Network Working Group                                         E. Harslem
Request for Comments: 40                                      J. Heafner
                                                                    RAND
                                                              March 1970

               More Comments on the Forthcoming Protocol

We have recently discussed NWG/RFC Nos. 36 and 39 with Steve Crocker,
UCLA.  Steve has asked that we elaborate on the errors, queries, and
HOST status that were mentioned in NWG/RFC #39.

Please voice your opinions soon in order to affect the forthcoming
protocol specifications.

ERROR MESSAGES

     <ERR> <Code> <Command length> <Command in error>

<Code> is an eight-bit field that specifies the error type.  The
assigned codes are shown below.  <Command length> is a 16-bit integer
that indicates the length of the <Command in error> in bits.  The
<Command in error> is the spurious command.

The ranges of <Code> are shown below in hexidecimal.

     00     Unspecified error types
     10-0F  Resource errors
     10-1F  Status errors
     20-2F  Content errors
     30-3F  Unused

Specific values of <Code> are shown below with their meaning.

     <Code> value   Semantics

         00         Unspecified errors.
         01         Request for an invalid resource.
         02         Request for an exhausted resource, try later.
        03-0F       Unused.
         10         Invalid <RSM>, i.e., link connected but unblocked.
         11         Invalid <SPD>.
         12         Invalid <ASG>, i.e., connected but no <RDY>
                      received.

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     <Code> value   Semantics

         13         Message received on blocked link.
        14-1F       Unused.
         20         Unknown command code.
         21         Message received on unconnected link.
         22         Invalid <RFC>.
         23         Invalid <CLS>.
         24         Invalid <RSM>, i.e., link not connected.
         25         Invalid <FND>.
         26         Invalid <END>.
         27         Invalid <RDY>.
         28         Invalid <ASG>, i.e., not connected.
        29-2F       Unused.
        30-FF       Unused.

QUERIES

     <QRY> <My Socket>
or   <RPY> <Your Socket> <Text>

The <QRY> is the query indicated in NWG/RFC #39 and <RPY> is the reply.
The format of <Text> is shown below; also refer to NWG/RFC #36, p. 3.

<Text>::= <16 bit count of relevant connection table entries>
          <relevant connection table entries>

<relevant connection table entries>::=
                                     <relevant connection table entries>
                                     <a relevant connection table entry>
                                     <a relevant connection table entry>

<a relevant connection table entry>::= <local socket> <foreign socket>
                                       <link> <connection state>
                                       <flow state and buffer control>
                                       <reconnection control state>

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HOST STATUS

     <NOP>

An NCP may be up, down, pending, etc.  When an NCP changes its
state to UP it should send a <NOP> to each remote NCP which
indicates the NCP is available.  The sending NCP can then
construct a vector of HOST status from the RFNMs it receives.  An
NCP receiving a <NOP> can update the availability of the sending
NCP in its HOST status vector.

       [ This RFC was put into machine readable form for entry ]
         [ into the online RFC archives by Richard Ames 6/97 ]

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