📄 rfc801.txt
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RFC 801 November 1981
NCP/TCP Transition Plan
Relay Service
The provision of relay services has started. There are two
concerns about the relay service: (1) reliability, and (2) load.
The reliability is a concern because relaying puts another host in
the chain of things that have to all work at the same time to get
the job done. It is desirable to provide alternate relay hosts if
possible. This seems quite feasible for mail, but it may be a bit
sticky for Telnet and FTP due to the need for access control of
the login accounts.
The load is a potential problem, since an overloaded relay host
will lead to unhappy users. This is another reason to provide a
number of relay hosts, to divide the load and provide better
service.
A Digression on the Numbers
How bad could it be, this relay load? Essentially any "dual
protocol" host takes itself out of the game (i.e., does not need
relay services). Let us postulate that the number of NCP-only
hosts times the number of TCP-only hosts is a measure of the relay
load.
Total Hosts Dual Hosts NCP Hosts TCP Hosts "Load" Date
200 20 178 2 356 Jan-82
210 40 158 12 1896 Mar-82
220 60 135 25 3375 May-82
225 95 90 40 3600 Jul-82
230 100 85 45 3825 Sep-82
240 125 55 60 3300 Nov-82
245 155 20 70 1400 Dec-82
250 170 0 80 0 31-Dec-82
250 0 0 250 0 1-Jan-83
This assumes that most NCP-only hosts (but not all) will become to
dual protocol hosts, and that 50 new host will show up over the
course of the year, and all the new hosts are TCP-only.
If the initial 200 hosts immediately split into 100 NCP-only and
100 TCP-only then the "load" would be 10,000, so the fact that
most of the hosts will be dual protocol hosts helps considerably.
This load measure (NCP hosts times TCP hosts) may over state the
load significantly.
Please note that this digression is rather speculative!
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]
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