Does Cisco consider ATM only suitable for LAN, not WANs

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A practice exam claims ATM is only suitable for LANs due to distance
limitatons.  The web pages I find on the WWW talk about ATM being used
by telcos for long distance communications.  Is the exam incorrect, or
is this a case of Cisco asserting their own opinion as the rule?



Re: Does Cisco consider ATM only suitable for LAN, not WANs



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The practice exam was written by an idiot. ATM was never intended to be a
LAN protocol (it uses a small, constant cell size for very fast switching,
to facilitate aggregating thousands of PVCs on a circuit) and LANE was the
biggest nightmare of Cisco's, 3com and Lucent's existence.

ATM is the primary layer-2 protocol for the internet backbone. It is the
primary layer-2 protocol for all WAN connections (that aren't PTP HDLC). In
fact, if you have a frame-relay connection, odds are it is ATM as soon as it
leaves the first switch.

LANE is dead (thank whatever higher power you believe in).



Jonathan




Re: Does Cisco consider ATM only suitable for LAN, not WANs


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<snip>
I'm interested, why was it so bad?

Dave.






Re: Does Cisco consider ATM only suitable for LAN, not WANs



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a
switching,
the

It didn't work.

Firt off, you have to replace the ethernet NICs in your PCs (at about $400
per), then you have to run fiber everywhere (the base connection was an
OC-3), then you had to start buying ATM servers for registration (BUS,
LECS), and let us not forget the complexities involved here. Insted of a MAC
address you use an NSAP (an example:
47.0091.8100.0000.1111.1111.1111.2222.2222.2222.00) Then, on top of all of
this crap, you are now running IP.

Of course, your infrastructure costs just spiked through infinity as you
started buying ATM switches and then wondering how you were going to make it
all work together.

The real problem is just beginning, because none of the vendors knew how to
make it work either.




Jonathan






Re: Does Cisco consider ATM only suitable for LAN, not WANs


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Jonathan,
Thanks for letting me know.

Dave.




Does Cisco consider ATM only suitable for LAN, not WANs


Then why was ATM just announced to be removed from the CCIE written ?


On Wed, 24 Aug 2005 11:34:49 -0500, "Jonathan"

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Re: Does Cisco consider ATM only suitable for LAN, not WANs


ATM has seen its days and will start going away. The trend is to go towards
GigE, even in the long haul/backbone.


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switching,
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In
it




Re: Does Cisco consider ATM only suitable for LAN, not WANs


j_agosta@remove_wideopenwest.kom says...
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The biggest stupidity in this is that companies like Cisco are putting
so much effor to create "ATM service like" form GigE that it becomes
funny...

--
Ivan

*** User rot13 to see my eMail address ***


Re: Does Cisco consider ATM only suitable for LAN, not WANs


vina.bfgerf@mt.g-pbz.ue says...
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This statement was about WAN connections (read MetroE) and not about
LAN. In LAN, ethernet was and is the top.


--
Ivan

*** User rot13 to see my eMail address ***


Re: Does Cisco consider ATM only suitable for LAN, not WANs



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towards

I don't know if I'd agree with this being a 'stupid' trend. The high speed
ether solutions are much more elegant, cleaner, simpler,
and are more bandwidth efficient than ATM. Some commercial DSLAMs are now
going GigE / dot1q instead of ATM on the backhaul side. I beleive that very
soon the only place ATM will be found is on DSL subscriber loops. Many
people feel there's no need any more for the hocus pocus, SAR/AAL that ATM
incorporates; there are more BW efficient means now to offer QoS, and
carriers like the idea of making more BW available for billable purposes.





Re: Does Cisco consider ATM only suitable for LAN, not WANs



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ROFLMAO


Really?

Except for the ONS stuff, most provider's backbones are pure ATM running
over OC-3s, 48s and 192s.

And what happens when you start aggregating a few hundred thousand customers
on ethernet?



Jonathan

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or
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as




Re: Does Cisco consider ATM only suitable for LAN, not WANs



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customers

Hope the floor is clean.   ;-)

I did not mean to imply that  carrier networks, as they are today, do not
deploy ATM. I meant to make a case that many people, including carriers, are
considering the future of their networks, and the possibility that ATM may
not be the fundamental building block of these future networks that it is
today.

Perhaps you've read me wrong, or I could have been clearer in what I stated.
Maybe the word 'trend' should read "future."
Many believe that soon all information will be IP based. Or at least a
majority of it. Some of these people also believe that when this happens,
placing packets directly on fiber with DWDM (and related/similar transports)
will reduce and/or eliminate the need for ATM.  There are many papers that
talk about this.  There are many standards working groups discussing these
issues. When discussing the all "optical internet," this idea is in the
forefront.

I have installed DSLAMs that have already moved away from the tradditional
ATM backside ('backside' being facing away from the DSL subscriber) to a
GigE/dot1q model.

The fact remains that ATM solutions include more overhead than GigE
solutions, and many organizations have recognized this.

So really, you can get up off the floor now.

Back to the original question, if I may.......

So why DID Cisco remove ATM from the exam? Surely not because they are
"stupid."
There must be some rationale for doing so, and I simply took a stab at
offering up one possibility for consideration.

Be well.

-ja



PS

Here's an interesting article sort of related to the topic. Lots more out
there, too in cyberspace....

http://www.cisco.com/en/US/netsol/ns341/ns396/ns223/ns227/networking_solutions_package.html

Scroll down to white papers, and click on the Ethernet in the WAN pdf.

Cheers, again.




Re: Does Cisco consider ATM only suitable for LAN, not WANs



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are

While I do not think ATM at and to the prem is going to be around forever,
as a long-haul, mass-aggregator of PVCs, ATM is the bomb.

Since each cell is a constant size, my switches don't need to look at every
single bit to determine when one chunk ends and another begins, so I can
just chop at every 53-bytes.

Also, ATM is the only layer-2 (read that again) protocol that has inherent
QoS built into from an initial design perspective (instead of Ethernet where
they have been modifying it constantly to keep it alive since the 1970s).

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stated.

So do I.

What does that have to do with ATM?

ATM is specifically a Layer-2 protocol, it doesn't care what layer-3
protocol is running on it.

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Except for ATM machines (which still run SDLC (because they are bloody
masochists), I see very little that will not be IP-based.

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transports)
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GigE is packet over Sonet... in a way...

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But from the prem to the DSLAM, it is pure, good-old-fashioned ATM.

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Yes, but if you are a service provider, your primary concern is aggregating
as many PVCs as possible.

Doing this on Ethernet is nuts... Even if you do VLAN tunneling, you are
still restricted to about 4000 Customers (that is very on the high side).

We have OC-192s carrying a hundred thousand PVCs (all DS0s).

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Well, they are.

ISDN BRI is a core technology for backing up frame-relay circuits. Why did
they remove that? Cuz they are dumb.



Jonathan




Re: Does Cisco consider ATM only suitable for LAN, not WANs



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running
not
may
is
every
where
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tradditional
aggregating

Maybe they see a "trend" to migrate to DSL for backup?

;-)






Re: Does Cisco consider ATM only suitable for LAN, not WANs



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Probably the same idiotic reason they removed ISDN.



Jonathan

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switching,
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