CCAMP Working Group Vishnu Pavan Beeram (Ed)
Internet Draft Juniper Networks
Intended status: Standards Track Igor Bryskin (Ed)
ADVA Optical Networking
Expires: August 12, 2014 February 12, 2014
Shared Resource Link Group (SRcLG)
draft-beeram-ccamp-srclg-01
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Abstract
This document introduces the concept of SRcLG ("Shared Resource Link
Group") and discusses its usage in the context of mutually exclusive
Virtual TE Links.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
Table of Contents
1. Introduction...................................................2
2. Dynamic Mutual Exclusivity.....................................3
3. Shared Resource Link Group (SRcLG).............................5
3.1. Construct.................................................6
3.2. Advertising Rules.........................................7
3.3. Processing Rules..........................................7
4. Security Considerations........................................7
5. IANA Considerations............................................7
6. Normative References...........................................7
7. Acknowledgments................................................8
1. Introduction
A Virtual TE Link (as defined in [RFC6001]) advertised into a Client
Network Domain represents a potentiality to setup an LSP in the
Server Network Domain to support the advertised TE link. The Virtual
TE Link gets advertised like any other TE link and follows the same
rules that are defined for the advertising, processing and use of
regular TE links [RFC4202]. However, "mutual exclusivity" is one
attribute that is specific to Virtual TE Links.
[DRAFT-MELG] discusses the different types of mutual exclusivity
(Static vs Dynamic) that come into play, explains the need to
advertise this information into the Client TE Domain and introduces
a new TE construct (MELG) to carry static mutual exclusivity
information.
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This document is a companion document to [DRAFT-MELG]. It discusses
"Dynamic Mutual Exclusivity" in detail and introduces a new TE
construct (SRcLG) to carry dynamic mutual exclusivity information.
2. Dynamic Mutual Exclusivity
As discussed in [DRAFT-MELG], this type of mutual exclusivity exists
temporarily within a given network configuration. It comes into play
when two or more Virtual TE Links depend on the usage of the same
shareable underlying server network domain resource. Mutual
Exclusivity exists when the amount of the said server resource that
is available for sharing is limited temporarily; it ceases to exist
when sufficient amount of the resource is available for
accommodating all corresponding Virtual TE Links.
|
| +---+ /-\
| | | Router ( ) WDM
| +---+ Node \-/ node
|________________________________
+---+ /-\ /-\ /-\ +---+
| R1|-------( A )--------( C )---------( E )---------| R3|
+---+ \-/ \-/ \-/ +---+
/ \ / \
/ \ / \
/ \ / \
/ \ / \
/ \ / \
+---+ /-\ /-\ /-\ +---+
| R2|---------( B )---------( D )---------( F )---------| R4|
+---+ \-/ \-/ \-/ +---+
Figure 1a: Sample topology
Consider the network topology depicted in Figure 1a. This is a
typical packet optical transport deployment scenario where the WDM
layer network domain serves as a Server Network Domain providing
transport connectivity to the packet layer network Domain (Client
Network Domain).
Nodes R1, R2, R3 and R4 are IP routers that are connected to an
Optical WDM transport network. A, B, C, D, E and F are WDM nodes
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that constitute the Server Network Domain. The border nodes (A, B, E
and F) operate in both the server and client domains. Figure 1b
depicts how the Client Network Domain TE topology looks like when
there are no Client TE Links provisioned across the optical domain.
------------- | [ ] Client TE Node
| Client TE | | +++ Client TE Link
| DataBase | |_____________________
-------------
[R1] ++++++++ [A] [E] +++++++++ [R3]
[R2] ++++++++ [B] [F] +++++++++ [R4]
Figure 1b: Client TE Database
| ***** B-F WDM Path
| @@@@@ B-E WDM Path
| ##### A-F WDM Path
|________________________________
+---+ /-\ ######## /-\ /-\ +---+
| R1|-------( A )--------( C )---------( E )---------| R3|
+---+ \-/ @\-/@# \-/@ +---+
@/ \@# / \@
@/ \@# / \@
@/ \@# / \@
@/ \@# / \@
@/ \@/ ######### \@
+---+ /-\ /-\ @@@@@@@@@ /-\ +---+
| R2|---------( B )---------( D )---------( F )---------| R4|
+---+ \-/ ********* \-/ ********* \-/ +---+
Figure 2a: Mutually Exclusive potential WDM paths
Now consider augmenting the Client TE topology by creating three
Virtual TE Links across the optical domain. The potential paths in
the WDM network catering to these three virtual TE links are as
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shown in Fig 2a and the corresponding augmented Client TE topology
is as illustrated in Fig 2b.
------------ | TE-Links B-F, B-E and A-F are mutually
| Client-TE| | exclusive; They depend on the usage of the
| Database | | same underlying shareable server resource
------------ |_____________________________________________
[R1] ++++++++ [A] [E] +++++++++ [R3]
++++ ++++
++++ ++++
++++
++++ ++++
++++ ++++
[R2] ++++++++ [B] ++++++++++++++++++++ [F] +++++++++ [R4]
Figure 2b: Client TE Database - Mutually Exclusive Virtual TE Links
In this particular example, all three potential paths traverse
through the WDM-Link {D-F}. Now assume that this link has only 2
lambda channels available. Also assume that any available lambda can
get picked for each of these 3 corresponding underlying server LSPs.
This means that only two out of the three Virtual TE Links can get
committed at the moment. This dynamic mutual exclusivity ceases to
exist when a third lambda channel becomes available on the WDM-link
{D-F}.
This document proposes the use of "Shared Resource Link Group
(SRcLG)" for catering to this scenario.
3. Shared Resource Link Group (SRcLG)
SRLG (Shared Risk Link Group - [RFC4202]) represents a set of links
that share a resource whose failure may affect all links in the set.
Since dynamic mutual exclusivity comes into play when the underlying
server resource is shareable, all corresponding Virtual TE-Links
would belong to the same SRLG. This document introduces the notion
of a "Shared Resource Link Group (SRcLG)", which is meaningful only
in the context of Virtual TE Links. SRcLG represents a set of
Virtual TE-links that depend on the usage of a shared server-layer
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resource that has a variable bandwidth capacity and as a result may
sometimes not be able to simultaneously accommodate all
corresponding Virtual TE-Links in the set. As is the case with
SRLGs, a given Virtual TE Link may belong to multiple SRcLGs.
3.1. Construct
In terms of the TE construct that gets advertised, an SRcLG is
nothing but an SRLG with some additional information to help
determine which and how many of the corresponding virtual TE Links
can get committed simultaneously. This additional information is the
per-priority available shared resource bandwidth associated with a
given SRLG. Since an SRcLG cannot exist without the presence of a
corresponding SRLG, the SRcLG is identified by the corresponding 32-
bit SRLG-ID. In other words, the SRcLG-ID is the same as the
identifier of the SRLG it represents.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Shared Resource Bandwidth at Priority 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The SRcLG information advertised into the Client TE Domain is an
unordered list of SRcLGs present in a given Virtual Topology. Unlike
the SRLG construct or the MELG construct, the SRcLG construct does
not get advertised per TE-Link. This is because the information
carried in this construct is quite dynamic in nature and advertising
it per TE-Link poses serious scaling concerns.
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3.2. Advertising Rules
As far as the advertisement of a Virtual TE-Link is concerned, there
is no perceived difference between SRLG and SRcLG. The 32-bit IDs of
all SRcLGs that a Virtual TE-Link belongs to are advertised via the
SRLG contruct. Additionally, all SRcLG information associated with a
given Virtual Topology is advertised into the Client TE Domain by
the provider of the Virtual Topology. It is the responsibility of
this provider to keep the bandwidth availability information for
each SRcLG current with timely updates. The draft envisions that one
or more server domain OSPF/ISIS TE speakers will be tasked to
provide these timely updates. This TE speaker may advertise all
SRcLG information (that it is responsible for) in the same OSPF-
LSA/ISIS-LSP or advertise each SRcLG TLV separately - one in each
OSPF-LSA/ISIS-LSP.
3.3. Processing Rules
The intended consumer of this SRcLG information is the PCE in the
Client TE Domain. The Client PCE should take this advertised
information into account when performing path selection for services
over the Virtual Topology provided by the network domain. In
particular, this information should be used when deciding how many
Virtual TE links could be accomodated simultaneously on a given
SRcLG at a given priority level.
4. Security Considerations
TBD
5. IANA Considerations
TBD
6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4202] K.Kompella, Y.Rekhter, "Routing Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC4202, October 2005.
[RFC6001] D.Papadimitriou, M.Vigoureax, K.Shiomoto, D.Brungard
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and JL. Le Roux, "GMPLS Protocol Extensions for Multi-
Layer and Multi-Region Networks", RFC 6001, October
2010.
[DRAFT-MELG] Beeram, V., "Mutual Exclusive Shared Link Group",
draft-beeram-ccamp-melg, February 2014
7. Acknowledgments
TBD
Authors' Addresses
Vishnu Pavan Beeram
Juniper Networks
Email: vbeeram@juniper.net
Igor Bryskin
ADVA Optical Networking
Email: ibryskin@advaoptical.com
Cyril Margaria
Juniper Networks
Email: cmargaria@gmail.com
Fatai Zhang
Huawei Technologies
Email: zhangfatai@huawei.com
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