Network Working Group Peter Ashwood-Smith (Nortel Networks Corp.)
Internet Draft Ayan Banerjee (Calient Networks)
Expiration Date: April 2001 Lou Berger (Movaz Networks)
Greg Bernstein (Ciena Corporation)
John Drake (Calient Networks)
Yanhe Fan (Axiowave Networks)
Kireeti Kompella (Juniper Networks, Inc.)
Eric Mannie (GTS Network Services)
Jonathan P. Lang (Calient Networks)
Bala Rajagopalan (Tellium, Inc.)
Yakov Rekhter (Cisco Systems)
Debanjan Saha (Tellium, Inc.)
Vishal Sharma (Tellabs)
George Swallow (Cisco Systems)
Z. Bo Tang (Tellium, Inc.)
October 2000
Generalized MPLS - Signaling Functional Description
draft-ietf-mpls-generalized-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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Internet-Drafts are draft documents valid for a maximum of six months
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To view the current status of any Internet-Draft, please check the
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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 ................................................ 3
2 Overview ................................................... 4
3 Label Related Formats ...................................... 6
3.1 Generalized Label Request ................................... 6
3.2 Generalized Label ........................................... 14
3.3 Waveband Switching .......................................... 20
3.4 Suggested Label ............................................. 21
3.5 Label Set ................................................... 22
4 Bidirectional LSPs .......................................... 25
4.1 Required Information ........................................ 26
4.2 Procedures .................................................. 26
4.3 Contention Resolution ....................................... 27
5 Notification ................................................ 29
5.1 Notify Request Object ....................................... 30
5.2 Notify Message .............................................. 31
5.3 Removing State with a PathErr message ....................... 32
6 Explicit Label Control ...................................... 33
6.1 Required Information ........................................ 34
6.2 Procedures .................................................. 35
7 RSVP Message Formats ........................................ 36
8 Acknowledgments ............................................. 37
9 Security Considerations ..................................... 37
10 References .................................................. 38
11 Authors' Addresses .......................................... 39
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Changes from previous version:
o Removed Link ID in labels, redundant with [MPLS-BUNDLE].
o Revised Generalized Label Request and SDH/SONET encodings
o Added Notify Request object
o Added multiple sender notifies per Notify message
o Added ability to remove path state on sending PathErr
o Removed Non-Adjacent Message Bundling
o Enabled label specification via ERO/ER
o Added Section 7
o Minor text cleanup
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
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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).
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
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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
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
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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.
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 that 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 [GMPLS-ISIS,
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GMPLS-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
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. 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. A Generalized Label
Request object/TLV is set by the ingress node, transparently passed
by transit nodes, and used by the egress node.
3.1.1. Generalized Label Request Format
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 (4)[TBA]|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Link Prot.Flags| G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of a Generalized Label Request (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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Link Prot.Flags| G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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LSP Encoding Type: 8 bits
Indicates the encoding of the LSP being requested. The
following shows permitted values and their meaning:
Value Type
----- ----
1 Packet
2 Ethernet
3 ANSI PDH
4 ETSI PDH
5 SDH
6 SONET
7 Digital Wrapper
8 Lambda (photonic)
9 Fiber
The ANSI PDH and ETSI PDH types designate these respective
networking technologies. DS1 and DS3 are examples of ANSI PDH
LSPs. An E1 LSP would be ETSI PDH. The Lambda encoding type
refers to the switching of wavelengths. The Fiber encoding
type refers to switching at the fiber port level.
Link Protection Flags: 8 bits
Link Protection Flags indicate the desired protection level(s)
for each link along the LSP. Note that the flags are distinct
from MPLS-level LSP protection, see [RECOVERY]. A value of 0
implies that this connection does not care about which, if any,
link protection is used. More than one bit may be set to
indicate when multiple protection types are acceptable. When
multiple bits are set and multiple protection types are
available, the choice of protection type is a local (policy)
decision.
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The following flags are defined:
0x01 Unprotected
Indicates that the LSP should not use any link layer
protection.
0x02 Shared
Indicates that a shared link layer protection scheme,
such as 1:N protection, should be used to support the
LSP.
0x04 Dedicated 1:1
Indicates that a dedicated link layer protection scheme,
i.e., 1:1 protection, should be used to support the LSP.
0x08 Dedicated 1+1
Indicates that a dedicated link layer protection scheme,
i.e., 1+1 protection, should be used to support the LSP.
0x10 Enhanced
Indicates that a protection scheme that is more reliable
than Dedicated 1+1 should be used, e.g., 4 fiber BLSR/MS-
SPRING.
Generalized PID (G-PID): 16 bits
An identifier of the payload carried by an LSP, i.e. an
identifier of the client layer of that LSP. This must be
interpreted according to the technology encoding type of the
LSP and is used by the nodes at the endpoints of the LSP.
Standard Ethertype values are used for packet and Ethernet
LSPs; other values are:
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Value Type Technology
----- ---- ----------
0 Unknown All
1 DS1 SF ANSI-PDH
2 DS1 ESF ANSI-PDH
3 DS3 M23 ANSI-PDH
4 DS3 C-Bit Parity ANSI-PDH
5 Asynchronous mapping of E4 SDH
6 Asynchronous mapping of DS3/T3 SDH
7 Asynchronous mapping of E3 SDH
8 Bit synchronous mapping of E3 SDH
9 Byte synchronous mapping of E3 SDH
10 Asynchronous mapping of DS2/T2 SDH
11 Bit synchronous mapping of DS2/T2 SDH
12 Byte synchronous mapping of DS2/T2 SDH
13 Asynchronous mapping of E1 SDH
14 Byte synchronous mapping of E1 SDH
15 Byte synchronous mapping of 31 * DS0 SDH
16 Asynchronous mapping of DS1/T1 SDH
17 Bit synchronous mapping of DS1/T1 SDH
18 Byte synchronous mapping of DS1/T1 SDH
19 Same as 12 but in a VC-12 SDH
20 Same as 13 but in a VC-12 SDH
21 Same as 14 but in a VC-12 SDH
22 ATM mapping SDH, SONET
22 DS1 SF Asynchronous SONET
23 DS1 ESF Asynchronous SONET
24 DS3 M23 Asynchronous SONET
25 DS3 C-Bit Parity Asynchronous SONET
26 VT SONET
27 POS SONET
28 STS SONET
29 Ethernet Lambda, Fiber
30 SDH Lambda, Fiber
31 SONET Lambda, Fiber
32 Digital Wrapper Lambda, Fiber
33 Lambda Fiber
3.1.2. Generalized Label Request with SONET/SDH Label Range
The Generalized Label Request with SONET/SDH Label Range object/TLV
is used to represent specific characteristics related to the two TDM
technologies. If the RGT, RT, and RNC, fields are all set to zero, it
means that no concatenation, bundling or transparency is requested.
If the requested LSP is itself a grouping of several components (e.g.
a SONET concatenation), it is assumed that all components have the
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same characteristics. Note that the bandwidth carried in the
signaling messages, see Section 3.1.4, are the aggregate bandwidth;
in the instance where multiple components are signaled for, the
individual component bandwidth is obtained by dividing this
aggregated value by the requested number of components.
The format of a Generalized Label Request with SONET/SDH Label Range
(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)[TBA]|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Link Prot.Flags| G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RGT | RT | Reserved | RNC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of a Generalized Label Request with SONET/SDH label range
(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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Link Prot.Flags| G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RGT | RT | Reserved | RNC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LSP Encoding Type: 8 bits
See Section 3.1.1.
Link Protection Flags: 8 bits
See Section 3.1.1.
Generalized PID (G-PID): 16 bits
See Section 3.1.1.
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Requested Grouping Type (RGT): 4 bits
This field indicates the SDH/SONET type of grouping requested
for the LSP, it is used to constraint the type of
concatenation. The values are defined in the following table:
Value Grouping type
----- ----------------------------------
0 (Implies no concatenation/bundling when RNC = RT = 0)
1 Virtual concatenation
2 Contiguous standard concatenation
3 Contiguous arbitrary concatenation
4 Inverse Multiplexing
Requested Transparency (RT): 4 bits
This field indicates the type of SDH/SONET transparency
("emulation") requested for that LSP. The values are defined in
the following table:
Value Requested transparency
----- ----------------------------------------------
0 (Implies no concatenation/bundling when RNC = RGT = 0)
1 SDH Regenerator Section/SONET Section transparency
2 SDH Multiplex Section/SONET Line transparency
3 SDH Path/SONET Path transparency
Requested Number of Components (RNC): 16 bits
This field indicates the number of identical SDH/SONET signal
types that are requested to be concatenated or inverse
multiplexed in that LSP, as specified in the previous field. In
these cases, the bandwidth of each component of that
concatenation/bundling is obtained by dividing the aggregate
bandwidth by the number of components requested. It is assumed
that all these components have identical characteristics. This
field is set to zero if non concatenation or bundling is
requested.
3.1.3. Procedures
A node processing the Path/REQUEST message containing the Generalized
Label Request must verify that the requested parameters can be
satisfied by the incoming interface, 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.
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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 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.
Transit nodes MUST verify that the outgoing interface or tunnel can
support the requested Link Protection Flags. If it cannot, the node
MUST generate a PathErr/NOTIFICATION message, with a "Routing
problem/Unsupported Link Protection" 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.
3.1.4. Bandwidth Encoding
Bandwidth encodings are carried in the SENDER_TSPEC and FLOWSPEC
objects in RSVP and in the Traffic Parameters TLV in CR-LDP. They
are carried in 32 bit number in IEEE floating point format (the unit
is bytes per second). For non-packet LSPs, it is useful to define
discrete values to identify the bandwidth of the LSP. Some typical
values for the requested bandwidth are enumerated below. Additional
values will be defined as needed. These values are set in the Peak
Data Rate field of Int-Serv objects carried in RSVP messages and in
the Peak and Committed Data Rate fields of the Traffic Parameters TLV
carried in CR-LDP messages. Other bandwidth/service related
parameters in the object/TLV are ignored and carried transparently.
Some typical values for the requested bandwidth are enumerated below.
Additional values will be defined as needed.
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Signal Type (Bit-rate) Value
----------- ----------- -----
DS0 (0.064 Mbps) 0x477A0000
DS1 (1.544 Mbps) 0x49BC7A00
E1 (2.048 Mbps) 0x49FA0000
DS2 (6.312 Mbps) 0x4AC0A080
E2 (8.448 Mbps) 0x4B00E800
Ethernet (10.00 Mbps) 0x4B189680
E3 (34.368 Mbps) 0x4C031A80
DS3 (44.736 Mbps) 0x4C2AA780
STS-1 (51.84 Mbps) 0x4C45C100
Fast Ethernet (100.00 Mbps) 0x4CBEBC20
E4 (139.264 Mbps) 0x4D04D000
OC-3/STM-1 (155.52 Mbps) 0x4D1450C0
OC-12/STM-4 (622.08 Mbps) 0x4E1450C0
GigE (1000.00 Mbps) 0x4E6E6B28
OC-48 (2488.32 Mbps) 0x4F1450C0
OC-192 (9953.28 Mbps) 0x501450C0
10GigE-LAN (10000.00 Mbps) 0x501502F9
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].
Each Generalized Label object carries a variable length label
parameter.
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3.2.1. Required Information
The format of a Generalized Label (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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of a Generalized Label (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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Label: Variable
Carries label information. The semantics of this field depends
on the type of the link over which the label is used.
3.2.1.1. SDH and SONET Labels
SDH and SONET define each a multiplexing structure. These two
structures are trees whose roots are respectively an STM-N or an STS-
N; and whose leaves are the signals (time-slots) that can be
transported and switched, i.e. a VC-x or a VT-x. A label will
identify the type of a particular signal and its exact position in a
multiplexing structure (both are related).
These multiplexing structures will be used as naming trees to create
unique multiplex entry names or labels. Since the SONET multiplexing
structure may be seen as a subset of the SDH multiplexing structure,
the same format of label is used for SDH and SONET. As explained
before (section 3.2), a label does not identify the "class" to which
the label belongs. This is implicitly determined by the link on which
the label is used. However, the encoding specified hereafter makes
directly the distinction between SDH and SONET.
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In case of signal concatenation or inverse multiplexing, a list of
labels may appear in the Label field of a Generalized Label.
In case of virtual or arbitrary concatenation, the explicit list of
all signals in the concatenation is given. The signals identified by
these labels are virtually concatenated to form the SDH or SONET
signal trail. The above representation limits virtual concatenation
to remain within a single (component) link.
In case of any type of contiguous concatenation (e.g. standard or
arbitrary SONET concatenation), only one label appears in the Label
field. That label is the lowest signal of the contiguously
concatenated signal. The bandwidth of the LSP request indicates the
number of labels to be concatenated to form the SDH or SONET signal
trail. By lowest signal we mean the one having the lowest label when
compared as integer values, i.e. the first component signal of the
concatenated signal encountered when descending the tree.
In case of inverse multiplexing, the explicit list of all signals
that take part into the inverse multiplexing is given. Inverse
multiplexing is useful when a higher order signal need to be
transported over a number of lower order signals, e.g. when a 10Gbps
signal must be transported over four 2.5Gbps signals. In that case,
the lower order signals must follow exactly the same path, and be
treated in the same way, in order to achieve the same characteristics
(e.g. delay). To support inverse multiplexing, a request is made to
open in parallel and in one single operation several LSPs at the same
time.
The format of the label for SDH and/or SONET TDM-LSR link 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For SDH, this is an extension of the numbering scheme defined in
G.707 section 7.3, i.e. the (K, L, M) numbering. For SONET, the U and
K fields are not significant and must be set to zero. Only the S, L
and M fields are significant for SONET and have a similar meaning as
for SDH.
Each letter indicates a possible branch number starting at the parent
node in the multiplex structure. Branches are considered as numbered
in the increasing order, starting from the top of the multiplexing
structure. The numbering starts at 1, zero is used to indicate a non-
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significant field.
When a field is not significant in a particular context it MUST be
set to zero when transmitted, and MUST be ignored when received. This
simple rule allows distinguishing very easily between an SDH label
and an SONET label. A label with U=0 will always indicate a SONET
label. This is a nice feature for debugging purposes. Note that it is
easier to test U and K together, rather than only the U field alone,
since they fit exactly in the third octet of the label.
1. S is the index of a particular STM-1/STS-1 signal. S=1->N
indicates a specific STM-1/STS-1 inside an STM-N/STS-N
multiplex. For example, S=1 indicates the first STM-1/STS-1,
and S=N indicates the last STM-1/STS-1 of this multiplex. S=0
is invalid.
2. U is only significant for SDH and must be ignored for SONET. It
indicates a specific VC inside a given STM-1. U=1 indicates a
single VC-4, while U=2->4 indicates a specific VC-3 inside the
given STM-1.
3. K is only significant for SDH and must be ignored for SONET. It
indicates a specific branch of a VC-4. K=1 indicates that the
VC-4 is not further sub- divided and contains a C-4. K=2->4
indicates a specific TUG-3 inside the VC-4. K is not
significant when the STM-1 is divided into VC-3s (easy to read
and test).
4. L indicates a specific branch of a TUG-3, VC-3 or STS-1 SPE. It
is not significant for an unstructured VC-4. L=1 indicates that
the TUG-3/VC-3/STS-1 SPE is not further sub-divided and
contains a VC-3/C-3 in SDH or the equivalent in SONET. L=2->8
indicates a specific TUG-2/VT Group inside the corresponding
higher order signal.
5. M indicates a specific branch of a TUG-2/VT Group. It is not
significant for an unstructured VC-4, TUG-3, VC-3 or STS-1
SPE. M=1 indicates that the TUG-2/VT Group is not further
sub-divided and contains a VC-2/VT-6. M=2->3 indicates a
specific VT-3 inside the corresponding VT Group, these values
MUST NOT be used for SDH since there is no equivalent of VT-3
with SDH. M=4->6 indicates a specific VC-12/VT-2 inside the
corresponding TUG-2/VT Group. M=7->10 indicates a specific
VC-11/VT-1.5 inside the corresponding TUG-2/VT Group. Note that
M=0 denotes an unstructured VC-4, VC-3 or STS-1 SPE (easy for
debugging).
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The M encoding is summarized in the following table:
M SDH SONET
----------------------------------------------------------
0 unstructured VC-4/VC-3 unstructured STS-1 SPE
1 VC-2 VT-6
2 - 1st VT-3
3 - 2nd VT-3
4 1st VC-12 1st VT-2
5 2nd VC-12 2nd VT-2
6 3rd VC-12 3rd VT-2
7 1st VC-11 1st VT-1.5
8 2nd VC-11 2nd VT-1.5
9 3rd VC-11 3rd VT-1.5
10 4th VC-11 4th VT-1.5
For instance,
Example 1: S>0, U=1, K=1, L=0, M=0
Denotes the unstructured VC-4 of the Sth STM-1.
Example 2: S>0, U=1, K>1, L=1, M=0
Denotes the unstructured VC-3 of the Kth-1 TUG-3 of the Sth STM-1.
Example 3: S>0, U=0, K=0, L=0, M=0)
Denotes the unstructured STS-1 SPE of the Sth STS-1.
Example 4: S>0, U=0, K=0, L>1, M=1
Denotes the VT-6 in the Lth-1 VT Group in the Sth STS-1.
Example 5: S>0, U=0, K=0, L>1, M=9
Denotes the 3rd VT-1.5 in the Lth-1 VT Group in the Sth STS-1.
3.2.1.2. 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].
3.2.1.3. 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
Resv/MAPPING message is a protocol error and should treated as a
malformed message by the recipient.
The recipient of a Resv/MAPPING message containing a Generalized
Label verifies that the values passed are acceptable. If the label
is unacceptable then the recipient MUST generate a
ResvErr/NOTIFICATION message with a "Routing problem/MPLS label
allocation failure" indication.
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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.
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.
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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
label parameter of the Generalized Label one PSC and LSC.
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
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
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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.
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.
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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 Label_Set 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.
The format of a Label_Set (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 Label_Set (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
0 means subchannel is a single element (inclusive)
1 means subchannel is a start element (inclusive)
2 means subchannel is an end element (inclusive)
3 means subchannel is a single element (exclusive)
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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=0) sorted
in increasing order of subchannel value.
A Label Set can be a set of ranges (Type=1 followed by Type=2). 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=3 (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
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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.
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
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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
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
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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 data traffic associated with the LSP upstream towards 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.
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.
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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
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).
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+------------+ +------------+
+ 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.
+------------+ +------------+
+ 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 three signaling extensions that modify error
handling, enable expedited notification of failures and other events
to nodes responsible for restoring failed LSPs. The first extension,
the Notify Request object, identifies where event notifications are
to be sent. The second, the Notify message, provides for general
event notification. The final extension allows for the removal of
Path state on handling of PathErr messages.
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5.1. Notify Request Object
Notifications may be sent via the Notify message defined below. The
Notify Request object is used to request the generation of
notifications. Notifications, i.e., the sending of a Notify message,
may be requested in both the upstream and downstream directions.
5.1.1. Required Information
The Notify Request Object may be carried in Path or Resv Messages,
see Section 7. The NOTIFY_REQUEST class number is TBA (of form
11bbbbbb). The format of a Notify Request 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(TBD)| C_Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Notify Node Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 Notify Node Address: 32 bits
The IP address of the node that should be notified when
generating an error message.
5.1.2. Procedures
A Notify Request object may be inserted in Path or Resv messages to
indicate the address of a node that should be notified of an LSP
failure. As previously mentioned, notifications may be requested in
both the upstream and downstream directions. Upstream notification is
indicated via the inclusion of a Notify Target Object in the
corresponding Path message. Downstream notification is indicated via
the inclusion of a Notify Target Object in the corresponding Resv
message.
A node receiving a message containing a Notify Request object SHOULD
store the Notify Node Address in the corresponding state block. If
the node is a transit node, it SHOULD also included a Notify Request
object in the outgoing Path or Resv message. The outgoing Notify
Node Address MAY be updated based on local policy.
Note that the inclusion of a Notify Request object does not guarantee
that a Notify message will be generated.
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5.2. Notify Message
The Notify message provides a mechanism to inform non-adjacent nodes
of LSP related events. Notify messages are only generated after a
Notify Request object has been received. The Notify 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.
See [RSVP-RR] for details on reliable RSVP message delivery.
5.2.1. 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.
<Notify message> ::= <Common Header> [<INTEGRITY>] <MESSAGE_ID>
<ERROR_SPEC> <notify session list>
<notify session list> :== [<notify session list>] <notify session>
<notify session> :== <SESSION> [<POLICY_DATA>...]
<sender descriptor>
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
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of available resources and can start rerouting much sooner.
5.2.2. Procedures
Notify messages are generated at nodes that detect an error that will
trigger the generation of a PathErr or ResvErr message. If a PathErr
message is to be generated and a Notify Request object has been
received in the corresponding Path message, then a Notify message
destined to the recorded node SHOULD be generated. If a ResvErr
message is to be generated and a Notify Request object has been
received in the corresponding Resv message, then a Notify message
destined to the recorded node SHOULD be generated. As previously
mentioned, a single error may generate a Notify message in both the
upstream and downstream directions. Note a Notify message MUST NOT
be generated unless an appropriate Notify Request object has been
received.
When generating Notify messages, a node SHOULD attempt to combine
notifications being sent to the same Notify Node and that share the
same ERROR_SPEC into a single Notify message. The means by which a
node determines which information may be combined is implementation
dependent. Implementations may use event, timer based or other
approaches. If using a timer based approach, the implementation
SHOULD allow the user to configure the interval over which
notifications are combined. When using a timer based approach, a
default "notification interval" of 1 ms SHOULD be used. Notify
messages SHOULD be delivered using the reliable message delivery
mechanisms defined in [RSVP-RR]
Upon receiving a Notify message, the Notify Node SHOULD send a
corresponding Ack message.
5.3. Removing State with a PathErr message
The PathErr message as currently defined in [RFC2205] is sent hop-by-
hop to the source of the associated Path message. Intermediate nodes
may inspect this message, but take no action upon it. In an
environment where Path messages are routed according to an IGP and
that route may change dynamically, this behavior is a fine design
choice.
However, when RSVP is used with explicit routes, it is often the case
that errors can only be corrected at the source node or some other
node further upstream. In order to clean up resources, the source
must receive the PathErr and then either send a PathTear (or wait for
the messages to timeout). This causes idle resources to be held
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longer than necessary increases control message load. In a situation
where the control plane is attempting to recover from a serious
outage, both the message load and the delay in freeing resources
hamper the ability to rapidly reconverge.
The situation can be greatly improved by allowing state to be removed
by intermediate nodes on certain error conditions. To facilitate
this a new flag is defined in the ERROR_SPEC object. The two
currently defined ERROR_SPEC objects (IPv4 and IPv6 error spec
objects) each contain a one byte flag field. Within that field two
flags are defined. This specification defines a third flag, 0x04,
Path_State_Removed.
The semantics of the Path_State_Removed flag are simply that the node
forwarding the error message has removed the Path state associated
with the PathErr. By default, the Path_State_Removed flag is always
set to zero when generating or forwarding a PathErr message. A node
which encounters an error MAY set this flag if the error results in
the associated Path state being discarded. If the node setting the
flag is not the session endpoint, the node SHOULD generate a
corresponding PathTear. A node receiving a PathErr message
containing an ERROR_SPEC object with the Path_State_Removed flag set
MAY also remove the associated Path state. If the Path state is
removed the Path_State_Removed flag SHOULD be set in the outgoing
PathErr message. A node which does not remove the associated Path
state MUST NOT set the Path_State_Removed flag. A node that receives
an error with the Path_State_Removed flag set to zero MUST NOT set
this flag unless it also generates a corresponding PathTear message.
Note that the use of this flag does not result in any
interoperability incompatibilities.
6. Explicit Label Control
The LSR at the initiator of an LSP can control nodes used by an LSP
and the termination of the LSP by using an explicit route, i.e., ERO
or ER-Hop. To require the usage of a particular node, that node is
included in the explicit route. To terminate an LSP on a particular
outgoing interface of the egress LSR, the head-end may specify the IP
address or the interface identifier [MPLS-UNNUM] of that interface as
the last element in the explicit route, provided that that interface
has an associated IP address.
There are cases where the existing explicit route semantics do not
provide enough information to control the LSP to the degree desired.
This occurs case when the LSP initiator wishes to select a label used
on a link. An example of this is when it is desirable to "splice"
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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.
To to cover this case, the Label ERO subobject is introduced.
6.1. Required Information
For RSVP, this ERO subobject - Label 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length |U| Reserved | C-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For CR-LDP the 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|U| Reserved | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label (continued) |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L
This bit must be set to 0.
Type (RSVP Only)
3 Label
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.
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U
This bit indicates the direction of the label. It is 0 for the
downstream label. It is set to 1 for the upstream label and is
only used on bidirectional LSPs.
C-Type (RSVP Only)
The C-Type of the included Label Object. Copied from the Label
Object.
Label
This field identifies the label to be used. The format of this
field is identical to the one used by the Label field in the
Generalized Label Object, see Section 3.2.1.
6.2. Procedures
The Label subobject follows a subobject containing the IP address, or
the interface identifier [MPLS-UNNUM], associated with the link on
which it is to be used. The preceding subobject must be a strict
object. Up to two label subobjects may be present, one for the
downstream label and one for the upstream label. The following
SHOULD result in "Bad EXPLICIT_ROUTE object" errors:
- For a label subobject to follow a subobject that has the L-bit
set
- On unidirectional LSP setup, for there to be a label subobject
with the U-bit set
- For there to be two label subobjects with the same U-bit values
To support the label subobject, a node must check to see if the
subobject following it's associate address/interface is a label
subobject. If it is, one subobject is examined for unidirectional
LSPs and two subobjects for bidirectional LSPs. If the U-bit of the
subobject being examined is clear (0), then value of the label is
copied into a new Label_Set object. This Label_Set object MUST be
included on the corresponding outgoing Path/Mapping message.
If the U-bit of the subobject being examined is set (1), then value
of the label is label to be used for upstream traffic associated with
the bidirectional LSP. If this label is not acceptable, a "Bad
EXPLICIT_ROUTE object" error SHOULD be generated. If the label is
acceptable, the label is copied into a new Upstream Label object.
This Upsteam Label object MUST be included on the corresponding
outgoing Path/Mapping message.
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After processing, the label subobjects are removed from the ERO/ER.
Note an implication of the above procedures is that the label
subobject should never be the first subobject in a newly received
message. If the label subobject is the the first subobject an a
received ERO/ER, then it SHOULD be treated as a "Bad strict node"
error.
Procedures by which an LSR at the head-end of an LSP obtains the
information needed to construct the Label subobject are outside the
scope of this document.
7. RSVP Message Formats
This section presents the RSVP message related formats as modified by
this document. Where they differ, formats for unidirection LSPs are
presented separately from bidirectional LSPs. Unmodified formats are
not listed.
The format of a Path message is as follows:
<Path Message> ::= <Common Header> [ <INTEGRITY> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
<LABEL_SET>
[ <SESSION_ATTRIBUTE> ]
[ <NOTIFY_REQUEST> ]
[ <POLICY_DATA> ... ]
<sender descriptor>
The format of the sender description for unidirectional LSPs is:
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
[ <ADSPEC> ]
[ <RECORD_ROUTE> ]
[ <SUGGESTED_LABEL> ]
The format of the sender description for bidirectional LSPs is:
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
[ <ADSPEC> ]
[ <RECORD_ROUTE> ]
[ <SUGGESTED_LABEL> ]
<UPSTREAM_LABEL>
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The format of a Resv message is as follows:
<Resv Message> ::= <Common Header> [ <INTEGRITY> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <RESV_CONFIRM> ] [ <SCOPE> ]
[ <NOTIFY_REQUEST> ]
[ <POLICY_DATA> ... ]
<STYLE> <flow descriptor list>
<flow descriptor list> is not modified by this document.
8. 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
Valuable comments and input were received from a number of people,
notably Adrian Farrel. Portions of Section 5 are based on
suggestions and text proposed by Adrian.
9. Security Considerations
Non-adjacent bundle messages, and the transmission of notify messages
using IP in IP, break RSVP's hop-by-hop integrity and authentication
model. Fortunately, such usage mirrors the IP end-to-end model. In
the case where RSVP is generating end-to-end messages and integrity
and/or authentication are desired, the standard IPSEC based integrity
and authentication methods SHOULD be used.
This draft introduce no other new security considerations to either
[CR-LDP] or [RSVP-TE].
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10. 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-11.txt, August 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.
[GMPLS-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 Generalized
MPLS", Internet Draft,
draft-ietf-isis-gmpls-extensions-00.txt, July 2000.
[GMPLS-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 MPLambdaS",
Internet Draft, draft-ompls-ospf-extensions-00.txt,
July 2000.
[RFC2205] Braden, R. Ed. et al, "Resource ReserVation Protocol
-- Version 1 Functional Specification", RFC 2205,
September 1997.
[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.
Berger, Ashwood-Smith, editors [Page 38]
Internet Draft draft-ietf-mpls-generalized-signaling-00.txt October 2000
[RSVP-RR] Berger L., Gan D., Swallow G., Pan P., Tommasi F.,
Molendini S., "RSVP Refresh Overhead Reduction Extensions",
draft-ietf-rsvp-refresh-reduct-05.txt, June 2000.
[RECOVERY] Makam, et al "A Framework for MPLS-based Recovery,"
draft-ieft-mpls-recovery-frmwrk-00.txt, August 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.
11. 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
Movaz Networks
Phone: +1 301 468 9228
Email: lberger@movaz.com
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
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Internet Draft draft-ietf-mpls-generalized-signaling-00.txt October 2000
Yanhe Fan
Axiowave Networks, Inc.
100 Nickerson Road
Marlborough, MA 01752
Phone: +1 508 460 6969 Ext. 627
Email: yfan@axiowave.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
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Internet Draft draft-ietf-mpls-generalized-signaling-00.txt October 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
George Swallow
Cisco Systems, Inc.
250 Apollo Drive
Chelmsford, MA 01824
Voice: +1 978 244 8143
Email: swallow@cisco.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
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