I can give some first hand knowledge being in the industry of ATM sales. We
haven't sold ATM in Portland metro for quite some time. Not because it is
dead or because it is not functional but simply because it's to difficult
for the average broadband consumer to understand. On paper it's simple. It's
the implementation, maintenance and tuning they find difficult to
understand. To overcome this ignorance and lack of willing we sell a product
called TLS (Transparent LAN Service.) This is essentially ATM handed off to
a device which converts to 10/100 Ethernet. Even this is getting harder to
sell as we move to an IP centric environment and customer's generally need
simple Internet access or a clear channel pipe. You'll still find ATM in
bigger shops who have had ATM for some time now and have found that it
suites their needs or have simply invested so much capital in hardware that
it wouldn't make sense for them to move away. With QoS being quickly
developed for Internet based applications most customer's find that these
new devices will suite their needs. This is just my opinion. ;)
-Bart Kurek
Sales Engineer
Electric Lightwave Inc. (ELIX)
http://www.eli.net
mailto:[EMAIL PROTECTED]
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, August 30, 2000 7:31 AM
Subject: RE: ATM Dead?
> Hi Group,
> I think labelling the ATM technology as dead would be an "overkill". ATM
has
> its advantages as well as disadvantages. Mere opinions don't change facts.
> Following are some facts about ATM:
>
> ATM has evolved as a stable connection oriented transport that currently
> operates, ATM switch to ATM switch at up to OC-48 line rates. It also
lends
> itself ably to traffic engineering (prior to MPLS it was the only
technology
> that offered traffic engineering features). It delivers many advanced
> features such as PVC creation from any ingress to any egress in a given
ATM
> backbone, sophisticated ( but complicated ) signaling to simplify path
> creation and re-routing around failures, and QoS features for bandwidth
> reservation, constant bit rate, variable bit rate, and unspecified bit
rate
> services, applied to the cell.
>
> However, with these advantages, ATM also has certain drawbacks. The first
> and foremost being that of "overhead". ATM consumes nearly 10% of
available
> bandwidth with a 5 byte cell header for each 48 byte payload cell, plus an
> additional 5% is needed for the adaption layer for IP over ATM as per RFC
> 1483. For example, an ATM OC-48 link requires 494Mbit/sec for overhead.
> Compounding the bandwidth issues is ATM's limited scalability at higher
link
> rates. ATM switches have only recently delivered OC-48 interface rates and
> it is questionable whether OC-192 is feasible considering the overhead
> associated with segmentation and reassembly, wasted bandwidth, and other
> inefficiencies of pushing 53bytes across 10Gbit/sec links. Today the
fastest
> IP router ATM interface is OC-12, which creates a bottleneck with the
advent
> of OC-192 capable transport systems.
>
> When ATM is used as the transport for delivering IP in the Internet core
we
> face a different set of issues. ATM requires its own administrative domain
> distinct from IP at Layer 3. The ATM network elements must be
interconnected
> in such a way to provide redundancy. The entire ATM topology is
transparent
> to the IP Layer 3 topology. Therefore a second topology at Layer 3 must be
> overlaid atop the ATM fabric. This is achieved by establishing PVC's
between
> layer 3 routers. This creates another set of problems:
>
> 1. Two separate modalities are required for element management adding
> complexity and cost to network management.
>
> 2. IP route exchange with an IGP requires direct peering/adjacency with
all
> neighbors, therefore the number of PVC's required grow by a factor of
> n-to-the-power-2; where n is the number of internal IGP routers. For
> example, for 300 routers: 44,850 PVC's would be necessary to establish a
> complete mesh. If 4 more routers are added the PVC count jumps to 46,056
(an
> increase of 1206 PVC's). This represents a substantial
network-provisioning
> problem. In the event of a router failure in this scenario, the surviving
> routers will issue IGP routing updates on the order of n-to-the-power-3
(300
> routers would issue 27 Million updates). This effect can be reduced by
> configuring route-reflectors/confederations, however, it still adds to the
> complexity and becomes a provisioning nightmare.
>
> 3. ATM uses its own signaling protocol (PNNI) to establish PVC's. IP uses
> OSPF, IS-IS, and BGP as its signaling protocols. The two signaling layers
> operate independently and therefore complicate interworking between the
> layers. To gain advantage of ATM traffic engineering features IP signaling
> protocols must run within the ATM PVCs.
>
> The question boils down to Howard's C. Berkowitz's often-quoted saying,
> "What is the problem that you are trying to solve ? Knowing the advantages
> and disadvantages that ATM offers, educated choices regarding its usage
can
> be made depending upon one's application.
>
> Aziz S. Islam
> marchFIRST Inc.; http://www.marchFIRST.com
> 55 York Street, Ste. 1500
> Toronto/ON M5J 1R7/CANADA
> ph:(416)368-2222 Ext. 211
> fx:(416)366-6667
> pg:(416)563-7355
> mailto:[EMAIL PROTECTED]
> mailto:[EMAIL PROTECTED]
>
>
> ___________________________________
> UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html
> FAQ, list archives, and subscription info: http://www.groupstudy.com
> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
>
___________________________________
UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html
FAQ, list archives, and subscription info: http://www.groupstudy.com
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
