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+Network Working Group                                        A. Shoshani
+Request for Comments: 44                                         R. Long
+                                                            A. Landsberg
+                                          System Development Corporation
+                                                           10 April 1970
+
+
+                     Comments on NWG/RFC 33 and 36
+
+   Generally, we are satisfied with the suggestions for the new Host-
+   to-Host protocol.  However, we think that a few refinements may be
+   helpful.
+
+   I.   It seems that there are two cases of reconnection:
+
+     1. Reconnect from a socket in a local Host to another socket in the
+        local Host.  This was referred to in RFC #33 as "switch".  The
+        local sockets can belong to different processes (such as the
+        "Login" process switching a connection to another process just
+        created) or can belong to the same process (such as a process
+        that accepts calls for connections on a particular socket, and
+        after a connection is established switches to another of his
+        sockets).
+
+     2. Reconnect from a socket at a local Host to a socket in a foreign
+        Host.
+
+     We suggest separation of these two cases for the following reasons:
+     a) Reconnection in Case 1 is necessary and useful, while the
+        usefulness of Case 2 is still in doubt.
+
+     b) Case 1 is simple to implement (at least conceptually) while Case
+        2 involves an elaborate mechanism of commands because of the
+        asynchronous nature of the network (four out of nine commands
+        were suggested to handle Case 2 in RFC #36).
+
+     Thus we think that at least in the first usage of the Host-to-Host
+     protocol reconnection in Case 2 should be left out.  An additional
+     system call (not a command) is therefore needed to permit Case 1,
+     which is SWITCH <socket 1> <socket 2>.
+
+   II.  The CLOSE command as suggested in RFC #36 seems to be used for
+        two purposes: block a connection and abort a connection.  To
+        avoid ambiguity it would be desirable to have two commands:
+        BLOCK and CLOSE.  As suggested in RFC #36, the response for both
+        commands can be the SUSPEND command which acknowledges the
+        reception of BLOCK or CLOSE commands.
+
+
+
+
+Shoshani, et al.                                                [Page 1]
+
+RFC 44                Comments on NWG/RFC 33 & 36             April 1970
+
+
+   III. After a connection has been established, we see no reason for
+        keeping the "foreign socket" in a local connection table.  Since
+        there is a one-to-one correspondence between a link number of
+        the foreign Host and a foreign socket number, we can use the
+        link number in the commands.  Thus, except for the RFC command,
+        all commands can use link numbers and therefore eliminate a 40-
+        bit foreign socket number in every entry of the connection table
+        (size being critical for some Hosts).  We note that if
+        connections will be multiplexed over links as suggested in RFC
+        #38, then the foreign socket would be needed in the connection
+        table.
+
+   IV.  In RFC#33 the term PORT was introduced.  Although this is
+        private to every Host, we have a comment.  If ports are used
+        such that there is a one-to-one correspondence between a port
+        for some user and a socket, then ports are completely redundant.
+        However, a Host may wish to multiplex ports over connections, in
+        which case an additional mechanism is needed.
+
+   To summarize the last four comments, we suggest that in the initial
+   version the following system calls and commands will be used (most of
+   them in RFC 33 and 36).
+
+   System Calls:
+   1) INITIATE <my socket> <your socket>
+   2) ACCEPT  <my socket>
+   3) SWITCH <socket 1> <socket 2>
+   4) LISTEN <my socket>
+   5) CLOSE <my socket>
+   6) TRANSMIT <my socket> <address>
+
+   Commands:
+   Commands 0, 1, 3, 4 as in RFC #36 (pp.5) and in addition:
+   1) BLOCK: BLK <link>
+   2) CLOSE: CLS <link>
+
+   V.   In addition to the above it seems necessary to decide on the
+        following issues one way or the other together with the first
+        version of the protocol (perhaps by setting a date for people to
+        express their preferences and decide accordingly).  All of these
+        issues were mentioned in the meeting at UCLA on March 17, 1970,
+        but were put aside.
+
+        1. "Double padding" - when a message does not end on a word
+           boundary.  Two possible solutions were mentioned:
+
+           a) Hosts provide their padding in addition to the IMP's
+              padding (double padding).
+
+
+
+Shoshani, et al.                                                [Page 2]
+
+RFC 44                Comments on NWG/RFC 33 & 36             April 1970
+
+
+           b) Hosts make sure that all messages end on a word boundary
+              by shifting their messages (when necessary) and adjusting
+              the "marking" accordingly.
+
+        2. "Echoing" - there are three apparent possibilities:
+           a) Echoing
+           b) No echoing
+           c) Optional Echoing - possibly a bit in the "Leader" can be
+              used to designate this option.
+
+        3. "Code Conversion" - originally, BB&N suggested doing the
+           conversion in the IMPs  using ASCII-8 as the common code.
+           This was rejected, mainly because of claims that ASCII-8 is
+           not large enough for some uses, such as graphics.  Also
+           conversion in the IMPs may slow them down and take up space
+           which could be used for buffers.  We feel that it is very
+           desirable to have a common code (even when the conversion is
+           not done by the IMPs), such that all incoming text messages
+           are in the same code and only one conversion table is needed.
+           Outgoing text messages should be converted into this common
+           code.  Obviously, the option "no translation" should be
+           possible for the purpose of binary data or data that is not
+           representable in the common code.  Since every known code can
+           be considered to be too restrictive for some purposes, we
+           suggest adopting a Network Common Code (NCC), and use all of
+           the 256 possible characters (for 8-bit code) to include the
+           "important" part of the union of the codes used throughout
+           the network.
+
+   VI.   Our preference to the above issues is as follows:
+        a) "Double padding" -it turns out to be easy for us to get our
+           messages to be sent on a word boundary by shifting the leader
+           of a message (and adjusting the "marking" accordingly) rather
+           than the data.  Thus we will prefer solution V.1.b).
+        b) "Echoing" - we prefer no echoing.  We think that character
+           echoing should be managed locally.
+        c) "Code Conversion" we prefer a Network Common Code.
+           Initially, ASCII-8 can be used, and then expanded according
+           to the needs of the Network.
+
+
+       [ This RFC was put into machine readable form for entry ]
+      [ into the online RFC archives by Alison De La Cruz 12/00 ]
+
+
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+Shoshani, et al.                                                [Page 3]
+