Internet DRAFT - draft-giordano-fax-method-priority
draft-giordano-fax-method-priority
Internet-Draft Daniele Giordano
Expires: 5 May 2008 2 November 2007
Priority of transport method for fax over IP
draft-giordano-fax-method-priority-01
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
In order to fax over IP networks different methods can be used. In
many countries fax are legal documents. What is the best way to
deliver fax? What is the most reliable method?
This document proposes a priority of transport method for fax over
IP.
Daniele Giordano [Page 1]
Internet-Draft priority of transport method for fax over IP Oct 2007
Table of Contents
1. Conventions Used In This Document . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Implementation and Operations . . . . . . . . . . . . . . . . . 3
4. Notes of implementation . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 6
Daniele Giordano [Page 2]
Internet-Draft priority of transport method for fax over IP Oct 2007
1. Conventions Used In This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction
In order to fax over IP networks different methods can be used. In
many countries fax are legal documents. What is the best way to
deliver fax? What is the most reliable method?
This document proposes a priority of negotiation of transport method
for fax over IP.
The goal of this draft is offer the best assurance in fax delivery.
The discussion is not focus on the efficiency of signaling voice
protocols over IP networks.
Traditionally, faxes uses TDM techniques with ensured synchronization
throughout the network. This strict clocking allowed faxes to use
complex audio techniques and high rates of throughput. Given the
burst nature of packet based networks the clocking synchronization is
not guaranteed so the transmission of facsimile can be problematic.
There are three techniques for sending faxes over IP consisting of
fax pass through, real-time fax relay and fax store and forward.
3. Implementation and Operations
The fax over IP transmission starts from the end user or the customer
premises equipment e.g. ATA, POTS or PSTN gateway, fax server, etc.
These devices MUST negotiate a facsimile method using this priority:
1) CONSIDERATION and FIRST SELECTION
----------------------------------------
| fax isn't an interactive application |
----------------------------------------
|
| ----------------------------------------------
-->| fax isn't a real time critical application |
----------------------------------------------
|
| ------------------------------------------------------------
-->| the first choice is Store and Forward fax on the network |
------------------------------------------------------------
Store and Forward faxing retry continuously until successful and
offer never busy fax service.
All Store and Forward fax services MUST be used in the FIRST
SELECTION. [T.37] protocol and subsequent similar implementations
MUST be used in the FIRST SELECTION.
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--------------------------------------------
| if Store and Forward is not supported or |
| not negotiated pass to second selection |
--------------------------------------------
2) SECOND SELECTION
----------------------------------
| fax is a real time application |
----------------------------------
|
| --------------------------------------
-->| the choice is real time fax relay |
--------------------------------------
All fax relay services MUST be used in SECOND SELECTION.
[T.38] protocol, vendor-proprietary fax relay method and subsequent
similar implementations MUST be used in the SECOND SELECTION.
----------------------------------------
| if fax relay is not supported or not |
| negotiated pass to third selection |
----------------------------------------
3) THIRD SELECTION or LAST CHANCE
-----------------------------------
| last choice is fax pass-through |
-----------------------------------
Fax pass-through is susceptible to packet loss, jitter, and latency
in the IP network. So this is the last chance. All fax pass-through
services like pass-through upspeeding, pass-through with [NSE],
clear channel transmission, transparent transmission and similar
implementation MUST be used in the THIRD SELECTION.
4. Notes of implementation
Redundancy transmission techniques, error correction mode and
variation of simple duration are not mentioned because the scope is
adopt a rigid priority during negotiation of fax over IP method.
This doesn't mean that all vendors must implement all fax services in
their devices. I explain this concept with an example. If an ATA or
Analog Telephone Adapter supports only pass-through method, It will
choose the THIRD SELECTION or LAST CHANCE. If it supports also T.38,
It MUST to try that before of other.
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5. IANA Considerations
None.
6. Security Considerations
This document is not directly concerned with security.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[T.38] International Telecommunication Union, "Procedures for
real-time group 3 facsimile communication over IP networks",
Recommendation T.38, Telecommunication Standardization Sector
of ITU, Geneva, Switzerland, June 1998.
[T.37] International Telecommunication Union, "Procedures for the
transfer of facsimile data via store-and-forward on the
Internet", Recommendation T.37, Telecommunication
Standardization Sector of ITU, Geneva, Switzerland, June 1998.
[NSE] AVT Working Group, Petrack, Vocaltec, "RTP Payload for
Telephone Signal Events", draft-ietf-avt-telephone-tones,
November 1998.
Daniele Giordano [Page 5]
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Author's Address
Daniele Giordano
Email: d.giordano@fastpiu.it
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Daniele Giordano Expires: 5 May 2008 [Page 6]
