Network Working Group Luca Martini
Internet Draft Eric C. Rosen
Expiration Date: May 2006 Cisco Systems, Inc.
Nasser El-Aawar Giles Heron
Level 3 Communications, LLC. Tellabs
November 2005
Encapsulation Methods for Transport of Ethernet Over MPLS Networks
draft-ietf-pwe3-ethernet-encap-11.txt
Status of this Memo
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Abstract
An Ethernet Pseudowire (PW) is used to carry Ethernet/802.3 Protocol
Data Units over an MPLS network. This enables service providers to
offer "emulated" Ethernet services over existing MPLS networks. This
document specifies the encapsulation of Ethernet/802.3 PDUs within a
pseudo wire. It also specifies the procedures for using a PW to
provide a "point-to-point Ethernet" service.
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Table of Contents
1 Specification of Requirements .......................... 2
2 Introduction ........................................... 3
3 Applicability Statement ................................ 6
4 Details Specific to Particular Emulated Services ....... 7
4.1 Ethernet Tagged Mode ................................... 7
4.2 Ethernet Raw Mode ...................................... 8
4.3 Ethernet Specific Interface Parameter LDP Sub-TLV ...... 8
4.4 Generic Procedures ..................................... 8
4.4.1 Raw Mode vs. Tagged Mode ............................... 9
4.4.2 MTU Management on the PE/CE Links ...................... 10
4.4.3 Frame Ordering ......................................... 11
4.4.4 Frame Error Processing ................................. 11
4.4.5 IEEE 802.3x Flow Control Interworking .................. 11
4.5 Management ............................................. 11
4.6 The Control Word ....................................... 12
4.7 QoS Considerations ..................................... 13
5 Security Considerations ................................ 13
6 PSN MTU Requirements ................................... 14
7 IANA Considerations .................................... 14
8 Full Copyright Statement ............................... 14
9 Intellectual Property Statement ........................ 14
10 Normative References ................................... 15
11 Informative References ................................. 16
12 Editor Information ..................................... 16
13 Author Information ..................................... 16
14 Significant Contributors ............................... 17
Ap A Interoperability Guidelines ............................ 20
Ap B QoS Details ............................................ 21
1. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119
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2. Introduction
An Ethernet Pseudowire (PW) allows Ethernet/802.3 [802.3] Protocol
Data Units (PDUs) to be carried over an Multi Protocol Label Switched
[MPLS-ARCH] network. In addressing the issues associated with
carrying an Ethernet PDU over a Public Switched Network (PSN), this
document assumes that a Pseudowire (PW) has been set up by using a
control protocol such as the one as described in [PWE3-CTRL]. The
design of Ethernet Pseudowire described in this document conforms to
the pseudo wire architecture described in [RFC3985]. It is also
assumed in the remainder of this document that the reader is familiar
with RFC3985.
The PWE3 Ethernet PDU consists of the Destination Address, Source
Address, Length/Type, MAC Client Data and padding extracted from a
MAC frame as a concatenated octet sequence in their original order
[PDU].
In addition to the Ethernet PDU format used within the pseudo wire,
this document discusses:
- Procedures for using a PW in order to provide a pair of Customer
Edge Routers (CE) with an emulated (point-to-point) Ethernet
service, including the procedures for the processing of Provider
Edge-bound and CE-bound Ethernet PDUs. [RFC3985]
- Ethernet-specific QoS and security considerations
- Inter-domain transport considerations for Ethernet PW
The following two figures describe the reference models which are
derived from [RFC3985] to support the Ethernet PW emulated services.
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|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudo Wire ------>| |
| | | |
| | |<-- PSN Tunnel -->| | |
| PW End V V V V PW End |
V Service +----+ +----+ Service V
+-----+ | | PE1|==================| PE2| | +-----+
| |----------|............PW1.............|----------| |
| CE1 | | | | | | | | CE2 |
| |----------|............PW2.............|----------| |
+-----+ ^ | | |==================| | | ^ +-----+
^ | +----+ +----+ | | ^
| | Provider Edge 1 Provider Edge 2 | |
| | | |
Customer | | Customer
Edge 1 | | Edge 2
| |
| |
Attachment Circuit (AC) Attachment Circuit (AC)
native Ethernet service native Ethernet service
Figure 1: PWE3 Ethernet/VLAN Interface Reference Configuration
The "emulated service" shown in Figure 1 is, strictly speaking, a
bridged LAN; the PEs have MAC interfaces, consume MAC control frames,
etc. However, the procedures specified herein only support the case
in which there are two CEs on the "emulated LAN". Hence we refer to
this service as "emulated point-to-point Ethernet". Specification of
the procedures for using pseudo wires to emulate LANs with more than
two CEs are out of scope of the current document.
+-------------+ +-------------+
| Emulated | | Emulated |
| Ethernet | | Ethernet |
| (including | Emulated Service | (including |
| VLAN) |<==============================>| VLAN) |
| Services | | Services |
+-------------+ Pseudo Wire +-------------+
|Demultiplexer|<==============================>|Demultiplexor|
+-------------+ +-------------+
| PSN | PSN Tunnel | PSN |
| MPLS |<==============================>| MPLS |
+-------------+ +-------------+
| Physical | | Physical |
+-----+-------+ +-----+-------+
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Figure 2: Ethernet PWE3 Protocol Stack Reference Model
For the purpose of this document, PE1 will be defined as the ingress
router, and PE2 as the egress router. A layer 2 PDU will be received
at PE1, encapsulated at PE1, transported, decapsulated at PE2, and
transmitted out on the attachment circuit of PE2.
An Ethernet PW emulates a single Ethernet link between exactly two
endpoints. The mechanisms described in this document are agnostic to
that which is beneath the "Pseudo Wire" level in Figure 2, concerning
itself only with the "Emulated Service" portion of the stack.
The following reference model describes the termination point of each
end of the PW within the PE:
+-----------------------------------+
| PE |
+---+ +-+ +-----+ +------+ +------+ +-+
| | |P| | | |PW ter| | PSN | |P|
| |<==|h|<=| NSP |<=|minati|<=|Tunnel|<=|h|<== From PSN
| | |y| | | |on | | | |y|
| C | +-+ +-----+ +------+ +------+ +-+
| E | | |
| | +-+ +-----+ +------+ +------+ +-+
| | |P| | | |PW ter| | PSN | |P|
| |==>|h|=>| NSP |=>|minati|=>|Tunnel|=>|h|==> To PSN
| | |y| | | |on | | | |y|
+---+ +-+ +-----+ +------+ +------+ +-+
| |
+-----------------------------------+
^ ^ ^
| | |
A B C
Figure 3: PW reference diagram
The PW terminates at a logical port within the PE, defined at point B
in the above diagram. This port provides an Ethernet MAC service that
will deliver each Ethernet frame that is received at point A,
unaltered, to the point A in the corresponding PE at the other end of
the PW.
The Native Service Processing (NSP) function includes frame
processing that is required for the Ethernet frames that are
forwarded to the PW termination point. Such functions may include
stripping, overwriting or adding VLAN tags, physical port
multiplexing and demultiplexing, PW-PW bridging, L2 encapsulation,
shaping, policing, etc. These functions are specific to the ethernet
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technology , and may not be required for the PW emulation service.
The points to the left of A, including the physical layer between the
CE and PE, and any adaptation (NSP) functions between it and the PW
terminations, are outside of the scope of PWE3 and are not defined
here.
"PW Termination", between A and B, represents the operations for
setting up and maintaining the PW, and for encapsulating and
decapsulating the Ethernet frames as necessary to transmit them
across the MPLS network.
An Ethernet PW operates in one of two modes: "raw mode" or "tagged
mode". In tagged mode, each frame MUST contain at least one 802.1Q
[802.1Q] VLAN tag, and the tag value is meaningful to the NSPs at the
two PW termination points. That is, the two PW termination points
must have some agreement (signaled or manually configured) on how to
process the tag. On a raw mode PW, a frame MAY contain an 802.1Q VLAN
tag, but if it does, the tag is not meaningful to the NSPs, and
passes transparently through them.
3. Applicability Statement
The Ethernet PW emulation allows a service provider to offer a "port
to port" Ethernet based service across an MPLS packet switched
network (PSN) while the Ethernet VLAN PW emulation allows an
"Ethernet VLAN to VLAN" based service across an MPLS packet switched
network (PSN).
The Ethernet or Ethernet VLAN PW has the following characteristics in
relationship to the respective native service:
- Ethernet PW connects two Ethernet ACs while Ethernet VLAN PW
connects two Ethernet VLAN ACs, supporting bi-directional
transport of variable length Ethernet frames. The ingress Native
Service Processing (NSP) function strips the preamble and FCS
from the Ethernet frame and transports the frame in its entirety
across the PW. This is done regardless of the presence of the
802.1Q tag in the frame. The egress NSP function receives the
Ethernet frame from the PW and regenerates the preamble or FCS
before forwarding the frame to the attachment circuit. Since FCS
is not being transported across either Ethernet or Ethernet VLAN
PWs, payload integrity transparency may be lost. The OPTIONAL
methods described in [FCS] can be used to achieve payload
integrity transparency on Ethernet or Ethernet VLAN PWs.
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- For Ethernet VLAN PW, VLAN tag rewrite can be achieved by NSP at
the egress PE which is outside the scope of this document.
- The Ethernet or Ethernet VLAN PW only supports homogeneous
Ethernet frame type across the PW; both ends of the PW must be
either tagged or untagged. Heterogeneous frame type support
achieved with NSP functionality is outside the scope of this
document.
- Ethernet port or Ethernet VLAN status notification is provided
using the PW Status TLV in the LDP status notification message.
Loss of connectivity between PEs can be detected by the LDP
session closing, or by using [VCCV] mechanisms. The PE can
convey these indications back to its attached Remote System.
- The maximum frame size that can be supported is limited by the
PSN MTU minus the MPLS header size, unless fragmentation and
reassembly is used [FRAG].
- The packet switched network may reorder, duplicate, or silently
drop packets. Sequencing MAY be enabled in the Ethernet or
Ethernet VLAN PW to detect lost, duplicate, or out-of-order
packets on a per-PW basis.
- The faithfulness of an Ethernet or Ethernet VLAN PW may be
increased by leveraging Quality of Service features of the PEs
and the underlying PSN. (see "QoS Considerations" section)
4. Details Specific to Particular Emulated Services
4.1. Ethernet Tagged Mode
The Ethernet frame will be encapsulated according to the procedures
defined later in this document for tagged mode. It should be noted
that if the VLAN identifier is modified by the egress PE, the
Ethernet spanning tree protocol might fail to work properly. If this
issue is of significance, the VLAN identifier MUST be selected in
such away that it matches on the Attachment Circuits at both ends of
the PW.
If the PE detects a failure on the Ethernet physical port, or the
port is administratively disabled, it MUST send PW status
notification message for all PWs associated with the port.
This mode uses service-delimiting tags to map input Ethernet frames
to respective PWs and is corresponds to PW type 0x0004 "Ethernet
Tagged Mode" [IANA].
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4.2. Ethernet Raw Mode
The Ethernet frame will be encapsulated according to the procedures
defined later in this document for raw mode. If the PE detects a
failure on the Ethernet input port, or the port is administratively
disabled, the PE MUST send an appropriate PW status notification
message to the corresponding remote PE.
In this mode all Ethernet frames received on the attachment circuit
of PE1 will be transmitted to PE2 on a single PW. This service
corresponds to PW type 0x0005 "Ethernet" [IANA].
4.3. Ethernet Specific Interface Parameter LDP Sub-TLV
This LDP sub-Type Length Value [LDP] specifies interface specific
parameters. When applicable, it MUST be used to validate that the
PEs, and the ingress and egress ports at the edges of the circuit,
have the necessary capabilities to interoperate with each other. The
Interface parameter TLV is defined in [PWE3-CTRL], the IANA registry
with initial values for interface parameter sub-TLV types is defined
in [IANA], but the Ethernet specific interface parameters are
specified as follows:
- 0x06 Requested VLAN ID Sub-TLV
An Optional 16 bit value indicating the requested VLAN ID. This
parameter MUST be used by a PE that is incapable of rewriting the
802.1Q Ethernet VLAN tag on output. If the ingress PE receives
this request, it MUST rewrite the VLAN ID contained inside the
VLAN Tag at the input to match the requested VLAN ID. If this is
not possible, and the VLAN ID does not already match the
configured ingress VLAN ID, the PW MUST not be enabled. This
parameter is applicable only to PW type 0x0004.
4.4. Generic Procedures
When the NSP/Forwarder hands a frame to the PW termination function:
- The preamble (if any) and FCS are stripped off.
- The control word as defined in the "The Control Word" section is,
if necessary, prepended to the resulting frame. The conditions
under which the control word is or is not used are specified
below.
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- The proper Pseudowire demultiplexor ( PW Label ) is prepended to
the resulting packet.
- The proper tunnel encapsulation is prepended to the resulting
packet.
- The packet is transmitted.
The way in which the proper tunnel encapsulation and pseudo wire
demultiplexor are chosen depends on the procedures that were used to
set up the pseudo wire.
The tunnel encapsulation depends on how the MPLS PSN is setup. This
can include no label, one label or more labels. The proper pseudo
wire demultiplexor is an MPLS label whose value is determined by the
PW setup and maintenance protocols.
When a packet arrives over a PW, the tunnel encapsulation and PW
demultiplexor are stripped off. If the control word is present, it is
processed and stripped off. The resulting frame is then handed to the
Forwarder/NSP. Regeneration of the FCS is considered to be an NSP
responsibility.
4.4.1. Raw Mode vs. Tagged Mode
When the PE receives an Ethernet frame, and the frame has a VLAN tag,
we can distinguish two cases:
1. The tag is "service-delimiting". This means that the tag was
placed on the frame by some piece of service provider-operated
equipment, and the tag is used by the service provider to
distinguish the traffic. For example, LANs from different
customers might be attached to the same service provider
switch, which applies VLAN tags to distinguish one customer's
traffic from another's, and then forwards the frames to the PE.
2. The tag is not service-delimiting. This means that the tag was
placed in the frame by a piece of customer equipment, and is
not meaningful to the PE.
Whether the tag is service delimiting or not , is determined by local
configuration on the PE.
If an Ethernet PW is operating in raw mode, service-delimiting tags
are NEVER sent over the PW. If a service-delimiting tag is present
when the frame is received from attachment circuit by the PE, it MUST
be stripped (by the NSP) from the frame before the frame is sent to
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the PW.
If an Ethernet PW is operating in tagged mode, every frame sent on
the PW MUST have a service-delimiting VLAN tag. If the frame as
received by the PE from the attachment circuit does not have a
service-delimiting VLAN tag, the PE must prepend the frame with a
dummy VLAN tag before sending the frame on the PW. This is the
default operating mode. This is the only REQUIRED mode.
In both modes, non-service-delimiting tags are passed transparently
across the PW as part of the payload. It should be noted that a
single Ethernet packet may contain more then one tag. At most one of
these tags may be service-delimiting. In any case the NSP function
may only inspect the outer most tag for the purpose of adapting the
Ethernet frame to the pseudo wire.
In both modes, the service-delimiting tag values have only local
significance, i.e., are meaningful only at a particular PE-CE
interface. When tagged mode is used, the PE that receives a frame
from the PW may rewrite the tag value, or may strip the tag entirely,
or may leave the tag unchanged, depending on its configuration. When
raw mode is used, the PE that receives a frame may or may not need to
add a service-delimiting tag before transmitting the frame on the
attachment circuit; however it MUST not rewrite or remove any tags
which are already present.
The following table illustrates the what operations might be
performed at input from the attachment circuit:
+-----------------------------------------------------------+
| Tag-> | service delimiting | non service delimiting|
|--------+---------------------+----------------------------|
| Raw Mode | 1st VLAN Tag Removed| no operation performed|
|--------+---------------------+----------------------------|
| Tagged Mode | NO OP or Tag Added | Tag Added |
+-----------------------------------------------------------+
4.4.2. MTU Management on the PE/CE Links
The Ethernet PW MUST NOT be enabled unless it is known that the MTUs
of the CE-PE links are the same at both ends of the PW. If an egress
router receives an encapsulated layer 2 PDU whose payload length
(i.e., the length of the PDU itself without any of the encapsulation
headers), exceeds the MTU of the destination layer 2 interface, the
PDU MUST be dropped.
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4.4.3. Frame Ordering
In general, applications running over Ethernet do not require strict
frame ordering. However the IEEE definition of 802.3 [802.3] requires
that frames from the same conversation in the context of link
aggregation (clause 43) are delivered in sequence. Moreover, the PSN
cannot (in the general case) be assumed to provide or to guarantee
frame ordering. An Ethernet PW can, through use of the control word,
provide strict frame ordering. If this option is enabled, any frames
which get mis-ordered by the PSN will be dropped or reordered by the
receiving PW endpoint. If strict frame ordering is a requirement for
a particular PW, this option MUST be enabled.
4.4.4. Frame Error Processing
An encapsulated Ethernet frame traversing a pseudo wire may be
dropped, corrupted or delivered out-of-order. As described in [PWE3-
REQ], frame-loss, corruption, and out-of-order delivery is considered
to be a "generalized bit error" of the pseudo wire. PW frames that
are corrupted will be detected at the PSN layer and dropped.
At the ingress of the PW the native Ethernet frame error processing
mechanisms MUST be enabled. Therefore, if a PE device receives an
Ethernet frame containing hardware level CRC errors, framing errors,
or a runt condition, the frame MUST be discarded on input. Note that
defining this processing is part of the NSP function and is outside
the scope of this document.
4.4.5. IEEE 802.3x Flow Control Interworking
In a standard Ethernet network, the flow control mechanism is
optional and typically configured between the two nodes on a point-
to-point link (e.g. between the CE and the PE). IEEE 802.3x PAUSE
frames MUST NOT be carried across the PW. See Appendix A for notes on
CE-PE flow control.
4.5. Management
The Ethernet PW management model follows the general management
defined in [RFC3985] and [PWE3-MIB]. Many common PW management
facilities are provided here, with no additional Ethernet specifics
necessary. Ethernet-specific parameters are defined in an additional
MIB module, [PW-MIB].
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4.6. The Control Word
When carrying Ethernet over an MPLS backbone, sequentiality may need
to be preserved. The OPTIONAL control word along the guidelines of
[PWE3-CW] is defined here, and addresses this requirement.
Implementations MUST support sending no control word, and MAY support
sending a control word. If the control word is not used all the
functionality defined in [PWE3-CW] is not available. In particular
the PW packet may be mistakenly recognized as an IP packet by PSN
devices that use the first nibble in the packet to identify it's
content. This problem is only significant if the PSN contain equal
cost load sharing links, and a source MAC address starting with 0x4
as it first byte is used.
A PW carried over an MPLS PSN that uses the contents of the MPLS
payload to select the ECMP path SHOULD employ the PW MPLS Control
Word, if strict packet ordering is required.
In all cases the egress router must be aware of whether the ingress
router will send a control word over a specific virtual circuit. This
may be achieved by configuration of the routers, or by signaling, as
defined in [PWE3-CTRL].
The control word is defined as follows:
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 0 0 0| Reserved | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the above diagram the first 4 bits MUST be set to 0 to indicate PW
data. The rest of the first 16 bits are reserved for future use.
They MUST be set to 0 when transmitting, and MUST be ignored upon
receipt.
The next 16 bits provide a sequence number that can be used to
guarantee ordered frame delivery. The processing of the sequence
number field is OPTIONAL.
The sequence number space is a 16 bit, unsigned circular space. The
sequence number value 0 is used to indicate that the sequence number
check algorithm is not used. The sequence number processing algorithm
is found in [PWE3-CW].
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4.7. QoS Considerations
The ingress PE MAY consider the user priority (PRI) field [802.1Q] of
the VLAN tag header when determining the value to be placed in a QoS
field of the encapsulating protocol (e.g., the EXP fields of the MPLS
label stack). In a similar way, the egress PE MAY consider the QoS
field of the MPLS (e.g., the EXP fields of the MPLS label stack)
protocol when queuing the frame for CE-bound.
A PE MUST support the ability to carry the Ethernet PW as a best
effort service over the MPLS PSN. PRI bits are kept transparent
between PE devices, regardless of the QoS support of the PSN.
If an 802.1Q VLAN field is added at the PE, a default PRI setting of
zero MUST be supported, a configured default value is recommended, or
the value may be mapped from the QoS field of the PSN, as referred to
above.
A PE may support additional QoS support by means of one or more of
the following methods:
-i. One COS per PW End Service (PWES), mapped to a single COS PW
at the PSN.
-ii. Multiple COS per PWES mapped to a single PW with multiple
COS at the PSN.
-iii. Multiple COS per PWES mapped to multiple PWs at the PSN.
Examples of the cases above and details of the service mapping
considerations are described in Appendix B.
The PW guaranteed rate at the MPLS PSN level is PW service provider
policy based on agreement with the customer, and may be different
from the Ethernet physical port rate.
5. Security Considerations
The Ethernet pseudo wire type is subject to all of the general
security considerations discussed in [RFC3985][PWE3-CTRL].
The Ethernet pseudo wire is transported on a MPLS PSN, therefore the
security of the pseudo wire itself will only be as good as the
security of the MPLS PSN. The MPLS PSN can be secured by various
methods, as described in [MPLS-ARCH].
Security achieved by access control of MAC addresses is out of scope
of this document. Additional security requirements related to the use
of PW in a switching (virtual bridging) environment are not discussed
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here as they are not within the scope of this document.
6. PSN MTU Requirements
The MPLS PSN MUST be configured with an MTU that is large enough to
transport a maximum sized Ethernet frame which has been encapsulated
with a control word, a pseudo wire demultiplexor, and a tunnel
encapsulation. With MPLS used as the tunneling protocol, for example,
this is likely to be 8 or more bytes greater than the largest frame
size. The methodology described in [FRAG] MAY be used to fragment
encapsulated frames that exceed the PSN MTU. However if [FRAG] is
not used and if the ingress router determines that an encapsulated
layer 2 PDU exceeds the MTU of the PSN tunnel through which it must
be sent, the PDU MUST be dropped.
7. IANA Considerations
This document has no IANA Actions.
8. Full Copyright Statement
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM 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.
9. Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
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found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
10. Normative References
[PWE3-CW] "PWE3 Control Word for use over an MPLS PSN", S. Bryant,
G. Swallow, D. McPherson, draft-ietf-pwe3-cw-01.txt, ( work in
progress ), December 2004.
[IANA] "IANA Allocations for pseudo Wire Edge to Edge Emulation
(PWE3)" Martini,Townsley, draft-ietf-pwe3-iana-allocation-08.txt
(work in progress), April 2004
[PWE3-CTRL] "Transport of Layer 2 Frames Over MPLS", Martini L.,et al
draft-ietf-pwe3-control-protocol-09.txt, ( work in progress ),
September 2004.
[MPLS-ARCH] RFC3031, "Multiprotocol Label Switching Architecture."
E. Rosen, A. Viswanathan, R. Callon. January 2001.
[802.3] IEEE802.3-2005, ISO/IEC 8802-3: 2000 (E), "IEEE Standard
for Information technology -- Telecommunications and
information exchange between systems -- Local and metropolitan
area networks -- Specific requirements -- Part 3: Carrier
Sense Multiple Access with Collision Detection (CSMA/CD)
Access Method and Physical Layer Specifications", 2005.
[802.1Q] ANSI/IEEE Standard 802.1Q-2005, "IEEE Standards for
Local and Metropolitan Area Networks: Virtual Bridged
Local Area Networks", 2005.
[PDU] IEEE Std 802.3, 1998 Edition, "Part 3: Carrier
sense multiple access with collision detection (CSMA/CD)
access method and physical layer specifications" figure 3.1,
1998
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Internet Draft draft-ietf-pwe3-ethernet-encap-11.txt November 2005
11. Informative References
[RFC3985] RFC3985, "PWE3 Architecture" Bryant, et al., RFC3985.
[PWE3-REQ] "Requirements for Pseudo Wire Emulation Edge-to-Edge",
Xiao, X., McPherson, D., Pate, P., White, C., Kompella,
K., Gill, V., Nadeau, T., draft-ietf-pwe3-requirements-08.txt,
(work in progress), September 2003.
[PWE3-MIB] "Pseudo Wire (PW) Management Information Base
using SMIv2", Zelig, D., Mantin, S., Nadeau, T., Danenberg,
D., draft-ietf-pwe3-pw-mib-04.txt, (work in progress),
February 2004.
[LDP] "LDP Specification." L. Andersson, P. Doolan, N. Feldman, A.
Fredette, B. Thomas. January 2001. RFC3036
[FRAG] "PWE3 Fragmentation and Reassembly", A. Malis, W. M. Townsley,
draft-ietf-pwe3-fragmentation-08.txt ( work in progress )
February 2005
[FCS] "PWE3 Frame Check Sequence Retention", A. Malis, D.Allan,
N. Del Regno, draft-ietf-pwe3-fcs-retention-04.txt (work in
progress) September 2005
12. Editor Information
Luca Martini
Cisco Systems, Inc.
9155 East Nichols Avenue, Suite 400
Englewood, CO, 80112
e-mail: lmartini@cisco.com
13. Author Information
Nasser El-Aawar
Level 3 Communications, LLC.
1025 Eldorado Blvd.
Broomfield, CO, 80021
e-mail: nna@level3.net
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Internet Draft draft-ietf-pwe3-ethernet-encap-11.txt November 2005
Giles Heron
Tellabs
Abbey Place
24-28 Easton Street
High Wycombe
Bucks
HP11 1NT
UK
e-mail: giles.heron@tellabs.com
Eric C. Rosen
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
e-mail: erosen@cisco.com
14. Significant Contributors
Andrew G. Malis
Tellabs
90 Rio Robles Dr.
San Jose, CA 95134
e-mail: Andy.Malis@tellabs.com
Dan Tappan
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
e-mail: tappan@cisco.com
Steve Vogelsang
ECI Telecom
Omega Corporate Center
1300 Omega Drive
Pittsburgh, PA 15205
e-mail: stephen.vogelsang@ecitele.com
Martini, et al. [Page 17]
Internet Draft draft-ietf-pwe3-ethernet-encap-11.txt November 2005
Vinai Sirkay
Reliance Infocomm
Dhirubai Ambani Knowledge City
Navi Mumbai 400 709
India
e-mail: vinai@sirkay.com
Vasile Radoaca
Nortel Networks
600 Technology Park
Billerica MA 01821
e-mail: vasile@nortelnetworks.com
Chris Liljenstolpe
Alcatel
11600 Sallie Mae Dr.
9th Floor
Reston, VA 20193
e-mail: chris.liljenstolpe@alcatel.com
Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
e-mail: kireeti@juniper.net
Tricci So
Nortel Networks 3500 Carling Ave.,
Nepean, Ontario,
Canada, K2H 8E9.
e-mail: tso@nortelnetworks.com
XiPeng Xiao
Riverstone Networks
5200 Great America Parkway
Santa Clara, CA 95054
e-mail: xxiao@riverstonenet.com
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Internet Draft draft-ietf-pwe3-ethernet-encap-11.txt November 2005
Christopher O. Flores
T-Systems
10700 Parkridge Boulevard
Reston, VA 20191
USA
e-mail: christopher.flores@usa.telekom.de
David Zelig
Corrigent Systems
126, Yigal Alon St.
Tel Aviv, ISRAEL
e-mail: davidz@corrigent.com
Raj Sharma
Luminous Netwokrs, Inc.
10460 Bubb Road
Cupertino, CA 95014
e-mail: raj@luminous.com
Nick Tingle
TiMetra Networks
274 Ferguson Drive
Mountain View, CA 94043
e-mail: nick@timetra.com
Sunil Khandekar
TiMetra Networks
274 Ferguson Drive
Mountain View, CA 94043
email: sunil@timetra.com
Loa Andersson
TLA-group
e-mail: loa@pi.se
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Ap A Interoperability Guidelines
Configuration Options
The following is a list of the configuration options for a point-to-
point Ethernet PW based on the reference points of Figure 3:
--------------|---------------|---------------|------------------
Service and | Encap on C |Operation at B | Remarks
Encap on A | |ingress/egress |
--------------|---------------|---------------|------------------
1) Raw | Raw - Same as | |
| A | |
| | |
--------------|---------------|---------------|------------------
2) Tag1 | Tag2 |Optional change| VLAN can be
| |of VLAN value | 0-4095
| | | Change allowed in
| | | both directions
--------------|---------------|---------------|------------------
3) No Tag | Tag |Add/remove Tag | Tag can be
| |field | 0-4095
| | | (note i)
| | |
--------------|---------------|---------------|------------------
4) Tag | No Tag |Remove/add Tag | (note ii)
| |field |
| | |
| | |
--------------|---------------|---------------|------------------
Figure 4: Configuration Options
Allowed combinations:
Raw and other services are not allowed on the same NSP virtual port
(A). All other combinations are allowed, except that conflicting
VLANs on (A) are not allowed. Note that in most point-to-point PW
application the NSP virtual port is the same entity as the physical
port.
Notes:
-i. Mode #3 MAY be limited to adding VLAN NULL only, since
change of VLAN or association to specific VLAN can be done
at the PW CE-bound side.
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-ii. Mode #4 exists in layer 2 switches, but is not recommended
when operating with PW since it may not preserve the user's
PRI bits. If there is a need to remove the VLAN tag (for
TLS at the other end of the PW) it is recommended to use
mode #2 with tag2=0 (NULL VLAN) on the PW and use mode #3 at
the other end of the PW.
IEEE 802.3x Flow Control Considerations
If the receiving node becomes congested, it can send a special frame,
called the PAUSE frame, to the source node at the opposite end of the
connection. The implementation MUST provide a mechanism for
terminating PAUSE frames locally (i.e. at the local PE). It MUST
operate as follows: PAUSE frames received on a local Ethernet port
SHOULD cause the PE device to buffer, or to discard, further Ethernet
frames for that port until the PAUSE condition is cleared.
Optionally, the PE MAY simply discard PAUSE frames.
If the PE device wishes to pause data received on a local Ethernet
port (perhaps because its own buffers are filling up or because it
has received notification of congestion within the PSN) then it MAY
issue a PAUSE frame on the local Ethernet port, but MUST clear this
condition when willing to receive more data.
Ap B QoS Details
Section 3.7 describes various modes for supporting PW QOS over the
PSN. Examples of the above for a point to point VLAN service are:
- The classification to the PW is based on VLAN field only,
regardless of the user PRI bits. The PW is assigned a specific
COS (marking, scheduling, etc.) at the tunnel level.
- The classification to the PW is based on VLAN field, but the PRI
bits of the user is mapped to different COS marking (and network
behavior) at the PW level. Examples are and E-LSP in an MPLS
network.
- The classification to the PW is based on VLAN field and the PRI
bits, and frames with different PRI bits are mapped to different
PWs. An example is to map a PWES to different L-LSPs in MPLS PSN
in order to support multiple COS over an L-LSP capable network,
or to multiple L2TPv3 sessions [L2TPv3].
The specific value to be assigned at the PSN for various COS is
out of scope for this document.
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Adaptation of 802.1Q COS to PSN COS
It is not required that the PSN will have the same COS definition of
COS as defined in [802.1Q], and the mapping of 802.1Q COS to PSN COS
is application specific and depends on the agreement between the
customer and the PW provider. However, the following principles
adopted from 802.1Q table 8-2 MUST be met when applying set of PSN
COS based on user's PRI bits.
----------------------------------
|#of available classes of service|
-------------||---+---+---+---+---+---+---+---|
User || 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
Priority || | | | | | | | |
===============================================
0 Best Effort|| 0 | 0 | 0 | 1 | 1 | 1 | 1 | 2 |
(Default) || | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
1 Background || 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
|| | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
2 Spare || 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
|| | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
3 Excellent || 0 | 0 | 0 | 1 | 1 | 2 | 2 | 3 |
Effort || | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
4 Controlled || 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 |
Load || | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
5 Interactive|| 0 | 1 | 1 | 2 | 3 | 4 | 4 | 5 |
Multimedia || | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
6 Interactive|| 0 | 1 | 2 | 3 | 4 | 5 | 5 | 6 |
Voice || | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
7 Network || 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
Control || | | | | | | | |
------------ ||---+---+---+---+---+---+---+---|
Figure 5: IEEE 802.1Q COS Service Mapping
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Drop precedence
The 802.1P standard does not support drop precedence, therefore from
the PW PE-bound point of view there is no mapping required. It is
however possible to mark different drop precedence for different PW
frames based on the operator policy and required network behavior.
This functionality is not discussed further here.
PSN QOS support and signaling of QOS is out of scope of this
document.
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