RE: [L2CP] RE: Wadhwa new draft 01- Encapsulation

["Derek Harkness" <[e-mail]>]

It would also seem to me desireable to keep the approach consistent with
other approaches such as the PPPoE IA/DHCP stuff from DSLF TR-101 as
then the internal handling can be easier as it has the encapsulation
information from local config, and/or PPPoE IA/DHCP Options and/or L2C,
depending on the application and customer preference. 
 
Then the BNG knows the local loop type (ATM or Eth) from the DSL type
and knows the local loop encapsulation - and its local encapsulation
where this differs (e.g. additional VLAN tags) - and should be able to
set the shaping accordingly.
 
The only potential fly in the ointment is that there is on some DSL
types a kind of "L1andabit" framing overhead - similar to say inter
packet gap on ethernet, or framing bits round HDLC/FR frames for us more
venerable members of the audience - which is not described by either the
BW or the L2 encapsulation. 
 
We have seen this from deployments using VDSL2 DSLAMs. My understanding
is that the overhead is due to the local loop framing which includes
FEC, trellis encoding and other factors. Possibly this can be derived
from the DSL type which we already have in the protocol - I am not
familiar enough with the details of all DSL encodings to be able to
judge that, maybe the access node experts could shed some light here ?
 
Cheers,
 
    Derek.
 
 
+=============================+
Derek Harkness
Systems Engineer
Juniper Networks 
Nymphenburger Strasse 13-15
80335 Munich
Germany
Tel: [phone]
Mobile: [phone]
Email: [e-mail]
+=============================+ 

 

________________________________

From: [e-mail] [mailto:[e-mail]] 
Sent: 24 May 2006 11:46
To: Sanjay Wadhwa
Cc: [e-mail]
Subject: RE: [L2CP] RE: Wadhwa new draft 01- Encapsulation 



Hi Sanjay and all, 
I support Sanjay's proposal to have this encapsulation transported by
ANCP, even if we may argue that 
we already have 2 protocols that may transport this information (DHCP
and PPPoE). 
About having a different TLV to transport the Encapsulation, it only
partially solves the problem of potentially mixing 
layer 1 and layer 2 information. Actually the DSL forum (TR-101) uses
same principle described in your document to transport this 
information, it is probably wise to follow the same mechanism.. 
Unless other people share this concern, I'll go with your proposal. 
Best Regards, 
Michel. 




"Sanjay Wadhwa" <[e-mail]> 

24/05/2006 00:01 

To
<[e-mail]> 
cc
[e-mail] 
Subject
RE: [L2CP] RE: Wadhwa new draft 01- Encapsulation + Remode Id comments

	






>-----Original Message-----
>From: [e-mail]
>[mailto:[e-mail]]
>Sent: Tuesday, May 23, 2006 1:07 PM
>To: Sanjay Wadhwa
>Cc: [e-mail]
>Subject: Re: [L2CP] RE: Wadhwa new draft 01- Encapsulation + Remode Id
>comments
>
>
>
>Hi Sanjay,
>
>> 
>>     - Why was the access loop encapsulation object included within a
>>     message where all parameters transmitted are layer 1 oriented?
>>     There might be several encapsulations available per 
>physical link, a
>>     new message could maybe better serve the purpose of
>>     transmitting the encapsulation parameters.
>>     [[SW]] I have sympathy for your arguement as I had a similar
>>     concern, which is why L2 encaps has been specified as a 
>seprate and
>>     optional TLV (although same message).
>>     It is to an extent useful for the BNG to learn l2 encaps on the
>>     local-loop as it can in some cases allow for more 
>accurate shaping
>>     of subscriber traffic.
>> 
>
>Why not specifying the bandwidth at L2? Then the BNG just takes this 
>bandwidth for shaping and it does not have to take care of what 
>encapsulation has been used. Why bottering the BNG with the 
>encap on the 
>DSL line. And what if later someone wants to do the same on non-DSL 
>access lines? Are we going to add encap types and updating the 
>BNG with 
>these new encap types to compute the correct shaping rate? I 
>believe it 
>would be better to specify the bandwidth at which the BNG has to shape.

[SW] Shaping on the BNG (based on counting bytes transmitted) needs to
know the "byte adjustment" (under/over-head) due to difference in encaps
on the aggregation network and access loop. I suppose the access-node
could indicate the absolute difference in terms of bytes between the two
encapsulations.. however, this might not be accurate as an aggregation
switch upstream of the DSLAM could change the encaps (e.g. insert an
outer VLAN tag). Ideally, the BNG needs to use the difference between
it's encaps and the encaps on the local-loop. Also, the BNG needs to
adjust for cell-tax if the local-loop is cell based.

-Sanjay


>regards,
>Stefaan
>
>
>>     *Chapter 5.4.2*
>>     - Typo:
>>     Type (Access-Loop-Circuit-ID = 0x01) : defined in section 5.4.1
>>     Type (Access-Aggregation-Circuit-ID-Binary = 0x02): defined in
>>     section 5.4.1.        
>>     Type (Access-Aggregation-Circuit-ID-ASCII = 0x03) : defined in
>>     section 5.4.1.  
>>     These lines should be updated to comply to Chapter 5.4.1.
>> 
>>     [[SW]] Will fix.
>>      
>>     Thanks
>>     -Sanjay 
>> 
>>     Thanks and Best Regards,
>>     Michel.
>> 
>> 
>> 
>> 
>>     *"Sanjay Wadhwa" <[e-mail]>*
>> 
>>     05/04/2006 19:22
>> 
>>                      
>>     To
>>                      "Busschbach, Peter B \(Peter\)" 
><[e-mail]>, "Wojciech
>>     Dec \(wdec\)" <[e-mail]>, <[e-mail]>
>>     cc
>>                      
>>     Subject
>>                      RE: [L2CP] Advantages of L2CP (was: Revised WG
Charter Draft)
>> 
>> 
>>                      
>> 
>> 
>> 
>> 
>> 
>>     Peter
>>      Please see inline..
>> 
>>      >-----Original Message-----
>>      >From: Busschbach, Peter B (Peter) 
>[mailto:[e-mail]]
>>      >Sent: Wednesday, April 05, 2006 10:51 AM
>>      >To: 'Wojciech Dec (wdec)'; [e-mail]
>>      >Subject: [L2CP] Advantages of L2CP (was: Revised WG 
>Charter Draft)
>>      >
>>      >
>>      >Hi Woj,
>>      >
>>      >To address the second half of our email exchange:
>>      >
>>      >I did notice the sentence that addressed Dave's concern.
>>      >However, my point was that the charter claims that L2CP will
>>      >have a specific benefit ("avoiding complex cross-organization
>>      >interactions"), while it is far from clear that in this
>>      >respect L2CP is any better than other solutions.
>> 
>>     [Sanjay] All that the charter is saying is that L2C work 
>will undertake
>>     use-cases that aim to simplify service management by 
>avoiding complex
>>     cross-organization interactions. It is a nobel goal that 
>L2C is striving
>>     to achieve.. What is wrong with that ? This is 
>irrespective of wether
>>     other solutions can provide this or not.
>>     So, as an example, charter for a new dynamic routing 
>protocol might say
>>     that it will strive to achieve fast network-wide 
>convergence (which is a
>>     clear benefit over static routing). But, obviously it is 
>ok for multiple
>>     dynamic routing protocols to work towards this goal and have this
>>     explicitly stated in their charter.
>> 
>>     -Sanjay
>> 
>> 
>>      >I believe that the charter should avoid stating benefits that
>>      >are debatable and therefore suggest that the text that I
>>      >quoted in my first email be deleted from the charter.
>>      >
>>      >Peter
>>      >
>>      >> -----Original Message-----
>>      >> From: Wojciech Dec (wdec) [mailto:[e-mail]]
>>      >> Sent: Wednesday, April 05, 2006 7:34 AM
>>      >> To: Busschbach, Peter B (Peter); [e-mail]
>>      >> Subject: RE: [L2CP] Re: Revised WG Charter Draft
>>      >>
>>      >>
>>      >> Hi Peter,
>>      >>
>>      >> To address 1) we have put in the following statement 
>in the charter
>>      >> which you may have not noticed.
>>      >>
>>      >> "The protocol design will not preclude other uses of L2CP."
>>      >>
>>      >> WRT 2) we do not lay any claims to how different 
>operators structure
>>      >> their data bases, and some are probably better at doing it
>>      >> than others.
>>      >> However it does seem to be a fairly common problem that the
>>      >> info related
>>      >> to a single subscriber's network service needs to be farmed
>>      >> out and fed
>>      >> into numerous custom built manager systems besides also the
>>      >Radius DB.
>>      >> The idea is to allow a mechanism, through the use of L2CP,
>>      >to have the
>>      >> Access node be provided with such information as and when
>>      >> needed by the
>>      >> NAS which in turn accesses a common repository like 
>a Radius DB.
>>      >> Dave's statement was, I believe, in relation to different
>>      >> subject; that
>>      >> of a wholesale-retail operation, where indeed the
>>      >relationship is more
>>      >> complex. However we do plan on addressing this as 
>evidenced by the
>>      >> statement in the charter:
>>      >> "L2CP will address security aspects of the control protocol,
>>      >including
>>      >> the trust model between NAS nodes and access nodes."
>>      >>
>>      >> Regards,
>>      >> Woj.
>>      >>
>>      >> -----Original Message-----
>>      >> From: Busschbach, Peter B (Peter) 
>[mailto:[e-mail]]
>>      >> Sent: 04 April 2006 21:23
>>      >> To: '[e-mail]'
>>      >> Subject: [L2CP] Re: Revised WG Charter Draft
>>      >>
>>      >> I have two comments on the revised charter.
>>      >>
>>      >> 1)                 At the end of the BOF, Mark 
>Townsley limited
>>     the scope of the
>>      >> working group. Unfortunately, this is not captured very
>>      >clearly in the
>>      >> meeting minutes. The critical sentence in the 
>meeting minutes is
>>     "DSL
>>      >> but good engineers ...". I.e. the focus of the WG is 
>to solve a
>>      >> particular issue in DSL access networks, but as good
>>      >> engineers we should
>>      >> not preclude the use of the protocol for other applications.
>>      >>
>>      >> I don't see the limited scope reflected in the new charter.
>>      >>
>>      >> 2)                 Under "Line Configuration". the 
>charter says:
>>      >>
>>      >> > L2CP is intended to simplify the OSS 
>infrastructure for service
>>      >> > management, allowing subscriber-related service data to be
>>      >> maintained
>>      >> > in fewer repositories (e.g. RADIUS server back-end 
>database)
>>     while
>>      >> > avoiding complex cross-organization interactions.
>>      >>
>>      >> I don't understand how L2CP leads to fewer Radius server
>>      >back end data
>>      >> bases. I also don't understand how L2CP avoids 
>cross-organizational
>>      >> interactions. There seems to be an assumption that it is ok
>>      >> for L2CP to
>>      >> cross organizational boundaries but not for other 
>protocols. I don't
>>      >> think that is correct. At the BOF, Dave Allan pointed out  
>>      >> that this is
>>      >> one of the more difficult problems to solve. Therefore, I
>>      >believe that
>>      >> this text should be removed from the charter.
>>      >>
>>      >> Peter
>>      >>
>>      >>
>>      >>
>>      >> _______________________________________________
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>>      >>
>>      >
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