Internet Draft XiPeng Xiao
Document: draft-ietf-pwe3-requirements-00.txt Photuris Inc.
Expires: November 17, 2001 Danny McPherson
Amber Networks
Prayson Pate
Overture Networks, Inc.
Craig White
Level 3 Communications, LLC.
Kireeti Kompella
Juniper Networks, Inc.
Requirements for
Pseudo Wire Emulation Edge-to-Edge (PWE3)
draft-ietf-pwe3-requirements-00.txt
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Abstract
This document describes generic requirements for Pseudo-Wire
Emulation Edge to Edge. It provides guidelines for other working
group documents that will define mechanisms for providing pseudo-wire
emulation of specific services such as Ethernet, PPP, (Cisco) HDLC,
ATM, Frame Relay and TDM. It should be noted that the PWE3 Working
Group (WG) standardizes mechanisms that can be used to provide
pseudo-wire emulation services, but not the services themselves.
Copyright Notice
Internet Draft draft-ietf-pwe3-requirements-00 May 17, 2001
Copyright (C) The Internet Society (2001). All Rights Reserved.
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Table of Contents
1 Introduction ................................................. 4
1.1 Reference Model of Pseudo-Wire Emulation Edge to Edge
(PWE3) .................................................... 4
1.2 Terminology ................................................ 5
2 PDU Encapsulation ............................................ 6
2.1 Conveyance of Necessary L2/L1 Header Information ........... 6
2.2 Location of the Pseudo-Wire Header ......................... 6
2.3 PDU Length ................................................. 6
2.4 Encapsulation of Signaling Messages of the Native
Services .................................................. 7
2.5 Timing Information ......................................... 7
2.6 Support for Circuit Multiplexing ........................... 7
2.7 Packet Ordering ............................................ 7
3 Packet Transport ............................................. 7
3.1 Setup of Pseudo-Wires ...................................... 7
3.2 Pseudo-Wire MTU ............................................ 8
3.3 Transport of Signaling Messages of the Native Services ..... 8
3.4 Transport Efficiency ....................................... 9
4 Faithfulness of Emulated Services ............................ 9
4.1 Characteristics of an Emulated Service ..................... 9
4.2 Service Quality of Emulated Services ....................... 10
4.3 Signaling of Native Services ............................... 10
5 Maintenance of Emulated Services ............................. 10
5.1 Signaling of Status Changes of an Emulated Service ......... 10
5.1.1 Up/Down Notification ..................................... 10
5.1.2 Packet Loss and/or Out-of-order Delivery ................. 11
5.1.3 Other Status Signaling ................................... 11
5.1.4 Collective Status Signaling .............................. 11
5.2 Clock Recovery ............................................. 12
6 Management of Emulated Services .............................. 12
6.1 MIB ........................................................ 12
6.2 Pseudo-Wire Traceroute ..................................... 12
7 Scalability .................................................. 12
8 Other Generic Requirements ................................... 13
9 Non-Requirements ............................................. 14
10 Quality of Service (QoS) Considerations ..................... 14
11 Inter-domain Pseudo-Wires ................................... 15
12 Security Considerations ..................................... 15
12.1 Security Considerations for the Signaling/Control
Channel ................................................... 15
12.2 Security Considerations for the Encapsulated PDUs ......... 15
13 Deployment Considerations ................................... 15
14 Acknowledgments ............................................. 15
15 References .................................................. 15
16 Authors' Addresses .......................................... 16
17 Full Copyright Section ...................................... 18
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1. Introduction
1.1. Reference Model of Pseudo-Wire Emulation Edge to Edge (PWE3)
To provide pseudo-wire emulation, two end-services of the same type
are first configured between each service endpoint (SE) and the
corresponding PWE3 Edge (PE) device (See Figure 1). An end-service
is either:
- an Ethernet link between two ports or two VLANs, or
- a PPP link, or
- a (Cisco) HDLC link, or
- an ATM VC or VP, or
- a Frame Relay VC, or
- a TDM circuit.
A connection is then set up between the two PEs to connect these two
end-services. This connection is called a pseudo-wire in the PWE3
context. During the setup of a pseudo-wire, the two pseudo-wire
endpoints will exchange information about the service to be emulated
so that later they know how to handle packets coming from the other
end of the pseudo-wire. After the pseudo-wire is set up, layer-2
(e.g. Ethernet, ATM and Frame Relay) or layer-1 (e.g. SONET/SDH) PDUs
of frames from an end-service are encapsulated at the pseudo-wire
ingress. The encapsulated PDUs are then transported over the pseudo-
wire to the egress, where L2 or L1 header information is re-
constructed and the resulted frames are forwarded in their native
format to the other end-service.
|<--------- pseudo-wire -------->|
end- | | end-
+-----+ service +------+ +------+ service +-----+
| SE1 |---------| PE1 |..................| PE2 |---------| SE2 |
+-----+ +------+ +------+ +-----+
service PW endpoint 1 PW endpoint 2 service
endpoint 1 endpoint 2
| |
|<---------------- emulated service ---------------->|
Figure 1: Pseudo-Wire Reference Model
Different carriers may choose different types of pseudo-wires. For
example, carriers may choose to use GRE tunnels [GRE], L2TP tunnels
[L2TP], or MPLS LSPs [MPLS] as pseudo-wires. This document does not
assume that a particular type of pseudo-wires is used. Instead, it
describes generic requirements that apply to all pseudo-wires, for
all services including Ethernet, PPP, (Cisco) HDLC, ATM, Frame Relay
and TDM.
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This document is not an introductory document. Readers are assumed to
be familiar with the PWE3 framework document [PATE], especially the
architecture assumptions stated in that document.
1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALLNOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
Below are the definitions for the terms used throughout the document.
End-Service An End-Service is either an Ethernet link
between two ports or two VLANs, or a PPP
link, or a (Cisco) HDLC link, or an ATM VC or
VP, or a Frame Relay VC, or a TDM circuit.
Pseudo-Wire Emulation Pseudo-Wire Emulation is an approach to
emulate the essential attributes of a service
over a packet network so that two remote
end-services appear directly connected by a
wire.
Emulated Service An Emulated Service is a service that is
provided via pseudo-wire emulation.
Service Endpoint A Service Endpoint (SE) is a device where one
end of an emulated service terminates.
Pseudo-Wire A Pseudo-Wire is a connection between two
end-services.
Pseudo-Wire Endpoint A Pseudo-Wire Endpoint is a device where one
end of a pseudo-wire terminates.
Path-oriented A Path-oriented Pseudo-Wire is a pseudo-wire
Pseudo-Wire for which core network devices must maintain
state information, for example, an MPLS LSP.
Non-path-oriented A Non-path-oriented Pseudo-Wire is a
Pseudo-Wire pseudo-wire for which core network devices
need not maintain state information, for
example, a L2TP tunnel.
Transport Tunnel A Transport Tunnel is a tunnel inside which
multiple pseudo-wires can be nested so that
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they are transparent to core network devices.
2. PDU Encapsulation
Every pseudo-wire edge device MUST provide service interfaces to use
common service-specific techniques for encapsulating PDUs. It should
be noted that the PDUs to be encapsulated may or may not contain L2
or L1 header information. This is service specific. Every PWE3
service MUST specify what a PDU is.
A pseudo-wire header must contain sufficient but not excessive
information so that the other end of the pseudo-wire, aided with
information obtained during the pseudo-wire setup process, knows
exactly how to handle the encapsulated PDUs. A pseudo-wire header
consists of all the header fields in an encapsulated PDU that are
used by the pseudo-wire egress to determine how to handled the PDU.
The header that is used for transporting the encapsulated PDUs from
the pseudo-wire ingress to the egress (e.g. the tunnel label in
[MART2]) is not considered as part of the pseudo-wire header. It is
called transport header instead. It should be noted that transport
headers are totally different from transport-layer headers (e.g.
TCP/UDP headers).
Specific requirements on PDU encapsulation for a PWE3 approach are
listed below.
2.1. Conveyance of Necessary L2/L1 Header Information
Sometimes the egress of a pseudo-wire needs some L2 or L1 header
information in order to know how to process the PDUs received. A
PWE3 approach SHOULD provide some mechanism (e.g. using one or more
control words) for conveying such L2/L1 header information from the
pseudo-wire ingress to the egress. The use of these mechanisms can be
REQUIRED or OPTIONAL, depending on services.
2.2. Location of the Pseudo-Wire Header
A pseudo-wire header MUST be between the PDU and the transport
header. This is necessary for the pseudo-wire egress to locate the
pseudo-wire header, and to process the PDU.
2.3. PDU Length
A PWE3 approach MUST accommodate variable length PDUs, if variable
length PDUs are allowed by the native service. For example, a PWE3
approach for Frame Relay MUST accommodate variable length frames.
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2.4. Encapsulation of Signaling Messages of the Native Services
PDUs that contain signaling information of the native service SHOULD
be encapsulated in the same way as data PDUs. This simplifies
handling at both the ingress and the egress of a pseudo-wire.
2.5. Timing Information
Timing information can be essential for the endpoints of a service.
If the original frames contain timing information, the encapsulation
mechanism SHOULD not cause loss of such timing information.
Requirements on clock recovery between pseudo-wire endpoints are
further discussed in the "Maintenance of Emulated Services" section.
2.6. Support for Circuit Multiplexing
If a service in its native form is capable of grouping multiple
circuits into a "trunk", e.g. an ATM VP, some mechanism SHOULD be
provided so that a single pseudo-wire can be used to connect two
end-trunks. From encapsulation perspective, the encapsulation header
MUST carry sufficient information, e.g. VCI of each cell, so that the
egress of the pseudo-wire can demultiplex individual circuits from
the pseudo-wire.
2.7. Packet Ordering
When packets carrying the encapsulated PDUs traverse a pseudo-wire,
they may arrive at the egress out of order. For some services, the
encapsulated PDUs must be delivered in order. For such services, some
mechanism MUST be provided to ensure that. Providing a sequence
number in the pseudo-wire header for each packet is one possible
approach. Every specific PWE3 approach MUST define as a mechanism if
in-order PDU delivery is required.
3. Packet Transport
This section describes requirements on how to transport packets
carrying the encapsulated PDUs over the network that provides PWE3
services.
3.1. Setup of Pseudo-Wires
A pseudo-wire is a tunnel that connects two end-services. After the
L2/L1 PDUs of a service are encapsulated, they must be transported
over the pseudo-wire to the other end-service.
Every PWE3 approach MUST define some signaling mechanism for setting
up the pseudo-wires. During the setup process, the pseudo-wire
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endpoints need to exchange some information (e.g. learn each other's
capability). The signaling mechanism MUST enable the pseudo-wire
endpoints to exchange all necessary information. For example, both
endpoints must agree on an encapsulation method and the MTU size for
the pseudo-wire. As another example, in order to support circuit
multiplexing using ATM VPs, both pseudo-wire endpoints must agree on
using the VCIs in the encapsulated PDUs to demultiplex individual VCs
from the VP at the pseudo-wire egress. Which signaling protocol to
use and what information to exchange are service specific. Every PWE3
approach MUST specify these. Manual configuration can be considered
as a special kind of signaling and is explicitly allowed.
This document does not assume a particular type of pseudo-wires. GRE
tunnels, L2TP tunnels, or MPLS LSPs can all be used. Selection of a
particular type of pseudo-wires is carrier-dependent and is outside
scope of the PWE3 WG.
A pseudo-wire can be either path-oriented or non-path-oriented. The
difference is core network devices need to maintain state information
for path-oriented pseudo-wires (e.g. LSPs) but not for non-path-
oriented ones (e.g. GRE/L2TP tunnels). This has scalability
implication that is further discussed in the "Scalability" section.
3.2. Pseudo-Wire MTU
A pseudo-wire MUST be able to be configured with an MTU that is
sufficient to transport packets whose size equals to the largest PDU
size of the native service plus the pseudo-wire header and transport
header. At a pseudo-wire ingress, if a packet's length exceeds the
pseudo-wire MTU, it MUST be dropped. At a pseudo-wire egress, if the
length of a frame that is restored from a PDU exceeds the MTU of
destination end-service, it MUST be dropped.
3.3. Transport of Signaling Messages of the Native Services
Some native services use signaling messages for maintaining the
circuits. These signaling messages may be in-band, e.g. Ethernet flow
control or ATM performance management, or out-of-band, e.g. the
signaling VC of an ATM VP (from the perspective of other VCs in that
VP). If such signaling messages are lost, functionality of the
services will be significantly affected. Therefore, it can be
desirable to provide higher reliability for transporting signaling
messages.
Each PWE3 approach MAY state what approach can be used to ensure that
signaling messages of the native service will be delivered over the
network with high probability. Differentiating signaling packets from
data packets and giving them preferable forwarding treatment in the
network is one possible approach. Such approaches NEED not be
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defined in a PWE3 approach itself.
3.4. Transport Efficiency
In order to reduce transport header overhead and increase bandwidth
efficiency, multiple PDUs MAY be concatenated before a transport
header is added. Each PDU still carries its own pseudo-wire header so
that the egress of the pseudo-wire knows how to handle it.
4. Faithfulness of Emulated Services
An emulated service SHOULD be as similar to the native service as
possible, but it is not REQUIRED that they should be identical. Each
difference between an emulated service and the corresponding native
service, if any, can be classified as either functional or non-
functional. Functional differences are those that cause some
features of the native service to become disabled in the emulated
one. For example, if an emulated Ethernet service introduces some
difference that can cause the Spanning Tree Protocol (STP) to mal-
function, such a difference will be classified as a functional
difference. Other differences are non-functional. For examples,
differences in service quality between an emulated service and the
native one are non-functional. In every PWE3 approach:
- All functional differences and the features disabled MUST be
pointed out;
- Non-functional differences SHOULD be pointed out.
Some basic requirements on faithfulness of an emulated service are
described below.
4.1. Characteristics of an Emulated Service
Functionally, two service endpoints that are connected by an emulated
service MUST appear directly connected by a native service, although
service quality of the emulated service may be different from that of
a native one. Specifically, this implies (but is not limited to) the
followings:
1) It MUST be possible to define type (e.g. Ethernet or PPP, which is
inherited from the native service), speed (e.g. 100Mbps), and MTU
size for an emulated service.
2) From the service endpoints' perspective, each emulated service
MUST appear as unshared.
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3) If an emulated service fails (either at one of the end-services or
in the middle of the pseudo-wire), both service endpoints MUST be
notified reasonably timely. The definition of "reasonable
timeliness" is service-dependent.
4) Two service endpoints connected by an emulated service MUST be
able to establish routing protocol (e.g. IGP) adjacency over the
emulated service. To be clear, the Spanning Tree Protocol (STP) is
not considered as a routing protocol and requirements on
support/non-support of STP is outside scope of this document.
5) When desired, an emulated service MUST be able to appear as a
normal link in the service endpoints' IGP routing table.
6) The TTL fields of the encapsulated PDUs, if exist, MUST not be
changed inside an emulated service.
4.2. Service Quality of Emulated Services
It is RECOMMENDED but not REQUIRED that an emulated service provide
as high service quality as the native service. However, the PWE3 WG
only defines mechanisms for providing pseudo-wire emulation, not the
services themselves. What quality to provide for a specific emulated
service is a matter between a service provider (SP) and its
customers, and is outside scope of the PWE3 WG. In fact, different
SPs can use the same PWE3 approach but different QoS approaches to
provide the same emulated service with different service quality.
4.3. Signaling of Native Services
A PWE3 approach SHOULD support signaling of the native service. This
is further discussed in the "Maintenance of Emulated Services"
section.
5. Maintenance of Emulated Services
Every PWE3 approach MUST provide mechanisms for maintaining the
working condition of an emulated service and for signaling any status
changes.
5.1. Signaling of Status Changes of an Emulated Service
5.1.1. Up/Down Notification
With pseudo-wire emulation, a failure may occur at a remote place
such that one or both physical links between the SEs and PEs remains
up. For example in Figure 1, if the physical link between SE1 and
PE1 fails, the physical link between SE2 and PE2 will not be affected
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and will remain up. Unless some signaling is done to notify SE2 of
the remote failure, SE2 will continue to send traffic over the
emulated service to SE1. Such traffic will be discarded at PE1.
Therefore, when an emulated service fails (either at an end-service
or in the middle of the pseudo-wire), both service endpoints MUST be
notified. Every PWE3 approach MUST provide such a signaling
mechanism. This functionality is equivalent to failure notification
of normal links.
Similarly, every PWE3 approach MUST provide some signaling mechanism
so that when a network failure is fixed, all the affected emulated
services will change status from "Down" to "Up".
5.1.2. Packet Loss and/or Out-of-order Delivery
A pseudo-wire can incur packet loss and/or out-of-order delivery.
This can significantly impact the working condition of an emulated
service. Number of packets lost or delivered out of order in unit
time can be considered as two new types of "generalized bit error
rate" of a pseudo-wire. Every PWE3 approach SHOULD provide some
mechanism so that if either type of "generalized bit error rate"
exceeds some configured threshold, the pseudo-wire and the emulated
service will be signaled down.
5.1.3. Other Status Signaling
A PWE3 approach MAY provide mechanism for other status signaling, if
any.
5.1.4. Collective Status Signaling
Status of a group of emulated services may be affected identically by
a single network incidence. For example, when the physical link
between a SE and a PE fails, all the emulated services that go
through that link will fail. It is likely that there exists a group
of emulated services which all terminate at a remote SE. (There can
be multiple such SEs). Therefore, it is desirable that a single
signaling message can be used to signal the failure of the whole
group of emulated services. A PWE3 approach MAY provide some
mechanism for signaling status changes of a group of emulated
circuits. One possible approach is to associate each emulated
service with a group ID when the pseudo-wire for that emulated
service is set up. Multiple emulated services can then be grouped by
associated them with identical group ID. In status signaling, that
group ID can then be used to refer all the emulated services in that
group.
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5.2. Clock Recovery
For some services, the pseudo-wire endpoints need to maintain some
kind of timing relationship (e.g. synchronization). A PWE3 approach
for such services MUST provide some mechanism to support that.
6. Management of Emulated Services
Each PWE3 approach SHOULD provide some mechanisms for network
operators to manage the emulated service.
A pseudo-wire MIB (PW-MIB) MAY be provided for managing each emulated
service. The MIB SHOULD have the following requirements:
- The counters in the MIB SHOULD NOT replicate existing MIB counters.
- Each end-service SHOULD appear as an interface in the ifTable.
- The MIB SHOULD describe how the existing counters are used for
pseudo-wire emulation.
- The MIB MAY support row creation to create new end-service pairs.
- The MIB MAY augment existing tables. For example, the ifTable
SHOULD be augmented to provide counts of out-of-order packets.
- The MIB SHOULD define meanings for the standard linkUp and linkDown
traps, as well as any protocol-specific traps that are needed.
- The MIB SHOULD be structured in a hierarchical fashion such that
generic PW objects and tables are not duplicated for each service.
6.2. Pseudo-Wire Traceroute
It can be desirable to know the exact path of a pseudo-wire,
especially for troubleshooting purpose. A pseudo-wire emulation
service MAY support pseudo-wire traceroute, even if the pseudo-wire
used is non-path-oriented.
7. Scalability
Scalability requirements for Pseudo-Wire Emulation Edge to Edge are
described below.
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- Pseudo-wire emulation services SHOULD be transparent to other
packet services (e.g. best effort Internet service).
- Only pseudo-wire endpoints should be aware of existence of pseudo-
wires and PWE3 services. Core network devices SHOULD NOT be exposed
to a large number of pseudo-wires.
Pseudo-wires can be path-oriented or non-path-oriented. For path-
oriented pseudo-wires, core network devices must maintain state
information for them. If a large number of path-oriented pseudo-
wires are used, core network devices will have to maintain a large
amount of state information. In order to avoid scalability problem,
transport tunnels between pseudo-wire endpoints can be introduced.
Pseudo-wires from the same ingress to the same egress are nested
inside the transport tunnel that is from that ingress to that
egress. By creating such a tunnel hierarchy, individual pseudo-
wires are transparent to the core devices. If a specific PWE3
approach uses path-oriented pseudo-wires, transport tunnels SHOULD
be used to improve scalability. However, a transport tunnel is not
part of any pseudo-wire. Signaling of transport tunnels NEED NOT be
defined in the PWE3 approach itself. As an example, if LSPs are
used as pseudo-wires in a PWE3 approach, they can be nested inside
a tunnel LSP from the pseudo-wire ingress to the pseudo-wire
egress. The tunnel LSPs can be signaled by any mechanism defined
in [MPLS].
- Circuit multiplexing: circuit multiplexing SHOULD be supported.
- Collective status signaling: Collective status signaling SHOULD be
supported.
8. Other Generic Requirements
Other generic requirements for Pseudo-Wire Emulation Edge to Edge
include:
- No New Protocol Operations:
No matter which protocol (e.g. GRE or L2TP or MPLS) is used for
packet transport, PWE3 SHOULD just be an application of that
protocol. In other words, no new protocol (GRE or L2TP or MPLS)
operations SHOULD be introduced. For example, if an MPLS label
switching operation is performed, a PWE3 approach SHOULD not
require that the TTL field of the top label remains unchanged.
(Otherwise, this label switching would be different from a normal
MPLS label switching and would be considered as a new protocol
operation). If any new operations are indeed introduced in a PWE3
approach, they MUST be clearly pointed out.
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- Minimum configuration work at the pseudo-wire endpoints;
- Easy to maintain and manage.
9. Non-Requirements
Some non-requirements are mentioned in various sections of this
document. Those work items are outside scope of the PWE3 WG. The
non-requirements are listed below:
- Selection of a particular type of pseudo-wires;
- Striving to make the emulated services perfectly match their native
services;
- Defining mechanisms for signaling the transport tunnels;
- Defining how to perform traffic management on packets that carry
encapsulated PDUs;
- Providing security for the encapsulated PDUs;
- Providing any multicast service that is not native to the emulated
medium.
To illustrate this point, Ethernet transmission to a multicast
IEEE-48 address is considered in scope, while multicast services
like [MARS] that are implemented on top of the medium are out of
scope;
10. Quality of Service (QoS) Considerations
In this document, QoS means satisfactory service quality. It should
not be confused with QoS mechanisms such as Weighted Fair Queueing
(WFQ) or Random Early Detection (RED).
QoS is essential for ensuring that the emulated services are similar
(but not necessarily identical) to their native forms. It is up to
network operators to decide how to provide QoS - They can choose to
rely on over-provisioning and/or deploy some QoS mechanisms.
In order to take advantage of some QoS mechanisms defined in other
working groups, e.g. the traffic management schemes defined in
DiffServ WG, it is desirable that some mechanisms exists for
differentiating the packets resulted from PDU encapsulation. These
mechanisms need not be defined in the PWE3 approaches themselves. For
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example, if the resulted packets are MPLS or IP packets, their EXP or
DSCP fields can be used for marking and differentiating,
respectively. Every PWE3 approach SHOULD provide guidelines for
marking and differentiating, e.g. what fields in the original L2 or
L1 headers should be used for determining the EXP/DSCP value. But the
exact procedure on how to perform marking and differentiating, e.g.
the mapping from Ethernet .1P field to EXP field, is out of scope.
11. Inter-domain Pseudo-Wires
The PWE3 WG will determine the requirements for having a pseudo-wire
pass across an administrative boundary. An edge could be a native
hand-off or hand-off to a further pseudo-wire. The working group may
analyze requirements for both security and performance for the
inter-administration technology. This topic is for further study.
12. Security Considerations
12.1. Security Considerations for the Signaling/Control Channel
If a signaling/control channel is used in a PWE3 approach, some
security mechanism SHOULD be provided to ensure integrity of the
information transmitted across the signaling/control channel.
12.2. Security Considerations for the Encapsulated PDUs
Providing security for the encapsulated PDUs is outside scope of the
PWE3 WG.
13. Deployment Considerations
Transition from using separate networks for TDM, ATM, Frame Relay and
IP services to using a single network for multiple services requires
careful planning and execution. This is an important topic for
further study.
14. Acknowledgments
Some requirements specified in this document were originally
articulated in a number of documents including [MART1], [MART2],
[CES], and [SFBS]. The authors would like to acknowledge authors of
those documents. The authors would also like to acknowledge the input
and comments from T. So.
15. References
[CES] A. Malis et al, "SONET/SDH Circuit Emulation Service Over
MPLS (CEM) Encapsulation" <draft-malis-sonet-ces-mpls-
04.txt>, work in progress, April 2001.
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[GRE] D. Farinacci, T. Li, S. Hanks, D. Meyer, P. Traina, "Generic
Routing Encapsulation (GRE)", RFC2784, March 2000.
[L2TP] W.M. Townsley, A. Valencia, A. Rubens, G. Singh Pall, G.
Zorn, B. Palter, "Layer Two Tunneling Protocol (L2TP)", RFC
2661, August 1999.
[MARS] G. Armitage, "Support for Multicast over UNI 3.0/3.1 based
ATM Networks", RFC2022, November 1996
[MART1] L. Martini et al, "Transport of Layer 2 Frames Over MPLS",
<draft-martini-l2circuit-trans-MPLS-06.txt>, work in
progress, May 2001.
[MART2] L. Martini et al, "Encapsulation Methods for Transport of
Layer 2 Frames Over MPLS", <draft-martini-l2circuit-encap-
MPLS-02.txt>, work in progress, May 2001.
[MPLS] E. Rosen, A. Viswanathan, and R. Callon, "Multiprotocol
Label Switching Architecture", RFC3031, January 2001
[PATE] P. Pate, X. Xiao, T. So, C. White, and K. Kompella,
"Framework for Pseudo Wire Emulation Edge-to-Edge (PWE3)",
<draft-pate-pwe3-framework-00.txt>, work in progress, May
2001.
[RTP] H. Schulzrinne, S. Casner, R. Frederick, V. Jacobson "RTP: A
Transport Protocol for Real-Time Applications", RFC1889,
January 1996.
[SFBS] B. St-Denis, D. Fedyk, A. Bhatnagar, A. Siddiqui, R.
Hartani, and T. So "Multi-service over MPLS", <draft-
stdenis-ms-over-mpls-00.txt>, work in progress, Nov. 2000.
16. Authors' Addresses
XiPeng Xiao
Photuris, Inc.
2025 Stierlin Court
Mountain View, CA 94043
Email: xxiao@photuris.com
Danny McPherson
Amber Networks, Inc.
48664 Milmont Drive
Fremont, CA 94538
Email: danny@ambernetworks.com
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Prayson Pate
Overture Networks
P. O. Box 14864
RTP, NC, USA 27709
Email: prayson.pate@overturenetworks.com
Craig White
Level 3 Communications, LLC.
1025 Eldorado Blvd.
Broomfield, CO, 80021
e-mail: Craig.White@Level3.com
Kireeti Kompella
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
Email: kireeti@juniper.net
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17. Full Copyright Section
Copyright (C) The Internet Society (2000). 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.
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