Network Working Group Luca Martini
Internet Draft Nasser El-Aawar
Expiration Date: May 2003 Level 3 Communications, LLC.
Giles Heron Eric C. Rosen
PacketExchange Ltd. Cisco Systems, Inc.
November 2002
Encapsulation Methods for Transport of Ethernet Frames Over IP/MPLS Networks
draft-ietf-pwe3-ethernet-encap-01.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Abstract
An Ethernet Pseudowire (PW) allows Ethernet/802.3 Protocol Data Units
(PDUs) to be carried over a Packet Switched Network (PSN) such as IP
or MPLS. This ability enables service providers to leverage an
existing PSN to offer ethernet services. This document addresses the
encapsulation of Ethernet/802.3 PDUs within a pseudowire, and issues
associated with the point-to-point emulation of ethernet within a PW.
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Table of Contents
1 Specification of Requirements .......................... 2
2 Introduction ........................................... 2
3 Requirements for Ethernet Pseudo-Wire Emulation ........ 4
3.1 Packet Processing ...................................... 6
3.1.1 Encapsulation .......................................... 6
3.1.2 Tagged Mode ............................................ 6
3.1.3 MTU Management ......................................... 6
3.1.4 Frame Ordering ......................................... 6
3.1.5 Frame Error Processing ................................. 6
3.1.6 IEEE 802.3x Flow Control Interworking .................. 7
3.2 PW Setup and Maintenance ............................... 7
3.3 Management ............................................. 7
3.4 The Control Word ....................................... 7
3.4.1 Setting the sequence number ............................ 8
3.4.2 Processing the sequence number ......................... 8
3.5 QoS Considerations ..................................... 9
3.6 Security Considerations ................................ 10
3.7 MTU Requirements ....................................... 10
4 Intellectual Property Disclaimer ....................... 11
5 References ............................................. 11
6 Author Information ..................................... 12
Appendix A - Interoperability Guidelines ............... 14
Appendix B - QoS Details ............................... 16
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
2. Introduction
An Ethernet Pseudowire (PW) allows Ethernet/802.3 Protocol Data Units
(PDUs) to be carried over Packet Switched Network (PSN) such as IP or
MPLS. In addressing the issues associated with carrying an Ethernet
PDU over a PSN, this document assumes that a Pseudowire (PW) has been
setup by some means outside the scope of this document. This may be
via manual configuration, or a signaling protocol such as that
defined in [PWE3-CTRL] or [L2TPv3]. As described in [PWE3-FRAME],
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this PW may ultimately operate over an MPLS, IPv4 or IPv6 PSN.
In addition to the Ethernet PDU format used within the pseudowire,
this document discusses:
- Pseudo-wire (PW) requirements for emulating Ethernet trunking and
switching behavior.
- PE-bound and CE-bound packet processing of Ethernet PDUs
- Ethernet-specific QoS and security considerations
- Inter-domain transport considerations for Ethernet PE
The following two figures describe the reference models which are
derived from [PWE3-FRAME] to support the Ethernet PW emulated
services.
Native |<----- Pseudo Wire ---->| Native
Ethernet | | Ethernet
or | |<-- PSN Tunnel -->| | or
VLAN V V V V VLAN
Service +----+ +----+ Service
+----+ | | PE1|==================| PE2| | +----+
| |----------|............PW1.............|----------| |
| CE1| | | | | | | |CE2 |
| |----------|............PW2.............|----------| |
+----+ | | |==================| | | +----+
^ +----+ +----+ | ^
| Provider Edge 1 Provider Edge 2 |
| |
|<-------------- Emulated Service ---------------->|
Figure 1: PWE3 Ethernet/VLAN Interface Reference Configuration
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+-------------+ +-------------+
| Emulated | | Emulated |
| Ethernet | | Ethernet |
| (including | Emulated Service | (including |
| VLAN) |<==============================>| VLAN) |
| Services | | Services |
+-------------+ Pseudo Wire +-------------+
|Demultiplexer|<==============================>|Demultiplexor|
+-------------+ +-------------+
| PSN | PSN Tunnel | PSN |
| MPLS or IP |<==============================>| MPLS or IP |
+-------------+ +-------------+
| Physical | | Physical |
+-----+-------+ +-----+-------+
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 of PE2.
3. Requirements for Ethernet Pseudo-Wire Emulation
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:
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+-----------------------------------+
| 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
Figure 3: PW reference diagram
The PW terminates at a logical port within the PE, defined at point A
in the above diagram. This port provides an Ethernet MAC service that
will deliver each Ethernet packet that is received at point A,
unaltered, to the point A in the corresponding PE at the other end of
the PW.
The "NSP" function includes packet processing needed to translate the
Ethernet packets that arrive at the CE-PE interface to/from the
Ethernet packets that are applied 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.
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 packets according to the PSN type in use.
A pseudo wire can be one of the two types: raw or tagged. This is a
property of the emulated Ethernet link and indicates whether the
pseudo wire MUST contain an 802.1Q VLAN tag (i.e. tagged mode) or MAY
contain a tag (i.e. raw mode).
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3.1. Packet Processing
3.1.1. Encapsulation
The entire Ethernet frame without any preamble or FCS is transported
as a single packet over the Pseudowire. Note that when using the
signaling procedures defined in [PWE3-CRTL] or [L2TPv3], a "Raw Mode"
PW should be signaled as being of type "Ethernet".
3.1.2. Tagged Mode
The ehternet packet may contain an 802.1Q tag, in this case the PE
MAY signal that the PW will is transporting ethernet frames including
802.1Q tags. In this case all frames in a PW MUST have the same
802.1Q tag value. Note that the tag may be overwritten by the NSP
function at ingress or at egress. Note that when using the signaling
procedures defined in [PWE3-CRTL] or [L2TPv3], a "Tagged Mode" PW
should be signaled as being of type "Ethernet VLAN".
3.1.3. MTU Management
Ingress and egress PWESs MUST agree on their maximum MTU size to be
transported over the PSN.
3.1.4. 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 are delivered in sequence.
Moreover, the PSN cannot (in the general case) be assumed to provide
or to guarantee frame ordering. Therefore if strict frame ordering
is required, this MUST be enabled by the PW.
3.1.5. Frame Error Processing
An encapsulated Ethernet frame traversing a psuedo-wire may be
dropped, corrupted or delivered out-of-order. As described in [PWE3-
REQ], packet-loss, corruption, and out-of-order delivery is
considered to be a "generalized bit error" of the psuedo-wire.
Therefore, the native Ethernet frame error processing mechanisms MUST
be extended to the corresponding psuedo-wire service. Therefore, if
a PE device receives an Ethernet frame containing hardware level CRC
errors, framing errors, or a runt condition, the frame MUST be
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discarded on input. Note that this processing is part of the NSP
function and is outside the scope of this draft.
3.1.6. 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.
3.2. PW Setup and Maintenance
This document assumes that a mechanism exists to setup the PW for
which the emulated ethernet connection operates over. Maintenance of
the PW (e.g. keepalives, status updates, etc) is generally tied
closely to the PW Setup mechanisms. [PWE3-CTRL] and [L2TPv3] define
two mechanisms for setup and maintenance of Ethernet PWs.
3.3. Management
The Ethernet PW management model follows the general management
defined in [PWE3-FRAME] 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-ENET-MIB].
As specified in [PWE3-FRAME], an implementation SHOULD support the
generic and specific PW MIB modules for PW set-up and monitoring.
Other mechanisms for PW set up (command line interface for example)
MAY be supported.
3.4. The Control Word
When carrying Ethernet over an IP or MPLS backbone sequentiality may
need to be preserved. The OPTIONAL control word defined here
addresses this requirement. Implementations MUST support sending no
control word, and MAY support sending a control word.
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, for example as defined in [PWE3-CRTL].
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the above diagram 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 packet 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 an unsequenced packet.
3.4.1. Setting the sequence number
For a given PW, and a pair of routers PE11 and PE2, if PE11 supports
packet sequencing then the following procedures should be used:
- the initial packet transmitted on the PW MUST use sequence number
1
- subsequent packets MUST increment the sequence number by one for
each packet
- when the transmit sequence number reaches the maximum 16 bit
value (65535) the sequence number MUST wrap to 1
If the transmitting router PE1 does not support sequence number
processing, then the sequence number field in the control word MUST
be set to 0.
3.4.2. Processing the sequence number
If a router PE2 supports receive sequence number processing, then the
following procedures should be used:
When a PW is initially set up, the "expected sequence number"
associated with it MUST be initialized to 1.
When a packet is received on that PW, the sequence number should be
processed as follows:
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- if the sequence number on the packet is 0, then the packet passes
the sequence number check
- otherwise if the packet sequence number >= the expected sequence
number and the packet sequence number - the expected sequence
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.
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
expected sequence number should be set using the algorithm:
expected_sequence_number := packet_sequence_number + 1 mod 2**16
if (expected_sequence_number = 0) then expected_sequence_number := 1;
Packets which are received out of order MAY be dropped or reordered
at the discretion of the receiver.
If a router PE2 does not support receive sequence number processing,
then the sequence number field MAY be ignored.
3.5. 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 or the DSCP of an IP packet). In a similar way, the
egress PE MAY consider the QoS field of the PSN's encapsulating
protocol when queuing the packet for CE-bound.
A PE MUST support the ability to carry the Ethernet PW as a best
effort service over the 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:
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-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 PSN level is PW provider policy based
on agreement with the customer, and may be different from the
Ethernet physical port rate.
3.6. Security Considerations
The ethernet pseudowire type is subject to all of the general
security considerations discussed in [PWE-FRAME].
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
here as they are not within the scope of this draft.
3.7. MTU Requirements
The network MUST be configured with an MTU that is sufficient to
transport the largest encapsulation frames. If MPLS is used as the
tunneling protocol, for example, this is likely to be 8 or more bytes
greater than the largest frame size. Other tunneling protocols may
have longer headers and require larger MTUs. If the ingress router
determines that an encapsulated layer 2 PDU exceeds the MTU of the
tunnel through which it must be sent, the PDU MUST be dropped. 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. Intellectual Property Disclaimer
This document is being submitted for use in IETF standards
discussions.
5. References
[PWE3-CRTL] "Transport of Layer 2 Frames Over MPLS",
Martini, L., et al., draft-ietf-pwe3-control-protocol-01.txt,
( work in progress ), February 2003.
[PWE3-REQ] "Requirements for Pseudo Wire Emulation Edge-to-Edge
(PWE3)", Xiao, X., McPherson, D., Pate, P., White, C.,
Kompella, K., Gill, V., Nadeau, T.,
draft-pwe3-requirements-03.txt, ( work in progress ), June 2002.
[PWE3-FRAME] "Framework for Pseudo Wire Emulation Edge-to-Edge
(PWE3)", Pate, P., Xiao, X., So, T., Malis, A., Nadeau, T.,
White, C., Kompella, K., Johnson, T., Bryant, S.,
draft-pate-pwe3-framework-03.txt, ( work in progress ),
June 2002.
[PW-MIB] "Pseudo Wire (PW) Management Information Base using SMIv2",
Zelig, D., Mantin, S., Nadeau, T., Danenberg, D.,
draft-zelig-pw-mib-02.txt, ( work in progress), February 2002.
[PW-ENET-MIB] "Ethernet Pseudo Wire (PW) Management Information
Base", Zelig, D., Nadeau, T., draft-zelig-pw-enet-mib-00.txt,
( work in progress ) February 2002.
[802.3] IEEE, 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", 2000.
[802.1Q] ANSI/IEEE Standard 802.1Q, "IEEE Standards for Local and
Metropolitan Area Networks: Virtual Bridged Local Area
Networks", 1998.
[L2TPv3] J. Lau, M. Townsley, A. Valencia, G. Zorn, I. Goyret,
G. Pall, A. Rubens, B. Palter, Layer Two Tunneling Protocol
(Version 3) "L2TPv3", work in progress,
draft-ietf-l2tpext-l2tp-base-03.txt, June 2002.
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6. Author Information
Luca Martini
Level 3 Communications, LLC.
1025 Eldorado Blvd.
Broomfield, CO, 80021
e-mail: luca@level3.net
Nasser El-Aawar
Level 3 Communications, LLC.
1025 Eldorado Blvd.
Broomfield, CO, 80021
e-mail: nna@level3.net
Giles Heron
PacketExchange Ltd.
The Truman Brewery
91 Brick Lane
LONDON E1 6QL
United Kingdom
e-mail: giles@packetexchange.net
Dan Tappan
Cisco Systems, Inc.
250 Apollo Drive
Chelmsford, MA, 01824
e-mail: tappan@cisco.com
Eric Rosen
Cisco Systems, Inc.
250 Apollo Drive
Chelmsford, MA, 01824
e-mail: erosen@cisco.com
Steve Vogelsang
Laurel Networks, Inc.
Omega Corporate Center
1300 Omega Drive
Pittsburgh, PA 15205
e-mail: sjv@laurelnetworks.com
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Andrew G. Malis
Vivace Networks, Inc.
2730 Orchard Parkway
San Jose, CA 95134
e-mail: Andy.Malis@vivacenetworks.com
Vinai Sirkay
Vivace Networks, Inc.
2730 Orchard Parkway
San Jose, CA 95134
e-mail: sirkay@technologist.com
Vasile Radoaca
Nortel Networks
600 Technology Park
Billerica MA 01821
e-mail: vasile@nortelnetworks.com
Chris Liljenstolpe
Cable & Wireless
11700 Plaza America Drive
Reston, VA 20190
e-mail: chris@cw.net
Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
e-mail: kireeti@juniper.net
Tricci So
e-mail: tricciso@yahoo.ca
XiPeng Xiao
Redback Networks
300 Holger Way,
San Jose, CA 95134
e-mail: xipeng@redback.com
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Chris Flores
Austin, Texas
e-mail: chris_flores@hotmail.com
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
Utfors
P.O. Box 525,
SE-169 29 Solna, Sweden
e-mail: loa.andersson@utfors.se
Appendix A - Interoperability Guidelines
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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 physical port (A).
All other combinations are allowed, except that conflicting VLANs on
(A) are not allowed.
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.
-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
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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.
Appendix 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 DiffServ coding in case
of IP PSN, and E-LSP in MPLS PSN.
- The classification to the PW is based on VLAN field and the PRI
bits, and packets 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
Martini, et al. [Page 17]
Internet Draft draft-ietf-pwe3-ethernet-encap-01.txt November 2002
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
packets 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.
Martini, et al. [Page 18]
