< draft-martini-l2circuit-trans-mpls-07.txt   draft-martini-l2circuit-trans-mpls-08.txt >
Network Working Group Luca Martini Network Working Group Luca Martini
Internet Draft Nasser El-Aawar Internet Draft Nasser El-Aawar
Expiration Date: January 2002 Level 3 Communications, LLC. Expiration Date: May 2002 Level 3 Communications, LLC.
Steve Vogelsang Daniel Tappan Steve Vogelsang Daniel Tappan
John Shirron Eric C. Rosen John Shirron Eric C. Rosen
Toby Smith Alex Hamilton Toby Smith Alex Hamilton
Laurel Networks, Inc. Jayakumar Jayakumar Laurel Networks, Inc. Jayakumar Jayakumar
Cisco Systems, Inc. Cisco Systems, Inc.
Vasile Radoaca Dimitri Stratton Vlachos Vasile Radoaca Dimitri Stratton Vlachos
Nortel Networks Mazu Networks, Inc. Nortel Networks Mazu Networks, Inc.
Andrew G. Malis Chris Liljenstolpe Andrew G. Malis Chris Liljenstolpe
Vinai Sirkay Cable & Wireless Vinai Sirkay Cable & Wireless
Vivace Networks, Inc. Vivace Networks, Inc.
Giles Heron Giles Heron
Dave Cooper Gone2 Ltd. Dave Cooper PacketExchange Ltd.
Global Crossing Global Crossing
Kireeti Kompella Kireeti Kompella
Juniper Networks Juniper Networks
July 2001 November 2001
Transport of Layer 2 Frames Over MPLS Transport of Layer 2 Frames Over MPLS
draft-martini-l2circuit-trans-mpls-07.txt draft-martini-l2circuit-trans-mpls-08.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
skipping to change at page 2, line 17 skipping to change at page 2, line 17
Abstract Abstract
This document describes methods for transporting the Protocol Data This document describes methods for transporting the Protocol Data
Units (PDUs) of layer 2 protocols such as Frame Relay, ATM AAL5, Units (PDUs) of layer 2 protocols such as Frame Relay, ATM AAL5,
Ethernet, and providing a SONET circuit emulation service across an Ethernet, and providing a SONET circuit emulation service across an
MPLS network. MPLS network.
Table of Contents Table of Contents
1 Specification of Requirements .......................... 2 1 Specification of Requirements .......................... 3
2 Introduction ........................................... 3 2 Introduction ........................................... 3
3 Tunnel Labels and VC Labels ............................ 3 3 Tunnel Labels and VC Labels ............................ 3
4 Protocol-Specific Details .............................. 5 4 Protocol-Specific Details .............................. 5
4.1 Frame Relay ............................................ 5 4.1 Frame Relay ............................................ 5
4.2 ATM .................................................... 5 4.2 ATM .................................................... 5
4.2.1 ATM AAL5 VCC Transport ................................. 5 4.2.1 ATM AAL5 VCC Transport ................................. 5
4.2.2 ATM Transparent Cell Transport ......................... 5 4.2.2 ATM Transparent Cell Transport ......................... 5
4.2.3 ATM VCC and VPC Cell Transport ......................... 6 4.2.3 ATM VCC and VPC Cell Transport ......................... 6
4.2.4 OAM Cell Support ....................................... 6 4.2.4 OAM Cell Support ....................................... 6
4.2.5 ILMI Support ........................................... 7 4.2.5 ILMI Support ........................................... 7
4.3 Ethernet VLAN .......................................... 7 4.3 Ethernet VLAN .......................................... 7
4.4 Ethernet ............................................... 7 4.4 Ethernet ............................................... 7
4.5 HDLC ................................................... 7 4.5 HDLC ................................................... 7
4.6 PPP .................................................... 8 4.6 PPP .................................................... 8
5 LDP .................................................... 8 5 LDP .................................................... 8
5.1 Interface Parameters Field ............................. 9 5.1 Interface Parameters Field ............................. 10
5.2 LDP label Withdrawal procedures ........................ 11 5.2 C Bit handling procedures .............................. 11
6 IANA Considerations .................................... 11 5.2.1 VC types for which the control word is REQUIRED ........ 11
7 Security Considerations ................................ 12 5.2.2 VC types for which the control word is NOT mandatory ... 11
8 References ............................................. 12 5.2.3 Status codes ........................................... 13
9 Author Information ..................................... 13 5.3 LDP label Withdrawal procedures ........................ 13
5.4 Sequencing Considerations .............................. 14
5.4.1 Label Mapping Advertisements ........................... 14
5.4.2 Label Mapping Release .................................. 14
6 IANA Considerations .................................... 15
7 Security Considerations ................................ 15
8 References ............................................. 15
9 Author Information ..................................... 16
1. Specification of Requirements 1. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119. document are to be interpreted as described in RFC 2119.
2. Introduction 2. Introduction
In an MPLS network, it is possible to carry the Protocol Data Units In an MPLS network, it is possible to carry the Protocol Data Units
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If the payload of the MPLS packet is, for example, an ATM AAL5 PDU, If the payload of the MPLS packet is, for example, an ATM AAL5 PDU,
the VC label will generally correspond to a particular ATM VC at R2. the VC label will generally correspond to a particular ATM VC at R2.
That is, R2 needs to be able to infer from the VC label the outgoing That is, R2 needs to be able to infer from the VC label the outgoing
interface and the VPI/VCI value for the AAL5 PDU. If the payload is a interface and the VPI/VCI value for the AAL5 PDU. If the payload is a
Frame Relay PDU, then R2 needs to be able to infer from the VC label Frame Relay PDU, then R2 needs to be able to infer from the VC label
the outgoing interface and the DLCI value. If the payload is an the outgoing interface and the DLCI value. If the payload is an
Ethernet frame, then R2 needs to be able to infer from the VC label Ethernet frame, then R2 needs to be able to infer from the VC label
the outgoing interface, and perhaps the VLAN identifier. This process the outgoing interface, and perhaps the VLAN identifier. This process
is unidirectional, and will be repeated independently for is unidirectional, and will be repeated independently for
bidirectional operation. It is REQUIRED to assign the same VC ID, and bidirectional operation. It is REQUIRED to assign the same VC ID, and
VC type for a given circuit in both directions. The group id MUST NOT VC type for a given circuit in both directions. The group ID (see
be required to match in both directions. The transported frame MAY be below) MUST NOT be required to match in both directions. The
modified when it reaches the egress router. If the header of the transported frame MAY be modified when it reaches the egress router.
transported layer 2 frame is modified, this MUST be done at the If the header of the transported layer 2 frame is modified, this MUST
egress LSR only. be done at the egress LSR only.
Note that the VC label must always be at the bottom of the label Note that the VC label must always be at the bottom of the label
stack, and the tunnel label, if present, must be immediately above stack, and the tunnel label, if present, must be immediately above
the VC label. Of course, as the packet is transported across the MPLS the VC label. Of course, as the packet is transported across the MPLS
network, additional labels may be pushed on (and then popped off) as network, additional labels may be pushed on (and then popped off) as
needed. Even R1 itself may push on additional labels above the tunnel needed. Even R1 itself may push on additional labels above the tunnel
label. If R1 and R2 are directly adjacent LSRs, then it may not be label. If R1 and R2 are directly adjacent LSRs, then it may not be
necessary to use a tunnel label at all. necessary to use a tunnel label at all.
This document does not specify a method for distributing the tunnel This document does not specify a method for distributing the tunnel
label or any other labels that may appear above the VC label on the label or any other labels that may appear above the VC label on the
stack. Any acceptable method of MPLS label distribution will do. stack. Any acceptable method of MPLS label distribution will do.
This document does specify a method for assigning and distributing This document does specify a method for assigning and distributing
the VC label. Static label assignment MAY be used, and the VC label. Static label assignment MAY be used, and
implementations SHOULD provide support for this. When signaling is implementations SHOULD provide support for this. When signaling is
used, the VC label MUST be distributed from R2 to R1 using LDP in the used, the VC label MUST be distributed from R2 to R1 using LDP in the
downstream unsolicited mode; this requires that an LDP session be downstream unsolicited mode; this requires that an LDP session be
created between R1 and R2. It should be noted that this LDP session created between R1 and R2. It should be noted that this LDP session
is not necessarily transported along the same path as the Layer2 is not necessarily transported along the same path as the Layer 2
PDUs. [1] In addition, when using LDP to distribute the VC label, PDUs. [1] In addition, when using LDP to distribute the VC label,
liberal label retention mode SHOULD be used. However, as required in liberal label retention mode SHOULD be used. However, as required in
[1], the label request operation (mainly used by conservative label [1], the label request operation (mainly used by conservative label
retention mode) MUST be implemented. VC labels MUST be allocated from retention mode) MUST be implemented. VC labels MUST be allocated from
the per-platform label space. the per-platform label space.
Note that this technique allows an unbounded number of layer 2 "VCs" Note that this technique allows an unbounded number of layer 2 "VCs"
to be carried together in a single "tunnel". Thus it scales quite to be carried together in a single "tunnel". Thus it scales quite
well in the network backbone. well in the network backbone.
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4. Protocol-Specific Details 4. Protocol-Specific Details
4.1. Frame Relay 4.1. Frame Relay
The Frame Relay PDUs are encapsulated according to the procedures The Frame Relay PDUs are encapsulated according to the procedures
defined in [7]. The MPLS edge LSR MUST provide Frame Relay PVC status defined in [7]. The MPLS edge LSR MUST provide Frame Relay PVC status
signaling to the Frame Relay network. If the MPLS edge LSR detects a signaling to the Frame Relay network. If the MPLS edge LSR detects a
service affecting condition as defined in [2] Q.933 Annex A.5 sited service affecting condition as defined in [2] Q.933 Annex A.5 sited
in IA FRF1.1, it MUST withdraw the label that corresponds to the in IA FRF1.1, it MUST withdraw the label that corresponds to the
frame relay DLCI. The Egress LSR SHOULD generate the corresponding frame relay DLCI. The Egress LSR SHOULD generate the corresponding
errors and alarms as defined in [2] on the Frame relay VC. errors and alarms as defined in [2] on the egress Frame relay VC.
4.2. ATM 4.2. ATM
4.2.1. ATM AAL5 VCC Transport 4.2.1. ATM AAL5 VCC Transport
ATM AAL5 CSPS-PDUs are encapsulated according to [7] ATM AAL5 CPCS- ATM AAL5 CSPS-SDUs are encapsulated according to [7] ATM AAL5 CPCS-
PDU mode. This mode allows the transport of ATM AAL5 CSPS-PDUs SDU mode. This mode allows the transport of ATM AAL5 CSPS-SDUs
traveling on a particular ATM PVC across the MPLS network to another traveling on a particular ATM PVC across the MPLS network to another
ATM PVC. ATM PVC.
4.2.2. ATM Transparent Cell Transport 4.2.2. ATM Transparent Cell Transport
This mode is similar to the Ethernet port mode. Every cell that is This mode is similar to the Ethernet port mode. Every cell that is
received at the ingress ATM port on the ingress LSR, R1, is received at the ingress ATM port on the ingress LSR, R1, is
encapsulated according to [7], ATM cell mode, and sent across the LSP encapsulated according to [7], ATM cell mode, and sent across the LSP
to the egress LSR, R2. This mode allows an ATM port to be connected to the egress LSR, R2. This mode allows an ATM port to be connected
to only one other ATM port. [7] allows for grouping of multiple cells to only one other ATM port. [7] allows for grouping of multiple cells
into a single MPLS frame. Grouping of ATM cells is OPTIONAL for into a single MPLS frame. Grouping of ATM cells is OPTIONAL for
transmission at the ingress LSR, R1. If the Egress LSR R2 supports transmission at the ingress LSR, R1. If the Egress LSR R2 supports
cell concatenation the ingress LSR, R1, should only concatenate cells cell concatenation the ingress LSR, R1, should only concatenate cells
up to the "Maximum Number of concatenated ATM cells" parameter up to the "Maximum Number of concatenated ATM cells" parameter
received as part of the FEC element. received as part of the FEC element.
4.2.3. ATM VCC and VPC Cell Transport 4.2.3. ATM VCC and VPC Cell Transport
This mode is similar to the ATM AAL5 VCC transport except that only This mode is similar to the ATM AAL5 VCC transport except that cells
cells are transported. Every cell that is received on a pre-defined are transported. Every cell that is received on a pre-defined ATM
ATM PVC, or ATM PVP, at the ingress ATM port on the ingress LSR, R1, PVC, or ATM PVP, at the ingress ATM port on the ingress LSR, R1, is
is encapsulated according to [7], ATM cell mode, and sent across the encapsulated according to [7], ATM cell mode, and sent across the LSP
LSP to the egress LSR R2. Grouping of ATM cells is OPTIONAL for to the egress LSR R2. Grouping of ATM cells is OPTIONAL for
transmission at the ingress LSR, R1. If the Egress LSR R2 supports transmission at the ingress LSR, R1. If the Egress LSR R2 supports
cell concatenation the ingress LSR, R1, MUST only concatenate cells cell concatenation the ingress LSR, R1, MUST only concatenate cells
up to the "Maximum Number of concatenated ATM cells in a frame" up to the "Maximum Number of concatenated ATM cells in a frame"
parameter received as part of the FEC element. parameter received as part of the FEC element.
4.2.4. OAM Cell Support 4.2.4. OAM Cell Support
OAM cells MAY be transported on the VC LSP. When the LSR is operating OAM cells MAY be transported on the VC LSP. When the LSR is operating
in AAL5 CPCS-PDU transport mode if it does not support transport of in AAL5 CPCS-SDU transport mode if it does not support transport of
ATM cells, the LSR MUST discard incoming MPLS frames on an ATM VC LSP ATM cells, the LSR MUST discard incoming MPLS frames on an ATM VC LSP
that contain a VC label with the T bit set [7]. When operating in that contain a VC label with the T bit set [7]. When operating in
AAL5 PDU transport mode an LSR that supports transport of OAM cells AAL5 SDU transport mode an LSR that supports transport of OAM cells
using the T bit defined in [7], or an LSR operating in any of the using the T bit defined in [7], or an LSR operating in any of the
three cell transport modes MUST follow the procedures outlined in [9] three cell transport modes MUST follow the procedures outlined in [9]
section 8 for mode 0 only, in addition to the applicable procedures section 8 for mode 0 only, in addition to the applicable procedures
specified in [6]. specified in [6].
4.2.4.1. OAM Cell Emulation Mode 4.2.4.1. OAM Cell Emulation Mode
AN LSR that does not support transport of OAM cells across an LSP MAY AN LSR that does not support transport of OAM cells across an LSP MAY
provide OAM support on ATM PVCs using the following procedures: provide OAM support on ATM PVCs using the following procedures:
A pair of LSRs may emulate a bidrectional ATM VC by two uni- A pair of LSRs MAY emulate a bidrectional ATM VC by two uni-
directioal LSPs. If an F5 end-to-end OAM cell is received from a ATM directional LSPs. If an F5 end-to-end OAM cell is received from a
VC, by either LSR that is transporting this ATM VC, with a loopback ATM VC, by either LSR that is transporting this ATM VC, with a
indication value of 1, and the LSR has a label mapping for the ATM loopback indication value of 1, and the LSR has a label mapping for
VC, then the LSR MUST decrement the loopback indication value and the ATM VC, then the LSR MUST decrement the loopback indication value
loop back the cell on the ATM VC. Otherwise the loopback cell MUST be and loop back the cell on the ATM VC. Otherwise the loopback cell
discarded by the LSR. MUST be discarded by the LSR.
The ingress LSR, R1, may also optionally be configured to The ingress LSR, R1, may also optionally be configured to
periodically generate F5 end-to-end loopback OAM cells on a VC. If periodically generate F5 end-to-end loopback OAM cells on a VC. If
the LSR fails to receive a response to an F5 end-to-end loopback OAM the LSR fails to receive a response to an F5 end-to-end loopback OAM
cell for a pre-defined period of time it MUST withdraw the label cell for a pre-defined period of time it MUST withdraw the label
mapping for the VC. mapping for the VC.
If an ingress LSR, R1, receives an AIS F5 OAM cell, fails to receive If an ingress LSR, R1, receives an AIS F5 OAM cell, fails to receive
a pre-defined number of the End-to-End loop OAM cells, or a physical a pre-defined number of the End-to-End loop OAM cells, or a physical
interface goes down, it MUST withdraw the label mappings for all VCs interface goes down, it MUST withdraw the label mappings for all VCs
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the MPLS edge LSR detects that the physical link has failed, or the the MPLS edge LSR detects that the physical link has failed, or the
port is adminstratively disabled, it MUST withdraw the label mapping port is adminstratively disabled, it MUST withdraw the label mapping
that corresponds to the PPP link. that corresponds to the PPP link.
5. LDP 5. LDP
The VC label bindings are distributed using the LDP downstream The VC label bindings are distributed using the LDP downstream
unsolicited mode described in [1]. The LSRs will establish an LDP unsolicited mode described in [1]. The LSRs will establish an LDP
session using the Extended Discovery mechanism described in [1, session using the Extended Discovery mechanism described in [1,
section 2.4.2 and 2.5], for this purpose a new type of FEC element is section 2.4.2 and 2.5], for this purpose a new type of FEC element is
defined. The FEC element type is 128. [note1] Note that if the tunnel defined. The FEC element type is 128. [note1] Only a single VC FEC
label is not available, the VC label SHOULD NOT be advertised. element MUST be advertised per LDP VC label. The Virtual Circuit FEC
element, is defined as follows:
The Virtual Circuit FEC element, is defined as follows:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VC tlv |C| VC Type |VC info Length | | VC tlv |C| VC Type |VC info Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group ID | | Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VC ID | | VC ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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0x0004 Ethernet VLAN 0x0004 Ethernet VLAN
0x0005 Ethernet 0x0005 Ethernet
0x0006 HDLC 0x0006 HDLC
0x0007 PPP 0x0007 PPP
0x8008 CEM [8] 0x8008 CEM [8]
0x0009 ATM VCC cell transport 0x0009 ATM VCC cell transport
0x000A ATM VPC cell transport 0x000A ATM VPC cell transport
- Control word bit (C) - Control word bit (C)
The highest order bit (C) of the Vc type is used to flag the The highest order bit (C) of the VC type is used to flag the
presence of a control word ( defined in [7] ) as follows: presence of a control word ( defined in [7] ) as follows:
bit 15 = 1 control word present on this VC. bit 15 = 1 control word present on this VC.
bit 15 = 0 no control word present on this VC. bit 15 = 0 no control word present on this VC.
Please see the section "C Bit handling procedures" for further
explenation.
- VC information length - VC information length
Length of the VC ID field and the interface parameters field in Length of the VC ID field and the interface parameters field in
octets. If this value is 0, then it references all VCs using the octets. If this value is 0, then it references all VCs using the
specified group ID and there is no VC ID present, nor any specified group ID and there is no VC ID present, nor any
interface parameters. interface parameters.
- Group ID - Group ID
An arbitrary 32 bit value which represents a group of VCs that is An arbitrary 32 bit value which represents a group of VCs that is
used to create groups in the VC space. The group ID is intended used to create groups in the VC space. The group ID is intended
to be used as a port index, or a virtual tunnel index. To to be used as a port index, or a virtual tunnel index. To
simplify configuration a particular VC ID at ingress could be simplify configuration a particular VC ID at ingress could be
part of the virtual tunnel for transport to the egress router. part of the virtual tunnel for transport to the egress router.
The Group ID is very useful to send a wild card label withdrawals The Group ID is very useful to send wild card label withdrawals
to remote LSRs upon physical port failure. to remote LSRs upon physical port failure.
- VC ID - VC ID
A non zero 32-bit connection ID that together with the VC type, A non zero 32-bit connection ID that together with the VC type,
identifies a particular VC. identifies a particular VC.
- Interface parameters - Interface parameters
This variable length field is used to provide interface specific This variable length field is used to provide interface specific
parameters, such as interface MTU. parameters, such as interface MTU.
5.1. Interface Parameters Field 5.1. Interface Parameters Field
This field specifies edge facing interface specific parameters and This field specifies interface specific parameters. When aplicable,
SHOULD be used to validate that the LSRs, and the ingress and egress it MUST be used to validate that the LSRs, and the ingress and egress
ports at the edges of the circuit, have the necessary capabilities to ports at the edges of the circuit, have the necessary capabilities to
interoperate with each other. The field structure is defined as interoperate with each other. The field structure is defined as
follows: follows:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter ID | Length | Variable Length Value | | Parameter ID | Length | Variable Length Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Length Value | | Variable Length Value |
| " | | " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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but MUST NOT exceed it. This parameter is applicable only to VC but MUST NOT exceed it. This parameter is applicable only to VC
types 3, 9, and 0x0a, and is REQUIRED for these VC types. This types 3, 9, and 0x0a, and is REQUIRED for these VC types. This
parameter does not need to match in both directions of a specific parameter does not need to match in both directions of a specific
VC. VC.
- Optional Interface Description string - Optional Interface Description string
This arbitrary, OPTIONAL, interface description string can be This arbitrary, OPTIONAL, interface description string can be
used to send an administrative description text string to the used to send an administrative description text string to the
remote LSR. This parameter is OPTIONAL, and is applicable to all remote LSR. This parameter is OPTIONAL, and is applicable to all
VC types. The interface description parameter length is variable, VC types. The interface description parameter string length is
and can be up to 80 octets. variable, and can be from 0 to 80 octets.
- Payload Bytes - Payload Bytes
A 2 octet value indicating the the number of TDM payload octets A 2 octet value indicating the the number of TDM payload octets
contained in all packets on the CEM stream, from 48 to 1,023 contained in all packets on the CEM stream, from 48 to 1,023
octets. All of the packets in a given CEM stream have the same octets. All of the packets in a given CEM stream have the same
number of payload bytes. Note that there is a possibility that number of payload bytes. Note that there is a possibility that
the packet size may exceed the SPE size in the case of an STS-1 the packet size may exceed the SPE size in the case of an STS-1
SPE, which could cause two pointers to be needed in the CEM SPE, which could cause two pointers to be needed in the CEM
header, since the payload may contain two J1 bytes for header, since the payload may contain two J1 bytes for
consecutive SPEs. For this reason, the number of payload bytes consecutive SPEs. For this reason, the number of payload bytes
must be less than or equal to 783 for STS-1 SPEs. must be less than or equal to 783 for STS-1 SPEs.
- CEM Options. An optional 16 Bit value of CEM Flags. See [8] for - CEM Options. An optional 16 Bit value of CEM Flags. See [8] for
the definition of the bit values. the definition of the bit values.
5.2. LDP label Withdrawal procedures 5.2. C Bit handling procedures
5.2.1. VC types for which the control word is REQUIRED
The Label Mapping messages which are sent in order to set up these
VCs MUST have c=1. When a Label Mapping message for a VC of one of
these types is received, and c=0, a Label Release MUST be sent, with
an "Illegal C-bit" status code. In this case, the VC will not come
up.
5.2.2. VC types for which the control word is NOT mandatory
If a system is capable of sending and receiving the control word on
VC types for which the control word is not mandatory, then each such
VC endpoint MUST be configurable with a parameter that specifies
whether the use of the control word is PREFERRED or NOT PREFERRED.
For each VC, there MUST be a default value of this parameter. This
specification does NOT state what the default value should.
If a system is NOT capable of sending and receiving the control word
on VC types for which the control word is not mandatory, then it
behaves as exactly as if it were configured for the use of the
control word to be NOT PREFERRED.
If a Label Mapping message for the VC has already been received, but
no Label Mapping message for the VC has yet been sent, then the
procedure is the following:
-i. If the received Label Mapping message has c=0, send a Label
Mapping message with c=0, and the control word is not used.
-ii. If the received Label Mapping message has c=1, and the VC is
locally configured such that the use of the control word is
preferred, then send a Label Mapping message with c=1, and
the control word is used.
-iii. If the received Label Mapping message has c=1, and the VC is
locally configured such that the use of the control word is
not preferred or the control word is not supported, then act
as if no Label Mapping message for the VC had been received
(i.e., proceed to the next paragraph).
If a Label Mapping message for the VC has not already been received
(or if the received Label Mapping message had c=1 and either local
configuration says that the use of the control word is not preferred
or the control word is not supported), then send a Label Mapping
message in which the c bit is set to correspond to the locally
configured preference for use of the control word. (I.e., set c=1 if
locally configured to prefer the control word, set c=0 if locally
configured to prefer not to use the control word or if the control
word is not supported).
The next action depends on what control message is next received for
that VC. The possibilities are:
-i. A Label Mapping message with the same c bit value as
specified in the Label Mapping message that was sent. VC
setup is now complete, and the control word is used if c=1
but not used if c=0.
-ii. A Label Mapping message with c=1, but the Label Mapping
message that was sent has c=0. In this case, ignore the
received Label Mapping message, and continue to wait for the
next control message for the VC.
-iii. A Label Mapping message with c=0, but the Label Mapping
message that was sent has c=1. In this case, send a Label
Withdraw message with a "Wrong c-bit" status code, followed
by a Label Mapping message that has c=0. VC setup is now
complete, and the control word is not used.
-iv. A Label Withdraw message with the "Wrong c-bit" status code.
Treat as a normal Label Withdraw, but do not respond.
Continue to wait for the next control message for the VC.
If at any time after a Label Mapping message has been received, a
corresponding Label Withdraw or Release is received, the action taken
is the same as for any Label Withdraw or Release that might be
received at any time. Note that receiving a Label Withdraw should not
cause a corresponding Label Release to be sent.
If both endpoints prefer the use of the control word, this procedure
will cause it to be used. If either endpoint prefers not to use the
control word, or does not support the control word, this procedure
will cause it not to be used. If one endpoint prefers to use the
control word but the other does not, the one that prefers not to use
it is has no extra protocol to execute, it just waits for a Label
Mapping message that has c=0.
5.2.3. Status codes
RFC 3036 has a range of Status Code values which are assigned by IANA
on a First Come, First Served basis. These are in the range
0x20000000-0x3effffff [note 2]. The following new status codes are
defined:
0x20000001 "Illegal C-Bit"
0x20000002 "Wrong C-Bit"
5.3. LDP label Withdrawal procedures
As mentioned above the Group ID field can be used to withdraw all VC As mentioned above the Group ID field can be used to withdraw all VC
labels associated with a particular group ID. This procedure is labels associated with a particular group ID. This procedure is
OPTIONAL, and if it is implemented the LDP label withdraw message OPTIONAL, and if it is implemented the LDP label withdraw message
should be as follows: the VC information length field is set to 0, should be as follows: the VC information length field is set to 0,
the VC ID field is not present, and the interface paramenters field the VC ID field is not present, and the interface paramenters field
is not present. For the purpose of this document this is called the is not present. For the purpose of this document this is called the
"wild card withdraw procedure", and all LSRs implementing this design "wild card withdraw procedure", and all LSRs implementing this design
are REQUIRED to accept such a withdraw message, but are not required are REQUIRED to accept such a withdraw message, but are not required
to send it. to send it.
The interface parameters field MUST NOT be present in any LDP VC The interface parameters field MUST NOT be present in any LDP VC
label withdrawal message or release message. A wildcard release label withdrawal message or release message. A wildcard release
message MUST include only the group ID. message MUST include only the group ID.A Label Release message
initiated from the imposition router must always include the VC ID.
5.4. Sequencing Considerations
In the case where the router considers the sequence number field in
the control word, it is important to note the following when
advertising labels
5.4.1. Label Mapping Advertisements
After a label has been withdrawn by the disposition router and/or
released by the imposition router, care must be taken to not re-
advertise (re-use) the released label until the disposition router
can be reasonably certain that old packets containing the released
label no longer persist in the MPLS network.
This precaution is required to prevent the imposition router from
restarting packet forwarding with sequence number of 1 when it
receives the same label mapping if there are still older packets
persisting in the network with sequence number between 1 and 32768.
For example, if there is a packet with sequence number=n where n is
in the interval[1,32768] travelling through the network, it would be
possible for the disposition router to receive that packet after it
re-advertises the label. Since the label has been released by the
imposition router, the disposition router SHOULD be expecting the
next packet to arrive with sequence number to be 1. Receipt of a
packet with sequence number equal to n will result in n packets
potentially being rejected by the disposition router until the
imposition router imposes a sequence number of n+1 into a packet.
Possible methods to avoid this is for the disposition router to
always advertise a different VC label, or for the disposition router
to wait for a sufficient time before attempting to re-advertised a
recently released label. This is only an issue when sequence number
processing at the disposition router is enabled.
5.4.2. Label Mapping Release
In situations where the imposition router wants to restart forwarding
of packets with sequence number 1, the router shall 1) Send to
disposition router a label mapping release, and 2) Send to
disposition router a label mapping request. When sequencing is
supported, advertisement of a vc label in response to a label mapping
request MUST also consider the issues discussed in 5.3.1
6. IANA Considerations 6. IANA Considerations
As specified in this document, a Virtual Circuit FEC element contains As specified in this document, a Virtual Circuit FEC element contains
the VC Type field. VC Type value 0 is reserved. VC Type values 1 the VC Type field. VC Type value 0 is reserved. VC Type values 1
through 10 are defined in this document. VC Type values 11 through 63 through 10 are defined in this document. VC Type values 11 through 63
are to be assigned by IANA using the "IETF Consensus" policy defined are to be assigned by IANA using the "IETF Consensus" policy defined
in RFC2434. VC Type values 64 through 127 are to be assigned by IANA, in RFC2434. VC Type values 64 through 127 are to be assigned by IANA,
using the "First Come First Served" policy defined in RFC2434. VC using the "First Come First Served" policy defined in RFC2434. VC
Type values 128 through 32767 are vendor-specific, and values in this Type values 128 through 32767 are vendor-specific, and values in this
range are not to be assigned by IANA. range are not to be assigned by IANA.
As specified in this document, a Virtual Circuit FEC element contains As specified in this document, a Virtual Circuit FEC element contains
the Interface Parameters field, which is a list of one or more the Interface Parameters field, which is a list of one or more
parameters, and each parameter is identified by the Parameter ID parameters, and each parameter is identified by the Parameter ID
field. Parameter ID value 0 is reserved. Parameter ID values 1 field. Parameter ID value 0 is reserved. Parameter ID values 1
through 6 are defined in this document. Parameter ID values 7 through 5 are defined in this document. Parameter ID values 6
through 63 are to be assigned by IANA using the "IETF Consensus" through 63 are to be assigned by IANA using the "IETF Consensus"
policy defined in RFC2434. Parameter ID values 64 through 127 are to policy defined in RFC2434. Parameter ID values 64 through 127 are to
be assigned by IANA, using the "First Come First Served" policy be assigned by IANA, using the "First Come First Served" policy
defined in RFC2434. Parameter ID values 128 through 255 are vendor- defined in RFC2434. Parameter ID values 128 through 255 are vendor-
specific, and values in this range are not to be assigned by IANA. specific, and values in this range are not to be assigned by IANA.
7. Security Considerations 7. Security Considerations
This document does not affect the underlying security issues of MPLS. This document does not affect the underlying security issues of MPLS.
skipping to change at page 12, line 40 skipping to change at page 15, line 51
[4] "IEEE 802.3ac-1998" IEEE standard specification. [4] "IEEE 802.3ac-1998" IEEE standard specification.
[5] American National Standards Institute, "Synchronous Optical [5] American National Standards Institute, "Synchronous Optical
Network Formats," ANSI T1.105-1995. Network Formats," ANSI T1.105-1995.
[6] ITU Recommendation G.707, "Network Node Interface For The [6] ITU Recommendation G.707, "Network Node Interface For The
Synchronous Digital Hierarchy", 1996. Synchronous Digital Hierarchy", 1996.
[7] "Encapsulation Methods for Transport of Layer 2 Frames Over [7] "Encapsulation Methods for Transport of Layer 2 Frames Over
MPLS", draft-martini-l2circuit-encap-mpls-02.txt ( Work in progress ) MPLS", draft-martini-l2circuit-encap-mpls-04.txt ( Work in progress )
[8] "SONET/SDH Circuit Emulation Service Over MPLS (CEM) [8] "SONET/SDH Circuit Emulation Service Over MPLS (CEM)
Encapsulation", draft-malis-sonet-ces-mpls-04.txt ( Work in progress Encapsulation", draft-malis-sonet-ces-mpls-05.txt ( Work in progress
) )
[9] "Frame Based ATM over SONET/SDH Transport (FAST)," 2000. [9] "Frame Based ATM over SONET/SDH Transport (FAST)," 2000.
[note1] FEC element type 128 is pending IANA approval. [note1] FEC element type 128 is pending IANA approval. [note2]
Status codes assigment is pending IANA approval.
9. Author Information 9. Author Information
Luca Martini Luca Martini
Level 3 Communications, LLC. Level 3 Communications, LLC.
1025 Eldorado Blvd. 1025 Eldorado Blvd.
Broomfield, CO, 80021 Broomfield, CO, 80021
e-mail: luca@level3.net e-mail: luca@level3.net
Nasser El-Aawar Nasser El-Aawar
Level 3 Communications, LLC. Level 3 Communications, LLC.
1025 Eldorado Blvd. 1025 Eldorado Blvd.
Broomfield, CO, 80021 Broomfield, CO, 80021
e-mail: nna@level3.net e-mail: nna@level3.net
Giles Heron Giles Heron
Gone2 Ltd. PacketExchange Ltd.
c/o MDP The Truman Brewery
One Curzon Street 91 Brick Lane
London LONDON E1 6QL
W1J 5HD
United Kingdom United Kingdom
e-mail: giles@goneto.net e-mail: giles@packetexchange.net
Dimitri Stratton Vlachos Dimitri Stratton Vlachos
Mazu Networks, Inc. Mazu Networks, Inc.
125 Cambridgepark Drive 125 Cambridgepark Drive
Cambridge, MA 02140 Cambridge, MA 02140
e-mail: d@mazunetworks.com e-mail: d@mazunetworks.com
Dan Tappan Dan Tappan
Cisco Systems, Inc. Cisco Systems, Inc.
250 Apollo Drive 250 Apollo Drive
skipping to change at page 13, line 39 skipping to change at page 17, line 4
Mazu Networks, Inc. Mazu Networks, Inc.
125 Cambridgepark Drive 125 Cambridgepark Drive
Cambridge, MA 02140 Cambridge, MA 02140
e-mail: d@mazunetworks.com e-mail: d@mazunetworks.com
Dan Tappan Dan Tappan
Cisco Systems, Inc. Cisco Systems, Inc.
250 Apollo Drive 250 Apollo Drive
Chelmsford, MA, 01824 Chelmsford, MA, 01824
e-mail: tappan@cisco.com e-mail: tappan@cisco.com
Jayakumar Jayakumar, Jayakumar Jayakumar,
Cisco Systems Inc. Cisco Systems Inc.
225, E.Tasman, MS-SJ3/3, 225, E.Tasman, MS-SJ3/3,
San Jose, CA, 95134 San Jose, CA, 95134
e-mail: jjayakum@cisco.com e-mail: jjayakum@cisco.com
Alex Hamilton, Alex Hamilton,
Cisco Systems Inc. Cisco Systems Inc.
285 W. Tasman, MS-SJCI/3/4, 285 W. Tasman, MS-SJCI/3/4,
San Jose, CA, 95134 San Jose, CA, 95134
e-mail: tahamilt@cisco.com e-mail: tahamilt@cisco.com
Eric Rosen Eric Rosen
Cisco Systems, Inc. Cisco Systems, Inc.
250 Apollo Drive 250 Apollo Drive
Chelmsford, MA, 01824 Chelmsford, MA, 01824
e-mail: erosen@cisco.com e-mail: erosen@cisco.com
Steve Vogelsang Steve Vogelsang
Laurel Networks, Inc. Laurel Networks, Inc.
Omega Corporate Center Omega Corporate Center
1300 Omega Drive 1300 Omega Drive
Pittsburg, PA 15205 Pittsburgh, PA 15205
e-mail: sjv@laurelnetworks.com e-mail: sjv@laurelnetworks.com
John Shirron John Shirron
Omega Corporate Center Omega Corporate Center
1300 Omega Drive 1300 Omega Drive
Pittsburg, PA 15205 Pittsburgh, PA 15205
Laurel Networks, Inc. Laurel Networks, Inc.
e-mail: jshirron@laurelnetworks.com e-mail: jshirron@laurelnetworks.com
Toby Smith
Omega Corporate Center
1300 Omega Drive
Pittsburgh, PA 15205
Laurel Networks, Inc.
e-mail: tob@laurelnetworks.com
Andrew G. Malis Andrew G. Malis
Vivace Networks, Inc. Vivace Networks, Inc.
2730 Orchard Parkway 2730 Orchard Parkway
San Jose, CA 95134 San Jose, CA 95134
Phone: +1 408 383 7223 Phone: +1 408 383 7223
Email: Andy.Malis@vivacenetworks.com Email: Andy.Malis@vivacenetworks.com
Vinai Sirkay Vinai Sirkay
Vivace Networks, Inc. Vivace Networks, Inc.
2730 Orchard Parkway 2730 Orchard Parkway
San Jose, CA 95134 San Jose, CA 95134
e-mail: vinai.sirkay@vivacenetworks.com e-mail: sirkay@technologist.com
Vasile Radoaca Vasile Radoaca
Nortel Networks Nortel Networks
600 Technology Park 600 Technology Park
Billerica MA 01821 Billerica MA 01821
e-mail: vasile@nortelnetworks.com e-mail: vasile@nortelnetworks.com
Chris Liljenstolpe Chris Liljenstolpe
Cable & Wireless Cable & Wireless
11700 Plaza America Drive 11700 Plaza America Drive
Reston, VA 20190 Reston, VA 20190
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