RFC39 - Comments on Protocol Re: NWG/RFC#36

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Network Working Group E. Harslem

Request for Comments: 39 J. Heafner

RAND

25 March 1970

COMMENTS ON PROTOCOL RE: NWG/RFC#36

We offer the following suggestions to be considered as additions to

the April 28th 1970 protocol grammar specifications.

ERROR MESSAGES

<ERR> <Code> <Command in error>

It is desirable to include debugging aids in the initial protocol for

checking out Network Control Programs, etc.

There are three classes of errors--content errors, status errors, and

resource allocation or exhaustion. <Code> specifies the class and the

offending member of the class. The command is returned to the

sending NCP for identification and analysis.

Examples of status errors are: messages sent over blocked links and

attempts to unblock an unblocked link. Examples of content errors

are: an invalid RFCcomplete; a message sent on a link not connected;

closing of an unconnected link; and an attempt to unblock an

unconnected link. Examples of resource errors are: a request for a

non-existent program and connection table over- flow, etc. Resource

errors should be followed by a <CLS> in response to the <RFC>.

QUERIES

<QRY> <My Socket> < >

or <QRY> <Your Socket> <Text>

Queries provide an extension to the <ERR> facility as well as limited

error recovery, thus avoiding re-initialization of an NCP.

The first command requests the remote NCP to supply the status of all

connections to the user specified by the user number in <My socket>.

The second is the reply; <Text> contains the connection status

information. If an NCP wants the status of all connections to a

remote HOST, the <My Socket> is zero.

PROGRAM TERMINATION NOTIFICATION

<TER> <My Socket>

This command supplements rather than replaces <CLS>. It severs all

communication between a program and those programs in a given HOST to

which it is connected. This command performs what would otherwise be

handled by multiple <CLS> commands. <My Socket> contains the sender's

user number.

HOST STATUS

<HCU>

<HGD>

These messages (HOST coming up and HOST voluntarily going down) are

compatible with asynchronous, interrupt-driven programs, as opposed

to the more conventional post/poll method.

TRANSMIT AND BROADCAST

<TRN> <Body>

<BDC> <Body>

Unlike the previous commands, these are not sent over the control

link, but rather over links assigned to user programs. The prefix of

<TRN> or <BDC> indicates, to the receiving NCP, the disposition of

the message body. <TRN> indicates a message to be passed to a single

process. <BDC> specifies to the destination NCP that the message is

to be distributed over all receiving connections linked to the

sender. In response to a system call by the user to an NCP

requesting <BDC>, the NCP generates one <BDC> to each HOST to which

the sender is connected.

RFCAND DYNAMIC RECONNECTION

This protocol is complex; it proliferates control messages; it causes

queues (to become associated with re-entrant procedures) that are

artificially imposed via the protocol (remote AEN assignment); and

discounts the situation where only controlling process "A" has

knowledge that slave process "B" should be "rung out" in a dynamic

reconnection.

The <ERR>, etc., are suggestions for inclusion as additions in the

April 28th protocol specifications. The above criticism is, of

course, not intended to affect modification of the RFCstrUCture by

April 28th, nor to reflect on those who planned it. We have not

studied the problem. It is meant, however, to voice our concern

about complexity and resulting response times. This is a difficult

problem and it deserves more study after we have exercised the

current RFCspecifications. We hope to offer constructive

suggestions with respect to the RFCin the future.

JFH:hs

[ This RFCwas put into machine readable form for entry ]

[ into the online RFCarchives by Mario Vitale 08/99 ]

 
 
 
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