卫衣上的油渍怎么去除Network Working Group J. Postel Request for Comments: 801 ISI November 1981
NCP/TCP TRANSITION PLAN
Introduction
------------
ARPA sponsored rearch on computer networks led to the development
of the ARPANET. The installation of the ARPANET began in September
1969, and regular operational u was underway by 1971. The ARPANET has been an operational rvice for at least 10 years. Even while it has provided a reliable rvice in support of a variety of computer
rearch activities, it has itlf been a subject of continuing
rearch, and has evolved significantly during that time.
给老师的赠言In the past veral years ARPA has sponsored additional rearch on
computer networks, principally networks bad 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 rearch on other networks that
the ba host-to-host protocol ud in the ARPANET was inadequate for u in the networks. In 1973 work was initiated on a host-to-host protocol for u across all the networks. The result of this long effort is the Internet Protocol (IP) and the Transmission Control
Protocol (TCP).
The protocols allow all hosts in the interconnected t of the
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 Defen 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 veral years. All new DoD packet
networks will be using the protocols exclusively.
The time has come to put the protocols into u 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, the problems can be solved and we Postel [Page 1]
can move into an environment with significantly broader communication rvices.
Discussion
----------
The implementation of IP/TCP on veral hosts has already been
completed, and the u of some rvices 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
ca. Any new host connected to the ARPANET should only implement
IP/TCP and TCP-bad rvices. Several important implementation
issues are discusd in the last ction of this memo.
Becau 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. The relay hosts will support
Telnet, FTP, and Mail rvices on both NCP and TCP. The relay
rvices 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宝宝长牙的症状
goes by, and the conversion progress, 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 ri, it will not be a
substantial portion of the total traffic.
The next ction expands on this plan, and the following ction
gives some milestones in the transition process. The last ction
lists the key documents describing the new protocols and rvices.
Appendices prent scenarios for u of the relay rvices.
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]
IP:
This is specified in RFCs 791 and 792. Implementations exist
for veral machines and operating systems. (See Appendix D.) TCP:
This is specified in RFC793. Implementations exist for veral machines and operating systems. (See Appendix D.)
It is not enough to implement the IP/TCP protocols, the principal
rvices must be available on this IP/TCP ba as well. The舅兄
principal rvices are: Telnet, File Transfer, and Mail.
It is the task of each host organization to implement the
principal rvices for its own hosts. The implementation tasks must begin by 1 January 1982.
Telnet:
This is specified in RFC 764. It is very similar to the Telnet ud 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
ud 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 u other
transmission byte sizes are eliminated.
Mail:
This is specified in RFC 788. Mail is parated completely
from FTP and handled by a distinct rver. The procedure is
医院船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 rvices 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 ur and rver Telnet in both environments. Urs
requiring Telnet rvice between hosts in different environments Postel [Page 3]
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 ur and rver Telnet, and both ur and rver FTP in both
environments. Urs requiring FTP rvice between hosts in
different environments will first connect via Telnet to an FTP
relay host, then u FTP to move the file from the file donor host to the FTP relay host, and finally u 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 veral protocol environments. For
TCP-only hosts, using SMTP will be sufficient. For NCP-only hosts that have not been modified to u SMTP, the special syntax
"ur.host@forwarder" may be ud to relay mail via one or more研究生实践报告
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 u TCP-bad rvices.
First TCP-only Host already The first TCP-only host begins u of TCP-bad rvices.
Telnet and FTP Relay Service already Special relay accounts are available to qualified urs with a
demonstrated need for the Telnet or FTP relay rvice.
Ad Hoc Mail Relay Service already An ad hoc mail relay rvice using the prototype MTP (RFC 780) is implemented and mail is relayed from the TCP-only hosts to总里
NCP-only hosts, but not vice versa. This rvice will be replaced by the SMTP rvice.
Last NCP Conversion Begins Jan 82 The last NCP-only host begins conversion to TCP.
Postel [Page 4]
Mail Relay Service Jan 82 The SMTP (RFC 788) mail rvice 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 u TCP-bad rvices.
Last NCP Conversion Completed Nov 82 The last NCP-only host completes conversion to TCP.
丝瓜皮
Full Internet Service Jan 83 All hosts are TCP-capable and u TCP-bad rvices. NCP is
removed from rvice, relay rvices end, all rvices are
TCP-bad.
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 The and associated documents are to be published in a notebook, and other information uful to implementers is to be gathered. The
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]
