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TCP-IP Digest, Vol 2 #1

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Feb 26, 1983, 7:47:11 PM2/26/83

TCP/IP Digest Saturday, 26 Feb 1983 Volume 2 : Issue 1

Today's Topics:
Administrivia -- Mail Programs for UNIX
MOS Driver for Interlan? -- "C" for TCP/IP?
Mail in FTP discontinued -- LH/DH-11 Driver for 3Com?
SMTP Specification Clarification
Gateway Table Availible -- Common SMTP Mail Problems
InterNet Software for PDP-11 UNIX Availible
TCP/IP above X.25?
TCP/IP Digest --- The InterNet Digest
For Research Use Only --- Not for Public Distribution

From: Mike Muuss <Mike@BRL>
Subject: Administrivia

While BRL's hosts started passing TCP traffic about 6-Jan, we were not
able to overcome all our mail difficulties until just recently, so
there have been no TCP Digest transmissions since 17-Dec-82.
At this time, it should be "business as normal" once again.

Remember, please address all submissions to the digest to
and administrative correspondence (addition, deletion, meta-chatter, ...) to

Since the big NCP to TCP conversion is (mostly) behind us now, I think that
the topic of the digest should broaden to

"Inter-Net Networking -- Design and Implimentation Issues",

or thereabouts.
Happy New Year!


Date: 19 Dec 82 02:06:42 EST (Sun)
From: Chris Torek <chris.umcp-cs@Udel-Relay>
Subject: Re: Mail Programs for UNIX ??
To: NADC at Usc-Eclb, TCP-IP at BRL, POSTEL at Usc-Isif

From: NADC at Usc-Eclb
Subject: Mail Programs for UNIX ??

... What are other sites with this environment (VAX, UNIX4.1
bsd, and BBN's TCP/IP) using? And what is a source for
information on the programs?

We are currently running MMDF and are not yet on the net, but have
looked into this. The next release of MMDF will have an Arpa channel
(an MMDF "channel" is a program that knows how to talk to a particular
mailer -- an elegant solution to the multiple-mail-format problem, if
you ask me). We were supposed to have received a version of this
sometime this week, I think (hello, Dave Farber?) but haven't yet. As
soon as we do I plan to hack at it so that it works "right". I'll let
you know if we get something working.


Return-Path: <DCl...@MIT-MULTICS.ARPA>
Date: 20 December 1982 11:26 est
From: DClark.INP at Mit-Multics
Subject: Merle:
To: neer at Usc-Eclb
cc: tcp-ip at BRL

We currently run MOS for our local net gateway. We expect to do an
Interlan driver during January, unless we hear of one already done. If
you can wait that long, you are welcome.
We have a non-kernel tcp for Unix written in C. That could be move
to a 68000, using the 68000 C compiler. The amount of work would depend
on what operating system you were going to run. If you wait somewhat
longer, we will do that too. I cannot predict the time, though.
Dave Clark


Date: 20 Dec 1982 1651-EST
From: Chris Ryland <CPR@Mit-Xx>
Subject: lightweight C version of TCP/IP
To: tcp-ip at BRL

I'm looking for a smallish C version of TCP/IP (for the 68000).
Any leads to same appreciated.


Date: 20 Dec 1982 1548-PST
From: POSTEL at Usc-Isif
Subject: Mail in FTP discontinued under TCP

Please note that even though the MAIL commands appear in the current
document for FTP on TCP (RFC 765) they are not to be used. In the
future all mail is to use the SMTP procedures documented in RFC 821.



Date: Tue, 21 Dec 1982 1629-EST
From: Graham Campbell <gc@Bnl>
To: tcp-ip at BRL
Subject: 3Com TCP/IP

Does anyone have the interface code for the 3Com implementation to run
an ACC LHDH-11? (We are running Unix v7, but anything would help)


Date: 27 Dec 1982 1612-PST
From: POSTEL at Usc-Isif
Subject: SMTP Problem
To: tcp-ip at BRL


There is a minor problem with many SMTP implementations due to a minor
difference between the old specification (RFC-788) and the current
specification (RFC-821).

The difference is in the details of the reverse-path of the FROM argument
of the MAIL command. In 788 the separator between all of the path elements
was comma, in 821 the last separator is a colon. For example, in 788 one
could have
but in 821 this must be

Certainly an obscure minor detail, but exactly the kind that computers are
good at checking. People that have programs built to RFC-788 should change
them soon so they can talk to new programs built to the current specification.

This difference also ocurrs in the forward-path argument of the RCPT command.



Return-path: ROODE@SRI-NIC
Date: 5 Jan 1983 2340-PST
From: ROODE at SRI-NIC (David Roode)
Subject: obtaining gateway table
To: tcp-ip@BRL
Location: EJ296 Phone: (415) 859-2774

With the cutover to TCP/IP on January 1, many more hosts now have
Internet capability. Besides the entries always present in the
ARPAnet host table, you now will have use for Internet Gateway
entries. These are included as part of the standardized DoD Internet
Host Table originally described in RFC 810, dated 1 March 1982.
You may wish to utilize the NIC Hostnames Server (RFC 811) to obtain
updated copies of the complete table. You can do this by
TCP telneting to the NIC on the Hostname Server port (101 decimal),
and entering a command line containing one of the following keys:

HNAME <name> --search for name
HADDR <addr> --search for address
ALL --dump entire table

(all of the above display entries in the standard format)

ALL-INGWAY --dump TENEX/TOPS-20 gateway file
ALL-HSTNAM --dump TENEX/TOPS-20 gateway file

<name> is a name or nicname
<addr> is a dotted Internet address (RFC 796), for example,
composed of the four octets of the full 32 bit Internet address,
each expressed in decimal

The command line is terminated by carriage return.

[ Hosts are strongly encouraged to reload their host tables frequently.
Either when booting the system, or at certain times during the week
seems to be the best approach. -Mike ]


Date: 17 Jan 1983 2255-PST
Subject: Common Mail Problems

You might consider this for the TCP-IP-DIGEST.

Date: 17 Jan 1983 2218-PST
Subject: common SMTP problems

In an effort to help mail implementers identify mail problems more
rapidly, we have created a list of problems we have encountered,
in the hope that others may not have to find them the same way we did.
The file will be kept in ISIF<SMTP>mail.errors, and we encourage any
contributions. It at least shows you some of the armor plating you
need on your mailer.

We have also set up a list of SMTP people in ISIF:<SMTP>SMTP.PEOPLE
which has contacts for those installations we know of.

Both files are ANONYMOUS accessible.

***** Accepting paths *****

Some mailers do not accept SMTP paths. In general,
an SMTP receiver should always accept a path in the FROM specifiaction,
even if it cannot relay mail, and hence can't accept paths in a TO

***** "," vs ":", bad syntax errors *****

During August 1982, the SMTP specification for
paths was changed. In the old specification, SMTP paths were specified
using only commas. For example:
whereas the new specification changes the last ",", if any, to a

Various mailers will accept only one or the other form, leading to
(typically) syntax errors. The recommended approach to this
problem is to accept both forms, and to generate ":" form addresses.
More clever mailers will try the other form when one fails, and will
avoid path creation when not necessary. That is send
rather than
where possible.

***** various marginal addresses *****

We have seen several instances of mail transfers with commands
RCPT to:<mockapetris>
rather than :
RCPT to:<mockapetris@isif>

We recommend that if your mailer accepts this sort of thing, it
should rewrite the address before forwarding. I.E. Its OK to
accept technically bad addresses, but you should not output them.

***** TCP PSH bit = timeouts *****

When sending SMTP data via TCP, the PSH bit should be set on the
last character of each command/response/DATA text. The PSH bit forces
the data through to the receiving SMTP. This is absolutely necessary
when talking to TOPS-20 SMTPs.

If PSH isn't set, TCP is free to buffer that data in either the sending
or receiving host without passing it to the SMTP receiver.

***** UNIX TCP BUG = duplicated mail, timeouts *****

In at least old versions of the TCP code distributed by BBN, there
is a bug that can cause buffered data to not be sent until more data
is transmitted. When used by SMTP, this typically causes the end of a DATA
transaction to appear to hang. When the sending SMTP times out, it sends
a QUIT. This QUIT forces out the buffered data, and causes the receiver to
see the end of the DATA commmand. Thus the sender thinks the transaction has
failed (it timed out), and the receiver thinks that the transaction has
succeeded. Later, the sender retransmits the whole message,
leading to duplications.

The fix is below:

In tcp-states.c, procedure sss_snd, under the comment "find end of send buffer
and append data", a while clause reading:

while (m->m_next != NULL) {
m = m->m_next;
last +=m->m_len;
is in error. The fix is to reverse the two statements in the clause.
As it is it counts the last buffer twice and the first buffer not at all.
With the fix, each buffer is counted once.

***** CRLF at end of message *****

There is a bug in many versions of XMAILR that will garbage the MAIL.TXT
file if asked to store a message that does not end in CRLF. The ISI
SMTP adds an extra CRLF to all messages as a temporary cludge to
avoid this problem.

***** CRLF and UNIX systems *****

Some UNIXes send mail that if full of LFs rather than CRLFs. This can
cause problems in mail reading programs such as MSG, which can type
the mail but not locate header fields.

***** Null FROM fields *****

The SMTP specification allows the FROM field to be null. Some mailers
don't accept null fields, and others add hops to a null FROM field
when forwarding mail.

***** Domain names ******

There is a great deal of disagrement regarding doamin names in host
identifiers. The only widely acceptable domain names are X.ARPA
for X, where X is a valid Internet (i.e. host table from NIC) host name.
This will undoubtedly change as domain naming is standardized.

***** HELO command *****

Many mailers demand a HELO command before they will accept mail. Its
best to give one before attempting to transmit.

***** QUIT command *****

Several mailers simply hang up rather than sending QUITs, particularly
after errors. The QUIT command, followed by a TCP close, is recommended.

***** TCP close ******

SMTP connections are supposed to be closed rather than aborted. Several
mailers don't do this, probably because TCP close can take a long
time, i.e. 30 seconds.

***** RCPT command responses in UNIX SMTP *****

Some versions of SMTP derived from the BBN code don't look at
the response to RCPT commands.

***** Multi-line responses *****

The SMTP protocol defines a method for giving multi-line response codes.
Many mailers generate multi-line responses; some even use them in the
message sent on initial connect.

Unfortunately, some mailers don't understand multi-line responses.
We have seen UNIX mailers that take each line of a multi-line response
as a separate response. Thus, for example, they take a 3 line
initial connect message and interpret it as the initial connect
message and positive responses to the first two commands sent, and
stay two commands out of phase in matching up commands and responses.
This leads to interesting behavior.

We have also observed the reverse problem. Some mailers send
multi-line responses without the "-" which would identify the response
as being multi-line.

***** sndmsg balks *****

Some versions of SMTP derived from the BBN SMTP seem to occasionally
send SMTP responses without numeric codes. The message typically contains
text "sndmsg balks ...". Other messages without codes are also seen.

***** TELNET protocol in SMTP transactions *****

The SMTP connection is not supposed to do TELNET negotiations, etc.
The control codes used can make otherwise understandable transmissions
unintelligible to SMTPs that don't implement TELNET codes. TELNET codes
should not be supported because they would destroy the ability
of the SMTP protocol to send arbitrary octets in the message body.
Admittedly this is not a real issue for DEC-10s and 20s, but could
prevent future use of mail to send arbitrary text.

***** \ and " in addresses ******

The use of the \ and " in addresses should be avoided when not necessary
because many mailers don't as yet do the right thing; those mailers
should be fixed.


Date: 26 Jan 1983 1028-EST (Wednesday)
Subject: Internet Software for Unix

This is probably an appropriate forum to mention
the existence of some internet software which is
running on our PDP 11/45 version 6 (with local mods)

In the kernel we have modules to drive a "Pronet"
device (10 Mb/s token-passing ringnet), to transmit
and receive internet packets, to demultiplex incoming
TCP and UDP packets, to reassemble internet fragments,
and to maintain a cache of internet hosts and their best
first hop gateways. Kernel code and data use from 9k
to 10.5k bytes depending on the size of the receive packets

Outside the kernel we have: TCP, user and server telnet,
SMTP, ICMP, and TFTP. All are running but are in varying
stages of development.

We are willing to give this software to anyone who wants
it, has a Unix source license, and will agree to a few constraints.
We should point out that it would be difficult for someone who is
not a Unix wizard to install this code. To find out more about the
software send mail to martin@mit-csr or to lwa@mit-csr.

Liza Martin
Larry Allen


Date: Fri 7 Jan 83 03:41:54-EST
From: Marc Shapiro <Sha...@MIT-XX.ARPA>
Subject: Request for info
To: tcp...@BRL.ARPA, prot...@MIT-MC.ARPA, human...@RUTGERS.ARPA

I need info on the following topics:

* Are there any implementations of either TCP/IP or TCP alone *above* X.25
for DEC-20 and/or Vax/unix

* all possible info on Ethernet/X.25 gateways, supported protocols
and what they are worth.

Thanks. Please reply directly to SHAPIRO@MIT-XX.

[ Replies might as well include the digest too. -Mike ]



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