Subject: MPLS using LDP and ATM VC Switching

From: [email-masked]
Date: Fri, 23 Feb 2001 16:44:42 -0500

Hi Everyone,

I have a question regarding RFC3035.  There is a paragraph in RFC3035, page
5 to page 6, says,
"Label switching is accomplished by associating labels with Forwarding
Equivalence Classes, and using the label value to forward packets,
including determining the value of any replacement label.  See [1] for
further details.  In an ATM-LSR, the label is carried in the VPI/VCI field,
or, when two ATM-LSRs are connected via an ATM "Virtual Path", in the VCI
field."

I am wondering why it is in the VCI field rather than VPI field.  I thought
if the two ATM-LSRs are connected via virtual circuit, then forwarding
should be based on the VPI/VCI field, if the two ATM-LSRs are connected
visa virtual path, then forwarding should be based on the VPI field.

Regards,
Jane D. Jiang

---

From: "Yi Chu" <[email-masked]>
Date: Fri, 23 Feb 2001 17:03:08 -0500

My interpretation is that if two ATM LSR are directly connected, say through
an OC3, then vpi/vci pair is used to carry the label encoding.  If on the
other hand, two ATM LSR are not directly connected, but connected with a VP
tunnel (through a carrier's ATM network, e.g.), then only vci is available
for label encoding.

yi

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
[email-masked]
Sent: Friday, February 23, 2001 4:45 PM
To: [email-masked]; [email-masked]; [email-masked]
Subject: MPLS using LDP and ATM VC Switching

Hi Everyone,

Regards,
Jane D. Jiang

---

From: "Yongjun Im" <[email-masked]>
Date: Fri, 23 Feb 2001 16:06:44 -0600

----- Original Message ----- 
From: <[email-masked]>
To: <[email-masked]>; <[email-masked]>; <[email-masked]>
Sent: Friday, February 23, 2001 3:44 PM
Subject: MPLS using LDP and ATM VC Switching

> visa virtual path, then forwarding should be based on the VPI field.
If the two ATM-LSRs ard connected via Virtual Path, VP switching is conducted by
native ATM switching function and can not be controlled (label allocation/deallocation)
by MPLS controller/function. In viewpoint of MPLS function, VP is a just virtual link, thus
VCI field should be used for MPLS label allcation/deallocation.

Take care.