< draft-martini-l2circuit-encap-mpls-01.txt   draft-martini-l2circuit-encap-mpls-02.txt >
Network Working Group Luca Martini Network Working Group Luca Martini
Internet Draft Nasser El-Aawar Internet Draft Nasser El-Aawar
Expiration Date: August 2001 Giles Heron Expiration Date: November 2001 Level 3 Communications, LLC.
Level 3 Communications, LLC.
Daniel Tappan Steve Vogelsang Daniel Tappan
Eric C. Rosen John Shirron Eric C. Rosen
Alex Hamilton Toby Smith Alex Hamilton
Jayakumar Jayakumar Laurel Networks, Inc. Jayakumar Jayakumar
Cisco Systems, Inc. Cisco Systems, Inc.
Steve Vogelsang Vasile Radoaca Dimitri Stratton Vlachos
John Shirron Nortel Networks Mazu Networks, Inc.
Toby Smith
Laurel Networks, Inc.
Andrew G. Malis
Vinai Sirkay
Vivace Networks, Inc.
Dimitri Stratton Vlachos
Mazu Networks, Inc.
Kireeti Kompella Andrew G. Malis Chris Liljenstolpe
Juniper Networks Vinai Sirkay Cable & Wireless
Vivace Networks, Inc.
Giles Heron
Gone2 Ltd.
February 2001 May 2001
Encapsulation Methods for Transport of Layer 2 Frames Over MPLS Encapsulation Methods for Transport of Layer 2 Frames Over MPLS
draft-martini-l2circuit-encap-mpls-01.txt draft-martini-l2circuit-encap-mpls-02.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 4 skipping to change at page 1, line 41
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.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
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Abstract Abstract
This document describes methods for encapsulating the Protocol Data This document describes methods for encapsulating the Protocol Data
Units (PDUs) of layer 2 protocols such as Frame Relay, ATM AAL5, or Units (PDUs) of layer 2 protocols such as Frame Relay, ATM AAL5, or
Ethernet for transport across an MPLS network. Ethernet for transport across an MPLS network.
Table of Contents Table of Contents
1 Specification of Requirements .......................... 3 1 Specification of Requirements .......................... 2
2 Introduction ........................................... 3 2 Introduction ........................................... 3
3 General encapsulation method ........................... 3 3 General encapsulation method ........................... 3
3.1 The Control Word ....................................... 3 3.1 The Control Word ....................................... 3
3.1.1 Setting the sequence number ............................ 4 3.1.1 Setting the sequence number ............................ 4
3.1.2 Processing the sequence number ......................... 5 3.1.2 Processing the sequence number ......................... 5
3.2 MTU Requirements ....................................... 5 3.2 MTU Requirements ....................................... 5
3.3 MPLS Shim EXP Bit Values ............................... 6 3.3 MPLS Shim EXP Bit Values ............................... 6
3.4 MPLS Shim TTL Values ................................... 6 3.4 MPLS Shim S Bit Value .................................. 6
3.5 MPLS Shim TTL Values ................................... 6
4 Protocol-Specific Details .............................. 6 4 Protocol-Specific Details .............................. 6
4.1 Frame Relay ............................................ 6 4.1 Frame Relay ............................................ 6
4.2 ATM .................................................... 8 4.2 ATM .................................................... 8
4.2.1 ATM AAL5 CPCS-PDU Mode ................................. 8 4.2.1 ATM AAL5 CPCS-PDU Mode ................................. 8
4.2.2 ATM Cell Mode .......................................... 10 4.2.2 ATM Cell Mode .......................................... 9
4.2.3 OAM Cell Support ....................................... 12 4.2.3 OAM Cell Support ....................................... 11
4.2.4 CLP bit to MPLS label stack EXP bit mapping ............ 12 4.2.4 CLP bit to MPLS label stack EXP bit mapping ............ 11
4.3 Ethernet VLAN .......................................... 12 4.3 Ethernet VLAN .......................................... 11
4.4 Ethernet ............................................... 12 4.4 Ethernet ............................................... 12
4.5 HDLC ( Cisco ) ......................................... 13 4.5 HDLC ( Cisco ) ......................................... 12
4.6 PPP .................................................... 13 4.6 PPP .................................................... 12
5 Security Considerations ................................ 13 5 Security Considerations ................................ 13
6 Intellectual Property Disclaimer ....................... 13 6 Intellectual Property Disclaimer ....................... 13
7 References ............................................. 13 7 References ............................................. 13
8 Author Information ..................................... 14 8 Author Information ..................................... 13
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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3.1.1. Setting the sequence number 3.1.1. Setting the sequence number
Given a VC label V and a pair of LSRs R1 and R2, where R2 has Given a VC label V and a pair of LSRs R1 and R2, where R2 has
distributed V to R1. If R1 supports packet sequencing then the distributed V to R1. If R1 supports packet sequencing then the
following procedures should be used: following procedures should be used:
- the initial packet transmitted to label V MUST use sequence - the initial packet transmitted to label V MUST use sequence
number 1 number 1
- subsequent packets MUST increment the sequence number by one for - subsequent packets MUST increment the sequence number by one for
each packet each packet
- when the transmit sequence number reaches the maximum 16 bit - when the transmit sequence number reaches the maximum 16 bit
value (65535) the sequence number MUST wrap to 1 value (65535) the sequence number MUST wrap to 1
If the transmitting LSR R1 does not support sequence number If the transmitting LSR R1 does not support sequence number
processing, then the sequence number field in the control word MUST processing, then the sequence number field in the control word MUST
be set to 0. be set to 0.
3.1.2. Processing the sequence number 3.1.2. Processing the sequence number
If an LSR R2 supports receive sequence number processing, then the If an LSR R2 supports receive sequence number processing, then the
following procedures should be used: following procedures should be used:
When a VC label V is first distributed, the "expected sequence When a VC label V is first distributed, the "expected sequence
number" associated with V MUST be initialized to 1 number" associated with V MUST be initialized to 1
When a packet is received with label V the sequence number should be When a packet is received with label V the sequence number should be
processed as follows: processed as follows:
- if the sequence number on the packet is 0, then the packet passes - if the sequence number on the packet is 0, then the packet passes
the sequence number check the sequence number check
- Otherwise if the packet sequence number >= the expected sequence - otherwise if the packet sequence number >= the expected sequence
number (using an unsigned comparison, modulo 2**16), then the number and the packet sequence number - the expected sequence
packet is in order. number < 32768, then the packet is in order.
- otherwise if the packet sequence number < the expected sequence
number and the expected sequence number - the packet sequence
number >= 32768, then the packet is in order.
- otherwise the packet is out of order. - otherwise the packet is out of order.
If a packet passes the sequence number check, or is in order then, it If a packet passes the sequence number check, or is in order then, it
can be delivered immediately. If the packet is in order, then the can be delivered immediately. If the packet is in order, then the
expected sequence number should be set using the algorithm: expected sequence number should be set using the algorithm:
expected_sequence_number := packet_sequence_number + 1 mod 2**16 expected_sequence_number := packet_sequence_number + 1 mod 2**16
if (expected_sequence_number = 0) then expected_sequence_number := 1; if (expected_sequence_number = 0) then expected_sequence_number := 1;
Packets which are received out of order MAY be dropped or reordered Packets which are received out of order MAY be dropped or reordered
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dropped. dropped.
3.3. MPLS Shim EXP Bit Values 3.3. MPLS Shim EXP Bit Values
The ingress LSR, R1, SHOULD set the EXP field of the VC label to the The ingress LSR, R1, SHOULD set the EXP field of the VC label to the
same value as the EXP field of the previous label in the stack (if in same value as the EXP field of the previous label in the stack (if in
fact a stack of more than one label is imposed at the ingress.) This fact a stack of more than one label is imposed at the ingress.) This
will ensure that the EXP field will be visible to the egress LSR, R2, will ensure that the EXP field will be visible to the egress LSR, R2,
in the event of the packet having been penultimate hop popped. in the event of the packet having been penultimate hop popped.
3.4. MPLS Shim TTL Values 3.4. MPLS Shim S Bit Value
The ingress LSP, R1, MAY set the TTL field of the VC label to a value The ingress LSR, R1, MUST set the S bit of the VC label to a value of
1 to denote that the VC label is at the bottom of the stack.
3.5. MPLS Shim TTL Values
The ingress LSR, R1, MAY set the TTL field of the VC label to a value
of 2. of 2.
4. Protocol-Specific Details 4. Protocol-Specific Details
4.1. Frame Relay 4.1. Frame Relay
A Frame Relay PDU is transported without the Frame Relay header or A Frame Relay PDU is transported without the Frame Relay header or
the FCS. The sequencing control word is REQUIRED. the FCS. The control word is REQUIRED.
The BECN, FECN, DE and C/R bits are carried across the network in the The BECN, FECN, DE and C/R bits are carried across the network in the
control word. The edge LSRs that implement this document MAY, when control word. The edge LSRs that implement this document MAY, when
either adding or removing the encapsulation described herein, change either adding or removing the encapsulation described herein, change
the BECN and/or FECN bits from zero to one in order to reflect the BECN and/or FECN bits from zero to one in order to reflect
congestion in the MPLS network that is known to the edge LSRs, and congestion in the MPLS network that is known to the edge LSRs, and
the D/E bit from zero to one to reflect marking from edge policing of the D/E bit from zero to one to reflect marking from edge policing of
the Frame Relay Committed Information Rate. The BECN, FECN, and D/E the Frame Relay Committed Information Rate. The BECN, FECN, and D/E
bits MUST NOT be changed from one to zero. bits MUST NOT be changed from one to zero.
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4.2. ATM 4.2. ATM
Two encapsulations are supported for ATM transport: one for ATM AAL5 Two encapsulations are supported for ATM transport: one for ATM AAL5
and another for ATM cells. and another for ATM cells.
The AAL5 CPCS-PDU encapsulation consists of the MPLS label stack, a The AAL5 CPCS-PDU encapsulation consists of the MPLS label stack, a
REQUIRED control word, and the AAL5 CPCS-PDU. REQUIRED control word, and the AAL5 CPCS-PDU.
The ATM cell encapsulation consists of an MPLS label stack, an The ATM cell encapsulation consists of an MPLS label stack, an
OPTIONAL sequencing control word, a 4 byte ATM cell header, and the OPTIONAL control word, a 4 byte ATM cell header, and the ATM cell
ATM cell payload. payload.
4.2.1. ATM AAL5 CPCS-PDU Mode 4.2.1. ATM AAL5 CPCS-PDU Mode
In ATM AAL5 mode the ingress LSR is required to reassemble AAL5 In ATM AAL5 mode the ingress LSR is required to reassemble AAL5
CPCS-PDUs from the incoming VC and transport each CPCS-PDU as a CPCS-PDUs from the incoming VC and transport each CPCS-PDU as a
single packet. No AAL5 trailer is transported. The sequencing control single packet. No AAL5 trailer is transported. The control word is
word is REQUIRED. REQUIRED.
The EFCI and CLP bits are carried across the network in the control The EFCI and CLP bits are carried across the network in the control
word. The edge LSRs that implement this document MAY, when either word. The edge LSRs that implement this document MAY, when either
adding or removing the encapsulation described herein, change the adding or removing the encapsulation described herein, change the
EFCI bit from zero to one in order to reflect congestion in the MPLS EFCI bit from zero to one in order to reflect congestion in the MPLS
network that is known to the edge LSRs, and the CLP bit from zero to network that is known to the edge LSRs, and the CLP bit from zero to
one to reflect marking from edge policing of the ATM Sustained Cell one to reflect marking from edge policing of the ATM Sustained Cell
Rate. The EFCI and CLP bits MUST NOT be changed from one to zero. Rate. The EFCI and CLP bits MUST NOT be changed from one to zero.
The AAL5 CPCS-PDU is prepended by the following header: The AAL5 CPCS-PDU is prepended by the following header:
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| " | | " |
| " | | " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* T (transport type) bit * T (transport type) bit
Bit (T) of the control word indicates whether the MPLS packet Bit (T) of the control word indicates whether the MPLS packet
contains an ATM cell or an AAL5 CPCS-PDU. If set the packet contains an ATM cell or an AAL5 CPCS-PDU. If set the packet
contains an ATM cell, encapsulated according to the ATM cell mode contains an ATM cell, encapsulated according to the ATM cell mode
section below, otherwise it contains an AAL5 CPCS-PDU. The section below, otherwise it contains an AAL5 CPCS-PDU. The
ability to transportan ATM cell in the AAL5 mode is intended to ability to transport an ATM cell in the AAL5 mode is intended to
provide a means of enabling OAM functionality over the AAL5 VC. provide a means of enabling OAM functionality over the AAL5 VC.
* E ( EFCI ) Bit * E ( EFCI ) Bit
The ingress LSR, R1, SHOULD set this bit to 1 if the EFCI bit of The ingress LSR, R1, SHOULD set this bit to 1 if the EFCI bit of
the final cell of those that transported the AAL5 CPCS-PDU is set the final cell of those that transported the AAL5 CPCS-PDU is set
to 1, or if the EFCI bit of the single ATM cell to be transported to 1, or if the EFCI bit of the single ATM cell to be transported
in the MPLS packet is set to 1. Otherwise this bit SHOULD be set in the MPLS packet is set to 1. Otherwise this bit SHOULD be set
to 0. The egress LSR, R2, SHOULD set the EFCI bit of all cells to 0. The egress LSR, R2, SHOULD set the EFCI bit of all cells
that transport the AAL5 CPCS-PDU to the value contained in this that transport the AAL5 CPCS-PDU to the value contained in this
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* L ( CLP ) Bit * L ( CLP ) Bit
The ingress LSR, R1, SHOULD set this bit to 1 if the CLP bit of The ingress LSR, R1, SHOULD set this bit to 1 if the CLP bit of
any of the ATM cells that transported the AAL5 CPCS-PDU is set to any of the ATM cells that transported the AAL5 CPCS-PDU is set to
1, or if the CLP bit of the single ATM cell to be transported in 1, or if the CLP bit of the single ATM cell to be transported in
the MPLS packet is set to 1. Otherwise this bit SHOULD be set to the MPLS packet is set to 1. Otherwise this bit SHOULD be set to
0. The egress LSR, R2, SHOULD set the CLP bit of all cells that 0. The egress LSR, R2, SHOULD set the CLP bit of all cells that
transport the AAL5 CPCS-PDU to the value contained in this field. transport the AAL5 CPCS-PDU to the value contained in this field.
The ingress LSR, R1, MAY consider the CLP bit of the ATM cell
header when determining the value to be placed in the EXP fields
of the MPLS label stack. In a similar way, the egress LSR, R2,
MAY consider the EXP field of the VC label when queuing the
packet for egress. Note however that frames from the same VC MUST
NOT be reordered by the MPLS network.
* C ( Command / Response Field ) Bit * C ( Command / Response Field ) Bit
When FRF.8.1 Frame Relay / ATM PVC Service Interworking [3] When FRF.8.1 Frame Relay / ATM PVC Service Interworking [3]
traffic is being transported, the CPCS-UU Least Significant Bit traffic is being transported, the CPCS-UU Least Significant Bit
(LSB) of the AAL5 CPCS-PDU may contain the Frame Relay C/R bit. (LSB) of the AAL5 CPCS-PDU may contain the Frame Relay C/R bit.
The ingress LSR, R1, SHOULD copy this bit to the C bit of the The ingress LSR, R1, SHOULD copy this bit to the C bit of the
control word. The egress LSR, R2, SHOULD copy the C bit to the control word. The egress LSR, R2, SHOULD copy the C bit to the
CPCS-UU Least Significant Bit (LSB) of the AAL5 CPCS PDU. CPCS-UU Least Significant Bit (LSB) of the AAL5 CPCS PDU.
The Label, EXP, S, and TTL fields are described in [2]. The Label, EXP, S, and TTL fields are described in [2].
4.2.2. ATM Cell Mode 4.2.2. ATM Cell Mode
In this encapsulation mode ATM cells are transported individually In this encapsulation mode ATM cells are transported individually
without a SAR process. Each ATM cell payload is prepended by a 4 byte without a SAR process. The ATM cell encapsulation consists of an MPLS
header and concatenated to form the MPLS frame. This ATM cell header label stack, an OPTIONAL control word, and one or more ATM cells -
is defined as in the FAST encapsulation [4] section 3.1.1, but each consisting of a 4 byte ATM cell header and the 48 byte ATM cell
without the trailer byte. The length of each frame, without the MPLS payload. This ATM cell header is defined as in the FAST encapsulation
header and the control word, is a multiple of 52 bytes long. The [4] section 3.1.1, but without the trailer byte. The length of each
maximum number of ATM cells that can be fitted in an MPLS frame, in frame, without the MPLS header and the control word, is a multiple of
this fashion, is limited only by the MPLS network MTU and by the 52 bytes long. The maximum number of ATM cells that can be fitted in
ability of the egress LSR to process them. The ingress LSR MUST NOT an MPLS frame, in this fashion, is limited only by the MPLS network
send more cells than the egress LSR is willing to receive. The number MTU and by the ability of the egress LSR to process them. The ingress
of cells that the egress LSR is willing to receive may either be LSR MUST NOT send more cells than the egress LSR is willing to
configured in the ingress LSR or may be signaled, for example using receive. The number of cells that the egress LSR is willing to
the methods described in [1]. The number of cells encapsulated in a receive may either be configured in the ingress LSR or may be
particular frame can be inferred by the frame length. The sequencing signaled, for example using the methods described in [1]. The number
control word is OPTIONAL. If the control word is used then the flag of cells encapsulated in a particular frame can be inferred by the
bits in the control word are not used, and MUST be set to 0 when frame length. The control word is OPTIONAL. If the control word is
transmitting, and MUST be ignored upon receipt. used then the flag bits in the control word are not used, and MUST be
set to 0 when transmitting, and MUST be ignored upon receipt.
The EFCI and CLP bits are carried across the network in the ATM cell The EFCI and CLP bits are carried across the network in the ATM cell
header. The edge LSRs that implement this document MAY, when either header. The edge LSRs that implement this document MAY, when either
adding or removing the encapsulation described herein, change the adding or removing the encapsulation described herein, change the
EFCI bit from zero to one in order to reflect congestion in the MPLS EFCI bit from zero to one in order to reflect congestion in the MPLS
network that is known to the edge LSRs, and the CLP bit from zero to network that is known to the edge LSRs, and the CLP bit from zero to
one to reflect marking from edge policing of the ATM Sustained Cell one to reflect marking from edge policing of the ATM Sustained Cell
Rate. The EFCI and CLP bits MUST NOT be changed from one to zero. Rate. The EFCI and CLP bits MUST NOT be changed from one to zero.
This diagram illustrates an encapsulation of two ATM cells: This diagram illustrates an encapsulation of two ATM cells:
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4.2.4. CLP bit to MPLS label stack EXP bit mapping 4.2.4. CLP bit to MPLS label stack EXP bit mapping
The ingress LSR MAY consider the CLP bit when determining the value The ingress LSR MAY consider the CLP bit when determining the value
to be placed in the EXP fields of the MPLS label stack. This will to be placed in the EXP fields of the MPLS label stack. This will
give the MPLS network visibility of the CLP bit. Note however that give the MPLS network visibility of the CLP bit. Note however that
cells from the same VC MUST NOT be reordered by the MPLS network. cells from the same VC MUST NOT be reordered by the MPLS network.
4.3. Ethernet VLAN 4.3. Ethernet VLAN
For an Ethernet 802.1q VLAN the entire Ethernet frame without the For an Ethernet 802.1q VLAN the entire Ethernet frame without the
preamble or FCS is transported as a single packet. The sequencing preamble or FCS is transported as a single packet. The control word
control word is OPTIONAL. If the control word is used then the flag is OPTIONAL. If the control word is used then the flag bits in the
bits in the control word are not used, and MUST be set to 0 when control word are not used, and MUST be set to 0 when transmitting,
transmitting, and MUST be ignored upon receipt. The 4 byte VLAN tag and MUST be ignored upon receipt. The 4 byte VLAN tag is transported
is transported as is, and MAY be overwritten by the egress LSR. as is, and MAY be overwritten by the egress LSR.
The ingress LSR MAY consider the user priority field [5] of the VLAN The ingress LSR MAY consider the user priority field [5] of the VLAN
tag header when determining the value to be placed in the EXP fields tag header when determining the value to be placed in the EXP fields
of the MPLS label stack. In a similar way, the egress LSR MAY of the MPLS label stack. In a similar way, the egress LSR MAY
consider the EXP field of the VC label when queuing the packet for consider the EXP field of the VC label when queuing the packet for
egress. Ethernet packets containing hardware level CRC errors, egress. Ethernet packets containing hardware level CRC errors,
framing errors, or runt packets MUST be discarded on input. framing errors, or runt packets MUST be discarded on input.
4.4. Ethernet 4.4. Ethernet
For simple Ethernet port to port transport, the entire Ethernet frame For simple Ethernet port to port transport, the entire Ethernet frame
without the preamble or FCS is transported as a single packet. The without the preamble or FCS is transported as a single packet. The
sequencing control word is OPTIONAL. If the control word is used then control word is OPTIONAL. If the control word is used then the flag
the flag bits in the control word are not used, and MUST be set to 0 bits in the control word are not used, and MUST be set to 0 when
when transmitting, and MUST be ignored upon receipt. As in the transmitting, and MUST be ignored upon receipt. As in the Ethernet
Ethernet VLAN case, Ethernet packets with hardware level CRC errors, VLAN case, Ethernet packets with hardware level CRC errors, framing
framing errors, and runt packets MUST be discarded on input. errors, and runt packets MUST be discarded on input.
4.5. HDLC ( Cisco ) 4.5. HDLC ( Cisco )
HDLC (Cisco) mode provides port to port transport of Cisco HDLC HDLC (Cisco) mode provides port to port transport of Cisco HDLC
encapsulated traffic. The HDLC PDU is transported in its entirety, encapsulated traffic. The HDLC PDU is transported in its entirety,
including the HDLC address, control and protocol fields, but including the HDLC address, control and protocol fields, but
excluding HDLC flags and the FCS. Bit stuffing is undone. The excluding HDLC flags and the FCS. Bit stuffing is undone. The
sequencing control word is OPTIONAL. control word is OPTIONAL. If the control word is used then the flag
bits in the control word are not used, and MUST be set to 0 when
transmitting, and MUST be ignored upon receipt.
4.6. PPP 4.6. PPP
PPP mode provides point to point transport of PPP encapsulated PPP mode provides point to point transport of PPP encapsulated
traffic, as specified in [6]. The PPP PDU is transported in its traffic, as specified in [6]. The PPP PDU is transported in its
entirety, including the protocol field, but excluding any media- entirety, including the protocol field (whether compressed using PFC
specific framing information, such as HDLC address and control fields or not), but excluding any media-specific framing information, such
or FCS. The sequencing control word is OPTIONAL. as HDLC address and control fields or FCS. Since media-specific
framing is not carried the following options will not operate
correctly if the PPP peers attempt to negotiate them:
Frame Check Sequence (FCS) Alternatives Address-and-Control-Field-
Compression (ACFC) Asynchronous-Control-Character-Map (ACCM)
Note also that VC LSP Interface MTU negotiation as specified in [1]
is not affected by PPP MRU advertisement. Thus if a PPP peer sends a
PDU with a length in excess of that negotiated for the VC LSP that
PDU will be discarded by the ingress LSR.
The control word is OPTIONAL. If the control word is used then the
flag bits in the control word are not used, and MUST be set to 0 when
transmitting, and MUST be ignored upon receipt.
5. Security Considerations 5. Security Considerations
This document does not affect the underlying security issues of MPLS. This document does not affect the underlying security issues of MPLS.
6. Intellectual Property Disclaimer 6. Intellectual Property Disclaimer
This document is being submitted for use in IETF standards This document is being submitted for use in IETF standards
discussions. discussions.
7. References 7. References
[1] "Transport of Layer 2 Frames Over MPLS", draft-martini- [1] "Transport of Layer 2 Frames Over MPLS", draft-martini-
l2circuit-trans-mpls-05.txt. ( work in progress ) l2circuit-trans-mpls-06.txt. ( work in progress )
[2] "MPLS Label Stack Encoding", E. Rosen, Y. Rekhter, D. Tappan, G. [2] "MPLS Label Stack Encoding", E. Rosen, Y. Rekhter, D. Tappan, G.
Fedorkow, D. Farinacci, T. Li, A. Conta. RFC3032 Fedorkow, D. Farinacci, T. Li, A. Conta. RFC3032
[3] "Frame Relay / ATM PVC Service Interworking Implementation [3] "Frame Relay / ATM PVC Service Interworking Implementation
Agreement", Frame Relay Forum 2000. Agreement", Frame Relay Forum 2000.
[4] "Frame Based ATM over SONET/SDH Transport (FAST)," 2000. [4] "Frame Based ATM over SONET/SDH Transport (FAST)," 2000.
[5] "IEEE 802.3ac-1998" IEEE standard specification. [5] "IEEE 802.3ac-1998" IEEE standard specification.
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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
Level 3 Communications Gone2 Ltd.
66 Prescot Street c/o MDP
One Curzon Street
London London
E1 8HG W1J 5HD
United Kingdom United Kingdom
e-mail: giles@level3.net e-mail: giles@goneto.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 16, line 4 skipping to change at page 15, line 33
Vivace Networks, Inc. Vivace Networks, Inc.
2730 Orchard Parkway 2730 Orchard Parkway
San Jose, CA 95134 San Jose, CA 95134
e-mail: Andy.Malis@vivacenetworks.com e-mail: 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: vinai.sirkay@vivacenetworks.com
Kireeti Kompella
Juniper Networks Vasile Radoaca
1194 N. Mathilda Ave Nortel Networks
Sunnyvale, CA 94089 600 Technology Park
e-mail: kireeti@juniper.net Billerica MA 01821
e-mail: vasile@nortelnetworks.com
Chris Liljenstolpe
Cable & Wireless
11700 Plaza America Drive
Reston, VA 20190
chris@cw.net
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