Subject: Re: [PWE3] Re: Bridge or

From: Muneyoshi Suzuki <[email-masked]>
Date: Mon, 09 Dec 2002 14:39:07 +0900

Stewart,

> > Needless to say, the IETF should not develop new LAN/Bridge protocol,
> > but the IETF should refer the IEEE work if it is needed.
> That is why we partitioned the system into a pseudo wire defined by PWE3
> (which just transports things that it is given), and an NSP + Forwarder
> which is defined by an expert in the media technolgy (in this case IEEE
> + IETF PPVPN) and which performs more complex functions.

Agreed. It seems to me, "NSP function" described in draft-ietf-pwe3-
ethernet-encap-01.txt consists of the following two functions (precisely, 
protocol entities in IEEE/ITU-T terminology)

(1)MAC function (entity) that terminates Ethernet LAN between CE and PE,
and is defined in IEEE 802.3-2002.

(2)MAC Relay function (entity) that forwards Ethernet MAC flames,
and is defined in IEEE 802.1D-1998, .1t-2001, and .1w-2001.
If VLAN tagging is performed, it also must conforms with IEEE 802.1Q-1998,
.1u-2001, and 802.1v-2001.

Then these protocols specifications for these functions (entities) are
out of scope of PWE3 protocol specification, it may define "PSN tunnel"
and "PW termination" functions.

The following text is extracted from the draft, and comments in-line.

>   The "NSP" function includes packet processing needed to translate the
>   Ethernet packets that arrive at the CE-PE interface to/from the
>   Ethernet packets that are applied to the PW termination point. Such

I think "Ethernet packets" may be "Ethernet MAC frames."

>   functions may include stripping, overwriting or adding VLAN tags,

In my understanding, 802.1Q specifies VLAN tag stripping and adding,
but I think, overwriting is not defined.

>   physical port multiplexing and demultiplexing, PW-PW bridging, 

I don't understand "physical port" in the above. Is it an Ethernet port 
to CE or PW port to PE? If it is an Ethernet port, what is "multiplexing
and demultiplexing" of Ethernet? If it is a PW port, multiplexing and 
demultiplexing function should be reside in "PW termination" function.

>   L2 encapsulation, shaping, policing, etc.

I also don't understand "L2 encapsulation" Does it encapsulate to Ethernet
frame or PSN tunnel packet? If it is PSN tunnel encapsulation, it should 
be reside in "PW termination" function.

>   The points to the left of A, including the physical layer between the
>   CE and PE, and any adaptation (NSP) functions between it and the PW
>   terminations, are outside of the scope of PWE3 and are not defined
>   here.

Right.

And the following is extracted from Danny's mail.

> We should also clarify other NSP functions such as handling CRC errors, 
> framing errors, runt conditions, etc.., and equally, PW functions that 
> result in PW "generalized bit errors" (e.g., out-of-order packets, packet 
> loss, etc..), as Akiva suggests.

I think the above functions are belongs to the "PW termination", if CRC
and framing errors in the above mean errors in PSN tunnel.

Thanks,

Muneyoshi Suzuki
Nippon Telegraph and Telephone Corp.