Subject: Re: Ethernet over MPLS

From: "Andrew G. Malis" <[email-masked]>
Date: Fri, 14 Mar 2003 10:18:38 -0500

Muneyoshi,

Thanks (?) for bringing this up.  The issue is actually more general than 
just tagged mode, since one conceivably could have more than one raw mode 
VC LSP between a pair of Ethernet ports, and use arbitrary ingress 
classification to assign frames to a particular LSP.  But the problem is 
most pronounced in tagged mode, since it is then impossible to maintain 
sequentiality for an arbitrary <sa, da, priority> combination over all 
VLANs between a pair of ports - sequentially can only be assured for <sa, 
da, priority, tag> combinations.

I don't think we have any easy way to fix this without getting rid of 
tagged mode.  I think the best we can do is note this violation in the 
draft, and say that if a SP wishes to comply with the 802.1D requirement of 
sequentially for all <sa, da, priority> combinations, then it MUST only use 
raw mode, and have at most one raw mode VC between each pair of Ethernet ports.

Cheers,
Andy

--------

At 3/14/2003 11:24 AM +0900, Muneyoshi Suzuki wrote:

>Andy,
>
> > In tagged mode, the PEs interpret the VLAN tag and have a one-to-one
> > association between tags and inner VC labels.  Since the ingress PE is
> > demultiplexing ingress frames by VLAN tag in order to associate them 
> with a
> > particular VC label, a priori all of the frames sent using a particular VC
> > label must have the same tag. This is similar in concept to ATM VPI/VCI 
> mode.
>
>According to the IEEE 802.1D-1998, frame misordering is defined as following.
>
>|6.3.3 Frame misordering
>|The MAC Service does not permit the reordering of frames with a given user
>|priority for a given combination of destination address and source address.
>|
>|Where Bridges in a Bridged LAN are capable of connecting the individual MACs
>|in such way that multiple paths between any source-destination station pairs
>|exist, the operation of a protocol is required to ensure that a single path
>|is used.
>
>And in the draft of update version of 802.1D, it is defined as following.
>
>|6.3.3 Frame misordering
>|The MAC Service (9.2 of ISO/IEC 15802-1) permits a negligible rate of the
>|reordering of frames with a given user priority for a given combination of
>|destination address and source address.
>|
>|NOTE 1-The Forwarding Process in Bridges (7.7) does not mis-order or 
>duplicate
>|frames.
>|
>|Where Bridges in a Bridged LAN are capable of connecting the individual MACs
>|in such way that multiple paths between any source-destination station pairs
>|exist, the operation of a protocol is required to ensure that a single path
>|is used.
>
>IEEE 802.1Q does not override the above definition. Therefore, Bridges must
>ensure frame ordering regardless VLAN ID value. And an end station may
>belong to multiple VLANs. So my question is how the tagged mode ensures
>frame ordering between LSPs. I think it must have some mechanism,
>otherwise it violates the standard.
>
>Thanks,
>
>Muneyoshi Suzuki
>Nippon Telegraph and Telephone Corp.

---

From: Ali Sajassi <[email-masked]>
Date: Fri, 14 Mar 2003 15:46:08 -0800

Let me also offer another perspective ...

To satisfy 802.1D negligible re-ordering requirement, we need to ensure that:

The same set of PWs is used for both customer's unicast and 
multicast/broadcast traffic for the end-to-end operation - e.g., if 
end-to-end operation requires several PW segments between intermediate 
service nodes, then the same sequence of PWs needs to be used for both 
unicast and broadcast/multicast traffic

This also implies that  between any pair of service nodes, the same PW 
needs to be used for both unicast and multicast/broadcast traffic of a 
given customer.

As Andy pointed out, we can do that easily with "raw mode" PW; however, if 
we want to do it with "tagged mode" PW, then we should first encapsulate 
all customers frames using a provider's tag (e.g., using QinQ) and then 
pass them through the tagged mode PW. In this case, all the frames over the 
PW contains a single outer tag which represents the customer.

-Ali

At 10:18 AM 3/14/2003 -0500, Andrew G. Malis wrote:
>draft, and say that if a SP wishes to comply with the 802.1D requirement 
>of sequentially for all <sa, da, priority> combinations, then it MUST only 
>use raw mode, and have at most one raw mode VC between each pair of 
>Ethernet ports.
>
>Cheers,
>Andy
>
>--------
>
>> > label must have the same tag. This is similar in concept to ATM 
>> VPI/VCI mode.
>>
>_______________________________________________
>pwe3 mailing list
>[email-masked]
>https://www1.ietf.org/mailman/listinfo/pwe3

---

From: Muneyoshi Suzuki <[email-masked]>
Date: Mon, 17 Mar 2003 11:19:15 +0900 (JST)

Andy,

> classification to assign frames to a particular LSP.

Thanks for clarification. I did not aware this issue.

Thanks,

Muneyoshi Suzuki