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: December, 2000
Document: draft-ietf-mpls-diff-ext-05.txt June, 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 June 2000
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 June 2000
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).
Furthermore, 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 relies 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.
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
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MPLS Support of Diff-Serv June 2000
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.'
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-
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MPLS Support of Diff-Serv June 2000
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).
1.6 Bandwidth Reservation for E-LSPs and L-LSPs
Regardless of which label binding protocol is used, E-LSPs and
L-LSPs may be established without bandwidth reservation or with
bandwidth reservation.
Establishing an E-LSP or L-LSP with bandwidth reservation means that
bandwidth requirements for the LSP are signaled at LSP establishment
time. Such signaled bandwidth requirements may be used by LSRs at
establishment time to perform admission control of the signaled LSP
over the Diff-Serv resources provisioned (e.g. via configuration,
SNMP or COPS) for the relevant PSC(s). Such signaled bandwidth
requirements may also be used by LSRs at establishment time to
perform adjustment to the Diff-Serv resources associated with the
relevant PSC(s) (e.g. adjust PSC scheduling weight).
Note that establishing an E-LSP or L-LSP with bandwidth reservation
does not mean that per-LSP scheduling is necessarily required. Since
E-LSPs and L-LSPs are specified in this document for support of
Differentiated Services, the required forwarding treatment
(scheduling and drop policy) is defined by the appropriate Diff-Serv
PHB. This forwarding treatment MUST be applied by the LSR at the
granularity of the BA and MUST be compliant with the relevant PHB
specification.
When bandwidth requirements are signaled at establishment of an
L-LSP, the signaled bandwidth is obviously associated with the
L-LSP's PSC. Thus, LSRs which use the signaled bandwidth to perform
admission control may perform admission control over Diff-Serv
resources which are dedicated to the PSC (e.g. over the bandwidth
guaranteed to the PSC through its scheduling weight).
When bandwidth requirements are signaled at establishment of an
E-LSP, the signaled bandwidth is associated collectively to the
whole LSP and therefore to the set of transported PSCs. Thus, LSRs
which use the signaled bandwidth to perform admission control may
perform admission control over global resources which are shared by
the set of PSCs (e.g. over the total bandwidth of the link).
Examples of scenarios where bandwidth reservation is not used and
scenarios where bandwidth reservation is used are provided for
information in APPENDIX B.
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MPLS Support of Diff-Serv June 2000
2. Label Forwarding Model for Diff-Serv LSRs and Tunneling Models
2.1 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.
Thus, 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)
Each stage is described in more details in the following sections.
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 \--------+
\----Forwarding-->
Treatment
(PHB)
`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.
(**) when the LSR performs label disposition, the outgoing packet is
transmitted unlabelled.
This model is presented here to describe the functional operations
of Diff-Serv LSRs and does not constrain actual implementation.
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MPLS Support of Diff-Serv June 2000
2.2 Incoming PHB Determination
This stage determines which Behavior Aggregate the received packet
belongs to.
2.2.1 Incoming PHB Determination Considering a Label Stack Entry
Sections 3.3 and 4.3 provide the details on how to perform incoming
PHB Determination considering a given received label stack entry
and/or received incoming MPLS encapsulation information depending on
the incoming LSP type corresponding to the considered stack entry
and depending on the incoming MPLS encapsulation.
Section 2.6 provides the details of which label stack entry to
consider for the Incoming PHB Determination depending on the
supported Diff-Serv tunneling mode.
2.2.2 Incoming PHB Determination Considering IP Header
Section 2.6 provides the details of when the IP Header is to be
considered for incoming PHB determination depending on the supported
Diff-Serv tunneling mode. In those cases where the IP header is to
be used, this stage operates exactly as with a non-MPLS IP Diff-Serv
Router and uses the DS field to determine incoming PHB.
2.3 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
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".
2.4 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'
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MPLS Support of Diff-Serv June 2000
- `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.
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] may be 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
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MPLS Support of Diff-Serv June 2000
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.
2.5 Encoding Diff-Serv Information Into Encapsulation Layer
This stage determines how to encode the fields which convey Diff-
Serv information in the transmitted packet (eg. MPLS Shim EXP, ATM
CLP, Frame Relay DE, 802.1 User_Priority).
2.5.1 Encoding Diff-Serv Information Into Transmitted Label Entry
Sections 3.5 and 4.5 provide the details on how to perform Diff-Serv
information encoding into a given transmitted label stack entry
and/or transmitted MPLS encapsulation information depending on the
corresponding outgoing LSP type and depending on the MPLS
encapsulation.
Section 2.6 provides the details of which label stack entry to
perform Diff-Serv information encoding into depending on the
supported Diff-Serv tunneling mode.
2.5.2 Encoding Diff-Serv Information Into Transmitted IP Header
This paragraph defines how to perform Diff-Serv Information Encoding
into the transmitted packet IP header.
To perform Diff-Serv Information Encoding into the transmitted
packet IP header, this stage operates exactly as with a non-MPLS IP
Diff-Serv Router and encodes the DSCP of the Outgoing PHB into the
DS field.
Section 2.6 provides the details of when Diff-Serv Information
Encoding is to be performed into transmitted IP header depending on
the supported Diff-Serv tunneling mode.
2.6 Diff-Serv Tunneling Models over MPLS
2.6.1 Terminology
As per [MPLS_ARCH],
"we can speak of the level m LSP for Packet P as the sequence of
routers:
1. which begins with an LSR (an "LSP Ingress") that pushes on a
level m label,
2. all of whose intermediate LSRs make their forwarding decision
by label Switching on a level m label,
3. which ends (at an "LSP Egress") when a forwarding decision is
made by label Switching on a level m-k label, where k>0, or when
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MPLS Support of Diff-Serv June 2000
a forwarding decision is made by "ordinary", non-MPLS forwarding
procedures."
We note that if Penultimate Hop Popping (PHP) is used on the LSP,
the label pop for the LSP is not performed by the LSP Egress but
instead is performed by the Penultimate LSR. If PHP is not used,
then the label pop for the LSP is performed by the LSP Egress.
In all the figures below, (I) indicates "LSP Ingress", (P) indicates
"LSP Penultimate Hop" and (E) indicates "LSP Egress".
2.6.2 Diff-Serv Tunneling Models
[DIFF_TUNNEL] considers the interaction of Differentiated Services
with IP tunnels of various forms. MPLS LSPs are not a form of "IP
tunnels" since the MPLS encapsulating header does not contain an IP
header and MPLS LSPs are thus clearly out of the scope of
[DIFF_TUNNEL]. However, although not a form of "IP tunnel", MPLS
LSPs are a form of "tunnel".
From the Diff-Serv standpoint, LSPs share a lot of characteristics
with IP Tunnels:
- intermediate nodes (ie. Nodes somewhere along the LSP span) only
see and operate on the "outer" Diff-Serv information.
- LSPs are unidirectional
- the "outer" Diff-Serv information can be modified at any
intermediate nodes.
However, from the Diff-Serv standpoint, LSPs also have a number of
distinctive properties compared to IP Tunnels:
- There is no behavior analogous to Penultimate Hop Popping (PHP)
for IP Tunnels. Furthermore, PHP results in the "outer"
Diff-Serv information associated with the LSP not being visible
to the LSP egress. In situations where this information is not
meaningful at the LSP Egress, this is obviously not an issue at
all. In situations where this information is meaningful at the
LSP Egress, then it must somehow be carried in some other means.
- Two-level hierarchical LSPs with the two nested LSPs starting on
the same Ingress LSR and finishing on the same Egress LSR, are
expected to be commonplace in MPLS networks for applications
such as MPLS VPNs [MPLS_VPN].
Based on these considerations, it is clear that the two important
conceptual models for Diff-Serv tunneling over IP Tunnels defined in
[DIFF_TUNNEL] are applicable and useful to Diff-Serv over MPLS and
that their respective detailed operations is somewhat different over
MPLS. These two models are the Uniform Model and the Pipe Model and
their operations over MPLS is described in the following sections.
2.6.3 Uniform Model
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MPLS Support of Diff-Serv June 2000
With the Uniform Model, MPLS tunnels (aka LSPs) are viewed as
artifacts of the end-to-end path from the Diff-Serv standpoint. MPLS
Tunnels may be used for forwarding purposes but have no significant
impact on Diff-Serv. In this model, any packet contains exactly one
piece of Diff-Serv information which is meaningful and is always
encoded in the outer most label entry (or in the IP DSCP where the
IP packet is transmitted unlabelled for instance at the egress of
the LSP). Any Diff-Serv information encoded somewhere else (eg. in
deeper label entries) is of no significance to intermediate nodes or
to the tunnel egress and is ignored. If Traffic Conditioning at
intermediate nodes on the LSP span affects the "outer" Diff-Serv
information, the updated Diff-Serv information is the one considered
meaningful at the egress of the LSP.
With this Uniform Model:
- the LSP Ingress, when performing the push operation, encodes the
meaningful Diff-Serv information in the label entry
corresponding to the pushed label.
- Intermediate LSRs only consider and operate on the LSP Diff-Serv
Information encoded in the "outer" label entry (ie label entry
on which they perform the label swap).
- Penultimate Hop Popping (PHP) can be used. In that case, the
meaningful Diff-Serv information is conveyed by the Penultimate
LSR to the LSP Egress in the header that is exposed by the pop
operation (ie. in the header that will be used for actual
forwarding by the LSP Egress).
Note that to do so, the Penultimate LSR needs to be aware of the
"Set of PHB-->Encaps mappings" for the label corresponding to
the exposed header (or the PHB-->DSCP mapping). Methods for
providing this mapping awareness are outside the scope of this
specification. As an example, the "PHB-->DSCP mapping" may be
locally configured. As another example, in some environments, it
may be appropriate for the Penultimate LSR to assume that the
"Set of PHB-->Encaps mappings" to be used for the outgoing label
in the exposed header is the "Set of PHB-->Encaps mappings" that
would be used by the LSR if the LSR was not doing PHP.
Note also that this specification assumes that the Penultimate
LSR does not perform label swapping over the label entry exposed
by the pop operation (and in fact that it does not even look at
the exposed label). Consequently, restrictions may apply to the
Diff-Serv Information Encoding that can be performed by the
Penultimate LSR. For example, this specification does not allow
situations where the Penultimate LSR pops a label corresponding
to an E-LSP supporting two PSCs, while the header exposed by the
pop contains label values for two L-LSPs each supporting one
PSC, since the Diff-Serv Information Encoding would require
selecting one label or the other.
- It is also possible to not use PHP. In that case, the meaningful
Diff-Serv information is conveyed by the Penultimate LSR to the
LSP Egress in the "outer" label entry (which corresponds to the
LSP label).
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MPLS Support of Diff-Serv June 2000
- When the pop operation is performed (ie. Penultimate hop with
PHP, LSP Egress without PHP), the incoming Diff-Serv information
contained in the outmost label entry before the pop is
considered as the meaningful information.
Operation of the Uniform Model with PHP is illustrated below :
========== LSP ==========================>
+--Swap-(M)-...-Swap-(M)--+
/ (outer header) \
(M) (M)
/ \
>--(M)--Push...............(x)............Pop-(M)--(E)--(M)->
(I) (inner header) (P)
(M) represents the Meaningful Diff-Serv information encoded in the
corresponding header.
(x) represents non-meaningful Diff-Serv information.
Operation of the Uniform Model without PHP is illustrated below:
========== LSP =============================>
+--Swap--(M)-...-Swap-(M)-swap--(M)--+
/ (outer header) (P) \
(M) (M)
/ \
>--(M)--Push...............(x).......................Pop--(M)->
(I) (inner header) (E)
(M) represents the Meaningful Diff-Serv information encoded in the
corresponding header.
(x) represents non-meaningful Diff-Serv information.
Use of the Uniform Model allows LSPs to span Diff-Serv domain
boundaries without any other measure in place than an inter-domain
Traffic Conditioning Agreement at the physical boundary between the
Diff-Serv domains and operating exclusively on the "outer" header,
since the meaningful Diff-Serv information is always visible and
modifiable in the outmost label entry.
The Uniform Model for Diff-Serv over MPLS is such that, from the
Diff-Serv perspective, operations are exactly identical to the
operations if MPLS was not used. In other words, MPLS is entirely
transparent to the Diff-Serv operations. For this reason, the
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MPLS Support of Diff-Serv June 2000
Uniform Model has been selected in this specification as the base
mandatory mode of operations and thus MUST be supported.
For support of the Uniform Model over an LSP (with and without PHP),
an LSR performs the Incoming PHB Determination and the Diff-Serv
information Encoding in the following manner:
- when receiving an unlabelled packet, the LSR performs Incoming
PHB Determination considering the received IP Header.
- when receiving a labeled packet, the LSR performs Incoming PHB
Determination considering the outer label entry in the received
label stack. In particular, when a pop operation is to be
performed for the considered LSP, the LSR performs Incoming PHB
Determination BEFORE the pop.
- when performing a swap-only operation for an LSP, the LSR
encodes Diff-Serv Information in the transmitted label entry
corresponding to the swapped label
- when performing a push operation for an LSP, the LSR encodes
Diff-Serv Information in the transmitted label entry
corresponding to the pushed label. The Diff-Serv Information
encoded in the encapsulated header (swapped label entry or IP
Header) is of no importance.
2.6.4 Pipe Model
With the Pipe Model, MPLS tunnels (aka LSPs) are used to hide the
intermediate MPLS nodes between LSP Ingress and Egress from the
Diff-Serv perspective. In this model, the LSP Egress uses the Diff-
Serv information conveyed from the LSP Ingress inside the
encapsulated header (be it an IP Header or an MPLS Header) and
ignores the Diff-Serv information conveyed in the encapsulating
header.
In this model, tunneled packets must convey two meaningful pieces of
Diff-Serv information:
- the Diff-Serv information which is meaningful to intermediate
nodes along the LSP span (which we refer to as the "LSP Diff-
Serv Information"). This LSP Diff-Serv Information is not
meaningful at the LSP Egress: Whether Traffic Conditioning at
intermediate nodes on the LSP span affects the LSP Diff-Serv
information or not, this updated Diff-Serv information is not
considered meaningful at the LSP Egress and is ignored.
- the Diff-Serv information which is meaningful at the LSP Egress
(which we refer to as the "Tunneled Diff-Serv Information").
This information is to be conveyed by the LSP Ingress to the LSP
Egress. This Diff-Serv information is not meaningful to the
intermediate nodes on the LSP span.
With this Pipe Model:
- the LSP Ingress, when performing the push operation, encodes the
LSP Diff-Serv information in the label entry that is pushed
("outer label entry") and encodes the Tunneled Diff-Serv
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MPLS Support of Diff-Serv June 2000
Information in the encapsulated header (IP header or swapped
label entry).
- Intermediate LSRs only consider and operate on the LSP Diff-Serv
Information encoded in the "outer" label entry (ie label entry
on which they perform the label swap).
- Penultimate Hop Popping (PHP) can be used. In that case, the LSP
Diff-Serv Information is simply not conveyed by the Penultimate
LSR to the LSP Egress. The Penultimate LSR conveys to the LSP
Egress the Tunneled Diff-Serv Information in the header that is
exposed by the pop operation (ie. in the header that will be
used for actual forwarding by the LSP Egress). However, since
the LSP Diff-Serv Information is the meaningful one over the
whole LSP including from the Penultimate LSR to the LSP Egress,
the Penultimate LSR performs Diff-Serv forwarding treatment (ie
PHB enforcement) based on the LSP Diff-Serv Information (even if
this information is not actually conveyed in the packet
transmitted to the LSP Egress).
- it is also possible to not use PHP. In that case, the LSP Diff-
Serv Information is conveyed by the Penultimate LSR to the LSP
Egress in the "outer" label entry (which corresponds to the LSP
label) where it will simply be ignored.
- When PHP is used, the LSP Egress directly uses the Diff-Serv
information received in the outer header (IP header or outer
label entry) since it carries the Tunneled Diff-Serv
Information.
- When PHP is not used, LSP Egress ignores the Diff-Serv
information contained in the label entry to be popped (since it
contains the LSP Diff-Serv information) and considers the Diff-
Serv information conveyed in the header (IP header or MPLS
header) which is used to do the actual forwarding (since it
contains the Tunneled LSP Diff-Serv information). In other
words, the LSP Egress considers the Diff-Serv information
conveyed in the header after the pop operation.
Operation of the Pipe Model with PHP is illustrated below:
========== LSP ===========================>
+--Swap--(M)-...-Swap--(M)--+
/ (outer header) \
(M) (M)
/ \
>--(m)-Push.................(m)............Pop-(m)-(E)-(m)-->
(I) (inner header) (P) (M*)
(M) represents the "LSP Diff-Serv information
(m) represents the "Tunneled Diff-Serv information"
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MPLS Support of Diff-Serv June 2000
(*) The Penultimate LSR considers the LSP Diff-Serv information
received in the outer header (ie. before the pop) in order to apply
its Diff-Serv forwarding treatment (ie actual PHB)
Operation of the Pipe Model without PHP is illustrated below:
========== LSP =============================>
+--Swap-(M)-...-Swap-(M)--Swap--(M)--+
/ (outer header) (P) \
(M) (M)
/ \
>--(m)-Push.................(m).....................Pop--(m)-->
(I) (inner header) (E)
(M) represents the "LSP Diff-Serv information
(m) represents the "Tunneled Diff-Serv information"
The Pipe Model is particularly appropriate to environments in which
the incoming interface of the LSP Ingress and the outgoing interface
of the LSP Egress are in the same Diff-Serv domain while the LSP
spans another (other) Diff-Serv domain(s).
As an example, consider the case where a service provider is
offering an MPLS VPN service including Diff-Serv differentiation.
Say that a collection of sites are interconnected via such an MPLS
VPN service. Now say that this collection of sites are managed under
a common administration and are also supporting Diff-Serv service
differentiation. If the VPN site administration and the Service
Provider are not sharing the exact same Diff-Serv policy (for
instance not supporting the same number of PHBs), then operation of
Diff-Serv in the Pipe Model over the MPLS VPN service would allow
the VPN Sites Diff-Serv domain policy to operate consistently
throughout the ingress VPN Site and Egress VPN Site and
transparently over the Service Provider Diff-Serv domain.
Support of the Pipe Model is defined in this specification as a
recommended option and thus SHOULD be supported.
For support of the Pipe Model over an LSP without PHP, an LSR
performs the Incoming PHB Determination and the Diff-Serv
information Encoding in the following manner:
- when receiving an unlabelled packet, the LSR performs Incoming
PHB Determination considering the received IP Header.
- when receiving a labeled packet, the LSR performs Incoming PHB
Determination considering the header (label entry or IP header)
which is used to do the actual forwarding. In particular, when a
pop operation is to be performed for the considered LSP, the LSR
performs Incoming PHB Determination AFTER the pop.
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MPLS Support of Diff-Serv June 2000
- when performing a swap-only operation for an LSP, the LSR
encodes Diff-Serv Information in the transmitted label entry
corresponding to the swapped label
- when performing a push operation for an LSP, the LSR:
o encodes Diff-Serv Information corresponding to the
OUTGOING PHB in the transmitted label entry corresponding
to the pushed label.
o encodes Diff-Serv Information corresponding to the
INCOMING PHB in the encapsulated header (swapped label
entry or IP header).
For support of the Pipe Model over an LSP with PHP, an LSR performs
Incoming PHB Determination and Diff-Serv information Encoding in the
same manner as without PHP with the following exception:
- the Penultimate LSR performs Incoming PHB Determination
considering the outer label entry in the received label stack.
In other words, when a pop operation is to be performed for the
considered LSP, the Penultimate LSR performs Incoming PHB
Determination BEFORE the pop.
- the Penultimate LSR does not perform Encoding of Diff-Serv
Information into the header exposed by the pop operation.
Note that LSR behaviors for the Uniform Model and for the Pipe Model
only differ when doing a push or a pop. Thus, Intermediate LSRs
which perform swap only operations for an LSP , behave exactly in
the same way regardless of whether they are behaving in the Uniform
Model or the Pipe model. With a Diff-Serv implementation supporting
both the Uniform Model and the Pipe Model, only LSRs behaving as LSP
Ingress, Penultimate LSR or LSP Egress need to be configured to
operate in a particular Model.
2.6.5 Other Models
Other Diff-Serv tunneling models are conceivable over MPLS for
support of more complex scenarios. For instance, the egress of an
LSP could conceivably make some complex Diff-Serv decision based on
both the Diff-Serv information conveyed in the encapsulating header
and in the encapsulated header. Models beyond the Uniform Model and
the Pipe Model are outside the scope of this specification and MAY
be supported as an option.
2.6.6 Hierarchy
Through the label stack mechanism, MPLS allows LSP tunneling to nest
to any depth. We observe that with such nesting, the push of level
N+1 takes place on a subsequent (or the same) LSR to the LSR doing
the push for level N, while the pop of level N+1 takes place on a
previous (or the same) LSR to the LSR doing the pop of level N. For
a given level N LSP, the Ingress LSR doing the push and the LSR
doing the pop (Penultimate LSR or LSP Egress) are expected to
operate in the same Tunneling Model (ie Uniform or Pipe). LSRs at
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MPLS Support of Diff-Serv June 2000
different levels of LSPs are expected to operate in the same or in
different Tunneling Models.
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MPLS Support of Diff-Serv June 2000
Hierarchical operations is illustrated below in the case of two
levels of tunnels:
+--------Swap--...---+
/ (outmost header) \
/ \
Push(2).................(2)Pop
/ (outer header) \
/ \
>>---Push(1)........................(1)Pop-->>
(inner header)
(1) Tunneling Model 1 (either Uniform or Pipe)
(2) Tunneling Model 2 (same as Tunneling Model 1 or different Model)
For support of M levels of push in the Uniform Model:
- when performing multiple push operations, the LSR encodes Diff-
Serv Information in the transmitted label entry corresponding to
the LAST pushed label (ie the label pushed in the outer label
entry). The Diff-Serv Information encoded in the encapsulated
header (swapped label entry or IP Header) as well as the Diff-
Serv Information encoded in label entries for other pushed
labels are of no importance.
For support of M levels of pop in the Uniform Model:
- when performing multiple pop operations for an LSP, the LSR
performs Incoming PHB Determination considering the outmost
label entry in the received label stack. In other words, when
multiple pop operations are to be performed, the LSR performs
Incoming PHB Determination BEFORE ANY pop operations.
- when the multiple pop operations are performed by the
Penultimate LSR, note that to perform Encoding of Diff-Serv
Information, the Penultimate LSR needs to be aware of the "Set
of PHB-->Encaps mappings" for the label corresponding to the
exposed header after all the pop operations (or the PHB-->DSCP
mapping). Methods for providing this mapping awareness are
outside the scope of this specification.
- when the multiple pop operations are performed by the
Penultimate LSR, note also that this specification assumes that
the Penultimate LSR does not perform label swapping over the
label entry exposed after all the pop operations (and in fact
that it does not even look at the header exposed after the last
pop operations). Consequently, restrictions may apply to the
Diff-Serv Information Encoding that can be performed by the
Penultimate LSR.
For support of M levels of push in the Pipe Model:
- when performing multiple push operations, the LSR:
o encodes Diff-Serv Information corresponding to the
Outgoing PHB in the transmitted label entry corresponding
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MPLS Support of Diff-Serv June 2000
to the LAST pushed label (ie the label pushed in the outer
label entry).
o encodes Diff-Serv Information corresponding to the
Incoming PHB in the encapsulated header (swapped label
entry or IP header) as well as in the label entries for
all the pushed labels (except the last pushed label).
For support of M levels of pop in the Pipe Model without PHP:
- when performing multiple pop operations for an LSP, the LSR
performs Incoming PHB Determination considering the header
(label entry or IP header) which is used to do the actual
forwarding. In other words, when a pop operation is to be
performed for the considered LSP, the LSR performs Incoming PHB
Determination AFTER ALL the pop operations.
For support of M levels of pop in the Pipe Model with PHP, the
Penultimate LSR:
- performs Incoming PHB Determination considering the outmost
label entry in the received label stack. In other words, when
multiple pop operations are to be performed for the considered
LSP, the LSR performs Incoming PHB Determination BEFORE ANY pop
operations.
- does not perform Encoding of Diff-Serv Information into the
header that is exposed after all the pop operations
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
- 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.
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MPLS Support of Diff-Serv June 2000
- 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 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 fewer, 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
This section defines how the `Encaps-->PHB mapping' of the Diff-Serv
Context is populated for an incoming E-LSP in order to allow
Incoming PHB determination.
The `Encaps-->PHB mapping' for an E-LSP 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 use 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.
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MPLS Support of Diff-Serv June 2000
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 how Incoming PHB Determination is carried out
when the considered label entry in the received label stack
corresponds to an E-LSP. This requires that the `Encaps-->PHB
mapping' is populated as defined above in section 3.2.
When considering a label entry corresponding to an incoming E-LSP
for Incoming PHB Determination, the LSR:
- determines the EXP-->PHB mapping by looking up the
`Encaps-->PHB mapping' of the Diff-Serv Context associated in
the ILM with the considered incoming E-LSP label.
- determines the incoming PHB by looking up the EXP field of the
considered label entry in the EXP-->PHB mapping table.
3.4 Populating the `Set of PHB-->Encaps mappings' for an outgoing E-LSP
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
allow Encoding of Diff-Serv information in the Encapsulation Layer.
3.4.1 `PHB-->EXP mapping'
An outgoing E-LSP must always have a `PHB-->EXP mapping' as part of
the `Set of PHB-->Encaps mappings' of its Diff-Serv Context.
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-->CLP mapping'
If the E-LSP is egressing over an ATM interface which is not label
switching controlled, 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 E-LSP. This `PHB-->CLP mapping' is populated in
the following way:
- it is a function of the PHBs supported on this LSP, and may use
the relevant mapping entries for these PHBs from the
Default PHB-->CLP Mapping defined in section 3.4.2.1. Other
mappings than the one defined in section 3.4.2.1 may be used. In
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MPLS Support of Diff-Serv June 2000
particular, if a mapping from PHBs to CLP is standardized in the
future for operations of Diff-Serv over ATM, such standardized
mapping may then be used.
For example if the outgoing label corresponds to an E-LSP supporting
the AF1 PSC and the EF PHB and egressing over an ATM interface, then
the `PHB-->CLP mapping' may be populated with:
PHB CLP Field
AF11 ----> 0
AF12 ----> 1
AF13 ----> 1
EF ----> 0
Notice that if the E-LSP is egressing over an ATM interface, then
the `Set of PHB-->Encaps mappings' contains both a `PHB-->EXP
mapping' and a `PHB-->CLP mapping'.
3.4.2.1 Default PHB-->CLP Mapping
PHB CLP Bit
DF ----> 0
CSn ----> 0
AFn1 ----> 0
AFn2 ----> 1
AFn3 ----> 1
EF ----> 0
3.4.3 `PHB-->DE mapping'
If the E-LSP is egressing over a Frame Relay interface which is not
label switching controlled, one `PHB-->DE mapping' is added at label
setup to the `Set of PHB-->Encaps mappings' in the Diff-Serv Context
for this outgoing E-LSP and is populated in the following way:
- it is a function of the PHBs supported on this LSP, and may use
the relevant mapping entries for these PHBs from the Default
PHB-->DE Mapping defined in section 3.4.3.1. Other mappings than
the one defined in section 3.4.3.1 may be used. In particular,
if a mapping from PHBs to DE is standardized in the future for
operations of Diff-Serv over Frame Relay, such standardized
mapping may then be used.
Notice that if the E-LSP is egressing over a Frame Relay interface,
then the `Set of PHB-->Encaps mappings' contains both a `PHB-->EXP
mapping' and a `PHB-->DE mapping'.
3.4.3.1 Default PHB-->DE Mapping
PHB DE Bit
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MPLS Support of Diff-Serv June 2000
DF ----> 0
CSn ----> 0
AFn1 ----> 0
AFn2 ----> 1
AFn3 ----> 1
EF ----> 0
3.4.4 `PHB-->802.1 mapping'
If the E-LSP is egressing over a LAN interface on which multiple
802.1 Traffic Classes are supported as per [IEEE_802.1], then one
`PHB-->802.1 mapping' is added at label setup to the `Set of
PHB-->Encaps mappings' of the Diff-Serv Context for this outgoing
E-LSP. This `PHB-->802.1 mapping' is populated in the following way:
- it is a function of the PHBs supported on this LSP, an uses the
relevant mapping entries for these PHBs from the Preconfigured
PHB-->802.1 Mapping defined in section 3.4.4.1.
Notice that the `Set of PHB-->Encaps mappings' then contains both a
`PHB-->EXP mapping' and a `PHB-->802.1 mapping'.
3.4.4.1 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 how to encode Diff-Serv information into the
MPLS encapsulation Layer for a given transmitted label entry
corresponding to an outgoing E-LSP. This 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 mappings' of the
Diff-Serv Context associated with the corresponding label in the
NHLFE.
3.5.1 `PHB-->EXP mapping'
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.
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MPLS Support of Diff-Serv June 2000
3.5.2 `PHB-->CLP mapping'
If the `Set of PHB-->Encaps mappings' 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
encapsulation header, by looking up the "outgoing PHB" in this
PHB-->CLP mapping table.
3.5.3 `PHB-->DE mapping'
If the `Set of PHB-->Encaps mappings' contains a mapping of the form
`PHB-->DE mapping', then the LSR:
- determines the value to be written in the DE field of the Frame
Relay encapsulation header, by looking up the "outgoing PHB" in
this PHB-->DE mapping table.
3.5.4 `PHB-->802.1 mapping'
If the `Set of PHB-->Encaps mappings' 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
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MPLS Support of Diff-Serv June 2000
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
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 be 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 the OA transported over the LSP are granted
different drop precedence by the 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 in order to allow
Incoming PHB determination.
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4.2.1 `EXP-->PHB mapping'
If the LSR terminates the MPLS Shim Layer over this incoming L-LSP
and the L-LSP ingresses on an interface which is not ATM nor Frame
Relay, then the `Encaps-->PHB mapping' is populated at label setup
in the following way:
- it must actually be a `EXP-->PHB mapping'
- this mapping is a function of the PSC which is carried on this
LSP, and must use the relevant mapping entries for this PSC from
the Mandatory EXP/PSC-->PHB Mapping defined in Section 4.2.1.1.
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
An LSR supporting L-LSPs over PPP interfaces and LAN interfaces is
an example of LSR terminating the Shim layer over ingress interfaces
which are not ATM nor Frame Relay.
If the LSR terminates the MPLS Shim Layer over this incoming L-LSP
and the L-LSP ingresses on an ATM or Frame Relay interface, then the
`Encaps-->PHB mapping' is populated at label setup in the following
way:
- it should actually be a `EXP-->PHB mapping'. Alternative
optional ways of populating the `Encaps-->PHB mapping' might be
defined in the future (e.g., using a 'CLP/EXP--> PHB mapping' or
a 'DE/EXP-->PHB mapping') but are outside the scope of this
document.
- when the `Encaps-->PHB mapping' is an `EXP-->PHB mapping', this
`EXP-->PHB mapping' mapping is a function of the PSC which is
carried on the L-LSP, and must use the relevant mapping entries
for this PSC from the Mandatory EXP/PSC-->PHB Mapping defined in
Section 4.2.1.1.
An Edge-LSR of an ATM-MPLS domain or of a FR-MPLS domain is an
example of LSR terminating the shim layer over an ingress ATM/FR
interface.
4.2.1.1 Mandatory EXP/PSC --> PHB mapping
EXP Field PSC PHB
000 DF ----> DF
000 CSn ----> CSn
000 AFn ----> AFn1
001 AFn ----> AFn2
010 AFn ----> AFn3
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MPLS Support of Diff-Serv June 2000
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), 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 should use the relevant mapping entries for this PSC
from the Default CLP/PSC-->PHB Mapping defined in Section
4.2.2.1.
For example if the incoming label corresponds to an L-LSP supporting
the AF1 PSC, then the `Encaps-->PHB mapping' should be populated
with:
CLP Field PHB
0 ----> AF11
1 ----> AF12
4.2.2.1 Default CLP/PSC --> PHB Mapping
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), 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 should use the relevant mapping entries for this PSC
from the Default DE/PSC-->PHB Mapping defined in Section
4.2.3.1.
4.2.3.1 Default DE/PSC --> PHB Mapping
DE Bit PSC PHB
0 DF ----> DF
0 CSn ----> CSn
0 AFn ----> AFn1
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MPLS Support of Diff-Serv June 2000
1 AFn ----> AFn2
0 EF ----> EF
4.3 Incoming PHB Determination On Incoming L-LSP
This section defines how Incoming PHB determination is carried out
when the considered label entry in the received label stack
corresponds to an L-LSP. This requires that the `Encaps-->PHB
mapping' is populated as defined above in section 4.2.
When considering a label entry corresponding to an incoming L-LSP
for Incoming PHB Determination, the LSR first determines the
`Encaps-->PHB mapping' associated with the incoming top level 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
considered label entry and by using the EXP-->PHB mapping.
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.
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.
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 in order to
allow Encoding of Diff-Serv Information.
4.4.1 `PHB-->EXP mapping'
If the LSR uses an MPLS Shim Layer over this outgoing L-LSP, then
one `PHB-->EXP 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-->EXP mapping' is populated in the following way:
- it is a function of the PSC supported on this LSP, and must use
the mapping entries relevant for this PSC from the Mandatory
PHB-->EXP Mapping defined in section 4.4.1.1.
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MPLS Support of Diff-Serv June 2000
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 Mandatory PHB-->EXP Mapping
PHB EXP Field
DF ----> 000
CSn ----> 000
AFn1 ----> 000
AFn2 ----> 001
AFn3 ----> 010
EF ----> 000
4.4.2 `PHB-->CLP mapping'
If the L-LSP is egressing on an ATM interface (i.e. it is an ATM-LSR
or it is a frame-based LSR sending packets on an LC-ATM interface or
on an ATM interface which is not label switching controlled), 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.
If the L-LSP is egressing over an LC-ATM interface, the `PHB-->CLP
mapping' is populated in the following way:
- it is a function of the PSC supported on this LSP, and should
use the relevant mapping entries for this PSC from the Default
PHB-->CLP Mapping defined in section 3.4.2.1.
For example if the outgoing label corresponds to an L-LSP supporting
the AF1 PSC, then the `PHB-->CLP mapping' should be populated with:
PHB CLP Field
AF11 ----> 0
AF12 ----> 1
AF13 ----> 1
If the L-LSP is egressing over an ATM interface which is not label
switching controlled, the `PHB-->CLP mapping' is populated in the
following way:
- it is a function of the PSC supported on this LSP, and may use
the relevant mapping entries for this PSC from the Default
PHB-->CLP Mapping defined in section 3.4.2.1. Other mappings
than the one defined in section 3.4.2.1 may be used. In
Le Faucheur et. al 29
MPLS Support of Diff-Serv June 2000
particular, if a mapping from PHBs to CLP is standardized in the
future for operations of Diff-Serv over ATM, such standardized
mapping may then be used.
Notice that if the LSR is a frame-based LSR supporting an L-LSP
egressing over an ATM interface, then the `Set of PHB-->Encaps
mappings' contains both a `PHB-->EXP mapping' and a `PHB-->CLP
mapping'. If the LSR is an ATM-LSR supporting an L-LSP, then the
`Set of PHB-->Encaps mappings' only contains a `PHB-->CLP mapping'.
4.4.3 `PHB-->DE mapping'
If the L-LSP is egressing over a Frame Relay interface (i.e. it is
an LSR sending packets on an LC-FR interface or on a Frame Relay
interface which is not label switching controlled), one `PHB-->DE
mapping' is added at label setup to the `Set of PHB-->Encaps
mappings' in the Diff-Serv Context for this outgoing L-LSP.
If the L-LSP is egressing over an LC-FR interface, the `PHB-->DE
mapping' is populated in the following way:
- it is a function of the PSC supported on this LSP, and should
use the relevant mapping entries for this PSC from the Default
PHB-->DE Mapping defined in section 3.4.3.1.
If the L-LSP is egressing over a FR interface which is not label
switching controlled, the `PHB-->DE mapping' is populated in the
following way:
- it is a function of the PSC supported on this LSP, and may use
the relevant mapping entries for this PSC from the Default
PHB-->DE Mapping defined in section 3.4.3.1. Other mappings than
the one defined in section 3.4.3.1 may be used. In particular,
if a mapping from PHBs to DE is standardized in the future for
operations of Diff-Serv over Frame Relay, such standardized
mapping may then be used.
Notice that if the LSR is an Edge-LSR supporting an L-LSP egressing
over a LC-FR interface, then the `Set of PHB-->Encaps mappings'
contains both a `PHB-->EXP mapping' and a `PHB-->DE mapping'. If the
LSR is a FR-LSR supporting an L-LSP, then the `Set of PHB-->Encaps
mappings' only contains a `PHB-->DE mapping'.
4.4.4 `PHB-->802.1 mapping'
If the L-LSP is egressing over a LAN interface on which multiple
802.1 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 mapping entries for this PSC from the Preconfigured
`PHB-->802.1 mapping' defined above in section 3.4.4.1.
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MPLS Support of Diff-Serv June 2000
Notice that if the LSR is supporting an L-LSP egressing 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 Layer on Outgoing
L-LSP
This section defines how to encode Diff-Serv information into the
MPLS encapsulation Layer for a transmitted label entry corresponding
to an outgoing L-LSP. This 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 mappings' of the
Diff-Serv Context associated with the corresponding label in the
NHLFE.
4.5.1 `PHB-->EXP mapping'
If the `Set of PHB-->Encaps mappings' of the transmitted label
contains a mapping of the form `PHB-->EXP mapping', then the LSR:
- 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 mappings' of the transmitted 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 mappings' of the transmitted label
contains a mapping of the form `PHB-->DE mapping', then the LSR:
- 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 mappings' of the transmitted 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
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MPLS Support of Diff-Serv June 2000
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.
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
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MPLS Support of Diff-Serv June 2000
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
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MPLS Support of Diff-Serv June 2000
Indicates the number of MAP entries included in the DIFFSERV
Object. This can be set to any value from 1 to 8.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
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MPLS Support of Diff-Serv June 2000
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,
- 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.
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MPLS Support of Diff-Serv June 2000
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
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 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).
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MPLS Support of Diff-Serv June 2000
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
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.
Note that this specification defines usage of E-LSPs and L-LSPs
for support of the Diff-Serv service only. Regardless of whether the
signaling messages actually indicate an Int-Serv service of COS, GS
or CL and regardless of whether the signaling messages contain a
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MPLS Support of Diff-Serv June 2000
signaled bandwidth reservation or not, E-LSPs and L-LSPs are defined
here for support of Diff-Serv services. Support of Int-Serv services
over an MPLS Diff-Serv backbone is outside the scope of this
specification.
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 is 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 is 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 L-LSP indicates to a Diff-Serv capable LSR that
the LSP to be established is 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).
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.
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MPLS Support of Diff-Serv June 2000
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| Diff-Serv (0x901) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T| Reserved | MAPnb |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAP (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAP (MAPnb) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T:1 bit
LSP Type. This is set to 0 for an E-LSP
Reserved : 27 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.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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MPLS Support of Diff-Serv June 2000
| 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 : 15 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
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MPLS Support of Diff-Serv June 2000
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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MPLS Support of Diff-Serv June 2000
| 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Diff-Serv TLV (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.4 Handling of the Diff-Serv TLV
6.4.1 Handling of the Diff-Serv TLV in Downstream Unsolicited Mode
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MPLS Support of Diff-Serv June 2000
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:
- the MAPnb field is not within the range 1 to 8, 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'.
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MPLS Support of Diff-Serv June 2000
6.4.2 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
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, or
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MPLS Support of Diff-Serv June 2000
- 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.
6.5 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.
6.6 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 interfaces
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.
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
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MPLS Support of Diff-Serv June 2000
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.
7.2 LSR implementation with non-LC ATM interfaces
The E-LSP/L-LSP support requirements for an LSR running MPLS over a
traditional ATM connection (ie. where the interface is not label
switching controlled) are the same as those specified in section 7.1
for an LSR with PPP interfaces.
7.3 LSR implementation with non-LC FR interfaces
The E-LSP/L-LSP support requirements for an LSR running MPLS over a
traditional Frame Relay connection (ie. where the interface is not
label switching controlled) are the same as those specified in
section 7.1 for an LSR with PPP interfaces.
8. MPLS Support of Diff-Serv over LC-ATM Interfaces
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 label switching
controlled ATM (LC-ATM) interfaces.
This document allows any number of L-LSPs per FEC within an MPLS ATM
Diff-Serv domain. E-LSPs are not supported over LC-ATM interfaces.
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
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MPLS Support of Diff-Serv June 2000
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 LC-ATM Interfaces
A Diff-Serv capable LSR with LC-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.
This specification assumes that Edge-LSRs of the ATM-LSR domain use
the "shim header" encapsulation method defined in [MPLS_ATM].
Operations without the "shim header" encapsulation is outside the
scope of this specification.
9. MPLS Support of Diff-Serv over LC-FR Interfaces
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 label switching
controlled Frame Relay (LC-FR) interfaces.
This document allows any number of L-LSPs per FEC within an MPLS
Frame Relay Diff-Serv domain. E-LSPs are not supported over LC-FR
interfaces.
9.1 Merging
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
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MPLS Support of Diff-Serv June 2000
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 LC-FR Interfaces
A Diff-Serv capable LSR with LC-FR 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.
Additionally, procedures specified in [MPLS_FR] MUST be followed by
compliant implementation.
This specification assumes that Edge-LSRs of the FR-LSR domain use
the "generic encapsulation" method as recommended in [MPLS_FR].
Operations without the "generic encapsulation" is outside the scope
of this specification.
10. MPLS Support of Diff-Serv over LAN Interfaces
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 interfaces.
This document allows the following set of LSP setup combinations per
FEC over a LAN interface:
- 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.
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
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MPLS Support of Diff-Serv June 2000
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-
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
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MPLS Support of Diff-Serv June 2000
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 LSPs, the mappings between EXP and PHB (be it the
E-LSP Preconfigured Mapping specified in section 3.2.1, the E-LSP
Signaled Mapping, the L-LSP Mappings defined in section 4.2.1.1 and
4.4.1.1) are adjusted accordingly to only take into account the last
2 bits of the 3-bit EXP field.
Note that when the E-LSP signaled mapping is used on an ECN-capable
E-LSP, the signaled mapping only needs to contain a single MAP entry
for a given PHBID, which includes an EXP value with its first bit
set to zero.
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.
12. Security Considerations
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MPLS Support of Diff-Serv June 2000
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
This document has benefited from discussions with K. K.
Ramakrishnan, Eric Rosen, Angela Chiu and Carol Iturralde. It has
also borrowed from the work done by D. Black regarding Diff-Serv and
IP Tunnels interaction.
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 fewer) BAs, no Traffic Engineering, no Fast
Reroute
A Service Provider running 8 (or fewer) 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
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MPLS Support of Diff-Serv June 2000
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:
- 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 (or fewer) BAs, Aggregate Traffic Engineering,
Aggregate Fast Reroute
A Service Provider running 8 (or fewer) 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
Le Faucheur et. al 52
MPLS Support of Diff-Serv June 2000
* 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
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 fewer) BAs, per-OA Traffic Engineering/Fast
Reroute
A Service Provider running 8 (or fewer) 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
Le Faucheur et. al 53
MPLS Support of Diff-Serv June 2000
* 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.
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 fewer) 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 fewer) 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
Le Faucheur et. al 54
MPLS Support of Diff-Serv June 2000
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)
- 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.
APPENDIX B. Example Bandwidth Reservation Scenarios
B.1 Scenario 1: No Bandwidth Reservation
Consider the case where a network administrator elects to:
- have Diff-Serv resources entirely provisioned off-line (e.g. via
Command Line Interface, via SNMP, via COPS,...)
- have Shortest Path Routing used for all the Diff-Serv traffic.
This is the closest model to provisioned Diff-Serv over non-MPLS IP.
In that case, E-LSPs and/or L-LSPs would be established without
signaled bandwidth.
B.2 Scenario 2: Bandwidth Reservation for per-PSC Admission Control
Consider the case where a network administrator elects to:
- have Diff-Serv resources entirely provisioned off-line (e.g. via
Command Line Interface, via SNMP, via COPS,...)
- use L-LSPs
- have Constraint Based Routing performed separately for each PSC,
where one of the constraints is availability of bandwidth from
the bandwidth allocated to the relevant PSC.
In that case, L-LSPs would be established with signaled bandwidth.
The bandwidth signaled at L-LSP establishment would be used by LSRs
to perform admission control at every hop to ensure that the
constraint on availability of bandwidth for the relevant PSC is met.
B.3 Scenario 3: Bandwidth Reservation for per-PSC Admission Control and
per-PSC Resource Adjustment
Consider the case where a network administrator elects to:
- use L-LSPs
Le Faucheur et. al 55
MPLS Support of Diff-Serv June 2000
- have Constraint Based Routing performed separately for each PSC,
where one of the constraints is availability of bandwidth from
the bandwidth allocated to the relevant PSC.
- have Diff-Serv resources dynamically adjusted
In that case, L-LSPs would be established with signaled bandwidth.
The bandwidth signaled at L-LSP establishment would be used by LSRs
to attempt to adjust the resources allocated to the relevant PSC
(e.g. scheduling weight) and then perform admission control to
ensure that the constraint on availability of bandwidth for the
relevant PSC is met after the adjustment.
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-03.txt), May 2000
[MPLS_FR] Conta et al., "Use of Label Switching on Frame Relay
Networks Specification", (draft-ietf-mpls-fr-04.txt), May 2000
[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-
06.txt, October 99
[RSVP_MPLS_TE] Awduche et al, "Extensions to RSVP for LSP Tunnels",
draft-ietf-mpls-rsvp-lsp-tunnel-05.txt, February 2000
[CR-LDP_MPLS_TE] Jamoussi et al., "Constraint-Based LSP Setup using
LDP", draft-ietf-mpls-cr-ldp-03.txt, October 1999
Le Faucheur et. al 56
MPLS Support of Diff-Serv June 2000
[PHBID] Brim et al., "Per Hop Behavior Identification Codes"
RFC 2836, May 2000
[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)
[DIFF_TUNNEL] Black, "Differentiated Services and Tunnels", draft-
ietf-diffserv-tunnels-00-txt, February 2000.
[MPLS_VPN] Rosen et al., "BGP/MPLS VPNs", draft-rosen-rfc2547bis-
00.txt, March 2000.
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.
555 Legget drive,
Suit 834, Tower B,
Ottawa, ON K2K 2X3
Canada
Phone: +1 (613) 271-4018
Email: shahram_davari@pmc-sierra.com
Le Faucheur et. al 57
MPLS Support of Diff-Serv June 2000
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
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 58
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