From: carl@macbeth.umd.edu (Carl Symborski)
Newsgroups: comp.dcom.cell-relay
Subject: cell-relay monthly FAQ posting (long)
Summary: First edition FAQ for this list
Keywords: FAQ
Date: 8 Oct 92 03:06:44 GMT
Organization: University of Maryland, College Park

[First edition: 01 Oct 92]

This article contains the answers to some Frequently Asked Questions (FAQ)
often seen in comp.dcom.cell-relay.  It is posted to provide information
of general interest to both new and experienced readers. 

The FAQ list includes answers to the following questions, which are loosely
grouped into categories.  Questions marked with a + indicate questions new to
this issue; those with significant changes of content since the last issue 
are marked by *:

 A)+ TOPIC: COMP.DCOM.CELL-RELAY BASIC INFORMATION
  A1)+ What is the CELL-RELAY group?
  A2)+ What is the archive site for this group?
  A3)+ Is there a parallel mailing list for this group?
  A4)+ What other mailing lists are related to ATM?
 B)+ TOPIC: INDUSTRY FORUMS AND VENDOR INFORMATION
  B1)+ How can I contact the ATM Forum?
  B2)+ What vendors are working on ATM technology?
 C)+ TOPIC: ATM REFERENCES 
  C1)+ What are some good getting started ATM references?
  C2)+ Where/What is the "Network Compatible ATM for LANs" document?
  C3)+ Where are hosts with ATM related information?
  C4)+ How can I get the ATM Forum's Interface Specification?
 D)+ TOPIC: ATM TECHNOLOGY QUESTIONS
  D1)+ What are the various ATM Access layers?
  D2)+ Are ATM cells delivered in order?
  D3)+ What do people mean by the term "traffic shaping"?
  D4)+ What is happening with signalling standards for ATM?
 E)+ TOPIC: ATM VS. XYZ TECHNOLOGY
  E1)+ How does ATM differ from SMDS?

If you have suggestions or corrections for any of these answers or any
additional information, please send them directly to carl@umd5.umd.edu;
the information will be included in the next revision (or possibly the one
after that).

This posting is intended to be distributed at approximately the beginning
of each month.  New versions may be archived on mythos.ucs.indiana.edu

The information contained herein has been gathered from a variety of sources.
Most derived from a consensus of postings on the group.  If you would like to
claim responsibility for a particular item, please let me know.

Carl Symborski
carl@umd5.umd.edu


-----------------------------------------------------------------------------
TOPIC:     A) + TOPIC: COMP.DCOM.CELL-RELAY BASIC INFORMATION
-----------------------------------------------------------------------------
SUBJECT:  A1) + What is the CELL-RELAY group?

	The purpose of this group is to provide a forum for the submission
of articles and inquiries dealing with networks using Cell Relay as a 
transport; including local, metropolitan, and wide area networks.  The
name cell-relay was chosen as a compromise over objections to the name
"ATM" during the creation of this group.  The acronym ATM in the context of
this group stands for Asynchronous Transfer Mode, not Automatic Teller 
Machines or Adobe Type Manager.  The term "cell" in cell-relay is taken to 
mean a small, fixed sized, information bearing unit that provides the 
foundation for transport and multiplexing of user traffic.  This topic 
area is not related to cellular phones or intra-cellular organisms.


SUBJECT:  A2) + What is the archive site for this group?

	The archives for comp.dcom.cell-relay are available via anonymous 
ftp to mythos.ucs.indiana.edu (129.79.17.52) as:

	pub/cell-relay/archive/YY-MM.mbox

where YY=year and MM=month.  There are available in both
compressed and normal formats.

	Additionally there is a WAIS-based bibliography of ATM related 
research papers.  This is available on the same host under:

	pub/cell-relay/bib


SUBJECT:  A3) + Is there a parallel mailing list for this group?

	A direct mailing list has been setup which is a mirror of the USEnet
newsgroup comp.dcom.cell-relay. To send mail TO the list, send it to:

	comp.dcom.cell-relay@news-relay.indiana.edu

To un/subscribe, or send other notes to the list management, please use the 
address:

	cell-relay-request@mail-relay.indiana.edu


SUBJECT:  A4) + What other mailing lists are related to ATM?

	There are two other mailing lists.  One is for an IETF group working 
on the issue of IP over ATM.  This work is on going and primarily focused on 
that task.  General ATM questions and blue-skying are inappropriate and 
discouraged by the members on the list.  To send mail TO the list, send it to:

	atm@sun.com

To un/subscribe, or send other notes to the list management, use the address:

	atm-request@sun.com

	The other list is associated with the general problem of IP over large
public networks.  As with the ATM list above, its purpose is for an IETF
working group.  The same restrictions apply.  To send mail TO the list, send
it to:

	iplpdn@NRI.Reston.VA.US

To un/subscribe, or send other notes to the list management, use the address:

	iplpdn-request@nri.reston.va.us


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TOPIC:     B) + INDUSTRY FORUMS AND VENDOR INFORMATION
-----------------------------------------------------------------------------
SUBJECT:  B1) + How can I contact the ATM Forum?
	
	Similar to the Frame Relay Forum, the ATM Forum is an open public 
forum with over 80 contributing and auditing companies.  Membership includes 
many international companies.  Some companies also participate in ANSI T1S1 
and other standards bodies.  Those interested in joining the forum or needing
additional information shoud contact the ATM Forum's secretariat, Interop Inc
at (415) 962-2585.  Audit membership of the Forum is $1000/year.


SUBJECT:  B2) + What vendors are working on ATM technology?

	It is tough to get a number on this.  There are a few companies with
hardware they can demonstrate.  More who have made product announcements.
Many more who have stated product intentions.  Some are building big
central office switches, others smaller ones for the LAN market.  Workstation
vendors are working on ATM interface boards.  Chip companies are working on
ATM chip sets, etc.  Some switch vendors mentioned on this list with 
hardware available this year include for the small switch market include:
Fore Systems, Adaptive, and MPR Teltech Ltd.  Naturally the big telco switch 
vendors (NEC, Hitachi, etc.) are developing big central office type switches.  

	In addition there is a group in North America working on a low-cost 
SONET-based ATM physical layer chips for local nets using optics and twisted 
pair interfaces.  This group is called the Saturn Development Group, and 
consists of PMC-Sierra, Sun Microsystems, Ungermann-Bass, Bell-Northern 
Research, Interphase, Optical Data Systems, SynOptics Communications, 
Newbridge, Themis Computer, BBN, MPR Tetltech, and the University of British 
Columbia. 

-----------------------------------------------------------------------------
TOPIC:     C) + ATM REFERENCES
-----------------------------------------------------------------------------
SUBJECT:  C1) + What are some good getting started ATM references?

	Generally it is hard to pick up any communications related technical
journal, conference, or trade publications and not find something about ATM.
Most of what has been written in the 1985 through 1990 time frame primarily
deals with the application of ATM to Broadband ISDN.  These provide the 
foundation on which other applications of ATM have been based and therefore
should not be over looked.

The following references offer a good base of background information.

--General:

"Data Communications Special Guide", IEEE Spectrum, 8/91, p.22.
   o Hi-level overview of high-speed lans, wans, bisdn, atm, with glossary
   and bibliography.

IEEE Communications Magazine, April 1992, VOL. 30, NO. 4
   o This is a special issue with six articles on gigabit networks technology.

"Cell Relay Switching", Data Communications, 9/91, p.58.
   o Looks at cell relay and switching in general, not just ATM.

Rainer Handel and Manfred Huber. "Integrated Broadband Networks: An
   Introduction to ATM-Based Networks". Addison-Wesley, 1991.
   ISBN 0-201-54444-X. 230 pp.


--ATM:

"Overview of ATM Networks: functions and procedures", Computer Communications,
   12/91, p.615.
   o Cell headers, bit definitions and the like. 33 References, including
   good list of CCITT recommendations.

"Broadband ISDN and Asynchronous Transfer Mode (ATM)", IEEE Communications,
   9/89.
   o Describes most of the jargon as well as the paradigm and unresolved
   issues.  One point to note is that the article is fairly old (1989) and
   some things have changed.  For example, the ATM cell headers described
   are no longer valid.

--SWITCH FABRICS:

These papers offer a fast jump start on ATM switch architectures, design
issues and tradeoffs.

H. Ahmadi and W. Denzel, "A Survey of Modern High-Performance Switching
   Techniques", IEEE J on Selected Areas in Comm, Vol. 7, No. 7, Sept 1989, 
   p. 1091-1103

F. Tobagi, "Fast Packet Switch Architectures for Broad-band Integrated
   Services Digital Networks", Proceedings of IEEE, Vol. 78, No. 1, Jan. 1990,
   p. 133-167

Joseph Y. Hui, "Switching and Traffic Theory for Integrated Broadband 
   Networks", Kluwer Academic Publishers, 1991,  ISBN 0-7923-9061-X
   o A back to basics text book explaining core switching concepts like
     batcher/banyon, clos, min, buffering, etc.


SUBJECT:  C2) + Where/What is the "Network Compatible ATM for Local Network 
                Applications" document?

"Network Compatible ATM for Local Network Applications", V1.0, April 3, 1992.
A proposal for a 150 Mb ATM LAN from Apple, Bellcore, Sun and Xerox.
Available in standard postscript and compressed standard postscript from:

thumper.bellcore.com: /pub/nclatm/nclatm.ps
/pub/nclatm/nclatm.ps.Z
ftp.apple.com:        /pub/latm/nclatm.ps
/pub/latm/nclatm.ps.Z
parcftp.xerox.com:    /pub/latm/nclatm.ps
/pub/latm/nclatm.ps.Z


SUBJECT:  C3) + Where are hosts with ATM related information?

	Here's a list of sites that that seem to cater to the 
ATM/broadband/real-time continuous-media crowd:

cc-hw.bbn.com                Rec_I_cls.ps, Rec_I_cls.hqx
icsi-ftp.Berkeley.EDU        Research, Continuous media
wuarchive.wustl.edu          Research, ATM Hardware
datanet.tele.fi              Standards drafts
lcs.mit.edu                  ??
nsco.network.com             HIPPI
gregorio.stanford.edu        IP Multicast

(Source: Allen Robel, robelr@mythos.ucs.indiana.edu)


SUBJECT:  C4) + How can I get the ATM Forum's Interface Specification?

	The ATM Forum has produced a document called the User-Network
Interface specification.  For those which are not ATM Forum members,
hard copy can be obtained for a nominal reproduction fee from the
ATM Forum's secretariat, Interop Inc. at (415) 962-2585.


-----------------------------------------------------------------------------
TOPIC:     D) + ATM TECHNOLOGY QUESTIONS	
-----------------------------------------------------------------------------
SUBJECT:  D1) + What are the various ATM Adaptation layers?

	In order for ATM to support many kinds of services with different
traffic characteristics and system requirements, it is necessary to adapt
the different classes of applications to the ATM layer.  This function is
performed by the AAL, which is service-dependent.  Four types of AAL were
originally recommended by CCITT.  Within the past year a fifth type of
AAL has been proposed. 

	Briefly the five ATM adaptation layers (AAL) have/are being defined:

AAL1 - Supports connection-oriented services that require constant bit rates
       and have specific timing and delay requirements.  Example are constant
       bit rate services like DS1 or DS3 transport.

AAL2 - Supports connection-oriented services that do not require constant
       bit rates.  In other words, variable bit rate applications like
       some video schemes.

AAL3 - Intended for connection-oriented variable bit rate data services and
       associated signalling.  Presumed application would be WAN interconnect.

AAL4 - Intended for connectionless variable bit rate data services.  Example
       application would be the interconnection of SMDS networks.

AAL5 - Supports connection-oriented variable bit rate data services.  It is
       a substantially lean AAL compaired with AAL3/4 at the expense of
       error recovery and built in retransmission.  This tradeoff provides
       a smaller bandwidth overhead, simpler processing requirements, and
       reduced implementation complexity.  Some organizations have proposed
       AAL5 for use with both connection-oriented and connectionless services.

A recent document which describes these (except AAL2) with frame formats is:
"Asynchronous Transfer Mode (ATM) and ATM Adaptation Layer (AAL) Protocols
Generic Requirements",  Bellcore Technical Advisory, TA-NWT-001113, Issue 1,
August 1992.


SUBJECT:  D2) + Are ATM cells delivered in order?

	Yes.  The ATM standards specify that all ATM cells will be delivered
in order.  Any switch and adaptation equipment design must take this into
consideration.


SUBJECT:  D3) + What do people mean by the term "traffic shaping"?

Traffic shaping is forcing your traffic to conform to a certain specified
behavior.  Usually the specified behavior is a worst case or a worst case
plus average case (i.e., at worst, this application will generate 100 Mbits/s
of data for a maximum burst of 2 seconds and its average over any 10 second
interval will be no more than 50 Mbit/s).

Of course, understand that the specified behavior may closely match the
way the traffic was going to behave anyway.  But by knowing precisely
how the traffic is going to behave, it is possible to allocate resources
inside the network such that guarantees about availability of bandwidth
and maximum delays can be given.

(Source: Craig Partridge, craig@bbn.com)

A variety of techniques have been investigated to implement traffic shaping.
Reference the literature for keywords such as "leaky bucket", "congestion",
"rate control", "policing".


SUBJECT:  D4) + What is happening with signalling standards for ATM?

The ATM Forum Technical Committee has a Sub-Working Group that is
actively working on signalling.  Most ATM LAN vendors, including Fore
Systems are members of this Sub-Working Group.  Currently focus is
in discussing the requirements for signalling in private ATM networks.

Additionally, the ANSI T1S1 as well as the CCITT sudygroup XI are concerned 
with ATM signalling.  An observation would lead one to believe
that because of the frequency of meetings of The ATM Forum, work
may progress more rapidly than work in T1S1 and CCITT. 


-----------------------------------------------------------------------------
TOPIC:     E) + TOPIC: ATM VS. XYZ TECHNOLOGY
-----------------------------------------------------------------------------
SUBJECT:  E1) + How does ATM differ from SMDS?

	SMDS is really just the "service offering interface" and doesn't
specify how the network carries data internally.  SMDS as a service is
based on 802.6 MAN specifications and provides a datagram service
with 60 bit global addresses and up to 9+KB of data.  But The lower
layers of SMDS break the traffic into ATM cells which are currently
encapsulated in a TDM transmission stream (T1, T3, E1, etc).  The intent
is obviously to employ an ATM switching fabric when that is available
within the telephone switching domain.  One of the main things SMDS
does is to hide the VCI/VPI managament (done by the entry switch) and
perform data duplication for a limited multicast capability.

(Source: Art Berggreen, art@acc.com)