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rfc:rfc801

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

Postel [Page 1]

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.

Postel [Page 2]

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

Postel [Page 3]

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.

Postel [Page 4]

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

Postel [Page 5]

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.

Postel [Page 6]

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.

Postel [Page 7]

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!

Postel [Page 8]

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.

Postel [Page 9]

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  |
       +---------+          +---------+          +---------+

Postel [Page 10]

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  |
          +---------+          +---------+          +---------+

Postel [Page 11]

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.

Postel [Page 12]

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  |
       +---------+          +---------+          +---------+

Postel [Page 13]

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  |
       +---------+          +---------+          +---------+

Postel [Page 14]

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).

Postel [Page 16]

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.

Postel [Page 17]

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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