📄 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 PlanAPPENDIX 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 PlanAPPENDIX 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 PlanAPPENDIX 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] ⌨️ 快捷键说明
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