RFC 840 HISTORIC META · STANDARDS · PROTOCOLS
Official protocols
An official registry of Internet protocols and their standardization status.
RFC EDITOR
Postel, J., "Official protocols", RFC 840, DOI 10.17487/RFC0840, April 1983, <https://www.rfc-editor.org/info/rfc840>.
BIBTEX
@misc{rfc840,
series = {Request for Comments},
number = 840,
howpublished = {RFC 840},
publisher = {RFC Editor},
doi = {10.17487/RFC0840},
url = {https://www.rfc-editor.org/info/rfc840},
author = {J. Postel},
title = {{Official protocols}},
pagetotal = 23,
year = 1983,
month = apr,
} LINEAGE · FROM THE RFC INDEXOpen full graph →
RFC text
Contents
Network Working Group J. Postel
Request for Comments: 840 ISI
April 1983
Official Protocols
This RFC identifies the documents specifying the official protocols used
in the Internet. Annotations identify any revisions or changes planned.
To first order, the official protocols are those in the Internet
Protocol Transition Workbook (IPTW) dated March 1982. There are several
protocols in use that are not in the IPTW. A few of the protocols in
the IPTW have been revised these are noted here. In particular, the
mail protocols have been revised and issued as a volume titled "Internet
Mail Protocols" dated November 1982. There is a volume of protocol
related information called the Internet Protocol Implementers Guide
(IPIG) dated August 1982. A few of the protocols (in particular the
Telnet Options) have not been revised for many years, these are found in
the old ARPANET Protocol Handbook (APH) dated January 1978.
This document is organized as a sketchy outline. The entries are
protocols (e.g., Transmission Control Protocol). In each entry there
are notes on status, specification, comments, other references,
dependencies, and contact.
The status is one of: required, recommended, elective, or
experimental.
The specification identifies the protocol defining documents.
The comments describe any differences from the specification or
problems with the protocol.
The other references identify documents that comment on or expand on
the protocol.
The dependencies indicate what other protocols are called upon by
this protocol.
The contact indicates a person who can answer questions about the
protocol.
Official Protocols
In particular, the status may need some further clarification:
required
- all hosts must implement the required protocol,
recommended
- all hosts are encouraged to implement the recommended
protocol,
elective
- hosts may implement or not the elective protocol,
experimental
- hosts should not implement the experimental protocol unless
they are participating in the experiment and have coordinated
their use of this protocol with the contact person, and
none
- this is not a protocol.
Overview
Catenet Model
STATUS: None
SPECIFICATION: IEN 48 (in IPTW)
COMMENTS:
Gives an overview of the organization and principles of the
Internet.
Could be revised and expanded.
OTHER REFERENCES:
DEPENDENCIES:
CONTACT: Postel@USC-ISIF
Official Protocols
Network Level
Internet Protocol (IP)
STATUS: Required
SPECIFICATION: RFC 791 (in IPTW)
COMMENTS:
A few minor problems have been noted in this document.
The most serious is a bit of confusion in the route options.
The route options have a pointer that indicates which octet of
the route is the next to be used. The confusion is between the
phrases "the pointer is relative to this option" and "the
smallest legal value for the pointer is 4". If you are
confused, forget about the relative part, the pointer begins
at 4.
Another important point is the alternate reassembly procedure
suggested in RFC 815.
Note that ICMP is defined to be an integral part of IP. You
have not completed an implementation of IP if it does not
include ICMP.
OTHER REFERENCES:
RFC 815 (in IPIG) - IP Datagram Reassembly Algorithms
RFC 814 (in IPIG) - Names, Addresses, Ports, and Routes
RFC 816 (in IPIG) - Fault Isolation and Recovery
RFC 817 (in IPIG) - Modularity and Efficiency in Protocol
Implementation
DEPENDENCIES:
CONTACT: Postel@USC-ISIF
Official Protocols
Internet Control Message Protocol (ICMP)
STATUS: Required
SPECIFICATION: RFC 792 (in IPTW)
COMMENTS:
A few minor errors in the document have been noted.
Suggestions have been made for additional types of redirect
message and additional destination unreachable messages.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol
CONTACT: Postel@USC-ISIF
Host Level
User Datagram Protocol (UDP)
STATUS: Recommended
SPECIFICATION: RFC 768 (in IPTW)
COMMENTS:
The only change noted for the UDP specification is a minor
clarification that if in computing the checksum a padding octet
is used for the computation it is not transmitted or counted in
the length.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol
CONTACT: Postel@USC-ISIF
Official Protocols
Transmission Control Protocol (TCP)
STATUS: Recommended
SPECIFICATION: RFC 793 (in IPTW)
COMMENTS:
Many comments and corrections have been received for the TCP
specification document. These are primarily document bugs
rather than protocol bugs.
Event Processing Section: There are many minor corrections and
clarifications needed in this section.
Push: There are still some phrases in the document that give a
"record mark" flavor to the push. These should be further
clarified. The push is not a record mark.
Listening Servers: Several comments have been received on
difficulties with contacting listening servers. There should
be some discussion of implementation issues for servers, and
some notes on alternative models of system and process
organization for servers.
Maximum Segment Size: The maximum segment size option should
be generalized and clarified. It can be used to either
increase or decrease the maximum segment size from the default.
The default should be established more clearly. The default is
based on the default maximum Internet Datagram size which is
576 octets counting the IP and TCP headers. The option counts
only the segment data. For each of IP and TCP the minimum
header is 20 octets and the maximum header is 60 octets. So the
default maximum data segment is could be anywhere from 456 to
536 octets. The current proposal is to set it at 536 data
octets.
Idle Connections: There have been questions about
automatically closing idle connections. Idle connections are
ok, and should not be closed. There are several cases where
idle connections arise, for example, in Telnet when a user is
thinking for a long time following a message from the server
computer before his next input. There is no TCP "probe"
mechanism, and none is needed.
Queued Receive Data on Closing: There are several points where
it is not clear from the description what to do about data
received by the TCP but not yet passed to the user,
particularly when the connection is being closed. In general,
Official Protocols
the data is to be kept to give to the user if he does a RECV
call.
Out of Order Segments: The description says that segments that
arrive out of order, that is, are not exactly the next segment
to be processed, may be kept on hand. It should also point out
that there is a very large performance penalty for not doing
so.
User Time Out: This is the time out started on an open or send
call. If this user time out occurs the user should be
notified, but the connection should not be closed or the TCB
deleted. The user should explicitly ABORT the connection if he
wants to give up.
OTHER REFERENCES:
RFC 813 (in IPIG) - Window and Acknowledgement Strategy in TCP
RFC 814 (in IPIG) - Names, Addresses, Ports, and Routes
RFC 816 (in IPIG) - Fault Isolation and Recovery
RFC 817 (in IPIG) - Modularity and Efficiency in Protocol
Implementation
DEPENDENCIES: Internet Protocol
CONTACT: Postel@USC-ISIF
Host Monitoring Protocol (HMP)
STATUS: Elective
SPECIFICATION: IEN 197
COMMENTS:
This is a good tool for debuging protocol implementations in
small remotely located computers.
This protocol is used to monitor Internet gateways and the
TACs.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol
CONTACT: Hinden@BBN-UNIX
Official Protocols
Cross Net Debugger (XNET)
STATUS: Elective
SPECIFICATION: IEN 158
COMMENTS:
This specification should be updated and reissued as an RFC.
OTHER REFERENCES:
RFC 643
DEPENDENCIES: Internet Protocol
CONTACT: Postel@USC-ISIF
Exterior Gateway Protocol (EGP)
STATUS: Experimental
SPECIFICATION: RFC 827
COMMENTS:
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol
CONTACT: Postel@USC-ISIF
Official Protocols
Gateway Gateway Protocol (GGP)
STATUS: Experimental
SPECIFICATION: RFC 823
COMMENTS:
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol
CONTACT: Brescia@BBN-UNIX
Multiplexing Protocol
STATUS: Experimental
SPECIFICATION: IEN 90
COMMENTS:
No current experiment in progress. There is some question as
to the extent to which the sharing this protocol envisions can
actually take place. Also, there are some issues about the
information captured in the multiplexing header being (a)
insufficient, or (b) over specific.
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol
CONTACT: Postel@USC-ISIF
Official Protocols
Stream Protocol (ST)
STATUS: Experimental
SPECIFICATION: IEN 119
COMMENTS:
The implementation of this protocol has evolved and may no
longer be consistent with this specification. The document
should be updated and issued as an RFC.
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol
CONTACT: Forgie@BBN
Network Voice Protocol (NVP-II)
STATUS: Experimental
SPECIFICATION: RFC xxx
COMMENTS:
The specification is an ISI Internal Memo which should be
updated and issued as an RFC.
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
DEPENDENCIES: Internet Protocol, Stream Protocol
CONTACT: Casner@USC-ISIB
Official Protocols
Application Level
Telnet Protocol (TELNET)
STATUS: Recommended
SPECIFICATION: RFC 764 (in IPTW)
COMMENTS:
A few minor typographical errors should be corrected and some
clarification of the SYNCH mechanism should be made.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
CONTACT: Postel@USC-ISIF
Telnet Options (TELNET)
Number Name RFC NIC APH USE
------ ------------------------------------ --- ----- --- ---
0 Binary Transmission ... 15389 yes yes
1 Echo ... 15390 yes yes
2 Reconnection ... 15391 yes no
3 Suppress Go Ahead ... 15392 yes yes
4 Approximate Message Size Negotiation ... 15393 yes no
5 Status 651 31154 yes yes
6 Timing Mark ... 16238 yes yes
7 Remote Controlled Trans and Echo 726 39237 yes no
8 Output Line Width ... 20196 yes no
9 Output Page Size ... 20197 yes no
10 Output Carriage-Return Disposition 652 31155 yes no
11 Output Horizontal Tabstops 653 31156 yes no
12 Output Horizontal Tab Disposition 654 31157 yes no
13 Output Formfeed Disposition 655 31158 yes no
14 Output Vertical Tabstops 656 31159 yes no
15 Output Vertical Tab Disposition 657 31160 yes no
16 Output Linefeed Disposition 658 31161 yes no
17 Extended ASCII 698 32964 yes no
18 Logout 727 40025 yes no
19 Byte Macro 735 42083 yes no
20 Data Entry Terminal 732 41762 yes no
21 SUPDUP 734 736 42213 yes no
22 SUPDUP Output 749 45449 no no
23 Send Location 779 ----- no no
255 Extended-Options-List ... 16239 yes yes
Official Protocols
STATUS: Elective
SPECIFICATION: (in APH)
COMMENTS:
There is an open question about some of these. Most of the
options are implemented by so few hosts that perhaps they
should be eliminated. These should all be studied and the
useful ones reissued as RFCs.
The last column (USE) of the table above indicates which
options are in general use.
The following are recommended: Binary Transmission, Echo,
Suppress Go Ahead, Status, Timing Mark, and Extended Options
List.
Many of these must be revised for use with TCP.
OTHER REFERENCES:
DEPENDENCIES: Telnet
CONTACT: Postel@USC-ISIF
File Transfer Protocol (FTP)
STATUS: Recommended
SPECIFICATION: RFC 765 (in IPTW)
COMMENTS:
There are a number of minor corrections to be made. A major
change is the deletion of the mail commands, and a major
clarification is needed in the discussion of the management of
the data connection. Also, a suggestion has been made to
include some directory manipulation commands (RFC 775).
Eventhough the MAIL features are defined in this document, they
are not to be used. The SMTP protocol is to be used for all
mail service in the Internet.
Data Connection Management:
a. Default Data Connection Ports: All FTP implementations
must support use of the default data connection ports, and
only the User-PI may initiate the use of non-default ports.
Official Protocols
b. Negotiating Non-Default Data Ports: The User-PI may
specify a non-default user side data port with the PORT
command. The User-PI may request the server side to
identify a non-default server side data port with the PASV
command. Since a connection is defined by the pair of
addresses, either of these actions is enough to get a
different data connection, still it is permitted to do both
commands to use new ports on both ends of the data
connection.
c. Reuse of the Data Connection: When using the stream
mode of data transfer the end of the file must be indicated
by closing the connection. This causes a problem if
multiple files are to be transfered in the session, due to
need for TCP to hold the connection record for a time out
period to guarantee the reliable communication. Thus the
connection can not be reopened at once.
There are two solutions to this problem. The first is to
negotiate a non-default port (as in (b) above). The
second is to use another transfer mode.
A comment on transfer modes. The stream transfer mode is
inherently unreliable, since one can not determine if the
connection closed prematurely or not. The other transfer
modes (Block, Compressed) do not close the connection to
indicate the end of file. They have enough FTP encoding
that the data connection can be parsed to determine the
end of the file. Thus using these modes one can leave
the data connection open for multiple file transfers.
Why this was not a problem with the old NCP FTP:
The NCP was designed with only the ARPANET in mind.
The ARPANET provides very reliable service, and the
NCP counted on it. If any packet of data from an NCP
connection were lost or damaged by the network the NCP
could not recover. It is a tribute to the ARPANET
designers that the NCP FTP worked so well.
The TCP is designed to provide reliable connections
over many different types of networks and
interconnections of networks. TCP must cope with a
set of networks that can not promise to work as well
as the ARPANET. TCP must make its own provisions for
end-to-end recovery from lost or damaged packets.
This leads to the need for the connection phase-down
time-out. The NCP never had to deal with
acknowledgements or retransmissions or many other
Official Protocols
things the TCP must do to make connection reliable in
a more complex world.
LIST and NLST:
There is some confusion about the LIST an NLST commands, and
what is appropriate to return. Some clarification and
motivation for these commands should be added to the
specification.
OTHER REFERENCES:
RFC 678 - Document File Format Standards
DEPENDENCIES: Transmission Control Protocol
CONTACT: Postel@USC-ISIF
Trivial File Transfer Protocol (TFTP)
STATUS: Elective
SPECIFICATION: RFC 783 (in IPTW)
COMMENTS:
No known problems with this specification. This is in use in
several local networks.
OTHER REFERENCES:
DEPENDENCIES: User Datagram Protocol
CONTACT: Postel@USC-ISIF
Simple Mail Transfer Protocol (SMTP)
STATUS: Recommended
SPECIFICATION: RFC 821
COMMENTS:
This has been revised since the IPTW, it is in the "Internet
Mail Protocols" volume of November 1982. RFC 788 (in IPTW) is
obsolete.
There have been many misunderstandings and errors in the early
Official Protocols
implementations. Some documentation of these problems can be
found in the file [ISIF]<SMTP>MAIL.ERRORS.
Some minor differences between RFC 821 and RFC 822 should be
resolved.
OTHER REFERENCES:
RFC 822 - Mail Header Format Standards
This has been revised since the IPTW, it is in the "Internet
Mail Protocols" volume of November 1982. RFC 733 (in IPTW)
is obsolete. Further revision of RFC 822 is needed to
correct some minor errors in the details of the
specification.
DEPENDENCIES: Transmission Control Protocol
CONTACT: Postel@USC-ISIF
Remote Job Entry (RJE)
STATUS: Elective
SPECIFICATION: RFC 407 (in APH)
COMMENTS:
Some changes needed for use with TCP.
No known active implementations.
OTHER REFERENCES:
DEPENDENCIES: File Transfer Protocol
Transmission Control Protocol
CONTACT: Postel@USC-ISIF
Official Protocols
Remote Job Service (NETRJS)
STATUS: Elective
SPECIFICATION: RFC 740 (in APH)
COMMENTS:
Used with the UCLA IBM OS system.
Please discuss any plans for implementation or use of this
protocol with the contact.
Revision in progress.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
CONTACT: Braden@USC-ISIA
Remote Telnet Service
STATUS: Elective
SPECIFICATION: RFC 818
COMMENTS:
OTHER REFERENCES:
DEPENDENCIES: Telnet, Transmission Control Protocol
CONTACT: Postel@USC-ISIF
Graphics Protocol
STATUS: Elective
SPECIFICATION: NIC 24308 (in APH)
COMMENTS:
Very minor changes needed for use with TCP.
No known active implementations.
OTHER REFERENCES:
Official Protocols
DEPENDENCIES: Telnet, Transmission Control Protocol
CONTACT: Postel@USC-ISIF
Echo Protocol
STATUS: Recommended
SPECIFICATION: RFC 347
COMMENTS:
This specification should be revised for use with TCP and
reissued.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
or User Datagram Protocol
CONTACT: Postel@USC-ISIF
Discard Protocol
STATUS: Elective
SPECIFICATION: RFC 348
COMMENTS:
This specification should be revised for use with TCP and
reissued.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
or User Datagram Protocol
CONTACT: Postel@USC-ISIF
Official Protocols
Character Generator Protocol
STATUS: Elective
SPECIFICATION: RFC 429
COMMENTS:
This specification should be revised for use with TCP and
reissued.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
or User Datagram Protocol
CONTACT: Postel@USC-ISIF
Quote of the Day Protocol
STATUS: Elective
SPECIFICATION: RFC xxx
COMMENTS:
Open a connection to this server, it sends you a quote (as a
character string), and closes the connection. This should be
described in an RFC.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
or User Datagram Protocol
CONTACT: Postel@USC-ISIF
Active Users Protocol
STATUS: Elective
SPECIFICATION: RFC xxx
COMMENTS:
Open a connection to this server, it sends you a list of the
currently logged in users (as a character string), and closes
the connection. This should be described in an RFC.
Official Protocols
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
or User Datagram Protocol
CONTACT: Postel@USC-ISIF
Finger Protocol
STATUS: Elective
SPECIFICATION: RFC 742 (in APH)
COMMENTS:
Some extensions have been suggested.
Some changes are are needed for TCP.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
CONTACT: Postel@USC-ISIF
NICNAME Protocol
STATUS: Elective
SPECIFICATION: RFC 812 (in IPTW)
COMMENTS:
Accesses the ARPANET Directory database.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
CONTACT: Feinler@SRI-NIC
Official Protocols
HOSTNAME Protocol
STATUS: Elective
SPECIFICATION: RFC 811 (in IPTW)
COMMENTS:
Accesses the Registered Internet Hosts database (HOSTS.TXT).
OTHER REFERENCES:
RFC 810 - Host Table Specification
DEPENDENCIES: Transmission Control Protocol
CONTACT: Feinler@SRI-NIC
Host Name Server Protocol
STATUS: Experimental
SPECIFICATION: IEN 116 (in IPTW)
COMMENTS:
This specification has significant problems: 1) The name
syntax is out of date. 2) The protocol details are ambiguous,
in particular, the length octet either does or doesn't include
itself and the op code. 3) The extensions are not supported by
any known implementation.
Work is in progress on a significant revision. Further
implementations of this protocol are not advised.
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
DEPENDENCIES: User Datagram Protocol
CONTACT: Postel@USC-ISIF
Official Protocols
CSNET Mailbox Name Server Protocol
STATUS: Experimental
SPECIFICATION: CS-DN-2
COMMENTS:
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
CONTACT: Solomon@UWISC
Daytime Protocol
STATUS: Elective
SPECIFICATION: RFC xxx
COMMENTS:
Open a connection to this server, it sends you the date and
time (as a character string), and closes the connection. This
should be described in an RFC.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
or User Datagram Protocol
CONTACT: Postel@USC-ISIF
Time Server Protocol
STATUS: Recommended
SPECIFICATION: IEN 142
COMMENTS:
Open a connection to this server, it sends you the date and
time (as a 32-bit number), and closes the connection. Or send
a user datagram and it send back a datagram containing the date
and time (as a 32-bit number).
Official Protocols
No known problems. Specification should be reissued as an RFC.
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
or User Datagram Protocol
CONTACT: Postel@USC-ISIF
DCNET Time Server Protocol (Internet Clock Service)
STATUS: Elective
SPECIFICATION: RFC 778
COMMENTS:
OTHER REFERENCES:
DEPENDENCIES: Internet Control Message Protocol
CONTACT: Mills@LINKABIT-DCN6
SUPDUP Protocol
STATUS: Elective
SPECIFICATION: RFC 734 (in APH)
COMMENTS:
OTHER REFERENCES:
DEPENDENCIES: Transmission Control Protocol
CONTACT: Admin.MRC@SU-SCORE
Internet Message Protocol (MPM)
STATUS: Experimental
SPECIFICATION: RFC 753
COMMENTS:
This is an experimental multimedia mail transfer protocol. The
implementation is called a Message Processing Module or MPM.
Official Protocols
Please discuss any plans for implementation or use of this
protocol with the contact.
OTHER REFERENCES:
RFC 767 - Structured Document Formats
DEPENDENCIES: Transmission Control Protocol
CONTACT: Postel@USC-ISIF
Appendices
Assigned Numbers
STATUS: None
SPECIFICATION: RFC 820
COMMENTS:
Describes the fields of various protocols that are assigned
specific values for actual use, and lists the currently
assigned values.
Issued January 1983, replaces RFC 790 in IPTW.
OTHER REFERENCES:
CONTACT: Postel@USC-ISIF
Pre-emption
STATUS: Elective
SPECIFICATION: RFC 794 (in IPTW)
COMMENTS:
Describes how to do pre-emption of TCP connections.
OTHER REFERENCES:
CONTACT: Postel@USC-ISIF
Official Protocols
Service Mappings
STATUS: None
SPECIFICATION: RFC 795 (in IPTW)
COMMENTS:
Describes the mapping of the IP type of service field onto the
parameters of some specific networks.
Out of date, needs revision.
OTHER REFERENCES:
CONTACT: Postel@USC-ISIF
Address Mappings
STATUS: None
SPECIFICATION: RFC 796 (in IPTW)
COMMENTS:
Describes the mapping of the IP address field onto the address
field of some specific networks.
Out of date, needs revision.
OTHER REFERENCES:
CONTACT: Postel@USC-ISIF
AI ELI5
On this page
PROBLEMThe early Internet needed a clear, authoritative list of which protocols were required, recommended, optional or experimental, and what issues had been found with each.
MECHANISMRFC 840 provides a catalog of protocols organized by layer (network, host, application) with annotations on status, specifications, known problems, references, dependencies and contact people.
HISTORIC STATUSThis RFC is Historic and was replaced by RFC 880 as protocols evolved and new standards emerged.
§1Overview and Purpose
RFC 840 identifies the official protocols of the Internet as of April 1983, drawing primarily from the Internet Protocol Transition Workbook (IPTW) dated March 1982. The RFC serves as a reference guide to the protocol specifications and their standardization status.
The document is organized as an outline with each protocol listed under its layer with five types of information: status (required, recommended, elective, or experimental), specification documents, comments on known issues and differences, references to related documents, dependencies on other protocols, and contact information for questions.
This RFC is a checklist of network rules. For each rule, it tells you if your computer must follow it, should follow it, can follow it, or should only try it in controlled experiments.
§2Status Levels Explained
Required protocols must be implemented by all Internet hosts. Recommended protocols should be implemented by all hosts but are not mandatory. Elective protocols are optional; hosts may implement them or not. Experimental protocols should only be used by hosts participating in coordinated experiments with the protocol contact person. There is also a status of None for documents that discuss concepts but are not themselves protocols.
The RFC notes that several protocols have undergone revisions since the IPTW, particularly the mail protocols (issued separately as Internet Mail Protocols in November 1982) and some Telnet options found in the older ARPANET Protocol Handbook from 1978.
Required means everyone must use it. Recommended means you should. Elective means you can choose. Experimental means only try it if you are part of a test.
§3Network and Transport Layer Protocols
At the network level, the RFC lists the Internet Protocol (IP, RFC 791) as required and notes several known issues in the specification, particularly confusion about route options and the pointer mechanism. The Internet Control Message Protocol (ICMP, RFC 792) is also required and integral to IP. The RFC emphasizes that implementations of IP that omit ICMP are incomplete.
The host level includes UDP (RFC 768, recommended) for simple datagram transmission, and TCP (RFC 793, recommended) for reliable stream delivery. The RFC documents numerous clarifications needed in TCP, including corrections to the Event Processing section, clarification of the push mechanism, guidance on listening servers, maximum segment size defaults, idle connection behavior, and out-of-order segment handling. It also lists several experimental protocols including the Exterior Gateway Protocol (EGP), Gateway Gateway Protocol (GGP), Stream Protocol, and Network Voice Protocol.
IP gets packets from one computer to another (required). ICMP helps with network problems (required). UDP sends quick messages without guarantees (recommended). TCP sends messages that are guaranteed to arrive in order (recommended).
§4Application Layer Protocols
At the application level, the RFC covers numerous protocols. Telnet (RFC 764, recommended) provides remote terminal access, though the RFC notes the SYNCH mechanism needs clarification. FTP (RFC 765, recommended) handles file transfer and is accompanied by detailed guidance on data connection management and stream mode reliability. SMTP (RFC 821, recommended) is the mail protocol, revised since the IPTW, with RFC 822 specifying mail header format.
The RFC also lists utility and diagnostic protocols at the elective level: Trivial FTP (TFTP), Remote Job Entry (RJE), NICNAME (directory lookup), HOSTNAME (host table access), Finger, Echo, Discard, and simple services like Daytime and Quote of the Day. Some protocols like the Time Server Protocol are recommended for basic network services.
Telnet lets you use a remote computer as if you were there. FTP copies files between computers. SMTP sends email. Other protocols do simpler things like tell you the time or list users.
§5Known Issues and Ongoing Work
The RFC includes detailed comments on several important protocols. TCP documentation needs significant revision for Event Processing, the push mechanism, listening server models, maximum segment size, and idle connection handling. FTP guidance addresses data connection port negotiation, the reuse of data connections between file transfers, and the difference in reliability between stream mode (which closes the connection to indicate end-of-file) and block or compressed modes (which do not).
Many protocols that predate TCP are noted as needing updates for use with it. The RFC also points out that some protocols are based on very old specifications (like Telnet options from 1978) that should be updated and reissued.
The RFC notes that many protocols have small bugs or unclear parts. Some older protocols were written for different networks and need changes to work with the new Internet.
§6References
[IPTW]Internet Protocol Transition Workbook, March 1982.
[IPIG]Internet Protocol Implementers Guide, August 1982.
[APH]ARPANET Protocol Handbook, January 1978.
[1]RFC 791Postel, J., "Internet Protocol", RFC 791, September 1981.September 1981[2]RFC 792Postel, J., "Internet Control Message Protocol", RFC 792, September 1981.September 1981[3]RFC 793Postel, J., "Transmission Control Protocol", RFC 793, September 1981.September 1981[4]RFC 768Postel, J., "User Datagram Protocol", RFC 768, August 1980.August 1980[5]RFC 764Postel, J., "Telnet Protocol", RFC 764, June 1980.June 1980[6]RFC 765Postel, J., "File Transfer Protocol", RFC 765, June 1980.June 1980[7]RFC 821Postel, J., "Simple Mail Transfer Protocol", RFC 821, August 1982.August 1982