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