Francois Le Faucheur
Liwen Wu
Bruce Davie
Cisco Systems
Shahram Davari
PMC-Sierra Inc.
Pasi Vaananen
Nokia
Ram Krishnan
Nexabit Networks
Pierrick Cheval
Alcatel
Juha Heinanen
Telia Finland
IETF Internet Draft
Expires: October, 2000
Document: draft-ietf-mpls-diff-ext-03.txt February, 2000
MPLS Support of Differentiated Services
Status of this Memo
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Abstract
This document defines a flexible solution for support of
Differentiated Services (Diff-Serv) over Multi-Protocol Label
Switching (MPLS) networks.
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MPLS Support of Diff-Serv February 00
This solution allows the MPLS network administrator to select how
Diff-Serv Behavior Aggregates (BAs) are mapped onto Label Switched
Paths so that he/she can best match the Diff-Serv, Traffic
Engineering and Fast Restoration objectives within his/her
particular network. For instance, this solution allows the network
administrator to decide whether different sets of BAs are to be
mapped onto the same LSP or mapped onto separate LSPs.
This solution relies on combined use of two types of LSPs:
- LSPs which can transport multiple Ordered Aggregates, so that
the EXP field of the MPLS Shim Header conveys to the LSR the PHB
to be applied to the packet (covering both information about the
packet's scheduling treatment and its drop precedence).
- LSPs which only transport a single Ordered Aggregate, so that
the packet's scheduling treatment is inferred by the LSR
exclusively from the packet's label value while the packet's
drop precedence is conveyed in the EXP field of the MPLS Shim
Header or in the encapsulating link layer specific selective
drop mechanism (ATM, Frame Relay, 802.1).
1. Introduction
In an MPLS domain [MPLS_ARCH], when a stream of data traverses a
common path, a Label Switched Path (LSP) can be established using
MPLS signaling protocols. At the ingress Label Switch Router (LSR),
each packet is assigned a label and is transmitted downstream. At
each LSR along the LSP, the label is used to forward the packet to
the next hop.
In a Differentiated Service (Diff-Serv) domain [DIFF_ARCH] all the
IP packets crossing a link and requiring the same Diff-Serv behavior
are said to constitute a Behavior Aggregate (BA). At the ingress
node of the Diff-Serv domain the packets are classified and marked
with a Diff-Serv Code Point (DSCP) which corresponds to their
Behavior Aggregate. At each transit node, the DSCP is used to select
the Per Hop Behavior (PHB) that determines the scheduling treatment
and, in some cases, drop probability for each packet.
This document specifies a solution for supporting the Diff-Serv
Behavior Aggregates whose corresponding PHBs are currently defined
(in [DIFF_HEADER], [DIFF_AF], [DIFF_EF]) over an MPLS network. This
solution also offers flexibility for easy support of PHBs that may
be defined in the future.
As mentioned in [DIFF_HEADER], "Service providers are not required
to use the same node mechanisms or configurations to enable service
differentiation within their networks, and are free to configure the
node parameters in whatever way that is appropriate for their
service offerings and traffic engineering objectives". Thus, the
solution defined in this document gives Service Providers
flexibility in selecting how Diff-Serv classes of service are Routed
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MPLS Support of Diff-Serv February 00
or Traffic Engineered within their domain (eg. separate classes of
services supported via separate LSPs and Routed separately, all
classes of service supported on the same LSP and Routed together).
Similarly, the solution gives Service Providers flexibility in how
Diff-Serv classes of service can be protected via MPLS Fast
Restoration (eg. some classes of service supported via LSPs which
are protected via MPLS Fast Restoration while some other classes of
service are supported via LSPs which are not protected).
Beside, the solution specified in this document achieves label space
conservation and reduces the volume of label set-up/tear-down
signaling where possible by only resorting to multiple LSPs for a
given Forwarding Equivalent Class (FEC) [MPLS_ARCH] when useful or
required.
This specification allows support of Differentiated Services for
both IPv4 and IPv6 traffic transported over an MPLS network.
This document only describes operations for unicast. Multicast
support is for future study
1.1 Ordered Aggregate (OA) and PHB Scheduling Class (PSC)
The Diff-Serv model defines [DIFF_NEW] the set of Behavior
Aggregates which share an ordering constraint to constitute an
"Ordered Aggregate (OA)". It also defines the set of one or more
PHBs that are applied to this set of Behavior Aggregates to
constitute a "PHB Scheduling Class (PSC)".
1.2 EXP-Inferred-PSC LSPs (E-LSP)
A single LSP can be used to support up to eight BAs of a given FEC,
regardless of how many OAs these BAs span. With such LSPs, the EXP
field of the MPLS Shim Header [MPLS_ENCAPS] is used by the LSR to
determine the PHB to be applied to the packet. This includes both
the PSC and the drop preference.
We refer to such LSPs as "EXP-inferred-PSC LSPs" (E-LSP), since the
PSC of a packet transported on this LSP depends on the EXP field
value for that packet.
The mapping from EXP field to PHB (ie to PSC and drop precedence)
for a given such LSP, is either explicitly signaled at label set-up
or relying on a pre-configured mapping.
Detailed operations of E-LSPs are specified in section 3 below.
1.3 Label-Only-Inferred-PSC LSPs (L-LSP)
A separate LSP can be established for a single <FEC, OA> pair.
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MPLS Support of Diff-Serv February 00
With such LSPs, the PSC is explicitly signaled at label
establishment time so that, after label establishment, the LSR can
infer exclusively from the label value the PSC to be applied to a
labeled packet. When the Shim Header is used, the Drop Precedence to
be applied by the LSR to the labeled packet, is conveyed inside the
labeled packet MPLS Shim Header using the EXP field [MPLS_ENCAPS].
When the Shim Header is not used (eg. MPLS Over ATM), the Drop
Precedence to be applied by the LSR to the labeled packet is
conveyed inside the link layer header encapsulation using link layer
specific drop precedence fields (eg. ATM Cell Loss Priority).
We refer to such LSPs as "Label-Only-Inferred-PSC LSPs" (L-LSP)
since the PSC can be fully inferred from the label without any other
information (eg. regardless of the EXP field value). Detailed
operations of L-LSPs are specified in section 4 below.
1.4 Overall Operations
For a given FEC, and unless media specific restrictions apply as
identified in the sections 7, 8, 9 and 10 below, this specification
allows any one of the following combinations within an MPLS Diff-
Serv domain:
- zero or any number of E-LSPs, and
- zero or any number of L-LSPs.
The network administrator selects the actual combination of LSPs
from the set of allowed combinations and selects how the Behavior
Aggregates are actually transported over this combination of LSPs,
in order to best match his/her environment and objectives in terms
of Diff-Serv support, Traffic Engineering and Fast Restoration.
Criteria for selecting such a combination are outside the scope of
this specification; However in order to respect ordering
constraints, all packets of a given microflow, possibly spanning
multiple BAs of a given Ordered Aggregate, MUST be transported over
the same LSP. Conversely, each LSP MUST be capable of supporting all
the (active) PHBs of a given PSC.
Examples of deployment scenarios are provided for information in
APPENPIX A.
1.5 Relationship between Label and FEC
[MPLS_ARCH] states in section `2.1. Overview' that:
`Some routers analyze a packet's network layer header not merely to
choose the packet's next hop, but also to determine a packet's
"precedence" or "class of service". They may then apply different
discard thresholds or scheduling disciplines to different packets.
MPLS allows (but does not require) the precedence or class of
service to be fully or partially inferred from the label. In this
case, one may say that the label represents the combination of a FEC
and a precedence or class of service.'
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In line with this, we observe that:
- With E-LSPs, the label represents the combination of a FEC and
the set of Behavior Aggregates (BAs) transported over the E-
LSP). Where all the supported BAs are transported over an E-LSP,
the label then represents the complete FEC.
- With L-LSPs, the label represents the combination of a FEC and
an Ordered Aggregate (OA).
2. Label Forwarding Model for Diff-Serv LSRs
Since different Ordered Aggregates of a given FEC may be transported
over different LSPs, the label swapping decision of a Diff-Serv LSR
clearly depends on the forwarded packet's Behavior Aggregate. Also,
since the IP DS field of a forwarded packet may not be directly
visible to an LSR, the way to determine the PHB to be applied to a
received packet and to encode the PHB into a transmitted packet is
different to a non-MPLS Diff-Serv Router.
In order to describe Label Forwarding by Diff-Serv LSRs, we model
the LSR Diff-Serv label switching behavior as comprising four
stages:
- Incoming PHB Determination (A)
- Optional Outgoing PHB Determination via Local Policy and Traffic
Conditioning (B)
- Label Swapping (C)
- Encoding of Diff-Serv information into Encapsulation Layer
(EXP,CLP,DE,User_Priority) (D)
Obviously, to enforce the Diff-Serv service differentiation the LSR
MUST also apply the forwarding treatment corresponding to the
Outgoing PHB.
This model is illustrated below:
--Inc_label(*)--------------------------->I===I---Outg_label (**)-->
\ I I \
\---->I===I I C I \-->I===I--Encaps->
I A I I===I--Outg_PHB->I===I I D I (**)
-Encaps->I===I--Inc_PHB->I B I \ /->I===I
(*) I===I \--------/
`Encaps' designates the Diff-Serv related information encoded in the
MPLS Encapsulation layer (eg EXP field, ATM CLP, Frame Relay DE,
802.1 User_Priority)
(*) when the LSR performs label imposition, the incoming packet is
received unlabelled.
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MPLS Support of Diff-Serv February 00
(**) when the LSR performs label disposition, the outgoing packet is
transmitted unlabelled.
This model is presented here to illustrate operations of Diff-Serv
LSRs and does not constrain actual implementation.
2.1 Incoming PHB Determination
This stage determines which Behavior Aggregate the received packet
belongs to.
2.1.1 Incoming PHB Determination for received labelled packets
This specification defines one default method for this determination
which allows for regular support of Diff-Serv over MPLS. This method
considers only the outer encapsulation (ie outer label entry or ATM
encapsulation or Frame Relay encapsulation) and ignores other label
entries which may be present in the stack. It combines:
- the Diff-Serv context associated with the incoming label and
stored in the Incoming Label Map (ILM). See section 2.3 below
for details on information comprising the Diff-Serv context.
- the Diff-Serv related information that is encoded in the
corresponding encapsulation layer (ie in EXP field of MPLS Shim
layer or in CLP/DE field of the link layer encapsulation) of the
received label packet.
The details of this method depend on the incoming LSP type and on
the incoming MPLS encapsulation and are defined below in sections
3.3 and 4.3.
Support for this default method is mandatory for compliance to this
specification.
Optionally, other methods for Incoming PHB Determination may also be
supported. Other methods may take into account other information in
addition to, or instead of, the information used by the mandatory
method. For instance, other method could take into account the DS
field of the encapsulated packet or the EXP field of a label header
deeper in the label stack. Such methods are beyond the scope of this
specification.
2.1.2 Incoming PHB Determination for received unlabelled packets
For packets received unlabelled, this stage operates exactly as with
a non-MPLS IP Diff-Serv Router and uses the DS field.
2.2 Optional Outgoing PHB Determination Via Local Policy And Traffic
Conditioning
This stage of Diff-Serv label switching is optional and may be used
on an LSR to perform traffic conditioning including Behavior
Aggregate demotion or promotion. It is outside the scope of this
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MPLS Support of Diff-Serv February 00
specification. For the purpose of specifying Diff-Serv over MPLS
forwarding, we simply note that the PHB to be actually enforced, and
conveyed to downstream LSRs, by an LSR (referred to as "outgoing
PHB") may be different to the PHB which had been associated with the
packet by the previous LSR (referred to as "incoming PHB").
When this stage is not present, the "outgoing PHB" is simply
identical to the "incoming PHB".
For packets received unlabelled, this stage operates as with a non-
MPLS IP Diff-Serv Router.
2.3 Label Swapping
[MPLS_ARCH] describes how label swapping is performed by LSRs on
incoming labeled packets using an Incoming Label Map (ILM), where
each incoming label is mapped to one or multiple NHLFEs. [MPLS_ARCH]
also describes how label imposition is performed by LSRs on incoming
unlabelled packets using a FEC-to-NHLFEs Map (FTN), where each
incoming FEC is mapped to one or multiple NHLFEs.
A Diff-Serv Context for a label is defined as comprising:
- `LSP type (ie E-LSP or L-LSP)'
- `supported PHBs'
- `Encaps-->PHB mapping' for an incoming label
- `Set of PHB-->Encaps mappings' for an outgoing label
The present specification defines that a Diff-Serv Context is stored
in the ILM for each incoming label.
[MPLS_ARCH] states that the `NHLFE may also contain any other
information needed in order to properly dispose of the packet'. In
accordance with this, the present specification defines that a Diff-
Serv context is stored in the NHLFE for each outgoing label which is
swapped or pushed.
This Diff-Serv context information is populated into the ILM and the
FTN at label establishment time.
If the label corresponds to an E-LSP for which no EXP<-->PHB mapping
has been explicitly signaled at LSP setup, the `supported PHBs' is
populated with the set of PHBs of the preconfigured
EXP<-->PHB Mapping, which is discussed below in section 3.2.1.
If the label corresponds to an E-LSP for which an EXP<-->PHB mapping
has been explicitly signaled at LSP setup, the `supported PHBs' is
populated with the set of PHBs of the signaled EXP<-->PHB mapping.
If the label corresponds to an L-LSP, the `supported PHBs' is
populated with the set of PHBs forming the PSC that is signaled at
LSP set-up.
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The details of how the `Encaps-->PHB mapping' or `Set of
PHB-->Encaps mappings' are populated are defined below in sections 3
and 4.
[MPLS_ARCH] also states that:
"If the ILM [respectively, FTN] maps a particular label to a set of
NHLFEs that contains more than one element, exactly one element of
the set must be chosen before the packet is forwarded. The
procedures for choosing an element from the set are beyond the scope
of this document. Having the ILM [respectively, FTN] map a label
[respectively, a FEC] to a set containing more than one NHLFE may be
useful if, e.g., it is desired to do load balancing over multiple
equal-cost paths."
In accordance with this, the present specification allows that an
incoming label [respectively FEC] is mapped, for Diff-Serv purposes,
to multiple NHLFEs (for instance where different NHLFEs correspond
to egress labels supporting different sets of PHBs). When a label
[respectively FEC] maps to multiple NHLFEs, the Diff-Serv LSR MUST
choose one of the NHLFEs whose Diff-Serv context indicates that it
supports the Outgoing PHB of the forwarded packet.
When a label [respectively FEC] maps to multiple NHLFEs which
supports the Outgoing PHB, the procedure for choosing one among
those is outside the scope of this document. This situation may be
encountered where it is desired to do load balancing of a Behavior
Aggregate over multiple LSPs. In such situations, in order to
respect ordering constraints, all packets of a given microflow MUST
be transported over the same LSP.
2.4 Encoding Diff-Serv information into Encapsulation Layer
This stage determines how to encode the fields of the MPLS
encapsulation layer which convey Diff-Serv information (eg MPLS Shim
EXP, ATM CLP, Frame Relay DE, 802.1 User_Priority).
2.4.1 Encoding Diff-Serv information for transmitted labeled packets
This specification defines one default method for this encoding
which allows regular support of Diff-Serv over MPLS. This method
takes into account:
- the Outgoing PHB
- the Diff-Serv context associated with each swapped/pushed label
of the selected NHLFE (`Set of PHB-->Encaps mappings').
This method defines that the Outgoing PHB is reflected into:
- the EXP field value of all the swapped or pushed label entries
- the CLP/DE bit when the packet is encapsulated into ATM/Frame
Relay,
- the 802.1 User_Priority field of the 802.1 Tag Control
Information when the packet is encapsulated into LAN interfaces
supporting multiple Traffic Classes,
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The details of this method depend on the outgoing LSP type and on
the outgoing MPLS encapsulation and are defined below in sections
3.5 and 4.5.
Support for this default method is mandatory for compliance to this
specification.
Optionally, other methods for encoding Diff-Serv information into
the Encapsulation layer may also be supported to allow for more
sophisticated Diff-Serv operations over MPLS. Other methods may
affect encapsulation fields differently.
2.4.2 Encoding Diff-Serv information for transmitted unlabelled packets
This specification defines one default method for this encoding
which allows regular support of Diff-Serv over MPLS.
Support for this default method is mandatory for compliance to this
specification.
For packets transmitted unlabelled (ie LSR performing label
disposition), the default encoding method writes the DSCP of the
Outgoing PHB into the DS field.
Optionally, other encoding methods may also be supported to allow
for more sophisticated Diff-Serv operations over MPLS. Other methods
may affect the DS field differently. One example would be a method
where the IP packet's DS field is left unchanged regardless of the
Outgoing PHB. Such a method would allow `MPLS Diff-Serv
Transparency' ie it would allow support of Differentiated Services
in the MPLS backbone based on a Diff-Serv policy which is specific
to the MPLS cloud (and different from the Diff-Serv policy applied
in the non-MPLS clouds around the MPLS cloud) since the IP DS field
would be transported transparently through the MPLS cloud. Details
of such methods are outside the scope of this specification.
3. Detailed Operations of E-LSPs
3.1 E-LSP Definition
Recognizing that:
- Certain MPLS encapsulations (such as PPP and LAN) make use of a
Shim Header which consists of a label stack with one or more
entries [MPLS_ENCAPS] each with a 3-bit EXP field;
- the Differentiated-Service (DS) field is 6-bit long
[DIFF_HEADER] potentially allowing support of up to 64 Behavior
Aggregates
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- any subset of 8 (or less) DSCP values can be mapped entirely
into the 3-bit long EXP field of the MPLS label stack entry;
We define that:
- an LSP established for a given Forwarding Equivalent Class (FEC)
may be used for transport of up to eight BAs of that FEC;
- the set of transported BAs can span multiple OAs;
- for a given OA transported over the LSP, all supported BAs of
this OA are transported over the LSP;
- such an LSP is referred to as an "EXP-inferred-PSC" LSP or
"E-LSP" because the PSC to be applied to a labeled packet by the
LSR depends on the EXP field value in the MPLS Shim Header;
- packets belonging to this given (FEC) and from the corresponding
set of BAs are sent down this E-LSP.
- multiple BAs belonging to the same FEC and transported over the
same E-LSP are granted different scheduling treatment and
different drop precedence by the MPLS LSR based on the EXP field
which is appropriately encoded to reflect both the PSC and the
drop precedence of the PHB corresponding to the packet's BA.
- the mapping between EXP field and PHB to be applied by the LSR
for a given E-LSP is either explicitly signaled at label set-up
or relies on a preconfigured mapping.
Within a given MPLS Diff-Serv domain, all the E-LSPs relying on the
pre-configured mapping are capable of transporting the same common
set of 8, or less, BAs. Each of those E-LSPs may actually transport
this full set of BAs or any arbitrary subset of it.
For a given FEC, two given E-LSPs using signaled EXP<-->PHB mapping
can support the same or different sets of Ordered Aggregates.
For a given FEC, there may be more than one E-LSP carrying the same
OA, for example for purposes of load balancing of the OA. In that
case, in order to respect ordering constraints, all packets of a
given microflow must be transported over the same LSP.
MPLS specifies how LSPs can be established via multiple signaling
protocols. Those include the Label Distribution Protocol (LDP),
RSVP, BGP and PIM. Sections 5 and 6 below specify how RSVP and LDP
are to be used for establishment of E-LSPs.
3.2 Populating the `Encaps-->PHB mapping' for an incoming E-LSP
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This section defines how the `Encaps-->PHB mapping' of the Diff-Serv
context is populated for an incoming E-LSP in order to support the
mandatory default method for Incoming PHB determination.
The `Encaps-->PHB mapping' is always of the form `EXP-->PHB
mapping'.
If the label corresponds to an E-LSP for which no EXP<-->PHB mapping
has been explicitly signaled at LSP setup, the `EXP-->PHB mapping'
is populated based on the Preconfigured EXP<-->PHB Mapping which is
discussed below in section 3.2.1.
If the label corresponds to an E-LSP for which an EXP<-->PHB mapping
has been explicitly signaled at LSP setup, the `EXP-->PHB mapping'
is populated as per the signaled EXP<-->PHB mapping.
3.2.1 Preconfigured EXP<-->PHB mapping
LSRs supporting E-LSPs which uses the preconfigured EXP<-->PHB
mapping must allow local configuration of this EXP<-->PHB mapping.
This mapping applies to all the E-LSPs established on this LSR
without a mapping explicitly signaled at set-up time.
The preconfigured EXP<-->PHB mapping must either be consistent at
every E-LSP hop throughout the MPLS Diff-Serv domain spanned by the
LSP or appropriate remarking of the EXP field must be performed by
the LSR whenever a different preconfigured mapping is used on the
ingress and egress interfaces.
3.3 Incoming PHB Determination On Incoming E-LSP
This section defines the mandatory default method for Incoming PHB
determination for a labeled packet received on an E-LSP. This method
requires that the `Encaps-->PHB mapping' is populated as defined
above in section 3.2.
When receiving a labeled packet over an E-LSP of an MPLS ingress
interface, the LSR:
-determines the EXP-->PHB mapping by looking up the
`Encaps-->PHB mapping' of the Diff-Serv context associated with
the incoming label in the ILM.
- determines the incoming PHB by looking up the EXP field of the
top level label entry into the EXP-->PHB mapping table.
If the EXP field value of a packet received on an E-LSP is not
included in the EXP-->PHB mapping associated with this LSP, this EXP
value should be considered invalid. LSR behavior in such situation
is a local matter and is outside the scope of this document.
3.4 Populating the `Set of PHB-->Encaps mappings' for an outgoing E-LSP
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This section defines how the `Set of PHB-->Encaps mappings' of the
Diff-Serv context is populated for an outgoing E-LSP in order to
support the mandatory default method for Encoding of Diff-Serv
information in the Encapsulation Layer.
3.4.1 `PHB-->EXP mapping'
One `PHB-->EXP mapping' is always added to the `Set of PHB-->Encaps
mappings' of the Diff-Serv context for an outgoing E-LSP.
If the label corresponds to an E-LSP for which no EXP<-->PHB mapping
has been explicitly signaled at LSP setup, this `PHB-->EXP mapping'
is populated based on the Preconfigured EXP<-->PHB Mapping which is
discussed above in section 3.2.1.
If the label corresponds to an E-LSP for which an EXP<-->PHB mapping
has been explicitly signaled at LSP setup, the `PHB-->EXP mapping'
is populated as per the signaled EXP<-->PHB mapping.
3.4.2 `PHB-->802.1 mapping'
If the outgoing interface is a LAN interface on which multiple 802.1
Traffic Classes are supported as per [IEEE_802.1], one `PHB-->802.1
mapping' is added to the `Set of PHB-->Encaps mappings' of the Diff-
Serv context for the outgoing E-LSP. This mapping is populated at
label set-up based on the Preconfigured PHB-->802.1 mapping defined
below in section 3.4.2.1.
Notice that the `Set of PHB-->Encaps mappings' then contains both a
`PHB-->EXP mapping' and a `PHB-->802.1 mapping'.
3.4.2.1 Preconfigured `PHB-->802.1 Mapping'
At the time of producing this specification, there are no
standardized mapping from PHBs to 802.1 Traffic Classes.
Consequently, an LSR supporting multiple 802.1 Traffic Classes over
LAN interfaces must allow local configuration of a `PHB-->802.1
Mapping'. This mapping applies to all the outgoing LSPs established
by the LSR on such LAN interfaces.
3.5 Encoding Diff-Serv information into Encapsulation Layer On Outgoing
E-LSP
This section defines the mandatory default method for encoding of
Diff-Serv related information into the MPLS encapsulation Layer to
be used when a packet is transmitted onto an E-LSP. This method
requires that the `Set of PHB-->Encaps mappings' is populated as
defined above in section 3.4.
The LSR first determines the `Set of PHB-->Encaps Mapping'
associated with the outer label of the NHLFE.
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3.5.1 `PHB-->EXP mapping'
For all the labels which are swapped or pushed, the LSR:
- determines the PHB-->EXP mapping by looking up the
`Set of PHB-->Encaps mapping' of the Diff-Serv context
associated with the corresponding label in the NHLFE.
- determines the value to be written in the EXP field of the
corresponding level label entry by looking up the "outgoing PHB"
in this PHB-->EXP mapping table.
3.5.2 `PHB-->802.1 mapping'
If the `Set of PHB-->Encaps mapping' of the outer label contains a
mapping of the form `PHB-->802.1 mapping', then the LSR:
- determines the value to be written in the User_Priority field of
the Tag Control Information of the 802.1 encapsulation header
[IEEE_802.1], by looking up the "outgoing PHB" in this PHB-->802.1
mapping table.
3.6 E-LSP Merging
In an MPLS domain, two or more LSPs can be merged into one LSP at
one LSR. E-LSPs are compatible with LSP Merging under the following
condition:
E-LSPs can only be merged into one LSP if they support the
exact same set of BAs.
For E-LSPs using signaled EXP<-->PHB mapping, the above merge
condition MUST be enforced by LSRs through explicit checking at
label setup that the exact same set of PHBs is supported on the
merged LSPs.
For E-LSPs using the preconfigured EXP<-->PHB mapping, since the
PHBs supported over an E-LSP is not signaled at establishment time,
an LSR can not rely on signaling information to enforce the above
merge. However all E-LSPs using the preconfigured EXP<-->PHB mapping
are required to support the same set of Behavior Aggregates within a
given MPLS Diff-Serv domain. Thus, merging of E-LSPs using the
preconfigured EXP<-->PHB mapping is allowed within a given MPLS
Diff-Serv domain.
4. Detailed Operation of L-LSPs
4.1 L-LSP Definition
Recognizing that:
- All currently defined MPLS encapsulation methods have a field of
3 bits or less for Diff-Serv encoding (i.e., 3-bit EXP field in
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MPLS Support of Diff-Serv February 00
case of Shim Header and 1-bit CLP/DE bit in case of ATM/Frame
Relay).
- The Differentiated-Services (DS) field is 6-bit long
[DIFF_HEADER] potentially allowing support of up to 64 Behavior
Aggregates. So that when more than a certain number of BAs are
used (i.e., more than 8 BAs in case of Shim Header and more than
2 BAs in case of ATM/Frame Relay), the DS field can not be
mapped entirely into the appropriate field of MPLS encapsulation
header (i.e., EXP field in case of Shim Header and CLP/DE field
in case of ATM/Frame Relay);
We define that:
- an LSP established for a given Forwarding Equivalent Class (FEC)
may be used for transport of the BAs comprised in one Ordered
Aggregate (OA) for that FEC;
- all BAs of this OA can be transported over the LSP;
- BAs from other OAs can not transported over the LSP;
- BAs from the OA transported over the LSP are given the
appropriate scheduling treatment based on the PSC which is
explicitly signaled at label set-up time.
- Such an LSP is referred to as a "Label-Only-inferred-PSC" LSP or
"L-LSP";
- Multiple BAs from OA transported over the LSP are granted
different drop precedence by the MPLS LSR based on the
appropriately encoded relevant field of MPLS encapsulation
header (EXP field of the top label entry for the shim header,
CLP/DE bit in case of ATM/Frame Relay); The mapping between the
relevant field of the MPLS encapsulation and the drop precedence
is a well-known mapping.
For a given FEC, there may be more than one L-LSP carrying the same
OA, for example for purposes of load balancing of the OA. In that
case, in order to respect ordering constraints, all packets of a
given microflow must be transported over the same LSP.
MPLS specifies how LSPs can be established via multiple signaling
protocols. Those include the Label Distribution Protocol (LDP),
RSVP, BGP and PIM. Sections 5 and 6 below specify how RSVP and LDP
are to be used for establishment of L-LSPs.
4.2 Populating the `Encaps-->PHB mapping' for an incoming L-LSP
This section defines how the `Encaps-->PHB mapping' of the Diff-Serv
context is populated for an incoming L-LSP for support of the
mandatory default method for Incoming PHB determination.
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MPLS Support of Diff-Serv February 00
4.2.1 `EXP-->PHB mapping'
If the LSR terminates the MPLS Shim Layer (i.e. it is not an
ATM-LSR or FR-LSR as defined in [MPLS ATM][MPLS FR], and it does not
receive packets without an MPLS shim layer on an LC-ATM or LC-FR
interface) then the `Encaps-->PHB mapping' is populated at label
setup in the following way:
- it is actually a `EXP-->PHB mapping'
- the mapping is a function of the PSC which is carried on this
LSP, and uses the relevant `EXP->PHB mapping' for this PSC as
defined in Section 4.2.1.1 below.
For example if the incoming label corresponds to an L-LSP supporting
the AF1 PSC, then the `Encaps-->PHB mapping' will be populated with:
EXP Field PHB
000 ----> AF11
001 ----> AF12
010 ----> AF13
4.2.1.1 EXP/PSC --> PHB mapping
In order to populate the `Encaps-->PHB mapping', the mapping from
the L-LSP PSCs and the EXP field of the shim header into PHBs is
specified as follows:
EXP Field PSC PHB
000 DF <----> DF
000 CSn <----> CSn
000 AFn <----> AFn1
001 AFn <----> AFn2
010 AFn <----> AFn3
000 EF <----> EF
4.2.2 `CLP-->PHB mapping'
If the LSR does not terminate an MPLS Shim Layer over this incoming
label and uses ATM encapsulation (i.e. it is an ATM-LSR or it
receives packets without a shim on an LC-ATM interface), then the
`Encaps-->PHB mapping' of the Diff-Serv context for this incoming
L-LSP is populated at label setup in the following way:
- it is actually a `CLP-->PHB mapping'
- the mapping is a function of the PSC which is carried on this
LSP, and uses the relevant `CLP-->PHB mapping' for this PSC as
defined in Section 4.2.2.1 below.
For example if the incoming label corresponds to an L-LSP supporting
the AF1 PSC, then the `Encaps-->PHB mapping' will be populated with:
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MPLS Support of Diff-Serv February 00
CLP Field PHB
0 ----> AF11
1 ----> AF12
4.2.2.1 CLP/PSC --> PHB mapping
In order to populate the `Encaps-->PHB mapping', the mapping from
the L-LSP PSCs and the CLP bit of the ATM cell header into PHBs is
specified as follows:
CLP Bit PSC PHB
0 DF ----> DF
0 CSn ----> CSn
0 AFn ----> AFn1
1 AFn ----> AFn2
0 EF ----> EF
4.2.3 `DE-->PHB mapping'
If the LSR does not terminate an MPLS Shim Layer over this incoming
label and uses Frame Relay encapsulation(i.e. it is a FR-LSR or it
receives packets without a shim on an LC-FR interface), then the
`Encaps-->PHB mapping' of the Diff-Serv context for this incoming
L-LSP is populated at label setup in the following way:
- it is actually a `DE-->PHB mapping'
- the mapping is a function of the PSC which is carried on this
LSP, and uses the relevant `DE-->PHB mapping' for this PSC as
defined in Section 4.2.3.1 below.
4.2.3.1 DE/PSC --> PHB mapping
In order to populate the `Encaps-->PHB mapping', the mapping from
the L-LSP PSCs and the DE bit of the Frame Relay header into PHBs is
specified as follows:
DE Bit PSC PHB
0 DF ----> DF
0 CSn ----> CSn
0 AFn ----> AFn1
1 AFn ----> AFn2
0 EF ----> EF
4.3 Incoming PHB Determination On Incoming L-LSP
This section defines the mandatory default method for Incoming PHB
determination for a labeled packet received on an L-LSP. This method
requires that the `Encaps-->PHB mapping' is populated as defined
above in section 4.2.
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MPLS Support of Diff-Serv February 00
When receiving a labeled packet over an L-LSP of an MPLS ingress
interface, the LSR first determines the `Encaps-->PHB mapping'
associated with the incoming label.
4.3.1 `EXP-->PHB mapping'
If the `Encaps-->PHB mapping' is of the form `EXP-->PHB mapping',
then the LSR:
- determines the incoming PHB by looking at the EXP field of the
top level label entry and by using the EXP-->PHB mapping.
If the received EXP field value is not included in the EXP-->PHB
mapping, this EXP value should be considered invalid. LSR behavior
in such situation is a local matter and is outside the scope of this
document.
4.3.2 `CLP-->PHB mapping'
If the `Encaps-->PHB mapping' is of the form `CLP-->PHB mapping',
then the LSR:
- determines the incoming PHB by looking at the CLP field of the
ATM Layer encapsulation and by using the CLP-->PHB mapping.
If the received CLP field value is not included in the CLP-->PHB
mapping, this CLP value should be considered invalid. LSR behavior
in such situation is a local matter and is outside the scope of this
document.
4.3.3 `DE-->PHB mapping'
If the `Encaps-->PHB mapping' is of the form `DE-->PHB mapping',
then the LSR:
- determines the incoming PHB by looking at the DE field of the
Frame Relay encapsulation and by using the DE-->PHB mapping.
If the received DE field value is not included in the DE-->PHB
mapping, this DE value should be considered invalid. LSR behavior in
such situation is a local matter and is outside the scope of this
document.
4.4 Populating the `Set of PHB-->Encaps mappings' for an outgoing L-LSP
This section defines how the `Set of PHB-->Encaps mappings' of the
Diff-Serv context is populated for an outgoing L-LSP for support of
the mandatory default method for Encoding Diff-Serv Information into
Encapsulation on Outgoing L-LSP.
4.4.1 `PHB-->EXP mapping'
If the LSR uses an MPLS Shim Layer over this outgoing label (i.e. it
is not an ATM-LSR or FR-LSR and it does not transmit packets without
an MPLS Shim Layer on a LC-ATM or LC-FR interface), then one
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MPLS Support of Diff-Serv February 00
`PHB-->EXP mapping' is added at label setup to the `Set of
PHB-->Encaps mapping' in the Diff-Serv context for this outgoing
L-LSP. This `PHB-->EXP mapping' is populated in the following way:
- it is a function of the PSC supported on this LSP, and uses the
relevant `PHB-->EXP mapping' for this PSC as defined in section
4.4.1.1 below.
For example if the outgoing label corresponds to an L-LSP supporting
the AF1 PSC, then the following `PHB-->EXP mapping' is added into
the `Set of PHB-->Encaps mappings':
PHB EXP Field
AF11 ----> 000
AF12 ----> 001
AF13 ----> 010
4.4.1.1 PHB-->PSC/EXP mapping
In order to populate the `Set of PHB-->Encaps mappings', the mapping
from the PHBs into the L-LSP PSC and the EXP field of the shim
header is specified as follows:
PHB PSC EXP Field
DF ----> DF 000
CSn ----> CSn 000
AFn1 ----> AFn 000
AFn2 ----> AFn 001
AFn3 ----> AFn 010
EF ----> EF 000
4.4.2 `PHB-->CLP mapping'
If the LSR uses ATM encapsulation (i.e. it is an ATM-LSR or sends
packets on an LC-ATM interface), then one `PHB-->CLP mapping' is
added at label setup to the `Set of PHB-->Encaps mappings' in the
Diff-Serv context for this outgoing L-LSP. This `PHB-->CLP mapping'
is populated in the following way:
- it is a function of the PSC supported on this LSP, and uses the
relevant `PHB-->CLP mapping' for this PSC as defined below in
section 4.4.2.1.
For example if the outgoing label corresponds to an L-LSP supporting
the AF1 PSC, then the `PHB-->Encaps mapping' will be populated with:
PHB CLP Field
AF11 ----> 0
AF12 ----> 1
AF13 ----> 1
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MPLS Support of Diff-Serv February 00
Notice that the if the LSR is transmitting packets over a LC-ATM
interface using the MPLS Shim Header, then the `Set of PHB-->Encaps
mappings' contains both a `PHB-->EXP mapping' and a `PHB-->CLP
mapping'.
4.4.2.1 PHB-->PSC/CLP mapping
In order to populate the `Set of PHB-->Encaps mappings', the mapping
from the PHBs into the L-LSP PSC and the CLP bit of the ATM cell
header is specified as follows:
PHB PSC CLP Bit
DF ----> DF 0
CSn ----> CSn 0
AFn1 ----> AFn 0
AFn2 ----> AFn 1
AFn3 ----> AFn 1
EF ----> EF 0
4.4.3 `PHB-->DE mapping'
If the LSR uses Frame Relay encapsulation (i.e. it is a FR-LSR or
sends packets on an LC-FR interface), one `PHB-->DE mapping' is
added at label setup to the `Set of PHB-->Encaps mapping' in the
Diff-Serv context for this outgoing L-LSP and is populated in the
following way:
- it is a function of the PSC supported on this LSP, and uses the
relevant `PHB-->DE mapping' for this PSC as defined below in
section 4.4.3.1.
Notice that if the LSR is sending packets over a LC-FR interfaces
using the MPLS Shim Header, then the `Set of PHB-->Encaps mappings'
contains both a `PHB-->EXP mapping' and a `PHB-->DE mapping'.
4.4.3.1 PHB-->PSC/DE mapping
In order to populate the `Set of PHB-->Encaps mappings', the mapping
from the PHBs into the L-LSP PSC and the DE bit of the Frame Relay
header is specified as follows:
PHB PSC DE Bit
DF ----> DF 0
CSn ----> CSn 0
AFn1 ----> AFn 0
AFn2 ----> AFn 1
AFn3 ----> AFn 1
EF ----> EF 0
4.4.4 `PHB-->802.1 mapping'
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MPLS Support of Diff-Serv February 00
If the outgoing interface is a LAN interface on which multiple
Traffic Classes are supported as defined in [IEEE_802.1], then one
`PHB-->802.1 mapping' is added at label setup to the `Set of
PHB-->Encaps mappings' in the Diff-Serv context for this outgoing
L-LSP. This `PHB-->802.1 mapping' is populated in the following way:
- it is a function of the PSC supported on this LSP, and uses the
relevant `PHB-->802.1 mapping' for this PSC from the
Preconfigured `PHB-->802.1 mapping' defined above in section
3.4.2.1.
Notice that if the LSR is transmitting packets over a LAN interface
supporting multiple 802.1 Traffic Classes, then the `Set of
PHB-->Encaps mappings' contains both a `PHB-->EXP mapping' and a
`PHB-->802.1 mapping'.
4.5 Encoding Diff-Serv Information into Encapsulation on Outgoing
L-LSP
This section defines the mandatory default method for encoding of
Diff-Serv related information into the MPLS encapsulation Layer to
be used when a packet is transmitted onto an L-LSP. This method
requires that the `Set of PHB-->Encaps mappings' is populated as
defined above in section 4.4.
The LSR first determines the `Set of PHB-->Encaps mapping'
associated with the outer label of the NHLFE.
4.5.1 `PHB-->EXP mapping'
If the `Set of PHB-->Encaps mapping' of the outer label contains a
mapping of the form `PHB-->EXP mapping', then, for all the labels
which are swapped or pushed, the LSR:
- determines the PHB-->EXP mapping by looking up the
`PHB-->Encaps mapping' of the Diff-Serv context associated with
the corresponding label in the NHLFE.
- determines the value to be written in the EXP field of the
corresponding level label entry by looking up the "outgoing PHB"
in this PHB-->EXP mapping table.
4.5.2 `PHB-->CLP mapping'
If the `Set of PHB-->Encaps mapping' of the outer label contains a
mapping of the form `PHB-->CLP mapping', then the LSR:
- determines the value to be written in the CLP field of the ATM
Layer encapsulation by looking up the "outgoing PHB" in this
PHB-->CLP mapping table.
4.5.3 `PHB-->DE mapping'
If the `Set of PHB-->Encaps mapping' of the outer label contains a
mapping of the form `PHB-->DE mapping', then the LSR:
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MPLS Support of Diff-Serv February 00
- determines the value to be written in the DE field of the Frame
Relay encapsulation by looking up the "outgoing PHB" in this
PHB-->DE mapping table.
4.5.4 `PHB-->802.1 mapping'
If the `Set of PHB-->Encaps mapping' of the outer label contains a
mapping of the form `PHB-->802.1 mapping', then the LSR:
- determines the value to be written in the User_Priority field of
the Tag Control Information of the 802.1 encapsulation header
[IEEE_802.1] by looking up the "outgoing PHB" in this
PHB-->802.1 mapping table.
4.6 L-LSP Merging
In an MPLS domain, two or more LSPs can be merged into one LSP at
one LSR. The proposed support of Diff-Serv in MPLS is compatible
with LSP Merging under the following condition:
L-LSPs can only be merged into one L-LSP if they support the
same PSC.
The above merge condition MUST be enforced by LSRs through explicit
checking at label setup that the same PSC is supported on the merged
LSPs.
Note that when L-LSPs merge, the bandwidth that is available for the
PSC downstream of the merge point must be sufficient to carry the
sum of the merged traffic. This is particularly important in the
case of EF traffic. This can be ensured in multiple ways (for
instance via provisioning, or via bandwidth signaling and explicit
admission control).
5. RSVP Extension for Diff-Serv Support
The MPLS architecture does not assume a single label distribution
protocol. [RSVP_MPLS_TE] defines the extension to RSVP for
establishing label switched paths (LSPs) in MPLS networks. This
section specifies the extensions to RSVP, beyond those defined in
[RSVP_MPLS_TE], to establish label switched path (LSPs) supporting
Differentiated Services in MPLS networks.
5.1 Diff-Serv related RSVP Messages Format
One new RSVP Object is defined in this document: the DIFFSERV
Object. Detailed description of this Object is provided below. This
new Object is applicable to Path messages. This specification only
defines the use of the DIFFSERV Object in Path messages used to
establish LSP Tunnels in accordance with [RSVP_MPLS_TE] and thus
containing a Session Object with a C-Type equal to LSP_TUNNEL_IPv4
and containing a LABEL_REQUEST object.
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MPLS Support of Diff-Serv February 00
Restrictions defined in [RSVP_MPLS_TE] for support of establishment
of LSP Tunnels via RSVP are also applicable to the establishment of
LSP Tunnels supporting Diff-Serv: for instance, only unicast LSPs
are supported and Multicast LSPs are for further study.
This new DIFFSERV object is optional with respect to RSVP so that
general RSVP implementations not concerned with MPLS LSP set up do
not have to support this object.
The DIFFSERV Object is optional for support of LSP Tunnels as
defined in [RSVP_MPLS_TE]. A Diff-Serv capable LSR supporting E-LSPs
using the preconfigured EXP<-->PHB mapping in compliance with this
specification MAY support the DIFFSERV Object. A Diff-Serv capable
LSR supporting E-LSPs using a signaled EXP<-->PHB mapping in
compliance with this specification MUST support the DIFFSERV Object.
A Diff-Serv capable LSR supporting L-LSPs in compliance with this
specification MUST support the DIFFSERV Object.
5.1.1 Path Message Format
The format of the Path message is as follows:
<Path Message> ::= <Common Header> [ <INTEGRITY> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
[ <SESSION_ATTRIBUTE> ]
[ <DIFFSERV> ]
[ <POLICY_DATA> ... ]
[ <sender descriptor> ]
<sender descriptor> ::= <SENDER_TEMPLATE> [ <SENDER_TSPEC> ]
[ <ADSPEC> ]
[ <RECORD_ROUTE> ]
5.2 DIFFSERV Object
The DIFFSERV object formats are shown below. Currently there are two
possible C_Types. Type 1 is a DIFFSERV object for an E-LSP. Type 2
is a DIFFSERV object for an L-LSP.
5.2.1. DIFFSERV object for an E-LSP:
class = TBD, C_Type = 1 (need to get an official class num from the
IANA with the form 0bbbbbbb)
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 | MAPnb |
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MPLS Support of Diff-Serv February 00
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAP (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// ... //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAP (MAPnb) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved : 28 bits
This field is reserved. It must be set to zero on transmission
and must be ignored on receipt.
MAPnb : 4 bits
Indicates the number of MAP entries included in the DIFFSERV
Object. This can be set to any value from 1 to 8 (decimal).
MAP : 32 bits
Each MAP entry defines the mapping between one EXP field value
and one PHB. The MAP entry has the following format:
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 | EXP | PHBID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved : 13 bits
This field is reserved. It must be set to zero on
transmission and must be ignored on receipt.
EXP : 3 bits
This field contains the value of the EXP field for the
EXP<-->PHB mapping defined in this MAP entry.
PHBID : 16 bits
This field contains the PHBID of the PHB for the
EXP<-->PHB mapping defined in this MAP entry. The PHBID
is encoded as specified in section 2 of [PHBID].
5.2.2 DIFFSERV object for an L-LSP:
class = TBD, C_Type = 2 (class num is the same as DIFFSERV object
for E-LSP))
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 | PSC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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MPLS Support of Diff-Serv February 00
Reserved : 16 bits
This field is reserved. It must be set to zero on transmission
and must be ignored on receipt.
PSC : 16 bits
The PSC indicates a PHB Scheduling Class to be supported by the
LSP. The PSC is encoded as specified in section 2 of [PHBID]:
- Where the PSC comprises a single PHB defined by standards
action, the encoding for the PSC is the encoding for this
single PHB. It is the recommended DSCP value for that PHB,
left-justified in the 16-bit field, with bits 6 through 15 set
to zero.
- Where the PSC comprises multiple PHBs defined by standards
action, the PSC encoding is the encoding for this set of PHB.
It is the smallest numerical value of the recommended DSCP for
the various PHBs in the PSC, left-justified in the 16 bit
field, with bits 6 through 13 and bit 15 set to zero and with
bit 14 set to one.
For instance, the encoding of the EF PSC is :
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 0 1 1 1 0|0 0 0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For instance, the encoding of the AF1 PSC is :
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0 1 0|0 0 0 0 0 0 0 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.3 Handling Diff-Serv Object
To establish an LSP tunnel with RSVP, the sender creates a Path
message with a session type of LSP_Tunnel_IPv4 and with a
LABEL_REQUEST object as per [RSVP_MPLS_TE].
Where the sender supports Diff-Serv, to establish with RSVP an E-LSP
tunnel which uses the Preconfigured EXP<-->PHB mapping, the sender
creates a Path message:
- with a session type of LSP_Tunnel_IPv4,
- with the LABEL_REQUEST object, and
- without the DIFFSERV object.
Where the sender supports Diff-Serv, to establish with RSVP an E-LSP
tunnel which uses a signaled EXP<-->PHB mapping, the sender creates
a Path message :
- with a session type of LSP_Tunnel_IPv4,
- with the LABEL_REQUEST object,
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MPLS Support of Diff-Serv February 00
- with the DIFFSERV object for an E-LSP containing one MAP entry
for each EXP value to be supported on this E-LSP.
Where the sender supports Diff-Serv, to establish with RSVP an L-LSP
tunnel, the sender creates a Path message:
- with a session type of LSP_Tunnel_IPv4,
- with the LABEL_REQUEST object,
- with the DIFFSERV object for an L-LSP containing the PHB
Scheduling Class (PSC) supported on this L-LSP.
If a path message contains multiple DIFFSERV objects, only the first
one is meaningful; subsequent DIFFSERV object(s) must be ignored and
not forwarded.
Each node along the path records the DIFFSERV object, when present,
in its path state block.
The destination node of an E-LSP or L-LSP responds to the Path
message containing the LABEL_REQUEST object by sending a Resv
message:
- with the LABEL object
- without a DIFFSERV object.
Assuming the reservation is accepted and a label is associated with
the reservation, the Diff-Serv LSRs (sender, destination,
intermediate nodes) must:
- update the Diff-Serv context associated with the established
LSPs in their ILM/FTN as specified in previous sections
(incoming and outgoing label),
- install the required Diff-Serv forwarding treatment (scheduling
and dropping behavior) for this NHLFE (outgoing label).
An RSVP router that does recognizes the DIFFSERV object and that
receives a path message which contains the DIFFSERV object but which
does not contain a LABEL_REQUEST object or which does not have a
session type of LSP_Tunnel_IPv4, sends a PathErr towards the sender
with the error code `Diff-Serv Error' and an error value of
`Unexpected DIFFSERV object'. Those are defined below in section
5.5.
A node receiving a Path message with the DIFFSERV object for E-LSP,
which recognizes the DIFFSERV object but does not support the
particular PHB encoded in one, or more, of the MAP entries, sends a
PathErr towards the sender with the error code `Diff-Serv Error' and
an error value of `Unsupported PHB'. Those are defined below in
section 5.5.
A node receiving a Path message with the DIFFSERV object for E-LSP,
which recognizes the DIFFSERV object but determines that the
signaled EXP<-->PHB mapping is invalid, sends a PathErr towards the
sender with the error code `Diff-Serv Error' and an error value of
`Invalid EXP<-->PHB mapping'. Those are defined below in section
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MPLS Support of Diff-Serv February 00
5.5. The EXP<-->PHB mapping signaled in the DIFFSERV Object for an
E-LSP is invalid when:
- the MAPnb field is not within the range 1 to 8 decimal, or
- a given EXP value appears in more than one MAP entry, or
- the PHBID encoding is invalid
A node receiving a Path message with the DIFFSERV object for L-LSP,
which recognizes the DIFFSERV object but does not support the
particular PSC encoded in the PSC field, sends a PathErr towards the
sender with the error code `Diff-Serv Error' and an error value of
`Unsupported PSC'. Those are defined below in section 5.5.
A Diff-Serv LSR MUST handle the situations where the reservation can
not be accepted for other reasons than those already discussed in
this section, in accordance with [RSVP_MPLS_TE] (eg. reservation
rejected by admission control, a label can not be associated).
5.4 Non-support of the Diff-Serv Object
An RSVP router that does not recognize the DIFFSERV object Class-Num
must behave in accordance with the procedures specified in [RSVP]
for an unknown Class-Num whose format is 0bbbbbbb ie. it must send a
PathErr with the error code `Unknown object class' toward the
sender.
An RSVP router that recognizes the DIFFSERV object Class-Num but
does not recognize the DIFFSERV object C-Type, must behave in
accordance with the procedures specified in [RSVP] for an unknown C-
type ie. It must send a PathErr with the error code `Unknown object
C-Type' toward the sender.
In both situations, this causes the path set-up to fail. The sender
should notify management that a L-LSP cannot be established and
possibly take action to retry reservation establishment without the
DIFFSERV object (eg. attempt to use E-LSPs with Preconfigured
EXP<-->PHB mapping as a fall-back strategy).
5.5 Error Codes For Diff-Serv
In the procedures described above, certain errors must be reported
as a `Diff-Serv Error'. The value of the `Diff-Serv Error' error
code is 26 (TBD).
The following defines error values for the Diff-Serv Error:
Value Error
1 Unexpected DIFFSERV object
2 Unsupported PHB
3 Invalid EXP<-->PHB mapping
4 Unsupported PSC
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5.6 Use of COS Service with E-LSPs and L-LSPs
Both E-LSPs and L-LSPs can be established with bandwidth reservation
or without bandwidth reservation.
To establish an E-LSP or an L-LSP with bandwidth reservation, Int-
Serv's Controlled Load service (or possibly Guaranteed Service) is
used and the bandwidth is signaled in the SENDER_TSPEC (respectively
FLOWSPEC) of the path (respectively Resv) message.
To establish an E-LSP or an L-LSP without bandwidth reservation, the
Class of Service service defined in [RSVP_MPLS_TE] is used.
A Path message containing a COS SENDER_TSPEC and not containing a
DIFFSERV object indicates to a Diff-Serv capable LSR that the LSP to
be established in an E-LSP using the Preconfigured mapping and
without any bandwidth reservation.
A Path message containing a COS SENDER_TSPEC and containing a
DIFFSERV object for E-LSP indicates to a Diff-Serv capable LSR that
the LSP to be established in an E-LSP using a signaled mapping and
without any bandwidth reservation.
A Path message containing a COS SENDER_TSPEC and containing a
DIFFSERV object for LSP indicates to a Diff-Serv capable LSR that
the LSP to be established in an L-LSP without any bandwidth
reservation.
The above is summarized in the following table:
Path Message LSP type
Service DIFFSERV
Object
GS/CL No E-LSP + preconf mapping + bandw reservation
GS/CL Yes/E-LSP E-LSP + signaled mapping + bandw reservation
GS/CL Yes/L-LSP L-LSP + bandw reservation
COS No E-LSP + preconf mapping + no bandw reservation
COS Yes/E-LSP E-LSP + signaled mapping + no band reservation
COS Yes/L-LSP L-LSP + no bandw reservation
Where:
- GS stands for Guaranteed Service
- CL stands for Controlled Load
- COS stands for COS service
When processing a path (respectively Resv) message for an E-LSP or
an L-LSP using the COS service, a Diff-Serv capable LSR must ignore
the value of the COS field within a COS SENDER_TSPEC (respectively a
COS FLOWSPEC).
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MPLS Support of Diff-Serv February 00
6. LDP Extensions for Diff-Serv Support
The MPLS architecture does not assume a single label distribution
protocol. [LDP] defines the Label Distribution Protocol and its
usage for establishment of label switched paths (LSPs) in MPLS
networks. This section specifies the extensions to LDP to establish
label switched path (LSPs) supporting Differentiated Services in
MPLS networks.
One new LDP TLV is defined in this document:
- the Diff-Serv TLV
Detailed description of this TLV is provided below.
The new Diff-Serv TLV is optional with respect to LDP. A Diff-Serv
capable LSR supporting E-LSPs which uses the Preconfigured
EXP<-->PHB mapping in compliance with this specification MAY support
the Diff-Serv TLV. A Diff-Serv capable LSR supporting E-LSPs which
uses the signaled EXP<-->PHB mapping in compliance with this
specification MUST support the Diff-Serv TLV. A Diff-Serv capable
LSR supporting L-LSPs in compliance with this specification MUST
support the Diff-Serv TLV.
6.1 Diff-Serv TLV
The Diff-Serv TLV has the following formats:
Diff-Serv TLV for an E-LSP:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type = PSC (0x901) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T| Reserved | MAPnb |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAP (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAP (MAPnb) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T:1 bit
LSP Type. This is set to 0 for an E-LSP
Reserved : 28 bits
This field is reserved. It must be set to zero on transmission
and must be ignored on receipt.
MAPnb : 4 bits
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MPLS Support of Diff-Serv February 00
Indicates the number of MAP entries included in the DIFFSERV
Object. This can be set to any value from 1 to 8 (decimal).
MAP : 32 bits
Each MAP entry defines the mapping between one EXP field value
and one PHB. The MAP entry has the following format:
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 | EXP | PHBID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved : 13 bits
This field is reserved. It must be set to zero on
transmission and must be ignored on receipt.
EXP : 3 bits
This field contains the value of the EXP field for the
EXP<-->PHB mapping defined in this MAP entry.
PHBID : 16 bits
This field contains the PHBID of the PHB for the
EXP<-->PHB mapping defined in this MAP entry. The PHBID
is encoded as specified in section 2 of [PHBID].
Diff-Serv TLV for an L-LSP:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type = PSC (0x901) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T| Reserved | PSC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T:1 bit
LSP Type. This is set to 1 for an L-LSP
Reserved : 16 bits
This field is reserved. It must be set to zero on transmission
and must be ignored on receipt.
PSC : 16 bits
The PSC indicates a PHB Scheduling Class to be supported by the
LSP. The PSC is encoded as specified in section 2 of [PHBID]:
- Where the PSC comprises a single PHB defined by standards
action, the encoding for the PSC is the encoding for this
single PHB. It is the recommended DSCP value for that PHB,
left-justified in the 16-bit field, with bits 6 through 15 set
to zero.
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MPLS Support of Diff-Serv February 00
- Where the PSC comprises multiple PHBs defined by standards
action, the PSC encoding is the encoding for this set of PHB.
It is the smallest numerical value of the recommended DSCP for
the various PHBs in the PSC, left-justified in the 16 bit
field, with bits 6 through 13 and bit 15 set to zero and with
bit 14 set to one.
For instance, the encoding of the EF PSC is :
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 0 1 1 1 0|0 0 0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For instance, the encoding of the AF1 PSC is :
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0 1 0|0 0 0 0 0 0 0 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.2 Diff-Serv Status Code Values
The following values are defined for the Status Code field of the
Status TLV:
Status Code E Status Data
Unsupported PHB 0 0x00000016
Invalid EXP<-->PHB mapping 0 0x00000017
Unsupported PSC 0 0x00000018
Unexpected Diff-Serv TLV 0 0x00000019
6.3 Diff-Serv Related LDP Messages
6.3.1 Label Request Message
The format of the Label Request message is extended as follows, to
optionally include the Diff-Serv TLV:
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| Label Request (0x0401) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Diff-Serv TLV (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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MPLS Support of Diff-Serv February 00
6.3.2 Label Mapping Message
The format of the Label Mapping message is extended as follows, to
optionally include the Diff-Serv TLV:
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| Label Mapping (0x0400) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Diff-Serv TLV (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.3.3 Label Release Message
The format of the Label Release message is extended as follows, to
optionally include the Status TLV:
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| Label Release (0x0403) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label TLV (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status TLV (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.3.4 Notification Message
The format of the Notification message is extended as follows, to
optionally include the Diff-Serv TLV:
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| Notification (0x0001) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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MPLS Support of Diff-Serv February 00
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Diff-Serv TLV (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.4 Handling of the Diff-Serv TLV
6.3.1 Handling of the Diff-Serv TLV in Downstream Unsolicited Mode
This section describes operations when the Downstream Unsolicited
Mode is used.
When allocating a label for an E-LSP which is to use the
preconfigured EXP<-->PHB mapping, a downstream Diff-Serv LSR issues
a Label Mapping message without the Diff-Serv TLV.
When allocating a label for an E-LSP which is to use a signaled
EXP<-->PHB mapping, a downstream Diff-Serv LSR issues a Label
Mapping message with the Diff-Serv TLV for an E-LSP which contains
one MAP entry for each EXP value to be supported on this E-LSP.
When allocating a label for an L-LSP, a downstream Diff-Serv LSR
issues a Label Mapping message with the Diff-Serv TLV for an L-LSP
which contains the PHB Scheduling Class (PSC) to be supported on
this L-LSP.
Assuming the label set-up is successful, the downstream and upstream
LSRs must:
- update the Diff-Serv context associated with the established
LSPs in their ILM/FTN as specified in previous sections
(incoming and outgoing label),
- install the required Diff-Serv forwarding treatment (scheduling
and dropping behavior) for this NHLFE (outgoing label).
An upstream Diff-Serv LSR receiving a Label Mapping message with
multiple Diff-Serv TLVs only considers the first one as meaningful.
The LSR must ignore and not forward the subsequent Diff-Serv TLV(s).
An upstream Diff-Serv LSR which receives a Label Mapping message
with the Diff-Serv TLV for an E-LSP and does not support the
particular PHB encoded in one, or more, of the MAP entries, must
reject the mapping by sending a Label Release message which includes
the Label TLV and the Status TLV with a Status Code of `Unsupported
PHB'.
An upstream Diff-Serv LSR receiving a Label Mapping message with the
Diff-Serv TLV for an E-LSP and determining that the signaled
EXP<-->PHB mapping is invalid, must reject the mapping by sending a
Label Release message which includes the Label TLV and the Status
TLV with a Status Code of `Invalid EXP<-->PHB Mapping'. The
EXP<-->PHB mapping signaled in the DIFFSERV Object for an E-LSP is
invalid when:
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MPLS Support of Diff-Serv February 00
- the MAPnb field is not within the range 1 to 8 decimal, or
- a given EXP value appears in more than one MAP entry, or
- the PHBID encoding is invalid
An upstream Diff-Serv LSR receiving a Label Mapping message with the
Diff-Serv TLV for an L-LSP containing a PSC value which is not
supported, must reject the mapping by sending a Label Release
message which includes the Label TLV and the Status TLV with a
Status Code of `Unsupported PSC'.
6.3.2 Handling of the Diff-Serv TLV in Downstream on Demand Mode
This section describes operations when the Downstream on Demand Mode
is used.
When requesting a label for an E-LSP which is to use the
preconfigured EXP<-->PHB mapping, an upstream Diff-Serv LSR sends a
Label Request message without the Diff-Serv TLV.
When requesting a label for an E-LSP which is to use a signaled
EXP<-->PHB mapping, an upstream Diff-Serv LSR sends a Label Request
message with the Diff-Serv TLV for an E-LSP which contains one MAP
entry for each EXP value to be supported on this E-LSP.
When requesting a label for an L-LSP, an upstream Diff-Serv LSR
sends a Label Request message with the Diff-Serv TLV for an L-LSP
which contains the PSC to be supported on this L-LSP.
A downstream Diff-Serv LSR sending a Label Mapping message in
response to a Label Request message for an E-LSP or an L-LSP must
not include a Diff-Serv TLV in this Label Mapping message.
Assuming the label set-up is successful, the downstream and upstream
LSRs must:
- update the Diff-Serv context associated with the established
LSPs in their ILM/FTN as specified in previous sections
(incoming and outgoing label),
- install the required Diff-Serv forwarding treatment (scheduling
and dropping behavior) for this NHLFE (outgoing label).
An upstream Diff-Serv LSR receiving a Label Mapping message
containing a Diff-Serv TLV in response to its Label Request message,
must reject the label mapping by sending a Label Release message
which includes the Label TLV and the Status TLV with a Status Code
of `Unexpected Diff-Serv TLV'.
A downstream Diff-Serv LSR receiving a Label Request message with
multiple Diff-Serv TLVs only considers the first one as meaningful.
The LSR must ignore and not forward the subsequent Diff-Serv TLV(s).
A downstream Diff-Serv LSR which receives a Label Request message
with the Diff-Serv TLV for an E-LSP and does not support the
Le Faucheur et. al 33
MPLS Support of Diff-Serv February 00
particular PHB encoded in one (or more) of the MAP entries, must
reject the request by sending a Notification message which includes
the Status TLV with a Status Code of `Unsupported PHB'.
A downstream Diff-Serv LSR receiving a Label Request message with
the Diff-Serv TLV for an E-LSP and determining that the signaled
EXP<-->PHB mapping is invalid, must reject the request by sending a
Notification message which includes the Status TLV with a Status
Code of `Invalid EXP<-->PHB Mapping'. The EXP<-->PHB mapping
signaled in the DIFFSERV TLV for an E-LSP is invalid when:
- the MAPnb field is not within the range 1 to 8 decimal, or
- a given EXP value appears in more than one MAP entry, or
- the PHBID encoding is invalid
A downstream Diff-Serv LSR receiving a Label Request message with
the Diff-Serv TLV for an L-LSP containing a PSC value which is not
supported, must reject the request by sending a Notification message
which includes the Status TLV with a Status Code of `Unsupported
PSC'.
A downstream Diff-Serv LSR that recognizes the Diff-Serv TLV Type in
a Label Request message and supports the requested PSC but is not
able to satisfy the label request for other reasons (eg. no label
available), must send a Notification message in accordance with
existing LDP procedures [LDP] (eg. with a `No Label Resource' Status
Code). This Notification message must include the requested
Diff-Serv TLV.
6.4 Non-Handling of the Diff-Serv TLV
An LSR that does not recognize the Diff-Serv TLV Type, on receipt of
a Label Request message or a Label Mapping message containing the
Diff-Serv TLV, must behave in accordance with the procedures
specified in [LDP] for an unknown TLV whose U Bit and F Bit are set
to 0 ie. it must ignore the message, return a Notification message
with `Unknown TLV' Status.
6.5 Bandwidth Information
Bandwidth information may also be signaled at establishment time of
E-LSP and L-LSP, for instance for the purpose of Traffic
Engineering, using the Traffic Parameters TLV as described in
[MPLS CR LDP].
7. MPLS Support of Diff-Serv over PPP
The general operations for MPLS support of Diff-Serv, including
label forwarding and LSP setup operations are specified in the
previous sections. This section describes the specific operations
required for MPLS support of Diff-Serv over PPP links. While
Le Faucheur et. al 34
MPLS Support of Diff-Serv February 00
sections 8, 9 and 10 focus on other media specific operations,
namely ATM, Frame Relay and LAN respectively.
This document allows any of the following LSP combinations per FEC
within an MPLS PPP Diff-Serv domain:
- Zero or any number of E-LSP, and
- Zero or any number of L-LSPs.
7.1 LSR implementation with PPP interfaces
A Diff-Serv capable LSR with PPP interfaces MUST support, over these
PPP interfaces, E-LSPs which use the pre-configured EXP<-->PHB
mapping, in compliance with all the material from this specification
pertaining to those types of LSPs.
A Diff-Serv capable LSR with PPP interfaces MAY support, over these
PPP interfaces, E-LSPs which use a signaled EXP<-->PHB mapping. If a
Diff-Serv LSR does support E-LSPs which use a signaled EXP<-->PHB
mapping over PPP interfaces, then it MUST do so in compliance with
all the material from this specification pertaining to those types
of LSPs.
A Diff-Serv capable LSR with PPP interfaces MAY support L-LSPs over
these PPP interfaces. If a Diff-Serv LSR does support L-LSPs over
PPP interfaces, then it MUST do so in compliance with all the
material from this specification pertaining to L-LSPs.
An LSR running MPLS over PPP over a traditional ATM connection (ie.
where the ATM switches do not participate in MPLS and where the ATM
connection VPI/VCI values have not been established via any label
distribution protocol) is to be considered as an LSR with PPP
interfaces from the point of view of compliance to this
specification.
Similarly, an LSR running MPLS over PPP over a traditional Frame
Relay connection (ie. where the Frame Relay switches do not
participate in MPLS and where the Frame Relay connection DLCI values
have not been established via any label distribution protocol) is to
be considered as an LSR with PPP interfaces from the point of view
of compliance to this specification.
8. MPLS Support of Diff-Serv by ATM LSRs
The general operations for MPLS support of Diff-Serv, including
label forwarding and LSP setup operations was specified in the
previous sections. This section describes the specific operations
required for MPLS support of Diff-Serv over ATM links.
This document allows the following set of LSP combinations per FEC
within an MPLS ATM Diff-Serv domain:
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MPLS Support of Diff-Serv February 00
- any number of L-LSPs.
8.1 Merging
The use of merging is optional. In case that merging of ATM LSPs is
used, procedures described in section 3.6 of this specification
apply. Additionally, to avoid cell interleaving problems with AAL-5
merging, procedures specified in [MPLS ATM] MUST be followed.
8.2 Use of ATM Traffic Classes and Traffic Management mechanisms
The use of the ATM traffic classes as specified by ITU-T and ATM-
Forum or of vendor specific ATM traffic classes is outside of the
scope of this specification. The only requirement for compliant
implementation is that the forwarding behavior experienced by a
Behavior Aggregate forwarded over an L-LSP by the ATM LSR MUST be
compliant with the corresponding Diff-Serv PHB specifications.
Since there is only one bit for encoding the PHB drop precedence
value over ATM links, only two different drop precedence levels are
supported in ATM LSRs. The behavior for AF MUST comply to procedures
described in [DIFF_AF] for the case when only two drop precedence
levels are supported.
To avoid discarding parts of the packets, frame discard mechanisms,
such as Early Packet Discard (EPD) SHOULD be enabled in the ATM-LSRs
for all PHBs described in this document.
8.3 LSR Implementation With ATM Interfaces
A Diff-Serv capable LSR with ATM interfaces MUST support L-LSPs over
these ATM interfaces in compliance with all the material from this
specification pertaining to those types of LSPs. Additionally,
procedures specified in [MPLS ATM] MUST be followed by compliant
implementation.
Support of E-LSPs over ATM interfaces running native ATM MPLS by an
LSR implementation is not allowed.
9. MPLS Support of Diff-Serv by Frame Relay LSRs
The general operations for MPLS support of Diff-Serv, including
label forwarding and LSP setup operations was specified in the
previous sections. This section describes the specific operations
required for MPLS support of Diff-Serv over Frame Relay links.
This document allows the following set of LSP combinations per FEC
within an MPLS Frame Relay Diff-Serv domain:
- any number of L-LSPs.
9.1 Merging
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MPLS Support of Diff-Serv February 00
The use of merging is optional. In case that merging of Frame Relay
LSPs is used, procedures described in section 3.6 of this
specification apply as well as procedures in [MPLS FR].
9.2 Use of Frame Relay Traffic parameters and Traffic Management
mechanisms
The use of the Frame Relay traffic parameters as specified by ITU-T
and Frame Relay-Forum or of vendor specific Frame Relay traffic
management mechanisms is outside of the scope of this specification.
The only requirement for compliant implementation is that the
forwarding behavior experienced by a Behavior Aggregate forwarded
over an L-LSP by the Frame Relay LSR MUST be compliant with the
corresponding Diff-Serv PHB specifications.
Since there is only one bit for encoding the PHB drop precedence
value over Frame Relay links, only two different drop precedence
levels are supported in Frame Relay LSRs. The behavior for AF MUST
comply to procedures described in [DIFF_AF] for the case when only
two drop precedence levels are supported.
9.3 LSR Implementation With Frame Relay Interfaces
A Diff-Serv capable LSR with Frame Relay interfaces MUST support
L-LSPs over these Frame Relay interfaces in compliance with all the
material from this specification pertaining to those types of LSPs.
Support of E-LSPs over Frame Relay interfaces running native Frame
Relay MPLS by an LSR implementation is not allowed.
10. MPLS Support of Diff-Serv over LAN Media
The general operations for MPLS support of Diff-Serv, including
label forwarding and LSP setup operations was specified in the
previous sections. This section describes the specific operations
required for MPLS support of Diff-Serv over LAN.
This document allows the following set of LSP setup combinations per
FEC over an MPLS link:
- Zero or any number of E-LSP, and
- Zero or any number of L-LSPs.
10.1 LSR Implementation With LAN Interfaces
A Diff-Serv capable LSR with LAN interfaces MUST support, over these
LAN interfaces, E-LSPs which use the pre-configured EXP<-->PHB
mapping, in compliance with all the material from this specification
pertaining to those types of LSPs.
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MPLS Support of Diff-Serv February 00
A Diff-Serv capable LSR with LAN interfaces MAY support, over these
LAN interfaces, E-LSPs which use a signaled EXP<-->PHB mapping. If a
Diff-Serv LSR does support E-LSPs which use a signaled EXP<-->PHB
mapping over LAN interfaces, then it MUST do so in compliance with
all the material from this specification pertaining to those types
of LSPs.
A Diff-Serv capable LSR MAY support L-LSPs over LAN interfaces. If a
Diff-Serv LSR does support L-LSPs over LAN interfaces, then it MUST
do so in compliance with all the material from this specification
pertaining to L-LSPs.
11. Explicit Congestion Notification
Explicit Congestion Notification is described in [ECN] and is
proposed as an Experimental extension to the IP protocol.
[MPLS_ECN] discusses deployment of ECN in an MPLS network using the
Shim Header as the MPLS encapsulation. It demonstrates that,
provided a given LSP is identified as ECN-capable or as non-ECN-
capable (and consistently recognized as such by all the involved
LSRs), then ECN can be supported in an MPLS domain where the Shim
Header is used as the MPLS encapsulation via a single bit of the EXP
field.
The details of how a given LSP is to be identified as ECN-capable or
non-ECN-capable (whether via extensions to the LSP establishment
signaling and procedures, via configuration or via other means) are
outside the scope of this specification.
However, this specification recognizes that, within an ECN-capable
MPLS domain where LSPs are identified as ECN-capable or not-ECN-
capable:
- Support of ECN does not require that any bit(s) from the EXP
field be reserved for ECN operations across all LSPs even when
those LSPs are not ECN-capable. Consequently, LSPs identified as
non-ECN-capable (regardless of whether this is because at least
one LSR on the LSP does not support ECN operations or whether
this is because the network administrator does not wish to use
ECN on this LSP) can make use of the full 3-bit EXP field for
Diff-Serv purposes. Thus, non-ECN-capable E-LSPs and non-ECN-
capable L-LSPs can operate as defined earlier in this document
without any restriction imposed by the fact that the MPLS domain
is ECN-capable. In particular, up to 8 BAs can still be
transported over a non-ECN-capable E-LSP within an ECN-capable
MPLS domain. Similarly, non-ECN-capable L-LSPs within an ECN-
capable MPLS domain can support all the drop precedence levels
of currently defined PSCs. Should a future PSC involve more than
4 drop precedence levels, non-ECN-capable L-LSPs within an ECN-
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MPLS Support of Diff-Serv February 00
capable MPLS domain could still use the full 3-bit field EXP.
- Because a single bit is required to encode the ECN information
inside the ECN-capable MPLS domain, LSPs identified as ECN-
capable can make use of two bits of the EXP field value for
Diff-Serv purposes. In particular, up to 4 BAs can be
transported over an ECN-capable E-LSP. Similarly, up to 4 drop
precedence levels can be supported over an ECN-capable L-LSP;
since all the PSCs corresponding to PHBs currently defined
through standards action involve less than 4 drop precedence
levels, ECN support does not currently restrict Diff-Serv
operations over L-LSPs. Should a PSC corresponding to future
PHBs defined by standards action or corresponding to local use
or experimental PHBs, involve more than 4 drop precedence
levels, then ECN support over the corresponding LSP would
constrain the PSC to 4 drop precedence levels; relative benefits
of additional precedence levels beyond 4, would then be weighted
by the network administrator over the benefits of ECN, to
determine whether it is preferable to support this PSC over an
ECN-capable or non-ECN-capable LSP.
11.1 MPLS ECN bit with Shim Header
Where the Shim Header is used as the MPLS encapsulation, ECN
information is to be encoded on ECN-capable LSPs in the first bit of
the 3-bit EXP field in the following way:
EXP field MPLS ECN Meaning
0xx --> `ECT, not CE'
1xx --> `not ECT, or ECT+CE'
where ECT stands for `ECN Capable Transport' and `CE' stands for
`Congestion experienced'.
Detailed specification for usage of this MPLS ECN bit is outside the
scope of this document.
For ECN-capable E-LSPs using preconfigured mapping, the
Preconfigured EXP<-->PHB mapping defined above in section 3.2.1 is
only operating over the last 2 bits of the 3-bit EXP field. For ECN-
capable E-LSPs using signaled mapping, the signaled EXP<-->PHB
mapping is only operating over the last 2 bits of the 3-bit EXP
field. Thus it has the following format:
EXP Field PHB
e00 <-----> a given PHB
e01 <-----> a given PHB
e10 <-----> a given PHB
e11 <-----> a given PHB
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MPLS Support of Diff-Serv February 00
where `e' is the MPLS ECN bit and can take the value zero or one
depending on ECN operations.
For ECN-capable L-LSPs, the `EXP/PSC-->PHB mapping' defined above in
section 4.2.1.1 is only operating over the last 2 bits of the 3-bit
EXP field and is the following:
EXP Field PSC PHB
e00 DF -----> DF
e00 CSn -----> CSn
e00 AFn -----> AFn1
e01 AFn -----> AFn2
e10 AFn -----> AFn3
e00 EF -----> EF
where `e' is the MPLS ECN bit and can take the value zero or one
depending on ECN operations.
For ECN-capable L-LSPs, the `PHB--> PSC/EXP mapping' defined above
in the section 4.4.1.1 is only operating over the last 2 bits of the
3-bit EXP field and is the following:
PHB EXP Field PSC
DF -----> e00 DF
CSn -----> e00 CSn
AFn1 -----> e00 AFn
AFn2 -----> e01 AFn
AFn3 -----> e10 AFn
EF -----> e00 EF
where `e' is the MPLS ECN bit and can take the value zero or one
depending on ECN operations.
For non-ECN-capable LSPs, the first bit of the 3-bit EXP field is
NOT reserved for ECN and can be used to encode any Diff-Serv
information. In particular, for non-ECN-capable E-LSPs, the
EXP<-->PHB mapping defined in the section titled `EXP<-->PHB Field
Mapping' and configured on the LSR is operating over the 3 bits of
the EXP field.
12. Security Considerations
This document does not introduce any new security issues beyond
those inherent in Diff-Serv, MPLS and RSVP, and may use the same
mechanisms proposed for those technologies.
13. Acknowledgments
Le Faucheur et. al 40
MPLS Support of Diff-Serv February 00
This document has benefited from discussions with K. K.
Ramakrishnan, Eric Rosen, Angela Chiu and Carol Iturralde.
APPENDIX A. Example Deployment Scenarios
This section does not provide additional specification and is only
here to provide examples of how this flexible approach for Diff-Serv
support over MPLS may be deployed. Pros and cons of various
deployment options for particular environments are beyond the scope
of this document.
A.1 Scenario 1: 8 (or less) BAs, no Traffic Engineering, no Fast
Reroute
A Service Provider running 8 (or less) BAs over MPLS, not performing
Traffic engineering, not performing protection via Fast Reroute and
using MPLS Shim Header encapsulation in his/her network, may elect
to run Diff-Serv over MPLS using a single E-LSP per FEC established
via LDP. Furthermore the Service Provider may elect to use the
preconfigured EXP<-->PHB mapping.
Operations can be summarized as follows:
- the Service Provider configures at every LSR the bi-directional
mapping between each PHB and a value of the EXP field
(eg. 000<-->AF11, 001<-->AF12, 010<-->AF13)
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC (eg bandwidth
allocated to AF1) and the dropping behavior for each PHB (eg
drop profile for AF11, AF12, AF13)
- LSRs signal establishment of a single E-LSP per FEC using LDP in
accordance with the specification above (ie no Diff-Serv TLV in
LDP Label Request/Label Mapping messages to implicitly indicate
that the LSP is an E-LSP and that it uses the preconfigured
mapping)
A.2 Scenario 2: More than 8 BAs, no Traffic Engineering, no Fast
Reroute
A Service Provider running more than 8 BAs over MPLS, not performing
Traffic Engineering and not performing protection via Fast Reroute
and using MPLS Shim encapsulation in his/her network may elect to
run Diff-Serv over MPLS using for each FEC:
- one E-LSP established via LDP and using the preconfigured
mapping to support a set of 8 (or less) BAs, AND
- one L-LSP per <FEC,OA> established via LDP for support of the
other BAs.
Operations can be summarized as follows:
Le Faucheur et. al 41
MPLS Support of Diff-Serv February 00
- the Service Provider configures at every LSR the bi-directional
mapping between each PHB and a value of the EXP field for the
BAs transported over the E-LSP
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC supported over
the E-LSP and the dropping behavior for each corresponding PHB
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC supported over
the L-LSPs and the dropping behavior for each corresponding PHB
- LSRs signal establishment of a single E-LSP per FEC for the set
of E-LSP transported BAs using LDP as specified above (ie no
Diff-Serv TLV in LDP Label Request/Label Mapping messages to
implicitly indicate that the LSP is an E-LSP and that it uses
the preconfigured mapping)
- LSRs signal establishment of one L-LSP per <FEC,OA> for the
other BAs using LDP as specified above (ie Diff-Serv TLV in LDP
Label Request/Label Mapping messages to indicate the L-LSP's
PSC).
A.3 Scenario 3: 8 BAs, Aggregate Traffic Engineering, Aggregate Fast
Reroute
A Service Provider running 8 (or less) BAs over MPLS, performing
aggregate Traffic Engineering (ie performing a single common path
selection for all BAs), performing aggregate protection via Fast
Reroute (ie performing Fast Reroute for all PSCs jointly) and using
MPLS Shim Header encapsulation in his/her network, may elect to run
Diff-Serv over MPLS using a single E-LSP per FEC established via
RSVP [RSVP_MPLS_TE] or CR-LDP [CR-LDP_MPLS_TE] and using the
preconfigured mapping.
Operations can be summarized as follows:
- the Service Provider configures at every LSR the bi-directional
mapping between each PHB and a value of the EXP field
(eg. 000<-->AF11, 001<-->AF12, 010<-->AF13)
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC (eg bandwidth
allocated to AF1) and the dropping behavior for each PHB (eg
drop profile for AF11, AF12, AF13)
- LSRs signal establishment of a single E-LSP per FEC which will
use the preconfigured mapping:
* using the RSVP protocol as specified above (ie no DIFFSERV
RSVP Object in the PATH message containing the LABEL_REQUEST
Object), OR
* using the CR-LDP protocol as specified above (ie no Diff-
Serv TLV in LDP Label Request/Label Mapping messages).
A.4 Scenario 4: per-OA Traffic Engineering/Fast Reroute
A Service Provider running any number of BAs over MPLS, performing
per-OA Traffic Engineering (ie performing a separate path selection
for each OA) and performing per-OA protection via Fast Reroute (ie
Le Faucheur et. al 42
MPLS Support of Diff-Serv February 00
performing protection with different Fast Reroute policies for the
different OAs) in his/her network, may elect to run Diff-Serv over
MPLS using one L-LSP per <FEC,OA> pair established via RSVP or
CR-LDP.
Operations can be summarized as follows:
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC (eg bandwidth
allocated to AF1) and the dropping behavior for each PHB (eg
drop profile for AF11, AF12, AF13)
- LSRs signal establishment of one L-LSP per <FEC,OA>:
* using the RSVP as specified above to signal the
L-LSP's PSC (ie DIFFSERV RSVP Object in the PATH message
containing the LABEL_REQUEST), OR
* using the CR-LDP protocol as specified above to
signal the L-LSP PSC (ie Diff-Serv TLV in LDP Label
Request/Label Mapping messages).
A.5 Scenario 5: 8 (or less) BAs, per-OA Traffic Engineering/Fast
Reroute
A Service Provider running 8 (or less) 8 BAs over MPLS, performing
per-OA Traffic Engineering (ie performing a separate path selection
for each OA) and performing per-OA protection via Fast Reroute (ie
performing protection with different Fast Reroute policies for the
different OAs) in his/her network, may elect to run Diff-Serv over
MPLS using one E-LSP per <FEC,OA> pair established via RSVP or
CR-LDP. Furthermore, the Service Provider may elect to use the
preconfigured mapping on all the E-LSPs.
Operations can be summarized as follows:
- the Service Provider configures at every LSR the bi-directional
mapping between each PHB and a value of the EXP field
(eg. 000<-->AF11, 001<-->AF12, 010<-->AF13)
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC (eg bandwidth
allocated to AF1) and the dropping behavior for each PHB (eg
drop profile for AF11, AF12, AF13)
- LSRs signal establishment of one E-LSP per <FEC,OA>:
* using the RSVP protocol as specified above to signal
that the LSP is an E-LSP which uses the preconfigured mapping
(ie no DIFFSERV RSVP Object in the PATH message containing the
LABEL_REQUEST), OR
* using the CR-LDP protocol as specified above to
signal that the LSP is an E-LSP which uses the preconfigured
mapping (ie no Diff-Serv TLV in LDP Label Request/Label Mapping
messages)
- the Service Provider configures, for each E-LSP, at the head-end
of that E-LSP, a filtering/forwarding criteria so that only the
packets belonging to a given OA are forwarded on the E-LSP
established for the corresponding FEC and corresponding OA.
Le Faucheur et. al 43
MPLS Support of Diff-Serv February 00
A.6 Scenario 6: no Traffic Engineering/Fast Reroute on 8 BAs, per-OA
Traffic Engineering/Fast Reroute on other BAs.
A Service Provider not performing Traffic Engineering/Fast Reroute
on 8 (or less) BAs, performing per-OA Traffic Engineering/Fast
Reroute on the other BAs (ie performing a separate path selection
for each OA corresponding to the other BAs and performing protection
with a different policy for each of these OA) and using the MPLS
Shim encapsulation in his/her network may elect to run Diff-Serv
over MPLS, using for each FEC:
- one E-LSP using the preconfigured mapping established via LDP to
support the set of 8 (or less) non-traffic-engineered/non-fast-
rerouted BAs, AND
- one L-LSP per <FEC,OA> pair established via RSVP or CR-LDP for
support of the other BAs.
Operations can be summarized as follows:
- the Service Provider configures at every LSR the bi-directional
mapping between each PHB and a value of the EXP field for the
BAs supported over the E-LSP
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC supported over
the E-LSP and the dropping behavior for each corresponding PHB
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC supported over
the L-LSPs and the dropping behavior for each corresponding PHB
- LSRs signal establishment of a single E-LSP per FEC for the non-
traffic engineered BAs using LDP as specified above (ie no Diff-
Serv TLV in LDP Label Request/Label Mapping messages)
- LSRs signal establishment of one L-LSP per <FEC,OA> for the
other BAs:
* using the RSVP protocol as specified above to signal
the L-LSP PSC (ie DIFFSERV RSVP Object in the PATH message
containing the LABEL_REQUEST Object), OR
* using the CR-LDP protocol as specified above to
signal the L-LSP PSC (ie Diff-Serv TLV in LDP Label
Request/Label Mapping messages).
A.7 Scenario 7: More than 8 BAs, no Traffic Engineering, no Fast
Reroute
A Service Provider running more than 8 BAs over MPLS, not performing
Traffic engineering, not performing protection via Fast Reroute and
using MPLS Shim Header encapsulation in his/her network, may elect
to run Diff-Serv over MPLS using two E-LSPs per FEC established via
LDP and using signaled EXP<-->PHB mapping.
Operations can be summarized as follows:
- the Service Provider configures at every LSR, and for every
interface, the scheduling behavior for each PSC (eg bandwidth
allocated to AF1) and the dropping behavior for each PHB (eg
drop profile for AF11, AF12, AF13)
Le Faucheur et. al 44
MPLS Support of Diff-Serv February 00
- LSRs signal establishment of two E-LSPs per FEC using LDP in
accordance with the specification above (ie Diff-Serv TLV in LDP
Label Request/Label Mapping messages to explicitly indicate that
the LSP is an E-LSP and its EXP<--> mapping). The signaled
mapping will indicate the subset of 8 (or less) BAs to be
transported on each E-LSP and what EXP values are mapped to each
BA on each E-LSP.
References
[MPLS_ARCH] Rosen et al., "Multiprotocol label switching
Architecture", work in progress, (draft-ietf-mpls-arch-06.txt),
August 1999.
[MPLS ATM] Davie et al., _MPLS using LDP and ATM VC Switching_, work
in progress, (draft-ietf-mpls-atm-02.txt), April 1999
[MPLS FR] Conta et al., _Use of Label Switching on Frame Relay
Networks Specification_, (draft-ietf-mpls-fr-03.txt), November 1998
[DIFF_ARCH] Blake et al., "An architecture for Differentiated
Services", RFC-2475, December 1998.
[DIFF_AF] Heinanen et al., "Assured Forwarding PHB Group", RFC-2597,
June 1999.
[DIFF_EF] Jacobson et al., "An Expedited Forwarding PHB", RFC-2598,
June 1999.
[DIFF_HEADER] Nichols et al., "Definition of the Differentiated
Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC-2474,
December 1998.
[ECN] Ramakrishnan et al., "A Proposal to add Explicit Congestion
Notification (ECN) to IP", RFC-2481, January 1999.
[MPLS_ECN] Ramakrishnan et al., "A Proposal to Incorporate ECN in
MPLS", draft-ietf-mpls-ecn-00.txt, June 1999.
[LDP] Andersson et al., "LDP Specification", draft-ietf-mpls-ldp-
05.txt, June 99
[RSVP_MPLS_TE] Awduche et al, "Extensions to RSVP for LSP Tunnels",
draft-ietf-mpls-rsvp-lsp-tunnel-03.txt, September 1999
[CR-LDP_MPLS_TE] Jamoussi et al., "Constraint-Based LSP Setup using
LDP", draft-ietf-mpls-cr-ldp-03.txt, October 1999
[PHBID] Brim et al., "Per Hop Behavior Identification Codes
draft-ietf-diffserv-phbid-00.txt, October 99
Le Faucheur et. al 45
MPLS Support of Diff-Serv February 00
[DIFF_NEW] Grossman, _New Terminology for Diffserv_, draft-ietf-
diffserv-new-terms-02.txt, November 99
[IEEE_802.1] ISO/IEC 15802-3: 1998 ANSI/IEEE Std 802.1D, 1998
Edition (Revision and redesignation of ISO/IEC 10038:98
[ANSI/IEEE Std 802.1D, 1993 Edition], incorporating IEEE
supplements P802.1p, 802.1j-1996, 802.6k-1992, 802.11c-1998, and
P802.12e)
Author's Addresses:
Francois Le Faucheur
Cisco Systems
Petra B - Les Lucioles - 291, rue Albert Caquot - 06560 Valbonne -
France
Phone: +33 4 92 96 75 64
Email: flefauch@cisco.com
Liwen Wu
Cisco Systems
250 Apollo Drive, Chelmsford, MA 01824,
USA
Phone: +1 (978) 244-3087
Email: liwwu@cisco.com
Bruce Davie
Cisco Systems
250 Apollo Drive, Chelmsford, MA 01824
USA
Phone: +1 (978) 244-8000
Email: bsd@cisco.com
Shahram Davari
PMC-Sierra Inc.
105-8555 Baxter Place
Burnaby, BC V5A 4V7
Canada
E-mail: Shahram_Davari@pmc-sierra.com
Pasi Vaananen
Nokia
3 Burlington Woods Drive, Suit 250
Burlington, MA 01803
USA
Phone +1 (781) 238-4981
Email: pasi.vaananen@nokia.com
Ram Krishnan
Nexabit Networks
200 Nickerson Road,
Marlboro, MA 01752
Le Faucheur et. al 46
MPLS Support of Diff-Serv February 00
USA
E-mail: ram@nexabit.com
Pierrick Cheval
Alcatel
5 rue Noel-Pons
92734 Nanterre Cedex
France
E-mail: pierrick.cheval@alcatel.fr
Juha Heinanen
Telia Finland
E-mail: jh@lohi.eng.telia.fi
Le Faucheur et. al 47
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