Internet Draft
Network Working Group Peter Ashwood-Smith
Internet Draft Yanhe Fan
Expiration Date: December 2000 Nortel Networks Corp.
Ayan Banerjee
John Drake
Jonathan P. Lang
Calient Networks
Lou Berger
LabN Consulting, LLC
Greg Bernstein
Ciena Corporation
Kireeti Kompella
Juniper Networks, Inc.
Eric Mannie
GTS Network Services
Bala Rajagopalan
Debanjan Saha
Z. Bo Tang
Tellium, Inc.
Yakov Rekhter
cisco Systems
Vishal Sharma
Tellabs
June 2000
Generalized MPLS - Signaling Functional Description
draft-ashwood-generalized-mpls-signaling-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
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Abstract
This document describes extensions to MPLS signaling required to
support Generalized MPLS. Generalized MPLS extends MPLS to encompass
time-division (e.g. SONET ADMs), wavelength (optical lambdas) and
spatial switching (e.g. incoming port or fiber to outgoing port or
fiber). This document presents a functional description of the
extensions. Protocol specific formats and mechanisms are currently
included in this draft but are expected to be split out into
separate, per protocol documents.
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Contents
1 Introduction ................................................ 4
2 Overview ................................................... 5
3 Label Related Formats ...................................... 7
3.1 Generalized Label Request ................................... 7
3.2 Generalized Label ........................................... 11
3.3 Waveband Switching .......................................... 16
3.4 Suggested Label ............................................. 18
3.5 Label Set ................................................... 19
4 Bidirectional LSPs .......................................... 22
4.1 Required Information ........................................ 23
4.2 Procedures .................................................. 23
4.3 Contention Resolution ....................................... 24
5 Notification ................................................ 26
5.1 Notify Message .............................................. 26
5.2 Non-Adjacent Message Bundling ............................... 27
6 Egress Control .............................................. 28
6.1 Required Information ........................................ 28
6.2 Procedures .................................................. 30
7 Acknowledgments ............................................. 30
8 Security Considerations ..................................... 31
9 References .................................................. 31
10 Authors' Addresses .......................................... 32
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Changes from previous version:
o First revision.
1. Introduction
The Multiprotocol Label Switching (MPLS) architecture [MPLS-ARCH] has
been defined to support the forwarding of data based on a label. In
this architecture, Label Switching Routers (LSRs) were assumed to
have a forwarding plane that is capable of (a) recognizing either
packet or cell boundaries, and (b) being able to process either
packet headers (for LSRs capable of recognizing packet boundaries) or
cell headers (for LSRs capable of recognizing cell boundaries).
The original architecture has recently been extended to include LSRs
whose forwarding plane recognizes neither packet, nor cell
boundaries, and therefore, can't forward data based on the
information carried in either packet or cell headers. Specifically,
such LSRs include devices where the forwarding decision is based on
time slots, wavelengths, or physical ports.
Given the above, LSRs, or more precisely interfaces on LSRs, can be
subdivided into the following classes:
1. Interfaces that recognize packet/cell boundaries and can forward
data based on the content of the packet/cell header. Examples
include interfaces on routers that forward data based on the
content of the "shim" header, interfaces on ATM-LSRs that forward
data based on the ATM VPI/VCI. Such interfaces are referred to as
Packet-Switch Capable (PSC).
2. Interfaces that forward data based on the data's time slot in a
repeating cycle. An example of such an interface is an interface
on a SONET Cross-Connect. Such interfaces are referred to as
Time-Division Multiplex Capable (TDM).
3. Interfaces that forward data based on the wavelength on which the
data is received. An example of such an interface is an interface
on an Optical Cross-Connect that can operate at the level of an
individual wavelength. Such interfaces are referred to as Lambda
Switch Capable (LSC).
4. Interfaces that forward data based on a position of the data in
the real world physical spaces. An example of such an interface
is an interface on an Optical Cross-Connect that can operate at
the level of a single (or multiple) fibers. Such interfaces are
referred to as Fiber-Switch Capable (FSC).
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Using the concept of nested LSPs (by using label stack) allows the
system to scale by building a forwarding hierarchy. At the top of
this hierarchy are FSC interfaces, followed by LSC interfaces,
followed by TDM interfaces, followed by PSC interfaces. This way, an
LSP that starts and ends on a PSC interface can be nested (together
with other LSPs) into an LSP that starts and ends on a TDM interface.
This LSP, in turn, can be nested (together with other LSPs) into an
LSP that starts and ends on a LSC interface, which in turn can be
nested (together with other LSPs) into an LSP that starts and ends on
a FSC interface. See [MPLS-HIERARCHY] for more information on LSP
hierarchies.
The establishment of LSPs that span only the first class of
interfaces is defined in the [LDP, CR-LDP, RSVP-TE]. This document
presents the extensions needed to support all four classes of
interfaces.
This document currently includes data formats for both CR-LDP and
RSVP-TE extensions. A future version of this document is expected to
move these protocol specific formats to per protocol drafts.
2. Overview
Generalized MPLS differs from traditional MPLS in that it supports
multiple types of switching, i.e., the addition of support for TDM,
lambda, and fiber (port) switching. The support for the additional
types of switching has driven generalized MPLS to extend certain base
functions of traditional MPLS and, in some cases, to add
functionality. These changes and additions impact basic LSP
properties, how labels are requested and communicated, the
unidirectional nature of LSPs, how errors are propagated, and
information provided for synchronizing the ingress and egress.
In traditional MPLS Traffic Engineering, links traversed by an LSP
can include an intermix of links with heterogeneous label encodings.
For example, an LSP may span links between routers, links between
routers and ATM-LSRs, and links between ATM-LSRs. Generalized MPLS
extends this by including links where the label is encoded as a time
slot, or a wavelength, or a position in the real world physical
space. Just like with traditional MPLS TE, where not all LSRs are
capable of recognizing (IP) packet boundaries (e.g., an ATM-LSR) in
their forwarding plane, generalized MPLS includes support for LSRs
that can't recognize (IP) packet boundaries in their forwarding
plane. In traditional MPLS TE an LSP that carries IP has to start
and end on a router. Generalized MPLS extends this by requiring an
LSP to start and end on similar type of LSRs. Also, in generalized
MPLS the type of a payload that can be carried by an LSP is extended
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to allow such payloads as SONET/SDH, or 1 or 10Gb Ethernet. These
changes from traditional MPLS are reflected in how labels are
requested and communicated in generalized MPLS, see Sections 3.1 and
3.2. A special case of Lambda switching, called Waveband switching
is also described in Section 3.3.
Another basic difference between traditional and and non-PSC types of
generalized MPLS LSPs, is that bandwidth allocation for an LSP can be
performed only in discrete units, see Section 3.1.1. There are also
likely to be (much) fewer labels on non-PSC links than on PSC links.
Note that the use of Forwarding Adjacencies (FA), see [MPLS-
HIERARCHY], provides a mechanism that may improve bandwidth
utilization, when bandwidth allocation can be performed only in
discrete units, as well as a mechanism to aggregate forwarding state,
thus allowing the number of required labels to be reduced.
Generalized MPLS allows for a label to be suggested by an upstream
node, see Section 3.4. This suggestion may be overridden by a
downstream node but, in some cases, at the cost of higher LSP setup
time. The suggested label is valuable when establishing LSPs through
certain kinds of optical equipment where there may be a lengthy (in
electrical terms) delay in configuring the switching fabric. For
example micro mirrors may have to be elevated or moved, and this
physical motion and subsequent damping takes time. If the labels and
hence switching fabric are configured in the reverse direction (the
norm) the MAPPING/Resv message may need to be delayed by 10's of
milliseconds per hop in order to establish a usable forwarding path.
Generalized MPLS extends on the notion of restricting the range of
labels that may be selected by a downstream node, see Section 3.5.
In generalized MPLS, an ingress or other upstream node may restrict
the labels that may be used by an LSP along either a single hop or
along the whole LSP path. This feature is driven from the optical
domain where there are cases where wavelengths used by the path must
be restricted either to a small subset of possible wavelengths, or to
one specific wavelength. This requirement occurs because some
equipment may only be able to generate a small set of the wavelengths
that intermediate equipment may be able to switch, or because
intermediate equipment may not be able to switch a wavelength at all,
being only able to redirect it to a different fiber.
While traditional traffic engineered MPLS (and even LDP) are
unidirectional, generalized MPLS supports the establishment of
bidirectional LSPs, see Section 4. The need for bidirectional LSPs
come from non-PSC applications. There are multiple reasons why such
LSPs are needed, particularly possible resource contention when
allocating reciprocal LSPs via separate signaling sessions, and
simplifying failure restoration procedures in the non-PSC case.
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Bidirectional LSPs also have the benefit of lower setup latency and
lower number of messages required during setup.
Other features supported by generalized MPLS are rapid failure
notification, see Section 5, and termination of an LSP on a specific
egress port, see Section 6.
3. Label Related Formats
To deal with the widening scope of MPLS into the optical and time
domain, several new forms of "label" are required. These new forms
of label are collectively referred to as a "generalized label". A
generalized label contains enough information to allow the receiving
node to program its cross connect, regardless of the type of this
cross connect, such at the ingress segments of the path are properly
joined. This section defines a generalized label request, a
generalized label, support for waveband switching, suggested label
and label sets.
Note that since the nodes sending and receiving the new form of label
know what kinds of link they are using, the generalized label does
not contain a type field, instead the nodes are expected to know from
context what type of label to expect.
3.1. Generalized Label Request
The Generalized Label Request supports communication of
characteristics required to support the LSP being requested. These
characteristics include desired link protection, LSP encoding, and
LSP payload.
The Generalized Label Request indicates the link protection type
desired for the LSP. If a particular protection type, i.e., 1+1, or
1:N, is requested, then a connection request is processed only if the
desired protection type can be honored. Note that the protection
capabilities of a link may be advertised in routing, see [OMPLS-ISIS,
OMPLS-OSPF]. Path computation algorithms may take this information
into account when computing paths for setting up LSPs.
The Generalized Label Request also carries an LSP encoding parameter,
called LSP Encoding Type. This parameter indicates the encoding
type, e.g., SONET/SDH/GigE etc., that will be used with the data
associated with the LSP. The LSP Encoding Type represents the nature
of the LSP, and not the nature of the links that the LSP traverses.
A link may support a set of encoding formats, where support means
that a link is able to carry and switch a signal of one or more of
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these encoding formats depending on the resource availability and
capacity of the link. For example, consider an LSP signaled with
"photonic" encoding. It is expected that such an LSP would be
supported with no electrical conversion and no knowledge of the
modulation and speed by the transit nodes. If the bit rate is known
but not the modulation then a Clear encoding suffixed with the rate
may be signaled. For example, a bit rate of OC-1 but an encoding
type of clear can be signaled. The transit nodes would not look at
the frames, but would know the bit rate and as a result can do OEO
switching but not OXO switching. All other formats require framing
knowledge, and field parameters are broken into the framing type and
speed as shown below. A REQUEST/Path message SHOULD contain as
specific a LSP Encoding Type as possible to allow the maximum
flexibility in switching by transit LSRs.
3.1.1. Required Information
The Generalized Label Request object/TLV carries the desired
information, the format of which is as follows:
The format of a Generalized Label Request (in RSVP) is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class Num (19)| C_Type (5) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |Link Prot. Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Encoding Type | G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of a Generalized Labels (in CR-LDP) is:
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| 0x0901 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |Link Prot. Type|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Encoding Type | G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Link Protection Type: 8 bits
Indicates the desired link protection type of the connection
setup. A value of 0 implies that this connection does not care
about the available protection type. Other values are defined
in the [OMPLS-ISIS, OMPLS-OSPF] draft, which also defines how
link protection capabilities may be advertised.
LSP Encoding Type: 16 bits
Indicates the required encoding. This field is set by the
ingress node, transparently passed by transit nodes, and used
by the egress node. The following shows permitted values and
their meaning:
Value Bit Rate Encoding
----- -------- --------
0 N/A Packets
OC- SONET 1 <= <= 3072
3072 + STS- SDH 1 <= <= 3072
6144 + OC- Clear 1 <= <= 3072
9217 DS0 DS0
9218 DS1 DS1
9219 E1 E1
9220 DS2 DS2
9221 E2 E2
9222 DS3 DS3
9223 E3 E3
9224 J3 J3
9225 DS4 DS4
9226 E4 E4
9227 J4 J4
9228 1Gbps GigE
9229 10Gbps 10GigE
9230 VT-1.5/TU-11;
9231 VT-2/TU-12;
9232 VT-3;
9233 VT-6/TU-2;
9234 TU-3;
9235 Photonic Lambda
9236 Photonic Waveband
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Generalized PID (G-PID): 16 bits
An identifier of the payload carried by an LSP. Standard
Ethertype values are used (with new Ethertype values defined as
needed). This field is set by the ingress node, transparently
passed by transit nodes, and used by the egress node.
3.1.2. Procedures
A node processing the Path/REQUEST message containing the Generalized
Label Request must verify that the requested parameters can be
satisfied by the node and by the outgoing interface. The node may
either directly support the LSP or it may use a tunnel (FA), i.e.,
another class of switching. In either case, each parameter must be
checked.
Note that local node policy dictates when tunnels may be used and
when they may be created. Local policy may allow for tunnels to be
dynamically established or may be solely administratively controlled.
For more information on tunnels and processing of ER hops when using
tunnels see [MPLS-HIERARCHY].
Transit nodes MUST verify that the outgoing interface or tunnel can
support the requested Link Protection Type. If it cannot, the node
MUST generate a PathErr/NOTIFICATION message, with a "Routing
problem/Unsupported Link Protection" indication.
Transit and egress nodes MUST verify that the node itself and, where
appropriate, that the outgoing interface or tunnel can support the
requested LSP Encoding Type. If encoding cannot be supported, the
node MUST generate a PathErr/NOTIFICATION message, with a "Routing
problem/Unsupported Encoding" indication.
The G-PID parameter is normally only examined at the egress. If the
indicated G-PID cannot be supported then the egress MUST generate a
PathErr/NOTIFICATION message, with a "Routing problem/Unsupported
GPID" indication. In the case of PSC and when penultimate hop
popping (PHP) is requested, the penultimate hop also examines the
(stored) G-PID during the processing of the Resv/MAPPING message. In
this case if the G-PID is not supported, then the penultimate hop
MUST generate a ResvErr/NOTIFICATION message with a "Routing
problem/Unacceptable label value" indication.
When an error message is not generated, normal processing occurs. In
the transit case this will typically result in a Path/REQUEST message
being propagated. In the egress case and PHP special case this will
typically result in a Resv/MAPPING message being generated.
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3.2. Generalized Label
The Generalized Label extends the traditional Label Object in that it
allows the representation of not only labels which travel in-band
with associated data packets, but also labels which identify time-
slots, wavelengths, or space division multiplexed positions. For
example, the Generalized Label may carry a label that represents (a)
a single fiber in a bundle, (b) a single waveband within fiber, (c) a
single wavelength within a waveband (or fiber), or (d) a set of time-
slots within a wavelength (or fiber). It may also carry a label that
represents a generic MPLS label, a Frame Relay label, or an ATM label
(VCI/VPI).
A Generalized Label does not identify the "class" to which the label
belongs. This is implicit in the multiplexing capabilities of the
link on which the label is used.
A Generalized Label object only carries a single level of label,
i.e., it is non-hierarchical. When multiple levels of label (LSPs
within LSPs) are required, each LSP must be established separately,
see [MPLS-HIERARCHY].
The Generalized Label supports link bundling by carrying the identity
of the component link. In the presence of link bundling, each
Generalized Label indicates label(s) within the context of a specific
component link, which is identified by the Link ID (which is carried
as part of Generalized Label). The values used to indicate Link ID
have local significance between two neighbors. Procedures for
determining Link ID are specified elsewhere, see [MPLS-BUNDLE].
Each Generalized Label object carries a variable length label
parameter.
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3.2.1. Required Information
The format of a Generalized Labels (in RSVP) is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class Num (16)| C_Type (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of a Generalized Labels (in CR-LDP) is:
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| 0x0902 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Link ID: 32 bits
Indicates link on which label is being request, from the
message sender's perspective. Used when bundling several
(parallel) links, see [MPLS-BUNDLE]. MUST be zero when
bundling is not being used. Note, values only have
significance between two neighbors and the receiver may need to
convert the received value into a value that has local
significance.
Label: Variable
Carries label information. The semantics of this field depends
on the type of the link over which the label is used.
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3.2.1.1. SDH Labels
For SDH time-slots, the format for the label is given below. If a
single label is given, that label is the lowest time-slot of a
contiguously concatenated signal; the bandwidth of the LSP request
indicates the number of labels to be concatenated to form the SDH
signal trail. If there are multiple labels, then the identified
labels are virtually concatenated to form the SDH signal trail. The
above representation limits virtual concatenation to remain within a
single (component) link.
The format of the label for TDM-LSRs is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S | U | K | L | M |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This is an extension of the numbering scheme defined in G.707 section
7.3, i.e. the (K, L, M) numbering. Each letter indicates a possible
branch number starting at the parent node in the naming tree.
Branches are considered as numbered starting from the high of the
figure, the numbering starts normally at 1 (0 is used to indicate an
exception).
1. S is the index of an STS signal in a multiplex. For SDH, S=1
denotes an STM-0 signal; otherwise, S must be a multiple of 3,
in which case, S/3 is the index of the STM signal.
2. U indicates a specific VC inside a given STS-1 or STM-1
signal. U=1 indicates a single VC-4, while U=2->4 indicates a
specific VC-3 inside the given signal.
3. K indicates possible branches of a VC-4. It is not meaningful
for the VC-3 multiplexing and must be 0 in that case. K=1
indicates that the VC-4 is not further sub-divided. K=2->4
indicates a specific TUG-3 inside the given VC-4. A multiplex
entry name with K=0 denotes a VC-3 multiplexing of an STM-1
(easy to test and read).
4. L indicates possible branches of either a TUG-3 or a VC-3. In
the first case, L=1 indicates that the TUG-3 is not further
sub-divided and contains simply a VC-3. L=2->8 indicates a
specific TUG-2 inside the given TUG-3. In the second case, L=1
indicates that the VC-3 is not further sub-divided. L=2->8
indicates a specific TUG-2 inside the given VC-3.
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5. M indicates possible branches of a TUG-2. It is not meaningful
for an unstructured VC-4, TUG-3 or VC-3, it must be 0 in that
case. M=1 indicates that the TUG-2 is not further sub-divided
and contains simply a VC-2. M=2->4 indicates a specific VC-12
inside the given TUG-2. M=5->8 indicates a specific VC-11
inside the given TUG-2. A multiplex entry name with M=0 denotes
a VC-4 or VC-3.
3.2.1.2. SONET Labels
For SONET time-slots, the format for the label is given below. If a
single label is given, that label is the lowest time-slot of a
contiguously concatenated signal; the bandwidth of the LSP request
indicates the number of labels to be concatenated to form the SONET
signal trail. If there are multiple labels, then the identified
labels are virtually concatenated to form the SONET signal trail. The
above representation limits virtual concatenation to remain within a
single (component) link.
A STS-1 signal can contain seven VT Groups, where each of the VT
Groups can contain only one type of VT (of the four defined types,
namely, VT1.5, VT2, VT3, and VT6). Furthermore, a VT Group can
contain up to four VT1.5s, or three VT2s, or two VT3, or one VT6.
The format of the label for SONET TDM-LSRs is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P | Q | R | S |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where, in the tuple (P,Q,R,S), P denotes the STS-1 number in the STS-
N signal, Q denotes the Virtual Tributary (VT) Group number, R
defines the VT type (one of VT1.5, VT2, VT3, or VT6), and S denotes
the VTx number in the VT type.
3.2.1.3. Port and Wavelength Labels
Some configurations of fiber switching (FSC) and lambda switching
(LSC) use multiple data channels/links controlled by a single control
channel. In such cases the label indicates the data channel/link to
be used for the LSP. Note that this case is not the same as when
[MPLS-BUNDLING] is being used.
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The format of a Port and Wavelength label is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Label: 32 bits
Indicates port/fiber or lambda to be used, from the sender's
perspective. Values used in this field only have significance
between two neighbors, and the receiver may need to convert the
received value into a value that has local significance.
Values may be configured or dynamically determined using a
protocol such as [LMP].
3.2.1.4. Other Labels
Generic MPLS labels and Frame Relay labels are encoded right
justified aligned in 32 bits (4 octets). ATM labels are encoded with
the VPI right justified in bits 0-15 and the VCI right justified in
bits 16-31.
3.2.2. Procedures
The Generalized Label travels in the upstream direction in
MAPPING/Resv messages.
The presence of both a generalized and normal label object in a
Path/REQUEST message is a protocol error and should treated as a
malformed message by the recipient.
If link bundling is not being used, the Link ID MUST be zero on
transmission and ignored when received.
When link bundling is being used, the Link ID MUST contain a non zero
value which uniquely identifies which link (e.g., fiber, waveband or
wavelength) is to contain the label(s). See [MPLS-BUNDLE] for
details.
In the case where the the Link ID uniquely identifies the LSP (e.g.,
wavelength) the label parameter SHOULD be set to zero (0) and MUST be
ignored when received.
The recipient of a Resv/MAPPING message containing a Generalized
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Label verifies that the values passed are acceptable. If the Link ID
is being used and the value is unknown, the recipient MUST generate a
ResvErr/NOTIFICATION message with a "Routing problem/Unknown Link ID"
indication. If the combination of the Link ID value (when
applicable) and label is unacceptable then the recipient MUST
generate a ResvErr/NOTIFICATION message with a "Routing problem/MPLS
label allocation failure" indication.
3.3. Waveband Switching
A special case of lambda switching is waveband switching. A waveband
represents a set of contiguous wavelengths which can be switched
together to a new waveband. For optimization reasons it may be
desirable for an optical cross connect to optically switch multiple
wavelengths as a unit. This may reduce the distortion on the
individual wavelengths and may allow tighter separation of the
individual wavelengths. The Waveband Label is defined to support
this special case.
Waveband switching naturally introduces another level of label
hierarchy and as such the waveband is treated the same way all other
upper layer labels are treated.
As far as the MPLS protocols are concerned there is little difference
between a waveband label and a wavelength label except that
semantically the waveband can be subdivided into wavelengths whereas
the wavelength can only be subdivided into time or statistically
multiplexed labels.
3.3.1. Required information
Waveband switching uses the same format as the generalized label, see
section 3.2.1. For compatibility reasons, a new RSVP c-type and CR-
LDP type is assigned for the Waveband Label.
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In the context of waveband switching, the generalized label 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Waveband Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Waveband Id: 32 bits
A waveband identifier. The value is selected by the sender and
reused in all subsequent related messages.
Start Label: 32 bits
Indicates the channel identifier, from the sender's
perspective, of the lowest value wavelength making up the
waveband.
End Label: 32 bits
Indicates the channel identifier, from the sender's
perspective, of the highest value wavelength making up the
waveband.
Channel identifiers are established either by configuration or by
means of a protocol such as LMP [LMP]. They are normally used in the
link id parameter of the Generalized Label Request when bundling is
being used or the label parameter for PSC and LSC links when bundling
is not being used.
3.3.2. Procedures
The procedures defined in Section 3.2.2 apply to waveband switching.
This includes generating a ResvErr/NOTIFICATION message with a
"Routing problem/MPLS label allocation failure" indication if any of
the label fields are unrecognized or unacceptable.
Additionally, when a waveband is switched to another waveband, it is
possible that the wavelengths within the waveband will be mirrored
about a center frequency. When this type of switching is employed,
the start and end label in the waveband label object MUST be flipped
before forwarding the label object with the new waveband Id. In this
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manner an egress/ingress LSR which receives a waveband label which
has these values inverted, knows that it must also invert its egress
association to pick up the proper wavelengths. Without this
mechanism and with an odd number of mirrored switching operations,
the egress LSRs will not know that an input wavelength of say L1 will
emerge from the waveband tunnel as L100.
This operation MUST be performed in both directions when a
bidirectional waveband tunnel is being established.
3.4. Suggested Label
The Suggested Label is used to provide a downstream node with the
upstream node's label preference. This permits the upstream node to
start configuring it's hardware with the proposed label before the
label is communicated by the downstream node. Such early
configuration is valuable to systems that take non-trivial time to
establish a label in hardware. Such early configuration can reduce
setup latency, and may be important for restoration purposes where
alternate LSPs may need to be rapidly established as a result of
network failures.
The use of Suggested Label is only an optimization. If a downstream
node passes a different label upstream, an upstream LSR MUST
reconfigure itself so that it uses the label specified by the
downstream node, thereby maintaining the downstream control of a
label.
3.4.1. Required Information and Processing
The format of a suggested label is identical to a generalized label.
It is used in Path/REQUEST messages. In RSVP the Suggested Label
uses a new class number (TBD of form 10bbbbbb) and the C-type of the
label being suggested. In CR-LDP, Suggested Label uses type = 0x904.
Errors in received Suggested Labels MUST be ignored. This includes
any received inconsistent or unacceptable values.
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3.5. Label Set
The Label Set is used to limit the label choices of a downstream node
to a set of acceptable labels. This limitation applies on a per hop
basis.
There are four cases where a Label Set is useful in the optical
domain. The first case is where the end equipment is only capable of
transmitting and receiving on a small specific set of
wavelengths/bands. The second case is where there are a sequence of
interfaces which cannot support wavelength conversion (CI-incapable)
and require the same wavelength be used end-to-end over a sequence of
hops, or even an entire path. The third case is where it is
desirable to limit the amount of wavelength conversion being
performed to reduce the distortion on the optical signals. The last
case is where two ends of a link support different sets of
wavelengths.
Label Set is used to restrict label ranges that may be used for a
particular LSP between two peers. The receiver of a Label Set must
restrict its choice of labels to one which is in the Label Set. Much
like a label, a Label Set may be present across multiple hops. In
this case each node generates it's own outgoing Label Set, possibly
based on the incoming Label Set and the node's hardware capabilities.
This case is expected to be the norm for nodes with conversion
incapable (CI-incapable) interfaces.
The use of Label Set is optional, if not present, all labels from the
valid label range may be used. Conceptually the absence of a Label
Set implies a Label Set whose value is {U}, the set of all valid
labels.
3.5.1. Required Information
This LabelSet is used in Path/REQUEST messages.
The data required to support the Label Set consists of a variable
sized array of labels, or label ranges. These labels are subchannel
identifiers and MUST lie within the link identified in Generalized
Label Request.
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The format of a LabelSet (in RSVP) is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class Num (xx)|C_Type (xx) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of a LabelSet (in CR-LDP) is:
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=0x0904 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 2 bits
0x00 means subchannel is a single element (inclusive)
0x01 means subchannel is a start element (inclusive)
0x02 means subchannel is an end element (inclusive)
0x03 means subchannel is a single element (exclusive)
Subchannel:
The subchannel represents the label (wavelength, fiber ... )
which is eligible for allocation. This field has the same
format as described for labels under section 3.2.
Since subchannel to local channel identifiers (e.g.,
wavelength) mappings are a local matter, when a Label Set is
propagated from one node to the next, the subchannels may have
to be remapped to new subchannel values for consistency.
A Label Set can be just a series of single elements (Type=0x00)
sorted in increasing order of subchannel value.
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A Label Set can be a set of ranges (Type=0x01 followed by Type=0x02).
The ranges MUST be sorted. A range which is missing a beginning or
an end implies no bound where the bound is missing. A range which
contains a Type=0x03 (exclusive) means all subchannels in the range
except that subchannel are eligible.
3.5.2. Procedures
The absence of a Label Set implies that all labels are acceptable. A
Label Set is included when a node wishes to restrict the label(s)
that may be used downstream.
On reception of a Path/REQUEST message a CI-capable interface will
restrict its choice of labels to one which is in the Label Set. The
CI-capable receiver may also remove the Label Set prior to forwarding
the Path/REQUEST message. If the node is unable to pick a label from
the Label Set, then the request is terminated and a
PathErr/NOTIFICATION message with a "Routing problem/Label Set"
indication MUST be generated. It is a local matter if the Label Set
is stored for later selection on the RESV/Mapping or if the selection
is made immediately for propagation in the RESV/Mapping.
On reception of a Path/REQUEST message for a CI-incapable interface,
the Label Set in the message is compared against the set of available
labels at the downstream interface and the resulting intersecting
Label Set is forwarded in a Path/REQUEST message. When the resulting
Label Set is empty, the Path/REQUEST must be terminated, and a
PathErr/NOTIFICATION message, and a "Routing problem/Label Set"
indication MUST be generated. Note that intersection is based on the
physical labels (actual wavelength/band values) which may have
different logical values on different links, as a result it is the
responsibility of the node to map these values so that they have a
consistent physical meaning, or to drop the particular values from
the set if no suitable logical label value exists.
On reception of a Resv/MAPPING message at an intermediate node, the
label to propagate upstream is selected from within the (stored)
Label Set (preferred) or may be preselected from that set to save
memory.
Note, on reception of a Resv/MAPPING message for an interface which
is CI-incapable it has no other choice than to use the same physical
label (wavelength/band) as received in the Resv/MAPPING. In this
case, the use and propagation of a Label Set will significantly
reduce the chances that this allocation will fail when CI-incapable
nodes are traversed.
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4. Bidirectional LSPs
This section defines direct support of bidirectional LSPs. Support
is defined for LSPs that have the same traffic engineering
requirements including fate sharing, protection and restoration, and
resource requirements (e.g., latency and jitter) in each direction.
In the remainder of this section, the term "initiator" is used to
refer to a node that starts the establishment of an LSP and the term
"terminator" is used to refer to the node that is the target of the
LSP. Note that for bidirectional LSPs, there is only one "initiator"
and one "terminator".
Normally to establish a bidirectional LSP when using [RSVP-TE] or
[CR-LDP] two unidirectional paths must be independently established.
This approach has the following disadvantages:
* The latency to establish the bidirectional LSP is equal to one
round trip signaling time plus one initiator-terminator signaling
transit delay. This not only extends the setup latency for
successful LSP establishment, but it extends the worst-case
latency for discovering an unsuccessful LSP to as much as two
times the initiator-terminator transit delay. These delays are
particularly significant for LSPs that are established for
restoration purposes.
* The control overhead is twice that of a unidirectional LSP.
This is because separate control messages (e.g. Path and Resv)
must be generated for both segments of the bidirectional LSP.
* Because the resources are established in separate segments,
route selection is complicated. There is also additional
potential race for conditions in assignment of resources, which
decreases the overall probability of successfully establishing
the bidirectional connection.
* It is more difficult to provide a clean interface for SONET
equipment that may rely on bidirectional hop-by-hop paths for
protection switching. Note that existing SONET gear transmits
the control information in-band with the data.
* Bidirectional optical LSPs (or lightpaths) are seen as a
requirement for many optical networking service providers.
With bidirectional LSPs both the downstream and upstream data paths,
i.e., from initiator to terminator and terminator to initiator, are
established using a single set of Path/REQUEST and Resv/MAPPING
messages. This reduces the setup latency to essentially one
initiator-terminator round trip time plus processing time, and limits
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the control overhead to the same number of messages as a
unidirectional LSP.
4.1. Required Information
For bidirectional LSPs, two labels must be allocated. Bidirectional
LSP setup is indicated by the presence of an Upstream Label in the
REQUEST/Path message. An Upstream Label has the same format as the
generalized label, see Section 3.2. In RSVP the Upstream Label uses
a new class number (TBD of form 0bbbbbbb) and the C-type of the label
being suggested. In CR-LDP, Upstream Label uses type=0x0906
4.2. Procedures
The process of establishing a bidirectional LSP follows the
establishment of a unidirectional LSP with some additions. To
support bidirectional LSPs an Upstream Label is added to the
Path/REQUEST message. The Upstream Label MUST indicate a label that
is valid for forwarding at the time the Path/REQUEST message is sent.
When a Path/REQUEST message containing an Upstream Label is received,
the receiver first verifies that the upstream label is acceptable.
If the label is not acceptable, the receiver MUST issue a
PathErr/NOTIFICATION message with a "Routing problem/Unacceptable
label value" indication.
An intermediate node must also allocate a label on the outgoing
interface and establish internal data paths before filling in an
outgoing Upstream Label and propagating the Path/REQUEST message. If
an intermediate node is unable to allocate a label or internal
resources, then it MUST issue a PathErr/NOTIFICATION message with a
"Routing problem/Label allocation failure" indication.
Terminator nodes process Path/REQUEST messages as usual, with the
exception that the upstream label can immediately be used to
transport associated data upstream to the initiator.
When a bidirectional LSP is removed, both upstream and downstream
labels are invalidated and it is no longer valid to send data using
the associated labels.
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4.3. Contention Resolution
Contention for labels may occur between two bidirectional LSP setup
requests traveling in opposite directions. This contention occurs
when both sides allocate the same resources (ports) at effectively
the same time. If there is no restriction on the ports that can be
used for bidirectional LSPs and if there are alternate resources,
then both nodes will pass different labels upstream and the
contention will be resolved naturally. However, if there is a
restriction on the ports that can be used for the bidirectional LSPs
(for example, if they must be physically coupled on a single I/O
card), or if there are no more resources available, then the
contention must be resolved by other means. To resolve contention,
the node with the higher node ID will win the contention and it MUST
issue a PathErr/NOTIFICATION message with a "Routing problem/Label
allocation failure" indication. Upon receipt of such an error, the
node SHOULD try to allocate a different Upstream label (and a
different Suggested Label if used) to the bidirectional path.
However, if no other resources are available, the node must proceed
with standard error handling. For the purposes of RSVP contention
resolution, the node ID is the IP address used in the RSVP_HOP
object.
To reduce the probability of contention, one may impose a policy that
the node with the lower ID never suggests a label in the downstream
direction and always accepts a Suggested Label from an upstream node
with a higher ID. Furthermore, since the label sets are exchanged
using LMP [LMP], an alternative local policy could further be imposed
such that (with respect to the higher numbered node's label set) the
higher numbered node could allocate labels from the high end of the
label range while the lower numbered node allocates labels from the
low end of the label range. This mechanism would augment any close
packing algorithms that may be used for bandwidth (or wavelength)
optimization.
An example of contention between two nodes (PXC 1 and PXC 2) is shown
in Figure 1. In this example PXC 1 assigns an Upstream Label for the
channel corresponding to local BCId=2 (local BCId=7 on PXC 2) and
sends a Suggested Label for the channel corresponding to local BCId=1
(local BCId=6 on PXC 2). Simultaneously, PXC 2 assigns an Upstream
Label for the channel corresponding to its local BCId=6 (local BCId=1
on PXC 1) and sends a Suggested Label for the channel corresponding
to its local BCId=7 (local BCId=2 on PXC 1). If there is no
restriction on the ports that can be used for bidirectional LSPs and
if there are alternate resources available, then both PXC 1 and PXC 2
will pass different labels upstream and the contention is resolved
naturally (see Fig. 2). However, if there is a restriction on the
ports that can be used for bidirectional LSPs (for example, if they
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must be physically coupled on a single I/O card), then the contention
must be resolved using the router Id (see Fig. 3).
+------------+ +------------+
+ PXC 1 + + PXC 2 +
+ + SL1,UL2 + +
+ 1 +------------------------>+ 6 +
+ + UL1, SL2 + +
+ 2 +<------------------------+ 7 +
+ + + +
+ + + +
+ 3 +------------------------>+ 8 +
+ + + +
+ 4 +<------------------------+ 9 +
+------------+ +------------+
Figure 1. Label Contention
In this example, PXC 1 assigns an Upstream Label using BCId=2 (BCId=7
on PXC 2) and a Suggested Label using BCId=1 (BCId=6 on PXC 2).
Simultaneously, PXC 2 assigns an Upstream Label using BCId=6 (BCId=1
on PXC 1) and a Suggested Label using BCId=7 (BCId=2 on PXC 1).
+------------+ +------------+
+ PXC 1 + + PXC 2 +
+ + UL2 + +
+ 1 +------------------------>+ 6 +
+ + UL1 + +
+ 2 +<------------------------+ 7 +
+ + + +
+ + L1 + +
+ 3 +------------------------>+ 8 +
+ + L2 + +
+ 4 +<------------------------+ 9 +
+------------+ +------------+
Figure 2. Label Contention Resolution without resource restrictions
In this example, there is no restriction on the ports that can be
used by the bidirectional connection and contention is resolved
naturally.
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+------------+ +------------+
+ PXC 1 + + PXC 2 +
+ + UL2 + +
+ 1 +------------------------>+ 6 +
+ + L2 + +
+ 2 +<------------------------+ 7 +
+ + + +
+ + L1 + +
+ 3 +------------------------>+ 8 +
+ + UL1 + +
+ 4 +<------------------------+ 9 +
+------------+ +------------+
Figure 3. Label Contention Resolution with resource restrictions
In this example, ports 1,2 and 3,4 on PXC 1 (ports 6,7 and 8,9 on PXC
2, respectively) must be used by the same bidirectional connection.
Since PXC 2 has a higher node ID, it wins the contention and PXC 1
must use a different set of labels.
5. Notification
This section defines two signaling extensions that enable expedited
notification of failures and other events to nodes responsible for
restoring failed LSPs. The first extension, the Notify message,
provides for general event notification. The second allows for the
combining of such notifications in a single message. These
extensions are RSVP specific.
5.1. Notify Message
The Notify message provides a mechanism to inform non-adjacent nodes
of LSP related events. This message differs from the currently
defined error messages (i.e., PathErr and ResvErr messages of RSVP)
in that it can be "targeted" to a node other than the immediate
upstream or downstream neighbor and that it is a generalized
notification mechanism. The Notify message does not replace existing
error messages. The Notify message may be sent either (a) normally,
where non-target nodes just forward the Notify message to the target
node, similar to ResvConf processing in [RSVP]; or (b) encapsulated
in a new IP header who's destination is equal to the target IP
address. Regardless of the transmission mechanism, nodes receiving a
Notify message not destined to the node forward the message,
unmodified, towards the target.
To support reliable delivery of the Notify message, an Ack Message
[RSVP-RR] is used to acknowledge the receipt of a Notify Message. A
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node that receives the a Notify message MUST send a Notify_Ack
message confirming receipt of the Notify message.
5.1.1. Required Information
The Notify message is a generalized notification message. The IP
destination address is set to the IP address of the intended
receiver. The Notify message is sent without the router alert
option.
::= []
[...]
[]
::=
[] []
The ERROR_SPEC object specifies the error and includes the IP address
of either the node that detected the error or the link that has
failed. See ERROR_SPEC definition in RFC2205. The MESSAGE_ID object
is defined in [RSVP-RR].
Note: for CR-LDP there is not currently a similar mechanism. In CR-
LDP, when a failure is detected it will be propagated with
RELEASE/WITHDRAW messages radially outward from the point of failure.
Resources are to be released in this phase and actual resource
information is fed back to the source using the feedback mechanisms
of [FEEDBACK]. In this manner the source will have an accurate view
of available resources and can start rerouting much sooner.
5.2. Non-Adjacent Message Bundling
[RSVP-RR] defines the bundle message which can be used to aggregate
multiple signaling messages into a single packet. The defined
mechanism is limited to adjacent RSVP nodes. This section defines
the use of the bundle message between non-adjacent nodes. This is
accomplished by setting the IP destination address of the bundle
message to the address of the target node. The non-adjacent bundle
message may be sent either (a) normally, where non-target nodes just
forward the message to the target node (see ResvConf processing in
[RSVP] for reference); or (b) encapsulated in a new IP header who's
destination is equal to the target IP address. Regardless of the
transmission mechanism, nodes receiving a bundle message not destined
to the node just forward the message, unmodified, towards the target.
The motivation for supporting non-adjacent message bundling is to
support the bundling of Notify Messages.
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Non-adjacent bundle messages can only be sent to RSVP nodes that
support bundling. Currently, the only method for discovering such
information about a non-adjacent node is through manual
configuration.
5.2.1. Required Information
The RSVP bundle message is defined in [RSVP-RR]. The only
modification from what is specified in [RSVP-RR] is that the IP
destination address does not have to be an immediate
upstream/downstream neighbor.
6. Egress Control
The LSR at the head-end of an LSP can control the termination of the
LSP by using the ERO. To terminate an LSP on a particular outgoing
interface of the egress LSR, the head-end may specify the IP address
of that interface as the last element in the ERO, provided that that
interface has an associated IP address.
There are cases where the use of IP address doesn't provide enough
information to uniquely identify the egress termination. One case is
when the outgoing interface on the egress LSR is a component link of
a link bundle. Another case is when it is desirable to "splice" two
LSPs together, i.e., where the tail of the first LSP would be
"spliced" into the head of the second LSP. This last case is more
likely to be used in the non-PSC classes of links.
6.1. Required Information
To handle scenarios described in the previous paragraph, the ERO
subobject Egress Label type is introduced.
For RSVP, this ERO subobject - Egress Label is defined as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For CR-LDP the Egress Label ER-Hop is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| 0x901 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Reserved | Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID (continued) | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (continued) |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L
This bit must be set to 0.
Type (RSVP Only)
3 Egress Label (To be assigned)
Length
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. The Length is always
divisible by 4.
Link ID
Same definition as in Generalized Label. See Section 3.2.1.
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Label
When an LSP has to be spliced into another LSP, this field
identifies the label that the tail of the first LSP has to use
in order to slice it into the head of the second LSP. In such
cases the format of this field is identical to the one used by
the Label field in the Generalized Label Object. In all other
cases this field is omitted.
6.2. Procedures
The Egress Label subobject may appear only as the last subobject in
the ERO/ER. Appearance of this subobject anywhere else in the ERO/ER
is treated as a "Bad strict node" error.
During an LSP setup, when a node processing the ERO/RR performs Next
Hop selection finds that the second subobject is an Egress Label
Subobject, the node uses the information carried in this subobject to
determine the handling of the data received over that LSP.
Specifically, if the Link ID field of the subobject is non zero, then
this field identifies a specific (outgoing) link of the node that
should be used for sending all the data received over the LSP. If
the Label field of the subobject is not Implicit NULL label, this
field specifies the label that should be used as an outgoing label on
the data received over the LSP.
Procedures by which an LSR at the head-end of an LSP obtains the
information needed to construct the Egress Label subobject are
outside the scope of this document.
7. Acknowledgments
This draft is the work of numerous authors and consists of a
composition of a number of previous drafts in this area. A list of
the drafts from which material and ideas were incorporated follows:
draft-saha-rsvp-optical-signaling-00.txt
draft-lang-mpls-rsvp-oxc-00.txt
draft-kompella-mpls-optical-00.txt
draft-fan-mpls-lambda-signaling-00.txt
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8. Security Considerations
This draft does not introduce any new security considerations to
either [CR-LDP] or [RSVP-TE].
9. References
[CR-LDP] Jamoussi et al., "Constraint-Based LSP Setup using LDP",
draft-ietf-mpls-cr-ldp-04.txt, July, 2000.
[LDP] Andersson et al., "LDP Specification",
draft-ietf-mpls-ldp-08.txt, June 2000.
[LMP] Lang, J.P., Mitra, K., Drake, J., Kompella, K., Rekhter, Y.,
Saha, D., Berger, L., Basak, D., "Link Management Protocol",
Internet Draft, draft-lang-mpls-lmp-01.txt, July 2000.
[MPLS-ARCH] Rosen et al., "Multiprotocol label switching
Architecture", Internet Draft,
draft-ietf-mpls-arch-06.txt, August 1999.
[MPLS-BUNDLE] Kompella, K., Rekhter, Y., and Berger, L., "Link Bundling
in MPLS Traffic Engineering", Internet Draft,
draft-kompella-mpls-bundle-02.txt, July 2000.
[MPLS-HIERARCHY] Kompella, K., and Rekhter, Y., "LSP Hierarchy with
MPLS TE", Internet Draft,
draft-ietf-mpls-lsp-hierarchy-00.txt, July 2000.
[OMPLS-ISIS] Kompella, K., Rekhter, Y., Banerjee, A., Drake, J.,
Bernstein, G., Fedyk, D., Mannie, E., Saha, D., and
Sharma, V., "IS-IS Extensions in Support of MPL(ambda)S",
Internet Draft, draft-ompls-isis-extensions-00.txt,
July 2000.
[OMPLS-OSPF] Kompella, K., Rekhter, Y., Banerjee, A., Drake, J.,
Bernstein, G., Fedyk, D., Mannie, E., Saha, D., and
Sharma, V., "OSPF Extensions in Support of MPL(ambda)S",
Internet Draft, draft-ompls-ospf-extensions-00.txt,
July 2000.
[RSVP-TE] Awduche, D.O., Berger, L., Gan, D.-H., Li, T., Swallow, G.,
and Srinivasan, V., "RSVP-TE: Extensions to RSVP for LSP
Tunnels," Internet Draft,
draft-ietf-mpls-rsvp-lsp-tunnel-06.txt, July 2000.
[RSVP-RR] Berger L., Gan D., Swallow G., Pan P., Tommasi F.,
Berger, Ashwood-Smith, editors [Page 31]
Internet Draftraft-ashwood-generalized-mpls-signaling-00.txt June 2000
Molendini S., "RSVP Refresh Overhead Reduction Extensions",
draft-ietf-rsvp-refresh-reduct-05.txt, June 2000.
[FEEDBACK] P. Ashwood-Smith, B. Jamoussi, D. Fedyk, D. Skalecki,
"Improving Topology Data Base Accuracy With LSP Feedback
via CR-LDP", Internet Draft, draft-ietf-mpls-te-feed-00.txt.
10. Authors' Addresses
Peter Ashwood-Smith
Nortel Networks Corp.
P.O. Box 3511 Station C,
Ottawa, ON K1Y 4H7
Canada
Phone: +1 613 763 4534
Email: petera@nortelnetworks.com
Ayan Banerjee
Calient Networks
5853 Rue Ferrari
San Jose, CA 95138
Phone: +1 408 972-3645
Email: abanerjee@calient.net
Lou Berger
LabN Consulting, LLC
Phone: +1 301 468 9228
Email: lberger@labn.net
Greg Bernstein
Ciena Corporation
10480 Ridgeview Court
Cupertino, CA 94014
Phone: +1 408 366 4713
Email: greg@ciena.com
John Drake
Calient Networks
5853 Rue Ferrari
San Jose, CA 95138
Phone: +1 408 972 3720
Email: jdrake@calient.net
Berger, Ashwood-Smith, editors [Page 32]
Internet Draftraft-ashwood-generalized-mpls-signaling-00.txt June 2000
Yanhe Fan
Nortel Networks
PO Box 3511 Station C
Ottawa, ON, K1Y 4H7
Canada
Phone: +1 613 765 2315
Email: yanhe@nortelnetworks.com
Kireeti Kompella
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
Email: kireeti@juniper.net
Jonathan P. Lang
Calient Networks
25 Castilian
Goleta, CA 93117
Email: jplang@calient.net
Eric Mannie
Optical Networking
Network R&D
GTS Network Services
Terhulpsesteenweg 6A
1560 Hoeilaart - Belgium
Phone: +32 2 658 56 52
Mobile: +32 496 58 56 52
Fax: +32 2 658 51 18
Email: eric.mannie@gtsgroup.com
Bala Rajagopalan
Tellium, Inc.
2 Crescent Place
P.O. Box 901
Oceanport, NJ 07757-0901
Phone: +1 732 923 4237
Fax: +1 732 923 9804
Email: braja@tellium.com
Yakov Rekhter
cisco Systems
Email: yakov@cisco.com
Berger, Ashwood-Smith, editors [Page 33]
Internet Draftraft-ashwood-generalized-mpls-signaling-00.txt June 2000
Debanjan Saha
Tellium Optical Systems
2 Crescent Place
Oceanport, NJ 07757-0901
Phone: +1 732 923 4264
Fax: +1 732 923 9804
Email: dsaha@tellium.com
Vishal Sharma
Tellabs Research Center
One Kendall Square
Bldg. 100, Ste. 121
Cambridge, MA 02139-1562
Phone: +1 617 577 8760
Email: Vishal.Sharma@tellabs.com
Z. Bo Tang
Tellium, Inc.
2 Crescent Place
P.O. Box 901
Oceanport, NJ 07757-0901
Phone: +1 732 923 4231
Fax: +1 732 923 9804
Email: btang@tellium.com
Berger, Ashwood-Smith, editors [Page 34]
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