  (See Appendix D.)

      TCP:

         This is specified in RFC793.  Implementations exist for several
         machines and operating systems.  (See Appendix D.)

   It is not enough to implement the IP/TCP protocols, the principal
   services must be available on this IP/TCP base as well.  The
   principal services are: Telnet, File Transfer, and Mail.

      It is the task of each host organization to implement the
      principal services for its own hosts.  These implementation tasks
      must begin by 1 January 1982.

      Telnet:

         This is specified in RFC 764.  It is very similar to the Telnet
         used with the NCP.  The primary differences are that the ICP is
         eliminated, and the NCP Interrupt is replaced with the TCP
         Urgent.

      FTP:

         This is specified in RFC 765.  It is very similar to the FTP
         used with the NCP.  The primary differences are that in
         addition to the changes for Telnet, that the data channel is
         limited to 8-bit bytes so FTP features to use other
         transmission byte sizes are eliminated.

      Mail:

         This is specified in RFC 788.  Mail is separated completely
         from FTP and handled by a distinct server.  The procedure is
         similar in concept to the old FTP/NCP mail procedure, but is
         very different in detail, and supports additional functions --
         especially mail relaying, and multi-recipient delivery.

   Beyond providing the principal services in the new environment, there
   must be provision for interworking between the new environment and
   the old environment between now and January 1983.

      For Telnet, there will be provided one or more relay hosts.  A
      Telnet relay host will implement both the NCP and TCP environments
      and both user and server Telnet in both environments.  Users
      requiring Telnet service between hosts in different environments


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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


      will first connect to a Telnet relay host and then connect to the
      destination host.  (See Appendix A.)

      For FTP, there will be provided one or more relay hosts.  An FTP
      relay host will implement both the NCP and TCP environments, both
      user and server Telnet, and both user and server FTP in both
      environments.  Users requiring FTP service between hosts in
      different environments will first connect via Telnet to an FTP
      relay host, then use FTP to move the file from the file donor host
      to the FTP relay host, and finally use FTP to move the file from
      the FTP relay host to the file acceptor host.  (See Appendix B.)

      For Mail, hosts will implement the new Simple Mail Transfer
      Protocol (SMTP) described in RFC 788.  The SMTP procedure provides
      for relaying mail among several protocol environments.  For
      TCP-only hosts, using SMTP will be sufficient.  For NCP-only hosts
      that have not been modified to use SMTP, the special syntax
      "user.host@forwarder" may be used to relay mail via one or more
      special forwarding host.  Several mail relay hosts will relay mail
      via SMTP procedures between the NCP and TCP environments, and at
      least one special forwarding host will be provided.  (See
      Appendix C.)

Milestones
----------

   First Internet Service                                        already

      A few hosts are TCP-capable and use TCP-based services.

   First TCP-only Host                                           already

      The first TCP-only host begins use of TCP-based services.

   Telnet and FTP Relay Service                                  already

      Special relay accounts are available to qualified users with a
      demonstrated need for the Telnet or FTP relay service.

   Ad Hoc Mail Relay Service                                     already

      An ad hoc mail relay service using the prototype MTP (RFC 780) is
      implemented and mail is relayed from the TCP-only hosts to
      NCP-only hosts, but not vice versa.  This service will be replaced
      by the SMTP service.

   Last NCP Conversion Begins                                     Jan 82

      The last NCP-only host begins conversion to TCP.


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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   Mail Relay Service                                             Jan 82

      The SMTP (RFC 788) mail service begins to operate and at least one
      mail relay host is operational, and at least one special forwarder
      is operational to provide NCP-only host to TCP-only host mail
      connectivity.

   Normal Internet Service                                        Jul 82

      Most hosts are TCP-capable and use TCP-based services.

   Last NCP Conversion Completed                                  Nov 82

      The last NCP-only host completes conversion to TCP.

   Full Internet Service                                          Jan 83

      All hosts are TCP-capable and use TCP-based services.  NCP is
      removed from service, relay services end, all services are
      TCP-based.

Documents
---------

   The following RFCs document the protocols to be implemented in the
   new IP/TCP environment:

      IP                                                         RFC 791
      ICMP                                                       RFC 792
      TCP                                                        RFC 793
      Telnet                                                     RFC 764
      FTP                                                        RFC 765
      SMTP                                                       RFC 788
      Name Server                                                IEN 116
      Assigned Numbers                                           RFC 790

   These and associated documents are to be published in a notebook, and
   other information useful to implementers is to be gathered.  These
   documents will be made available on the following schedule:

      Internet Protocol Handbook                                  Jan 82

      Implementers Hints                                          Jan 82

      SDC IP/TCP Specifications                                   Jan 82

      Expanded Host Table                                         Jan 82




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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


Implementation Issues
---------------------

   There are several implementation issues that need attention, and
   there are some associated facilities with these protocols that are
   not necessarily obvious.  Some of these may need to be upgraded or
   redesigned to work with the new protocols.

   Name Tables

      Most hosts have a table for converting character string names of
      hosts to numeric addresses.  There are two effects of this
      transition that may impact a host's table of host names: (1) there
      will be many more names, and (2) there may be a need to note the
      protocol capability of each host (SMTP/TCP, SMTP/NCP, FTP/NCP,
      etc.).

      Some hosts have kept this table in the operating system address
      space to provide for fast translation using a system call.  This
      may not be practical in the future.

      There may be applications that could take alternate actions if
      they could easily determine if a remote host supported a
      particular protocol.  It might be useful to extend host name
      tables to note which protocols are supported.

      It might be necessary for the host name table to contain names of
      hosts reachable only via relays if this name table is used to
      verify the spelling of host names in application programs such as
      mail composition programs.

      It might be advantageous to do away with the host name table and
      use a Name Server instead, or to keep a relatively small table as
      a cache of recently used host names.

      A format, distribution, and update procedure for the expanded host
      table will be published soon.

   Mail Programs

      It may be possible to move to the new SMTP mail procedures by
      changing only the mailer-daemon and implementing the SMTP-server,
      but in some hosts there may be a need to make some small changes
      to some or all of the mail composition programs.

      There may be a need to allow users to identify relay hosts for
      messages they send.  This may require a new command or address
      syntax not now currently allowed.



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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   IP/TCP

      Continuing use of IP and TCP will lead to a better understanding
      of the performance characteristics and parameters.  Implementers
      should expect to make small changes from time to time to improve
      performance.

   Shortcuts

      There are some very tempting shortcuts in the implementation of IP
      and TCP.  DO NOT BE TEMPTED!  Others have and they have been
      caught!  Some deficiencies with past implementations that must be
      remedied and are not allowed in the future are the following:

         IP problems:

            Some IP implementations did not verify the IP header
            checksum.

            Some IP implementations did not implement fragment
            reassembly.

            Some IP implementations used static and limited routing
            information, and did not make use of the ICMP redirect
            message information.

            Some IP implementations did not process options.

            Some IP implementations did not report errors they detected
            in a useful way.

         TCP problems:

            Some TCP implementations did not verify the TCP checksum.

            Some TCP implementations did not reorder segments.

            Some TCP implementations did not protect against silly
            window syndrome.

            Some TCP implementations did not report errors they detected
            in a useful way.

            Some TCP implementations did not process options.

         Host problems:

            Some hosts had limited or static name tables.



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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   Relay Service

      The provision of relay services has started.  There are two
      concerns about the relay service: (1) reliability, and (2) load.

      The reliability is a concern because relaying puts another host in
      the chain of things that have to all work at the same time to get
      the job done.  It is desirable to provide alternate relay hosts if
      possible.  This seems quite feasible for mail, but it may be a bit
      sticky for Telnet and FTP due to the need for access control of
      the login accounts.

      The load is a potential problem, since an overloaded relay host
      will lead to unhappy users.  This is another reason to provide a
      number of relay hosts, to divide the load and provide better
      service.

      A Digression on the Numbers

      How bad could it be, this relay load?  Essentially any "dual
      protocol" host takes itself out of the game (i.e., does not need
      relay services). Let us postulate that the number of NCP-only
      hosts times the number of TCP-only hosts is a measure of the relay
      load.

      Total Hosts  Dual Hosts  NCP Hosts  TCP Hosts  "Load"    Date
          200          20        178          2        356     Jan-82
          210          40        158         12       1896     Mar-82
          220          60        135         25       3375     May-82
          225          95         90         40       3600     Jul-82
          230         100         85         45       3825     Sep-82
          240         125         55         60       3300     Nov-82
          245         155         20         70       1400     Dec-82
          250         170          0         80          0  31-Dec-82
          250           0          0        250          0   1-Jan-83

      This assumes that most NCP-only hosts (but not all) will become to
      dual protocol hosts, and that 50 new host will show up over the
      course of the year, and all the new hosts are TCP-only.

      If the initial 200 hosts immediately split into 100 NCP-only and
      100 TCP-only then the "load" would be 10,000, so the fact that
      most of the hosts will be dual protocol hosts helps considerably.

      This load measure (NCP hosts times TCP hosts) may over state the
      load significantly.

      Please note that this digression is rather speculative!



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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   Gateways

      There must be continuing development of the internet gateways.
      The following items need attention:

         Congestion Control via ICMP

         Gateways use connected networks intelligently

         Gateways have adequate buffers

         Gateways have fault isolation instrumentation

      Note that the work in progress on the existing gateways will
      provide the capability to deal with many of these issues early in
      1982.  Work is also underway to provide improved capability
      gateways based on new hardware late in 1982.


































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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


APPENDIX A.  Telnet Relay Scenario

   Suppose a user at a TCP-only host wishes to use the interactive
   services of an NCP-only service host.

      1)  Use the local user Telnet program to connect via Telnet/TCP to
          the RELAY host.

      2)  Login on the RELAY host using a special account for the relay
          service.

      3)  Use the user Telnet on the RELAY host to connect via
          Telnet/NCP to the service host.  Since both Telnet/TCP and
          Telnet/NCP are available on the RELAY host the user must
          select which is to be used in this step.

      4)  Login on the service host using the regular account.

         +---------+          +---------+          +---------+
         |         |  Telnet  |         |  Telnet  |         |
         | Local   |<-------->|  Relay  |<-------->| Service |
         |  Host   |   TCP    |   Host  |   NCP    |   Host  |
         +---------+          +---------+          +---------+

   Suppose a user at a NCP-only host wishes to use the interactive
   services of an TCP-only service host.

      1)  Use the local user Telnet program to connect via Telnet/NCP to
          the RELAY host.

      2)  Login on the RELAY host using a special account for the relay
          service.

      3)  Use the user Telnet on the RELAY host to connect via
          Telnet/NCP to the service host.  Since both Telnet/TCP and
          Telnet/NCP are available on the RELAY host the user must
          select which is to be used in this step.

      4)  Login on the service host using the regular account.

         +---------+          +---------+          +---------+
         |         |  Telnet  |         |  Telnet  |         |
         | Local   |<-------->|  Relay  |<-------->| Service |
         |  Host   |   NCP    |   Host  |   TCP    |   Host  |
         +---------+          +---------+          +---------+






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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


APPENDIX B.  FTP Relay Scenario

   Suppose a user at a TCP-only host wishes copy a file from a NCP-only
   donor host.

      Phase 1:

         1)  Use the local user Telnet program to connect via Telnet/TCP
             to the RELAY host.

         2)  Login on the RELAY host using a special account for the
             relay service.

         3)  Use the user FTP on the RELAY host to connect via FTP/NCP
             to the donor host.

         4)  FTP login on the donor host using the regular account.

         5)  Copy the file from the donor host to the RELAY host.

         6)  End the FTP session, and disconnect from the donor host.

         7)  Logout of the RELAY host, close the Telnet/TCP connection,
             and quit Telnet on the local host.

            +---------+          +---------+          +---------+
            |         |  Telnet  |         |   FTP    |         |
            | Local   |<-------->|  Relay  |<-------->| Service |
            |  Host   |   TCP    |   Host  |   NCP    |   Host  |
            +---------+          +---------+          +---------+





















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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


      Phase 2:

         1)  Use the local user FTP to connect via FTP/TCP to the RELAY
             host.

         2)  FTP login on the RELAY host using the special account for
             the relay service.

         3)  Copy the file from the RELAY host to the local host, and
             delete the file from the RELAY host.

         4)  End the FTP session, and disconnect from the RELAY host.

            +---------+          +---------+
            |         |   FTP    |         |
            | Local   |<-------->|  Relay  |
            |  Host   |   TCP    |   Host  |
            +---------+          +---------+

   Note that the relay host may have a policy of deleting files more
   than a few hours or days old.






























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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


APPENDIX C.  Mail Relay Scenario

   Suppose a user on a TCP-only host wishes to send a message to a user
   on an NCP-only host which has implemented SMTP.

      1)  Use the local mail composition program to prepare the message.
          Address the message to the recipient at his or her host.  Tell
          the composition program to queue the message.

      2)  The background mailer-daemon finds the queued message.  It
          checks the destination host name in a table to find the
          internet address.  Instead it finds that the destination host
          is a NCP-only host.  The mailer-daemon then checks a list of
          mail RELAY hosts and selects one.  It send the message to the
          selected mail RELAY host using the SMTP procedure.

      3)  The mail RELAY host accepts the message for relaying.  It
          checks the destination host name and discovers that it is a
          NCP-only host which has implemented SMTP.  The mail RELAY host
          then sends the message to the destination using the SMTP/NCP
          procedure.

         +---------+          +---------+          +---------+
         |         |   SMTP   |         |   SMTP   |         |
         | Source  |<-------->|  Relay  |<-------->|  Dest.  |
         |  Host   |   TCP    |   Host  |   NCP    |   Host  |
         +---------+          +---------+          +---------+
























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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   Suppose a user on a TCP-only host wishes to send a message to a user
   on an NCP-only non-SMTP host.

      1)  Use the local mail composition program to prepare the message.
          Address the message to the recipient at his or her host.  Tell
          the composition program to queue the message.

      2)  The background mailer-daemon finds the queued message.  It
          checks the destination host name in a table to find the
          internet address.  Instead it finds that the destination host
          is a NCP-only host.  The mailer-daemon then checks a list of
          mail RELAY hosts and selects one.  It send the message to the
          selected mail RELAY host using the SMTP procedure.

      3)  The mail RELAY host accepts the message for relaying.  It
          checks the destination host name and discovers that it is a
          NCP-only non-SMTP host.  The mail RELAY host then sends the
          message to the destination using the old FTP/NCP mail
          procedure.

         +---------+          +---------+          +---------+
         |         |   SMTP   |         |   FTP    |         |
         | Source  |<-------->|  Relay  |<-------->|  Dest.  |
         |  Host   |   TCP    |   Host  |   NCP    |   Host  |
         +---------+          +---------+          +---------+


























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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   Suppose a user on a NCP-only non-SMTP host wishes to send a message
   to a user on an TCP-only host.  Suppose the destination user is
   "Smith" and the host is "ABC-X".

      1)  Use the local mail composition program to prepare the message.
          Address the message to "Smith.ABC-X@FORWARDER".  Tell the
          composition program to queue the message.

      2)  The background mailer-daemon finds my queued message.  It
          sends the message to host FORWARDER using the old FTP/NCP mail
          procedure.

      3)  The special forwarder host converts the "user name" supplied
          by the FTP/NCP mail procedure (in the MAIL or MLFL command) to
          "Smith@ABC-X" (in the SMTP RCTP command) and queues the
          message to be processed by the SMTP mailer-daemon program on
          this same host.  No conversion of the mailbox addresses in
          made in thr message header or body.

      4)  The SMTP mailer-daemon program on the forwarder host finds
          this queued message and checks the destination host name in a
          table to find the internet address.  It finds the destination
          address and send the mail using the SMTP procedure.

         +---------+          +---------+          +---------+
         |         |   FTP    |         |   SMTP   |         |
         | Source  |<-------->|Forwarder|<-------->|  Dest.  |
         |  Host   |   NCP    |   Host  |   TCP    |   Host  |
         +---------+          +---------+          +---------+






















Postel                                                         [Page 15]

RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


APPENDIX D.  IP/TCP Implementation Status

   Please note that the information in this section may become quickly
   dated.  Current information on the status of IP and TCP
   implementations can be obtained from the file
   <INTERNET-NOTEBOOK>TCP-IP-STATUS.TXT on ISIF.

   BBN C70 UNIX

      Date:  18 Nov 1981
      From:  Rob Gurwitz <gurwitz at BBN-RSM>

      The C/70 processor is a BBN-designed system with a native
      instruction set oriented toward executing the C language.  It
      supports UNIX Version 7 and provides for user processes with a
      20-bit address space.  The TCP/IP implementation for the C/70 was
      ported from the BBN VAX TCP/IP, and shares all of its features.

      This version of TCP/IP is running experimentally at BBN, but is
      still under development.  Performance tuning is underway, to make
      it more compatible with the C/70's memory management system.

   BBN GATEWAYS

      Date:  19 Nov 1981
      From:  Alan Sheltzer <sheltzer at BBN-UNIX>

      In an effort to provide improved service in the gateways
      controlled by BBN, a new gateway implementation written in
      macro-11 instead of BCPL is being developed.  The macro-11 gateway
      will provide users with internet service that is functionally
      equivalent to that provided by the current BCPL gateways with some
      performance improvements.

         ARPANET/SATNET gateway at BBN (10.3.0.40),
         ARPANET/SATNET gateway at NDRE (10.3.0.41),
         Comsat DCN Net/SATNET gateway at COMSAT (4.0.0.39),
         SATNET/UCL Net/RSRE Net gateway at UCL (4.0.0.60),
         PR Net/RCC Net gateway at BBN (3.0.0.62),
         PR Net/ARPANET gateways at SRI (10.3.0.51, 10.1.0.51),
         PR Net/ARPANET gateway at Ft. Bragg (10.0.0.38).










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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   BBN H316 and C/30 TAC

      Date:  18 November 1981
      From:  Bob Hinden <Hinden@BBN-UNIX>

      The Terminal Access Controller (TAC) is user Telnet host that
      supports TCP/IP and NCP host to host protocols.  It runs in 32K
      H-316 and 64K C/30 computers.  It supports up to 63 terminal
      ports.  It connects to a network via an 1822 host interface.

      For more information on the TAC's design, see IEN-166.

   BBN HP-3000

      Date:  14 May 1981
      From:  Jack Sax <sax@BBN-UNIX>

      The HP3000 TCP code is in its final testing stages.  The code
      includes under the MPE IV operating system as a special high
      priority process.  It is not a part of the operating system kernel
      because MPE IV has no kernel.  The protocol process includes TCP,
      IP, 1822 and a new protocol called HDH which allows 1822 messages
      to be sent over HDLC links.  The protocol process has about 8k
      bytes of code and at least 20k bytes of data depending on the
      number of buffers allocated.

      In addition to the TCP the HP3000 has user and server TELNET as
      well as user FTP.  A server FTP may be added later.

      A complete description of the implementation software can be found
      in IEN-167.

   BBN PDP-11 UNIX

      Date:  14 May 1981
      From:  Jack Haverty <haverty@BBN-UNIX>

      This TCP implementation was written in C.  It runs as a user
      process in version 6 UNIX, with modifications added by BBN for
      network access.  It supports user and server Telnet.

      This implementation was done under contract to DCEC.  It is
      installed currently on several PDP-11/70s and PDP-11/44s.  Contact
      Ed Cain at DCEC <cain@EDN-UNIX> for details of further
      development.






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RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   BBN TENEX & TOPS20

      Date:  23 Nov 1981
      From:  Charles Lynn <CLynn@BBNA>

      TCP4 and IP4 are available for use with the TENEX operating system
      running on a Digital KA10 processor with BBN pager.  TCP4 and IP4
      are also available as part of TOPS20 Release 3A and Release 4 for
      the Digital KL10 and KL20 processors.

      Above the IP layer, there are two Internet protocols within the
      monitor itself (TCP4 and GGP).  In addition up to eight (actually
      a monitor assembly parameter) protocols may be implemented by
      user-mode programs via the "Internet User Queue" interface. The
      GGP or Gateway-Gateway Protocol is used to receive advice from
      Internet Gateways in order to control message flow.  The GGP code
      is in the process of being changed and the ICMP protocol is being
      added.

      TCP4 is the other monitor-supplied protocol and it has two types
      of connections -- normal data connections and "TCP Virtual
      Terminal" (TVT) connections.  The former are used for bulk data
      transfers while the latter provide terminal access for remote
      terminals.

      Note that TVTs use the standard ("New") TELNET protocol.  This is
      identical to that used on the ARPANET with NCP and in fact, is
      largely implemented by the same code.

      Performance improvements, support for the new address formats, and
      User and Server FTP processes above the TCP layer are under
      development.

   BBN VAX UNIX

      Date:  18 Nov 1981
      From:  Rob Gurwitz <gurwitz at BBN-RSM>

      The VAX TCP/IP implementation is written in C for Berkeley 4.1BSD
      UNIX, and runs in the UNIX kernel.  It has been run on VAX 11/780s
      and 750s at several sites, and is due to be generally available in
      early 1982.

      The implementation conforms to the TCP and IP specifications (RFC
      791, 793).  The implementation supports the new extended internet
      address formats, and both GGP and ICMP.  It also supports multiple
      network access protocols and device drivers.  Aside from ARPANET
      1822 and the ACC LH/DH-11 driver, experimental drivers have also
      been developed for ETHERNET.  There are user interfaces for


Postel                                                         [Page 18]

RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


      accessing the IP and local network access layers independent of
      the TCP.

      Higher level protocol services include user and server TELNET,
      MTP, and FTP, implemented as user level programs.  There are also
      tools available for monitoring and recording network traffic for
      debugging purposes.

      Continuing development includes performance enhancements.  The
      implementation is described in IEN-168.

   COMSAT

      Date:  30 Apr 1980
      From:  Dave Mills <Mills@ISIE>


      The TCP/IP implementation here runs in an LSI-11 with a homegrown
      operating system compatible in most respects to RT-11. Besides the
      TCP/IP levels the system includes many of the common high-level
      protocols used in the ARPANET community, such as TELNET, FTP and
      XNET.

   DCEC PDP-11 UNIX

      Date:  23 Nov 1981
      From:  Ed Cain <cain@EDN-UNIX>

      This TCP/IP/ICMP implementation runs as a user process in version
      6 UNIX, with modifications obtained from BBN for network access.
      IP reassembles fragments into datagrams, but has no separate IP
      user interface.  TCP supports user and server Telnet, echo,
      discard, internet mail, and a file transfer service. ICMP
      generates replies to Echo Requests, and sends Source-Quench when
      reassembly buffers are full.

      Hardware - PDP-11/70 and PDP-11/45 running UNIX version 6, with
      BBN IPC additions.  Software - written in C, requiring 25K
      instruction space, 20K data space.  Supports 10 connections.












Postel                                                         [Page 19]

RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


   DTI VAX

      Date:  15 May 1981
      From:  Gary Grossman <grg@DTI)>

      Digital Technology Incorporated (DTI) IP/TCP for VAX/VMS

      The following describes the IP and TCP implementation that DTI
      plans to begin marketing in 4th Quarter 1981 as part of its
      VAX/VMS network software package.

      Hardware:  VAX-11/780 or /750.  Operating System:  DEC standard
      VAX/VMS Release 2.0 and above.  Implementation Language:   Mostly
      C, with some MACRO.  Connections supported:  Maximum of 64.

      User level protocols available:  TELNET, FTP, and MTP will be
      available. (The NFE version uses AUTODIN II protocols.)

   MIT MULTICS

      Date:  13 May 1981
      From:  Dave Clark <Clark@MIT-Multics>

      Multics TCP/IP is implemented in PL/1 for the HISI 68/80. It has
      been in experimental operation for about 18 months; it can be
      distributed informally as soon as certain modifications to the
      system are released by Honeywell.  The TCP and IP package are
      currently being tuned for performance, especially high throughput
      data transfer.

      Higher level services include user and server telnet, and a full
      function MTP mail forwarding package.

      The TCP and IP contain good logging and debugging facilities,
      which have proved useful in the checkout of other implementations.
      Please contact us for further information.

   SRI LSI-11

      Date:  15 May 1981
      From:  Jim Mathis <mathis.tscb@Sri-Unix>

      The IP/TCP implementation for the Packet Radio terminal interface
      unit is intended to run on an LSI-11 under the MOS real-time
      operating system.  The TCP is written in MACRO-11 assembler
      language.  The IP is currently written in assembler language; but
      is being converted into C. There are no plans to convert the TCP
      from assembler into C.



Postel                                                         [Page 20]

RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan


      The TCP implements the full specification.  The TCP appears to be
      functionally compatible with all other major implementations.  In
      particular, it is used on a daily basis to provide communications
      between users on the Ft. Bragg PRNET and ISID on the ARPANET.

      The IP implementation is reasonably complete, providing
      fragmentation and reassembly; routing to the first gateway; and a
      complete host-side GGP process.

      A measurement collection mechanism is currently under development
      to collect TCP and IP statistics and deliver them to a measurement
      host for data reduction.

   UCLA IBM

      Date:  13 May 1981
      From:  Bob Braden <Braden@ISIA>

      Hardware:  IBM 360 or 370, with a "Santa Barbara" interface to the
      IMP.

      Operating System:  OS/MVS with ACF/VTAM.  An OS/MVT version is
      also available.  The UCLA NCP operates as a user job, with its own
      internal multiprogramming and resource management mechanisms.

      Implementation Language:  BAL (IBM's macro assembly language)

      User-Level Protocols Available:  User and Server Telnet























Postel                                                         [Page 21]


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