328 lines
13 KiB
HTML
Executable File
328 lines
13 KiB
HTML
Executable File
<HTML>
|
|
<!-- $Id$ -->
|
|
<HEAD>
|
|
<TITLE>Compatibility and Link Qualifier Extensions for EMSI Sessions</TITLE>
|
|
</HEAD>
|
|
|
|
<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
|
|
<BODY
|
|
BGCOLOR="#FFFFFF"
|
|
TEXT="#000000"
|
|
LINK="#0000FF"
|
|
VLINK="#000080"
|
|
ALINK="#FF0000"
|
|
>
|
|
<PRE>
|
|
| Document: FSC-0088
|
|
| Version: 001
|
|
| Date: 31 October, 1995
|
|
|
|
|
| Robert Williamson FidoNet#1:167/104.0
|
|
|
|
Compatibility and Link Qualifier Extensions for EMSI Sessions
|
|
Robert Williamson FidoNet#1:167/104.0 robert@ecs.mtlnet.org
|
|
|
|
Purpose:
|
|
|
|
The basic purpose of this document is to start discussions which will
|
|
hopefully result in an improved handshake negotiation protocol.
|
|
|
|
Scope:
|
|
|
|
Relation of flags to Types of files transferred:
|
|
|
|
The FSC-0056 EMSI specification (hereafter referred to as EMSI-I)
|
|
makes little distinction between ARCmail/packets and other types of
|
|
files, such as files attached and TIC'ed files. In EMSI-I, the term
|
|
'Mail' when not used in conjunction with the term 'compressed', is
|
|
interpreted to mean ANY file.
|
|
|
|
This extension (hereafter referred to as EMSI-II) makes reference to
|
|
and allows control of types of files in addition to 'compressed mail'.
|
|
References to 'Mail' are changed to 'File' where common practice so
|
|
indicates. The additional qualifier flags described provide for more
|
|
control as to the types of files a system is prepared to receive.
|
|
|
|
|
|
Relation of flags to presented addresses:
|
|
|
|
The EMSI-I specification does not allow qualification for any address
|
|
other than the PRIMARY address. This means that Link flags are limited
|
|
in application to either all presented addresses or to the primary
|
|
presented address only.
|
|
|
|
This extension also allows application of Link flags to specific
|
|
addresses other than the primary.
|
|
|
|
|
|
Distinctions between Calling and Answering System:
|
|
|
|
In the EMSI-I spec, the type of flags that may be presented is limited
|
|
by the status of the site. Certain flags may only be presented when
|
|
the site is the caller and other flags may only be presented when the
|
|
site is the answerer. This proposed extension removes this
|
|
distinction.
|
|
|
|
In the EMSI-I spec, certain Link and Capability (a.k.a: Compatibility)
|
|
flags are caller-driven, while others are controlled by the answering
|
|
system. This specification attempts to harmonize these discrepancies.
|
|
|
|
A attempt is made to remain somewhat backwards compatible and to have
|
|
new flags follow the original flag naming convention. However, IMHO,
|
|
it would be preferable to harmonize the flags; reducing the number of
|
|
them while retaining the fine type control, so that the same codes are
|
|
used in all sessions.
|
|
|
|
Under both EMSI-I and EMSI-II, any flags that are not understood, are
|
|
to be ignored. Therfore, if a site presents it's flags in EMSI-II
|
|
format and the other site does not do EMSI-II, it is permissable for
|
|
that site to interpret all flags according to EMSI-I specifications.
|
|
|
|
|
|
Specifics:
|
|
|
|
Compatibility flags:
|
|
|
|
Compatibility flags consist of a string of codes that specify the
|
|
PROTOCOL CAPABILITIES and ENABLED FEATURES of the mailer.
|
|
|
|
ARC, XMA
|
|
These EMSI-I compatibility flags have no meaning relavant to the
|
|
transfer of files and are not to be presented under EMSI-II. If
|
|
received, they are to be ignored.
|
|
|
|
|
|
FNC
|
|
The FNC EMSI-I compatibility flag has been identified as a 'mistake' by
|
|
the author of EMSI-I. This is agreeable as that specification called
|
|
for the creation of a filename that was ALWAYS 8.3, not
|
|
up-to-8.up-to-3.
|
|
It is not to be presented under EMSI-II. If received as a
|
|
compatibility flag, it is to be ignored.
|
|
|
|
|
|
Protocol Selection:
|
|
|
|
In the EMSI-I spec, a requirement is placed upon the calling system to
|
|
present it's available protocols in order of preference. A quote
|
|
follows:
|
|
|
|
The calling system must list supported protocols first and
|
|
descending order of preference (the most desirable protocol
|
|
should be listed first).
|
|
The answering system should only present one protocol and it
|
|
should be the first item in the compatibility_codes field.
|
|
|
|
Some mailer authors have interpreted 'the compatibility_codes field' in
|
|
the second sentence to mean that of the answering system, thereby
|
|
making protocol selection RECEIVER-PREFS driven. This interpretation
|
|
makes unnecessary the 'decending order' requirement placed upon the
|
|
calling system, so shall be considered in conflict with that
|
|
requirement.
|
|
|
|
Most mailer authors have interpreted that phrase to mean the
|
|
'compatibility_codes field' OF THE CALLER, thereby making protocol
|
|
selection CALLER-PREFS driven. Since EMSI-I was intended to be "a
|
|
clear protocol definition for state-of-the-art E-Mail systems to
|
|
follow", they cannot be faulted for interpretation. Caller-prefs
|
|
driven selection is state-of-the-art, receiver-prefs driven selection
|
|
is older technolgy, such as Wazoo.
|
|
|
|
This specification requires that the second interpretation,
|
|
CALLER-PREFS driven, be mandatory.
|
|
|
|
|
|
New Compatibilty Flags:
|
|
----------------------
|
|
|
|
EII
|
|
Indicates that the system will interpret flags under this
|
|
specification, if other end also presents this flag. IF either or both
|
|
systems do not present this flag, all interpretations are done
|
|
according to EMSI-I.
|
|
|
|
DFB
|
|
Indicates that the system presenting is capabable of fall-back to
|
|
FTS1/WAZOO negotiation in the case of failure of EMSI handshake or no
|
|
common protocol. Since ZMO is the minimum required protocol, NCP
|
|
should only occur if the answering system presents more than one
|
|
protocol.. (ie. it's broken)
|
|
|
|
FRQ
|
|
Indicates that the system will accept and process file requests
|
|
received during outbound calls. In other words, the calling system
|
|
will do a second turnaround for uni-directional protocols, to send the
|
|
files requested, at his cost.
|
|
|
|
NRQ
|
|
NRQ should be presented ONLY IF the mailer does not have a file request
|
|
server, task or function and cannot accept requests.. It should NOT be
|
|
used to indicate that the function is temporarly disabled.
|
|
|
|
When examined, No requests will be sent. It would be advisable that
|
|
the mailer alert the system operator of this occurance to prevent
|
|
continued polling of the remote site.
|
|
|
|
|
|
Protocol Capabilities:
|
|
|
|
Protocol capability flags are presented in decending order of
|
|
preference by the caller. The answering system selects and presents
|
|
the FIRST protocol from the callers list that it supports. The
|
|
answering system must present only ONE protocol.
|
|
|
|
HYD Hydra bi-directional (link flags define parameters)
|
|
JAN Janus bi-directional
|
|
TZA DirectZap (TrapDoor DirectZap varient)
|
|
DZA DirectZap (Zmodem variant, reduced escape set)
|
|
ZAP ZedZap (Zmodem variant, upe 8K blocks)
|
|
ZMO Zmodem w/1,024 packets (Wazoo ZedZip)
|
|
SLK SeaLink (no TYSNC, No MDM7, No TeLink)
|
|
(8-32k window/ReSync/OverDrive/LongNames)
|
|
|
|
NCP
|
|
This is presented if no compatible protocol can be negotiated under
|
|
EMSI. Since in most FTN networks, a common protocol DOES exist,
|
|
fallback to WaZoo and FTS1 negotiation is expected. If these
|
|
negotiation methods are not available, the session is terminated.
|
|
|
|
This condition should never occur under normal circumstances. It
|
|
should be considered as a problem with the design or configuration of
|
|
one of the mailers involved.
|
|
|
|
Link flags:
|
|
----------
|
|
|
|
Link flags consist of a string of codes that specify DESIRED CONNECT
|
|
CONDITIONS. They apply to the CURRENT SESSION ONLY. Under EMSI-I,
|
|
there are four TYPES of link flags: communications parameters, session
|
|
parameters, pickup options and hold options. Under EMSI-II, only three
|
|
types are used, the communications parameters type is REMOVED, as it
|
|
serves no purpose whatsoever in FTN operations.
|
|
|
|
|
|
Link Session options:
|
|
|
|
FNC
|
|
If either system presents this flag, it is an indication that the
|
|
presenting system requires filename conversion to cp/m-msdos
|
|
conventions. The other system will convert filenames to cp/m cpm/msdos
|
|
8.3 conventions before sending.
|
|
The convention is defined as a filename consisting of two
|
|
parts, the filepart and extension. The filepart and extension are
|
|
separated by a period ".". The filepart may be from 1 to 8 characters
|
|
in length and the extension may be from 0 to 3 characters. The
|
|
character set shall be any uppercase character in the range A-Z and any
|
|
numeric character in the range 0-9. If the extension is of zero
|
|
length, the period may or may not be present.
|
|
|
|
|
|
RMA
|
|
Indicates that the presenting site is able to send and process multiple
|
|
file requests. If both sites present this flag, the caller will send
|
|
any REQ files found for each AKA presented by the answering system.
|
|
The answering system will process each received REQ.
|
|
|
|
RH1
|
|
Indicates that under the Hydra protocol, batch one contains file
|
|
requests only, while batch 2 is reserved for all other files.
|
|
|
|
|
|
(others to be defined)
|
|
|
|
Pickup and Hold Flags:
|
|
|
|
Under the EMSI-I specification, Link Pickup flags are only presented
|
|
when calling (an Outbound Session) and are examined and processed only
|
|
when answering (an Inbound Session) and Link Hold flags are only
|
|
presented when answering (an Inbound Session) and are examined and
|
|
processed only when calling (an Outbound Session).
|
|
|
|
With EMSI-II, BOTH Pickup and Hold flags are presented by both sites
|
|
during a session. This allows more control for those systems, for
|
|
example, which cannot modify addresses presented or rotate akas to
|
|
change the primary address presented on a per-session or per-site
|
|
basis.
|
|
|
|
|
|
Link Pickup and Hold:
|
|
|
|
Each system can present one of three (or more) Link options related to
|
|
application of addresses. If neither of these flags are presented, PUA
|
|
is to be assumed.
|
|
|
|
Neither PUA nor PUP is to be presented if only one address was
|
|
presented.
|
|
|
|
PUP Pickup FILES for primary address only
|
|
/ PUA Pickup FILES for all presented addresses
|
|
/ PUn Pickup FILES for address number n in AKA list
|
|
one of |
|
|
\
|
|
\ NPU No FILE pickup desired. (calling system)
|
|
HAT Hold all FILES (answering system)
|
|
HAn Hold all FILES for address number n in AKA list
|
|
|
|
|
|
Qualifiers:
|
|
|
|
Qualifiers are processed in the order presented, with any conflict
|
|
being resolved by subsequent qualifiers overridding any conflicting
|
|
previous qualifier in the list.
|
|
|
|
Qualifiers may be not be presented with either NPU or HAT and should be
|
|
ignored if received with NPU or HAT.
|
|
|
|
PickUp:
|
|
|
|
PMO PickUp Mail (ARCmail and Packets) ONLY
|
|
PMn PickUp Mail ONLY for address number n in AKA list
|
|
|
|
NFE No TIC'S, associated files or files
|
|
attachs desired
|
|
NFn No TIC'S, associated files or file attaches,
|
|
for address number n in AKA list
|
|
|
|
NXP No compressed mail pickup desired
|
|
NXn No compressed mail pickup desired,
|
|
for address number n in AKA list
|
|
|
|
NRQ File requests not accepted by caller
|
|
This flag is presented if file request processing
|
|
is disabled TEMPORARILY for any reason
|
|
NRn File requests not accepted by caller
|
|
for address number n in AKA list
|
|
|
|
Note that NFE,NPX,NRQ != NPU
|
|
|
|
Hold:
|
|
|
|
HNM Hold all traffic EXCEPT Mail (ARCmail and Packets)
|
|
HNn Hold all traffic EXCEPT Mail (ARCmail and Packets)
|
|
for address number n in AKA list
|
|
|
|
HXT Hold compressed mail traffic.
|
|
HXn Hold compressed mail traffic.
|
|
for address number n in AKA list
|
|
|
|
HFE Hold tic's and associated files
|
|
and file attaches other than mail
|
|
HFn Hold tic's and associated files
|
|
and file attaches other than mail
|
|
for address number n in AKA list
|
|
|
|
HRQ Hold file requests (not processed at this time)
|
|
This flag is presented if file request processing
|
|
is disabled TEMPORARILY for any reason
|
|
HRn Hold file requests (not processed at this time)
|
|
for address number n in AKA list
|
|
|
|
Note that HXT,HRQ,HFE == HAT
|
|
</PRE>
|
|
|
|
<A HREF="index.htm"><IMG SRC="../images/b_arrow.png" ALT="Back" Border="0">Go Back</A>
|
|
|
|
</BODY>
|
|
</HTML>
|
|
|