Re: RFC 4591 and RFC 4349: DLCI at egress LCCE

Javi,

Please note from RFC4349:

http://tools.ietf.org/html/rfc4349#section-4.1

   Since all packets are passed in a largely transparent manner over the
   HDLCPW, any protocol that has HDLC-like framing may utilize the
   HDLCPW mode, including PPP, Frame-Relay ("port to port" Frame-Relay
   transport), X.25 (LAPB), etc.  In such cases, the negotiations and
   signaling of the specific protocols transported over the HDLCPW take
   place between the Remote Systems.  A non-exhaustive list of examples
   and considerations of this transparent nature include:
[...]
      o When the HDLCPW transports Frame-Relay traffic, PVC status
        management procedures (Local Management Interface) take place
        between Remote Systems, and LCCEs do not participate in LMI.
        Additionally, individual Frame-Relay virtual-circuits are not
        visible to the LCCEs, and the FECN, BECN, and DE bits are
        transported transparently.

Think of the HDLCoPW as a cable, with "CEs" connected back-to-back on
that port. Any configuration would need to use the same DLCIs, and any
potential signaling would be CE to CE (needing to match DLCIs).

So, again, if DLCIs are different then you cannot use the HDLCoPW.

Thanks,

-- Carlos.


On 6/16/2010 7:29 AM, Javi wrote:
> Carlos,
> 
> Each CE decides the DLCI by itself (and dinamically for switched virtual 
> circuits, sopported by HDLCoPW).
> 
> How may you know if both CEs use different DLCIs?. If you want to use 
> HDLCoPW, you would need to ensure that.
> 
> Thanks,
> 
> Javi
> 
> 
> El 16/06/2010 5:45, Carlos Pignataro (cpignata) escribió:
>> Javi,
>>
>> If the DLCIs are different then you cannot use the HDLCoPW. Or a 
>> different way, for port mode DLCIs need to match (it is extending a 
>> port) and for different DLCIs you need FRoPW.
>>
>> Thanks,
>>
>> Thumb typed by Carlos Pignataro.
>>
>> On Jun 15, 2010, at 7:29 PM, "Javi" <[email protected]> wrote:
>>
>>> Carlos,
>>>
>>> I agree, but I don't understand why. If a Frame Relay circuit is 
>>> transported over a L2TPv3 HDLCoPW, the egress LCCE builds a FR frame 
>>> with the same DLCI as the FR frame received by the ingress LCCE. If 
>>> DLCI has local significance, CE/ingress_LCCE may use a different DLCI 
>>> as CE/egress_LCCE. Why is not required here that the egress LCCE 
>>> re-writes the DLCI (although it's not visible to PW)?.
>>>
>>> Thanks,
>>>
>>> Javi
>>>
>>>
>>>
>>> Carlos Pignataro (cpignata) escribió:
>>>> Javi,
>>>>
>>>> Because the "port mode" does not have granularity/visibility into the
>>>> DLCI level.
>>>>
>>>> Thanks,
>>>>
>>>> -- Carlos.
>>>>
>>>> -----Original Message-----
>>>> From: [email protected] [mailto:[email protected]] On
>>>> Behalf Of Javi
>>>> Sent: Tuesday, June 15, 2010 1:46 PM
>>>> To: [email protected]
>>>> Subject: [L2tpext] RFC 4591 and RFC 4349: DLCI at egress LCCE
>>>>
>>>> + Frame Relay traffic transported in a "virtual circuit-to-virtual 
>>>> circuit" mode by L2TPv3 FRPW: Due to local significance of the DLCI, 
>>>> the
>>>>
>>>> egress LCCE re-writes the DLCI.
>>>>
>>>>     RFC 4591 (L2TPv3 FRPW), clause 5
>>>>     The Frame Relay frame is transported in its entirety, including the
>>>>
>>>> DLCI ...  The egress LCCE re-writes the DLCI...
>>>>
>>>> + Frame Relay traffic transported in a "port" mode by L2TPv3 HDLCoPW 
>>>> (RFC 4349): It's not mentioned any DLCI modification at the egress 
>>>> LCCE.
>>>>
>>>> Why is it not necessary here (similarly, DLCI significance is local)?
>>>>
>>>> Javi
>>>> _______________________________________________
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