Subject: [PWE3] FW: RFC 4448

From: "Sprecher, Nurit (NSN - IL/Hod HaSharon)" <[email-masked]>
Date: Thu, 13 May 2010 09:27:40 +0200

Hi Luca,

I have some questions about RFC 4448, and will appreciate your response.

*         The document refers to Service-delimiting and non
service-delimiting configuration on the CE-PE interface. Is it only
relevant at the Ingress PE? What about the Egress PE? It seems that the
document differentiate between the cases only at the Ingress PE. Is it
so?

*         The document allows for more than one 802.1Q tags. How such a
situation is possible? The IEEE802.1Q supports only one tag.

*         Usually SP tag is implemented using 802.1ad S-tag. However
the document considers service-delimiting tag (which is placed on the
frame by some piece of service provider-operated equipment) as 802.1Q
tag. It seems that the document refers to 802.1Q tag only and not to
802.1ad S-tag. Is that correct? Why 802.1ad tags are not considered by
the document? If supported, we could have at most two tags. 

*         Can we have a situation where the configuration is
service-delimiting tag, and no tag exists on a frame coming from the CE?

*         When a PE gets a tagged frame, how can the PE identify that
the tag was really inserted by a SP equipment and it is not a customer
tag? Is it so that it just relies on the configuration?

*         Assuming that the CE is connected to the PE via a MEF UNI, the
frame is always 802.1Q and is considered as a customer tag. In such a
case is it true that the CE/PE interface must be configured as non
service-delimiting? If so, it seems that many of the options in the
document are not applicable (assuming standard IEEE behavior J).

Thanks and best regards,

Nurit

---

From: "Sprecher, Nurit (NSN - IL/Hod HaSharon)" <[email-masked]>
Date: Mon, 24 May 2010 21:24:47 +0200

Re-sent as I have got no response.

Luca, I'll appreciate your response. 

From: [email-masked] [mailto:[email-masked]] On Behalf Of
ext Sprecher, Nurit (NSN - IL/Hod HaSharon)
Sent: Thursday, May 13, 2010 10:28 AM
To: [email-masked]
Cc: [email-masked]
Subject: [PWE3] FW: RFC 4448

Hi Luca,

Thanks and best regards,

Nurit

---

From: Luca Martini <[email-masked]>
Date: Mon, 24 May 2010 16:09:47 -0600

Sprecher, Nurit (NSN - IL/Hod HaSharon) wrote:
> Luca, I’ll appreciate your response.
>
I was crafting one a while back , but then i got distracted .
Sorry for the delay.

> *From:* [email-masked] [mailto:[email-masked]] *On 
> Behalf Of *ext Sprecher, Nurit (NSN - IL/Hod HaSharon)
> *Sent:* Thursday, May 13, 2010 10:28 AM
> *To:* [email-masked]
> *Cc:* [email-masked]
> *Subject:* [PWE3] FW: RFC 4448
>
> Hi Luca,
>
> · The document refers to Service-delimiting and non service-delimiting 
> configuration on the CE-PE interface. Is it only relevant at the 
> Ingress PE? What about the Egress PE? It seems that the document 
> differentiate between the cases only at the Ingress PE. Is it so?
>
I assume you are referring to the vlan tags in the ethernet PW. The 
definition is for the ingress PE , and ingress to the PW. Note that both 
PEs are ingress PEs in one direction.... So , for a particular direction 
we only discuss the ingress part.

> · The document allows for more than one 802.1Q tags. How such a 
IEEE802.1Q might only have one tag in scope , but there is in theory no 
limit to the number of tags you can have. So even if the IEEE did not 
define more then one tag, there are several implementations that handle 
that case.
>
> · Usually SP tag is implemented using 802.1ad S-tag. However the 
> document considers service-delimiting tag (which is placed on the 
> frame by some piece of /_service provider-operated_/ equipment) as 
> 802.1Q tag. It seems that the document refers to 802.1Q tag only and 
> not to 802.1ad S-tag. Is that correct? Why 802.1ad tags are not 
> considered by the document? If supported, we could have at most two tags.
>
Given that the document was frozen sometime in 2001 , and 802.1ad was 
published in 2006 , it could not possibly reference it ( I cannot 
predict the future ;-) ). RFC4448 only talks about Q tags with ethertype 
0x8100 not the 802.1ad which 0x88A8.

> · Can we have a situation where the configuration is 
no. the packet would be dropped.
>
> · When a PE gets a tagged frame, how can the PE identify that the tag 
> was really inserted by a SP equipment and it is not a customer tag? Is 
> it so that it just relies on the configuration?
>
the egress PE relies only on provisioning and a label lookup to 
determine the disposition of the packet. I'm not sure that i understand 
this question fully.
A tag is just a tag. You cannot determine from it where it was applied.
>
> · Assuming that the CE is connected to the PE via a MEF UNI, the frame 
> is always 802.1Q and is considered as a customer tag. In such a case 
> is it true that the CE/PE interface must be configured as non 

The MEF defines a service that is a subset of what is possible. So your 
statement seems correct.

Luca