Network Working Group K. Nagami

Network Working Group K. Nagami
Request for Comments: 3038 Y. Katsube
Category: Standards Track Toshiba Corp.
N. Demizu
WaterSprings.ORG
H. Esaki
Univ. of Tokyo
P. Doolan
Ennovate Networks
January 2001

VCID Notification over ATM link for LDP

Status of this Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2001). All Rights Reserved.

Abstract

The Asynchronous Transfer Mode Label Switching Router (ATM-LSR) is
one of the major applications of label switching. Because the ATM
layer labels (VPI and VCI) associated with a VC rewritten with new
value at every ATM switch nodes, it is not possible to use them to
identify a VC in label mapping messages. The concept of Virtual
Connection Identifier (VCID) is introduced to solve this problem.
VCID has the same value at both ends of a VC. This document
specifies the procedures for the communication of VCID values between
neighboring ATM-LSRs that must occur in order to ensure this
property.

1. Introduction

Several label switching schemes have been proposed to integrate Layer
2 and Layer 3. The ATM Label Switching Router (ATM-LSR) is one of
the major applications of label switching.

In the case of ATM VCs, the VPI and VCI labels are, in the general
case, rewritten with new values at every switch node through which
the VC passes and cannot be used to provide end to end identification
of a VC.

Nagami, et al. Standards Track [Page 1]

RFC 3038 VCID Notification for LDP January 2001

In the context of MPLS 'stream', which are classes of packets that
have some common characteristic that may be deduced by examination of
the layer 3 header in the packets, are bound to layer 2 'labels'. We
speak of stream being 'bound' to labels. These bindings are conveyed
between peer LSRs by means of a Label Distribution Protocol [LDP].

In order to apply MPLS to ATM links, we need some way to identify ATM
VCs in LDP mapping messages. An identifier called a Virtual
Connection ID (VCID) is introduced. VCID has the same value at both
ends of a VC. This document specifies the procedures for the
communication of VCID values between neighboring ATM-LSRs that must
occur in order to ensure this property.

2. Overview of VCID Notification Procedures

2.1 VCID Notification procedures

The ATM has several types of VCs (transparent point-to-point
link/VP/PVC/SVC). A transparent point-to-point link is defined as
one that has the same VPI/VCI label at both ends of a VC. For
example, two nodes are directly connected (i.e., without intervening
ATM switches) or are connected through a VP with the same VPI value
at both ends of the VP.

There are two broad categories of VCID notification procedures;
inband and outband. The categorization refers to the connection over
which the messages of the VCID notification procedure are forwarded.
In the case of the inband procedures, those messages are forwarded
over the VC to which they refer. In contrast the out of band
procedures transmit the messages over some other connection (than the
VC to which they refer).

We list below the various types of link and briefly mention the VCID
notification procedures employed and the rational for that choice.
The procedures themselves are discussed in detail in later sections.

Transparent point-to-point link : no VCID notification
VCID notification procedure is not necessary because the label
(i.e., VPI/VCI) is the same at each end of the VC.

VP : inband notification or VPID notification or no notification
- Inband notification
VCID notification is needed because the VPI at each end of the VC
may not be the same. Inband VCID notification is used in this
case.

Nagami, et al. Standards Track [Page 2]

RFC 3038 VCID Notification for LDP January 2001

- VPID notification
VCID notification is needed because the VPI at each end of the VC
may not be the same. VPID notification is used in this case.

- No notification
If a node has only one VP to a neighboring node, VCID notification
procedure is not mandatory. The VCI can be used as the VCID.
This is because the VCI value is the same at each end of the VP.

PVC : inband notification
Inband VCID notification is used in this case because the labels
at each end of the VC may not be the same.

SVC : there are three possibilities
- Outband notification
If a signaling message has a field which is large enough to carry
a VCID value (e.g., GIT [GIT]), then the VCID is carried directly
in it.

- Outband notification using a small-sized field
If a signaling message has a field which is not large enough to
carry a VCID value, this procedure is used.

- Inband notification
If a signaling message can not carry user information, this
procedure is used.

When an LSP is a point-to-multipoint VC and an ATM switch in an
LSR is not capable of VC merge, it may cause problems in
performance and quality of service. When the LSR wants to add a
new leaf to the LSP, it needs to split the active LSP temporarily
to send an inband notification message.

2.2 VC direction

A VC has a directionality. The VCID procedure for a VC is always
triggered from the upstream node of the VC, i.e., the upstream node
notifies the downstream node of the VCID.

If bidirectional use of a label switched VC is allowed, the label
switched VC is said to be bidirectional. In this case, two VCID
procedures are taken, one for each direction.

If bidirectional use of a label switched VC is not allowed, the label
switched VC is said to be unidirectional. In this case, only one
VCID procedure is taken for the allowed direction.

VC directionality is communicated through LDP.

Nagami, et al. Standards Track [Page 3]

RFC 3038 VCID Notification for LDP January 2001

3. VCID Notification Procedures

3.1 Inband Notification Procedures

3.1.1 Inband Notification for Point-to-point VC

VCID notification is performed by transmitting a control message
through the VC newly established (by signalling or management) for
use as an label switched path (LSP). The procedure for VCID
notification between two nodes A and B is detailed below.

0. The node A establishes a VC to the destination node B (by
signalling or management).

1. The node A selects a VCID value.

2. The node A sends a VCID PROPOSE message which contains the VCID
value and a message ID through the newly established VC to the
node B.

3. The node A establishes an association between the outgoing label
(VPI/VCI) for the VC and the VCID value.

4. The node B receives the message from the VC and establishes an
association between the VCID in the message and the incoming
label(VPI/VCI) for the VC. Until the node B receives the LDP
Request message, the node B discards any packet received over the
VC other than the VCID PROPOSE message.

5. The node B sends an ACK message to the node A. This message
contains the same VCID and message ID as specified in the received
message. This message is sent through the VC for LDP.

6. When node A receives the ACK message, it checks whether the VCID
and the message ID in the message are the same as the registered
ones. If they are the same, node A regards that node B has
established the association between the VC and VCID. Otherwise,
the message is ignored. If the node A does not receive the ACK
message with the expected message ID and VCID during a given
period, the node A resends the VCID PROPOSE message to the node B.

7. After receiving the proposer ACK message, the node A sends an LDP
REQUEST message to the node B. It contains the message ID used
for VCID PROPOSE. When the node B receives the LDP REQUEST
message, it regards that the node A has received the ACK
correctly. The message exchange using VCID PROPOSE, VCID ACK, and
LDP REQUEST messages constitutes a 3-way handshake. The 3-way
handshake mechanism is required since the transmission of VCID

Nagami, et al. Standards Track [Page 4]

RFC 3038 VCID Notification for LDP January 2001

PROPOSE message is unreliable. Once the 3-way handshake
completes, the node B ignores all VCID PROPOSE messages received
over the VC. The node B sends an LDP Mapping message, which
contains the VCID value in the label TLV.

Node A Node B
| |
|--------------->| VCID PROPOSE
| |
|<---------------| VCID ACK
| |
|--------------->| LDP Label Request
| |
|<---------------| LDP Label Mapping

3.1.2 Inband notification for point-to-multipoint VC

Current LDP specification does not support multicast. But the VCID
notification procedure is defined for future use. VCID notification
is performed by sending a control message through the VC to be used
as an LSP. The upstream node assigns the VCID value. The procedure
by which it notifies the downstream node of that value is given
below. The procedure is used when a new VC is created or a new leaf
is added to the VC.

First, the procedure for establishing the first VC is described.

1. The upstream node assigns a VCID value for the VC. When the VCID
value is already assigned to a VC, it is used for VCID.

2. The upstream node sends a message which contains the VCID value
and a message ID through the VC used for an LSP. This message is
transferred to all leaf nodes.

3. The upstream node establishes an association between the outgoing
label for the VC and the VCID value.

4. When the downstream nodes receiving the message already received
the LDP REQUEST message for the VC, the received message is
discarded. Otherwise, the downstream nodes establish an
association between the VCID in the message and the VC from which
the message is received.

5. The downstream nodes send an ACK message to the upstream node.

6. After the upstream node receives the ACK messages, the upstream
node and the downstream nodes share the VCID. The upstream node
sends the LDP REQUEST message in order to make a 3-way handshake.

Nagami, et al. Standards Track [Page 5]

RFC 3038 VCID Notification for LDP January 2001

Upstream Downstream 1 Downstream 2
| | |
|-----------+--->| | VCID PROPOSE
| +------------------->|
| | |
|<---------------| |
| VCID ACK | |
|<-------------------------------| VCID ACK

Second, the procedure for adding a leaf to the existing point-to-
multipoint VC is described.

0. The upstream node adds the downstream node, using the ATM
signaling.

1. The VCID value which already assigned to the VC is used.

2. The upstream node sends a message which contains the VCID value
and a message ID through the VC used for an LSP. This message is
transferred to all leaf nodes.

3. When the downstream nodes receiving the message already received
the LDP REQUEST message for the VC, the received message is
discarded. Otherwise, the downstream nodes establish an
association between the VCID in the message and the VC from which
the message is received.

4. After the upstream node receives the ACK messages, the upstream
node and the downstream nodes share the VCID. The upstream node
sends the LDP REQUEST message in order to make a 3-way handshake.

3.2 Outband Notification using a small-sized field

This method can be applied when a VC is established using an ATM
signaling message and the message has a field which is not large
enough to carry a VCID value.

SETUP message of the ATM Forum UNI 3.1/4.0 has a 7-bit mandatory
field for the user. This is a user specific field in the Layer 3
protocol field in the BLLI IE (Broadband Low Layer Information
Information Element).

The BLLI value is used as a temporary identifier for a VC during a
VCID notification procedure. This mechanism is defined as "Outband
Notification using a small-sized field". The BLLI value of a new VC
must not be assigned to other VCs during the procedure to avoid
identifier conflict. When the association among the BLLI value, a

Nagami, et al. Standards Track [Page 6]

RFC 3038 VCID Notification for LDP January 2001

VCID value, and the corresponding VC is established, the BLLI value
can be reused for a new VC. VCID values can be assigned
independently from BLLI values.

Node A Node B
| |
|--------------->| ATM Signaling with BLLI
|<---------------|
| |
|--------------->| VCID PROPOSE with BLLI
| |
|<---------------| VCID ACK
| |
|--------------->| LDP Label Request
| |
|<---------------| LDP Label Mapping

A point-to-multipoint VC can also be established using ADD_PARTY of
the ATM Forum Signaling. ADD_PARTY adds a new VC leaf to an existing
VC or an existing VC tree. In this procedure, the BLLI value of
ADD_PARTY has to be the same value as that used to establish the
first point-to-point VC of the tree. The same BLLI value can be used
in different VC trees only when these VC trees can not add a leaf at
the same time. As a result, the BLLI value used in the signaling
must be determined by the root node of the multicast tree.

[note]
BLLI value is unique at the sender node. But BLLI value is not
unique at the receiver node because multiple sender nodes may
allocate the same BLLI value. So, the receiver node must
recognize BLLI value and the sender address. ATM Signaling
messages (SETUP and ADD_PARTY) carry both the BLLI and the sender
ATM address. The receiver node can realize which node sends the
BLLI message.

3.2.1 Outband notification using a small-sized field for
point-to-point VC

This subsection describes procedures for establishing a VC and for
notification of its VCID between neighboring LSRs for unicast
traffic.

Nagami, et al. Standards Track [Page 7]

RFC 3038 VCID Notification for LDP January 2001

The procedure employed when the upstream LSR assigns a VCID is as
follows.

1. An upstream LSR establishes a VC to the downstream LSR using ATM
signaling and supplies a value in the BLLI field that it is not
currently using for any other (incomplete) VCID notification
transaction with this peer.

2. The upstream LSR sends the VCID PROPOSE message through the VC for
LDP to notify the downstream LSR of the association between the
BLLI and VCID values.

3. The downstream LSR establishes the association between the VC with
the BLLI value and the VCID and sends an ACK message to the
upstream LSR.

4. After the upstream LSR receives the ACK message, it establishes
the association between the VC and the VCID. The VC is ready to
be used. At this time the BLLI value employed in this transaction
is free for reuse.

5. After VCID notification, the upstream node sends the LDP REQUEST
message to the downstream node. The downstream node sends the LDP
mapping message, which contains the VCID value in the label TLV of
LDP.

3.2.2 Outband notification using a small-sized field
for point-to-multipoint VC

This subsection describes procedures for establishing the first VC
for a multicast tree and for adding a new VC leaf to an existing VC
tree including the notification of its VCID for a multicast stream
using point-to-multipoint VCs.

In this procedure, an upstream LSR determines both the VCID and BLLI
value in the multicast case. The reason that the BLLI value is
determined by an upstream LSR is described above.

First, the procedure for establishing the first VC is described.

1. An upstream LSR establishes a VC by the ATM Forum Signaling
between the downstream LSR with a unique BLLI value at this time.

2. The upstream LSR notifies the downstream LSR of a paired BLLI
value and VCID using a message dedicated for this purpose.

Nagami, et al. Standards Track [Page 8]

RFC 3038 VCID Notification for LDP January 2001

3. The downstream LSR establishes the association between the VC with
the BLLI value and the VCID and sends an ACK message to the
upstream LSR. If the VCID is used by some other VC between the
upstream and downstream LSRs, the old VC is discarded.

4. After the upstream LSR receives the ACK message, the VC is ready
to be used and the BLLI value can be used for another VC.

Second, the procedure for adding a leaf to the existing point-to-
multipoint VC is described.

1. The upstream LSR establishes a VC by the ATM Forum Signaling
between its downstream LSR with the BLLI value that was used
during the first signaling procedure. If another VC is using the
BLLI value at the same time, the upstream waits for the completion
of the signaling procedure that is using this BLLI value.

2. Go to step 2 of the procedure for the first VC.

3.3 Outband notification

This method can be applied when a VC is established using a ATM
signaling message and the message has a field (e.g., GIT [GIT]) which
is large enough to carry a VCID value. Message format is described
in [GIT]. After the VCID notification, the node A sends the LDP
request message is sent to the node B. Then, the node B sends the
LDP mapping message to the node A.

Node A Node B
| |
|--------------->| ATM signaling with VCID
|<---------------|
| |
|--------------->| LDP Label Request
| |
|<---------------| LDP Label Mapping

4 VPID Notification Procedure

The approach that is used for the VCID notification procedure is also
applicable to share the same identifier between both ends for a VP.
VPID notification procedure is defined for this purpose.

A distinct VPID notification procedure is performed for each
direction of each VP.

Nagami, et al. Standards Track [Page 9]

RFC 3038 VCID Notification for LDP January 2001

After the VPID notification is finished for a VP, a VCID of a VC in
the VP is constructed with the VPID(MSB) and VCI(LSB) of the VC. The
VCID can be used by LDP without performing VCID notification
procedure. The message sequence is given below.

1. An upstream node sends the VPID PROPOSE message. In the case of
bidirectional label switched VC, both the upstream and downstream
nodes use VCI=33. In the case of unidirectional label switched
VC, the node which has larger LDP Identifier uses VCI=33 and the
other node uses VCI=34. Note that VCI=32, which is used for
unlabeled packet transfer, is not used for VPID notification
procedure so that the same encapsulation method can be applied for
both VPID procedure and inband VCID procedure.

2. The downstream node sends the VPID ACK message.

3. The upstream node sends the LDP Label Request message.

4. The downstream node sends the LDP Label Mapping message.

5 VCID Message Format

5.1 VCID Messages

An LDP VCID message consists of the LDP [LDP] fixed header followed
by one or more TLV. A VCID PROPOSE inband message and a VPID PROPOSE
message are sent as a null encapsulation packet through a VC to be
used as an LSP. There is only the label stack header before the LDP
VCID PDU. A label value in the label stack entry [ENCAPS] for the
VCID PROPOSE inband message and the VPID PROPOSE message are 4.
Other messages are sent as TCP packets. This is the same as LDP.

The VCID message type field is as follows:

VCID Propose inband Message = 0x0501
VCID Propose Message = 0x0502
VCID ACK Message = 0x0503
VCID NACK Message = 0x0504
VPID Propose inband Message = 0x0505
VPID ACK Message = 0x0506
VPID NACK Message = 0x0507

5.1.1 VCID Propose inband Message

This message is sent as a null encapsulation packet with LDP header
and label stack header through a VC to be used as an LSP. The label
value is 4. The reserved label value is required because the
downstream node may receive this message after receiving the LDP

Nagami, et al. Standards Track [Page 10]

RFC 3038 VCID Notification for LDP January 2001

Label Request message in the case of point-to-multipoint VC. The
downstream node must distinguish the VCID PROPOSE message from other
messages and ignore the VCID PROPOSE message when the node already
received the LDP Label Request message for the VC.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|VCID Inband Propose (0x0501) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Message Id
Four octet integer used to identify this message.

Label TLV
Label TLV contains VCID value. Type of label TLV is VCID(0x0203).

5.1.2 VCID Propose Message

An LSR uses the VCID PROPOSE message for the VCID notification
procedure of the outband notification using a small-sized field.
This message is sent through the VC for the LDP.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| VCID Propose (0x0502) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Temporary ID TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Message ID
Four octet integer used to identify this message.

Label TLV
Label TLV contains VCID value. Type of label TLV is VCID(0x0203).

Nagami, et al. Standards Track [Page 11]

RFC 3038 VCID Notification for LDP January 2001

Temporary ID TLV
The value carried in the user specific field in the layer 3
protocol field in the BLLI ID in the ATM Forum UNI 3.1/4.0 Type of
label TLV is VCID temporary ID(0x0702).

5.1.3 VCID ACK Message

An LSR send the VCID ACK message when the LSR accepts the VCID
PROPOSE message.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| VCID ACK (0x0503) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCID Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Message ID
Four octet integer used to identify this message.

Label TLV
The label TLV contains the VCID value of the received VCID PROPOSE
message. Type of label TLV is VCID(0x0203).

VCID Message ID
This value is the same as that of received VCID PROPOSE message.

5.1.4 VCID NACK Message

An LSR send the VCID NACK message when the LSR does not accept the
VCID PROPOSE message.

Nagami, et al. Standards Track [Page 12]

RFC 3038 VCID Notification for LDP January 2001

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| VCID NACK (0x0504) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCID Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Message ID
Four octet integer used to identify this message.

Label TLV
The label TLV contains the VCID value of the received VCID PROPOSE
message. Type of label TLV is VCID(0x0203).

VCID Message ID
This value is the same as that of received VCID PROPOSE message.

5.1.5 VPID Propose inband Message

This message is sent as a null encapsulation packet with LDP header
and label stack header through a VC to be used as an LSP. The label
value is 4. The downstream node must distinguish the VPID PROPOSE
message from other messages and ignore the VPID PROPOSE message when
the node already received the LDP Label Request message for the VC.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|VPID Inband Propose (0x0505) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPID TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Message Id
Four octet integer used to identify this message.

Nagami, et al. Standards Track [Page 13]

RFC 3038 VCID Notification for LDP January 2001

VPID TLV
VPID TLV contains VPID value. Type of label TLV is VPID(0x0703).

5.1.6 VPID ACK Message

An LSR send the VPID ACK message when the LSR accepts the VPID
PROPOSE message.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| VPID ACK (0x0506) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPID TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCID Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Message ID
Four octet integer used to identify this message.

VPID TLV
The VPID TLV contains the VPID value of the received VPID PROPOSE
message.

VCID Message ID
This value is the same as that of received VCID PROPOSE message.

Nagami, et al. Standards Track [Page 14]

RFC 3038 VCID Notification for LDP January 2001

5.1.7 VPID NACK Message

An LSR send the VPID NACK message when the LSR accepts the VPID
PROPOSE message.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| VPID NACK (0x0507) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPID TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCID Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Message ID
Four octet integer used to identify this message.

VPID TLV
The VPID TLV contains the VPID value of the received VPID PROPOSE
message.

VCID Message ID
This value is the same as that of received VCID PROPOSE message.

5.2 Objects

5.2.1 VCID Label TLV

An LSR uses VCID Label TLV to encode labels for use on the link which
does not have the same data link label at both ends of a VC.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F|VCID Label (0x0203) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

VCID
This is 4 byte VCID value.

Nagami, et al. Standards Track [Page 15]

RFC 3038 VCID Notification for LDP January 2001

5.2.2 VCID Message ID TLV

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F|VCID Message ID(0x0701) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCID Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

VCID Message ID
This is 4 byte VCID Message ID

5.2.3 VCID Temporary ID TLV

An LSR uses the VCID temporary ID TLV for the VCID notification
procedure of the outband notification using a small-sized field.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| VCID Temporary ID (0x0702)| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Temporary ID |
+-+-+-+-+-+-+-+-+

Temporary ID:
The value carried in the user specific field in the layer 3
protocol field in the BLLI ID in the ATM Forum UNI 3.1/4.0

5.2.4 VPID Label TLV

An LSR uses VPID TLV for the VPID notification procedure.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| VPID (0x0703) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

VPID
This is 2 byte VPID value.

Nagami, et al. Standards Track [Page 16]

RFC 3038 VCID Notification for LDP January 2001

Security Considerations

This document does not introduce new security issues other than those
present in the LDP and may use the same mechanisms proposed for this
technology.

Acknowledgments

The authors would like to acknowledge the valuable technical comments
of Yoshihiro Ohba, Shigeo Matsuzawa, Akiyoshi Mogi, Muneyoshi Suzuki,
George Swallow and members of the LAST-WG of the WIDE Project.

References

[LDP] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and B.
Thomas, "LDP Specification", RFC 3036, January 2001.

[GIT] Suzuki, M., "The Assignment of the Information Field and
Protocol Identifier in the Q.2941 Generic Identifier and
Q.2957 User-to-user Signaling for the Internet Protocol",
RFC 3033, January 2001.

[ENCAPS] Rosen, E., Viswanathan, A. and R. Callon, "MPLS Label Stack
Encoding", RFC 3032, January 2001.

Nagami, et al. Standards Track [Page 17]

RFC 3038 VCID Notification for LDP January 2001

Authors' Addresses

Ken-ichi Nagami
Computer & Network Development Center, Toshiba Corporation,
1, Toshiba-cho, Fuchu-shi,
Tokyo, 183-8511, Japan

Phone: +81-42-333-2884
EMail: [email protected]

Noritoshi Demizu
WaterSprings.ORG
1-6-11-501, Honjo, Sumida-ku, Tokyo, 130-0004, Japan

EMail: [email protected]

Hiroshi Esaki
Computer Center, University of Tokyo,
2-11-16 Yayoi, Bunkyo-ku,
Tokyo, 113-8658, Japan

Phone: +81-3-3812-1111
EMail: [email protected]

Yasuhiro Katsube
Computer & Network Development Center, Toshiba Corporation,
1, Toshiba-cho, Fuchu-shi,
Tokyo, 183-8511, Japan

Phone: +81-42-333-2844
EMail: [email protected]

Paul Doolan
Ennovate Networks
60 Codman Hill Road
Boxborough, MA

Phone: 978-263-2002 x103
EMail: [email protected]

Nagami, et al. Standards Track [Page 18]

RFC 3038 VCID Notification for LDP January 2001

Full Copyright Statement

Copyright (C) The Internet Society (2001). All Rights Reserved.

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

Funding for the RFC Editor function is currently provided by the
Internet Society.

Nagami, et al. Standards Track [Page 19]