Why ATM protocol is used for DSL.

1. Conversion of signals and FDM is DSL's concern and not that of ATM ... ATM runs over DSL
2. IP has a tendency to club together packets for the same destination in order to minimize the number of packets that need to be processed and put on wire .... The resulting delay *IS* a concern
3. Any host in the path cannot cannot fragment IP packets at will .... specifically IPv6 requires the host to return failure if it cannot transmit packets of a given size and NOT to fragment them ... v4 does not have that regulation but it cannot fragment a packet if a particular bit in the header is set ...

Hi Venabili,

ZiaTioN's answer is misleading and does not address the original question at all !!

sunnycoder

I am not going to argue what is misleading and what is not. I also will not argue semantics over a topic that all depends on how you look at it.

Bottom line is normal DSL connectivity is not "real time traffic" like voice or streaming video therefore the delay issues are NOT a concern. Also if you want to talk delay then you should point out that no carrier in the world has a network completely comprised of ATM gear and technology so the conversion from ATM to IP through the SAR (Segmentation and Re-assembly) process WILL be performed at some time throughout the connection (if not more than once) and this in and of itself adds more delay than anything else you could think of. Especially if the SPVC is overcommited which is a very common practice among Telco's

I could care less about these points. I am only interested in people not getting biased or narrow minded information such as sunnycoder has posted. If you want all the points, take them. Hell you can have all the points I currently have too if that is what makes you happy.

Oh and every aspect of my original answer addressed the question. They asked why IP could not be used for DSL like ATM and I stated that it can be and is used. I also addressed why it is more common to see an ATM ADSL line for residental than it would be to see an IP SDSL line.
I also never stated that FDM was an ATM function and quiet clearly stated it was a DSL function in the DSLAM equipment used to mux and demux the broadband signalling from the voice signalling.

Maybe you do not understand the topic and therefore did not understand my response.

>Bottom line is normal DSL connectivity is not "real time traffic" like voice or streaming video
>therefore the delay issues are NOT a concern.
What are the kind of service you would typically run when you get a DSL connection? Yahoo messenger perhaps?
Moreover, I did not say this was the only reason for using ATM over DSL. This was one reason. Another was fast switching.

>Also if you want to talk delay then you should point out that no carrier in the world has a
>network completely comprised of ATM gear and technology so the conversion from ATM to IP
>through the SAR (Segmentation and Re-assembly) process WILL be performed at some time
>throughout the connection (if not more than once) and this in and of itself adds more delay than
>anything else you could think of. Especially if the SPVC is overcommited which is a very common
>practice among Telco's
ATM is quite prevelant in core and IP exists there solely because it was there before ATM ... This is what makes interoperability with IP necessary .... If what you say were remotely true, no ATM networks would ever have been setup much less the new tier0 providers would have preferred to use ATM

>I could care less about these points. I am only interested in people not getting biased or narrow
>minded information such as sunnycoder has posted. If you want all the points, take them. Hell
>you can have all the points I currently have too if that is what makes you happy.
This is personal comment and I am not going to respond to it since I am not interested in starting a flame war.

>Oh and every aspect of my original answer addressed the question. They asked why IP could
>not be used for DSL like ATM and I stated that it can be and is used.
"Why not TCP/IP protocol is used for these networks." was what asker said ... I believe we all understand the difference between could not be used and not used

>I also addressed why it is more common to see an ATM ADSL line for residental than it would
>be to see an IP SDSL line.
I can't see it

>I also never stated that FDM was an ATM function and quiet clearly stated it was a DSL function
>in the DSLAM equipment used to mux and demux the broadband signalling from the voice signalling.
I never claimed that you said that. However, your description of the technology was quite untechnical (for the lack of better term). Moreover, FDM is not the only for "ADSL" echo cancellation can also be used. "VDSL" uses TDMA and a variation of FDM and other DSLs use different techniques

>Maybe you do not understand the topic and therefore did not understand my response.
Again a personal comment. I digress.


Venabili,

I shall be leaving for a vacation in a couple of hours so I shall not be replying in this question anymore. I leave the disposition upto you.

Regards,
sunnycoder

>If what you say were remotely true, no ATM networks would ever have been setup much less the new tier0 providers would have preferred to use ATM
This is probably the most redicilous thing you have said so far. This could not be farther from the truth.

>I never claimed that you said that.
Proof: Conversion of signals and FDM is DSL's concern and not that of ATM ... ATM runs over DSL

>However, your description of the technology was quite untechnical (for the lack of better term).
I can get as technical as you want here anytime. I choose to put it in terms someone who does not know ATM technology might be able to understand it. I have no interest in spouting out industry terms and technical data to make myself appear smart or knowledgable.  The understanding of the material at hand is what interest me and what helps the average user.

>Moreover, FDM is not the only for "ADSL" echo cancellation can also be used. "VDSL" uses TDMA and a variation of FDM and other DSLs use different techniques
Now you are being rediculous. I also never stated this and made it quiet clear that ADSL was one beast and SDSL (and any other DSL for that matter) is completely different. Stop trying to fish for a fight, you will not get one here.

I work with carrier class Cisco and Marconi ATM switches daily that are capable of doing terabyte switching. Anyone who reads this can choose to beleive what I say or not. It makes absolutely no difference to me.