One document matched: draft-so-yong-rtgwg-cl-framework-02.txt
Differences from draft-so-yong-rtgwg-cl-framework-01.txt
Network Working Group N. So
Internet Draft A. Malis
Intended Status: Informational D. McDysan
Expires: April 2011 Verizon
L. Yong
Huawei
F. Jounay
France Telecom
Y. Kamite
NTT
October 20, 2010
Composite Link Framework in Multi Protocol Label Switching (MPLS)
draft-so-yong-rtgwg-cl-framework-02
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Abstract
This document specifies a composite link framework in MPLS network.
A composite link consists of a group of homogenous or non-homogenous
links that have the same forward adjacency and can be considered as
a single TE link or an IP link in routing. The composite link relies
on its component links to carry the traffic over composite link. The
document specifies composite link model. Applicability is described
for a single pair of MPLS-capable nodes, a sequence of MPLS-capable
nodes, or a set of layer networks connecting MPLS-capable nodes.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................3
2.1. Terminology...............................................3
3. Composite Link Framework.......................................4
4. Composite Link in Control Plane................................5
5. Composite Link in Data Plane...................................6
6. Security Considerations........................................7
7. IANA Considerations............................................7
8. References.....................................................7
8.1. Normative References......................................7
8.2. Informative References....................................7
9. Acknowledgments................................................7
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1. Introduction
Composite link functional requirement are specified in [CL-REQ].
This document specifies a framework of Composite Link in IP/MPLS
network to meet the requirements. Single link and link bundle
[RFC4201] have been widely used in today's IP/MPLS networks. A link
bundle bundles a group of homogeneous links as a TE link to make
routing approach more scalable. A composite link allows bundling
non-homogenous links together as a single logical link. The
motivations for using a composite link are descried in the document
[CL-REQ]. This document describes composite link framework in the
context of MPLS network with MPLS control plane.
A composite link is a single logical link in MPLS network that
contains multiple parallel component links between two routers.
Unlike a link bundle [RFC4201], the component links in a composite
link can have different properties such as cost or capacity. A
composite link can transport aggregated traffic as other physical
links from the network perspective and use its component links to
carry the traffic internally.
Specific protocol solutions are outside the scope of this document.
2. 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 [RFC2119].
2.1. Terminology
Composite Link: a group of component links, which can be considered
as a single MPLS TE link or as a single IP link used for MPLS.
Component Link: a physical link (e.g., Lambda, Ethernet PHY, SONET/
SDH, OTN, etc.) with packet transport capability, or a logical link
(e.g., MPLS LSP, Ethernet VLAN, MPLS-TP LSP, etc.)
Traffic Flow: A set of packets with a common identifier and
characteristics that is used by Composite link interior functions to
place the set of packets on the same component link. Identifiers can
be an MPLS label stack or any combination of IP addresses and
protocol types for routing, signaling, and management packets.
Virtual Interface: Composite link is advertised as an interface in
IGP
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3. Composite Link Framework
A Composite Link in the context of MPLS network is a set of parallel
links between two routers that form a single logical link within the
network. Composite link model is illustrated in Figure 1, where a
composite link is configured between routers R1 and R2. The
composite link has three component links. Individual component
links in a composite link may be supported by different transport
technologies such as wavelength, Ethernet VLAN. Even if the
transport technology implementing the component links is identical,
the characteristics (e.g., bandwidth, latency) of the component
links may differ.
As shown in Figure 1, the composite link may carry LSP traffic flows
and control plane packets. A LSP may be established over the link by
either RSVP-TE or LDP signaling protocols. All component links in a
composite link have the same forwarding adjacency. The composite
link forms one routing interface at the composite link end points
for MPLS control plane. In other words, two routers connected via a
composite link have forwarding adjacency and routing adjacency. Each
component link only has significance to the composite link, i.e. it
does not appear as a link in the control plane.
Management Plane
Configuration and Measurement <------------+
^ |
| |
+-------+-+ +-+-------+
| | | | | |
CP Packets V | | V CP Packets
| V | | Component Link 1 | | ^ |
| | |=|===========================|=| | |
| +----| | Component Link 2 | |----+ |
| |=|===========================|=| |
Aggregated LSPs | | | | |
~|~~~~~~>| | Component Link 3 | |~~~~>~~|~~
| |=|===========================|=| |
| | | | | |
| LSR | | LSR |
+---------+ +---------+
! !
! !
!<------ Composite Link ------->!
Figure 1 Composite Link Architecture Model
A component link in a composite link may be constructed in different
ways.[CL-REQ] Figure 2 shows three common ways that may be deployed
in a network.
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+-------+ 1. Physical Link +-------+
| |-|----------------------------------------------|-| |
| | | | | |
| | | +------+ +------+ | | |
| | | | MPLS | 2. Logical Link | MPLS | | | |
| |.|.... |......|.....................|......|....|.| |
| | |-----| R3 |---------------------| R4 |----| | |
| | | +------+ +------+ | | |
| | | | | |
| | | | | |
| | | +------+ +------+ | | |
| | | |GMPLS | 3. Logical Link |GMPLS | | | |
| |.|. ...|......|.....................|......|....|.| |
| | |-----| R5 |---------------------| R6 |----| | |
| | +------+ +------+ | |
| R1 | | R2 |
+-------+ +-------+
|<------------- Composite Link ------------------->|
Figure 2 Illustration of Component Link Variances
As shown, the first component link is configured with direct
physical media wire. The second component link is a TE tunnel that
traverses R3 and R4. Both R3 and R4 are the nodes in the MPLS. The
third component link is formed by lower layer network that has GMPLS
enabled. In this case, R5 and R6 are not the nodes controlled by the
MPLS but provide the connectivity for the component link.
Composite link forms one logical link between connected routers and
is used to carry aggregated traffic.[CL-REQ] Composite link relies
on its component links to carry the traffic over the composite link.
This means that a composite link maps incoming traffic into
component links. At the transmitting end (R1 in Figure 1), composite
link maps a set of traffic flows including control plane packets to
a specific component link. At the receiving end (R2 in Figure 1),
composite link receives the packets from its component links and
sends them to MPLS forwarding engine like a regular link.
Traffic mapping to component links may be done by control plane,
management plane, or data plane.[CL-REQ] The objective is to keep
the individual flow packets in sequence and do not overload any
component link.[CL-REQ] Operator may have other objectives such as
load balance over component links. A flow may be a LSP, or sub-LSP
[MLSP], PW, a flow within PW [FAT-PW], entropy flow in LSP
[Entropy].
4. Composite Link in Control Plane
A composite Link is advertised as a single logical interface between
two connected routers, which forms routing and forwarding adjacency
between the routers in IGP. The interface parameters for the
composite link can be pre-configured by operator or be derived from
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its component links. Composite link advertisement requirements are
specified in [CL-REQ].
In IGP-TE, a composite link is advertised as a single TE link
between two connected routers. This is similar to a link bundle
[RFC4201]. Link bundle applies to a set of homogenous component
links. Composite link allows homogenous and non-homogenous component
links. The link bundle protocol extension for composite link
advertisement is for further study.
Both LDP [RFC5036] and RSVP-TE [RFC3209] can be used to signal a LSP
over a composite link. Since composite link capacity is aggregated
capacity and is often larger than individual component link
capacity, it is possible to signal a LSP whose BW is larger than
individual component link capacity.[CL-REQ] Assumption is such LSP
carrying an aggregated traffic.
A composite link may contain the set of component links. A component
link may be configured by operator or signaled by the control plane.
In both cases, it is necessary to convey component link parameters
to the composite link.[CL-REQ]
When a component link is supported by lower layer network (third
component link in figure 2), the control plane that the composite
link resides is able to interoperate with the GMPLS or MPLS-TP
control plane that lower layer network uses for component link
addition and deletion. [CL-REQ]
5. Composite Link in Data Plane
Composite link may appear as one single interface or multiple
interfaces in data plane.
The traffic over composite link is distributed over individual
component links. Traffic dissemination may be determined by control
plane, management plane, or data plane, and may be changed due to
component link status change.[CL-REQ]
A component link in a composite link may fail independently. The
composite link functions are able to recognize component link
failure and re-assign impacted flows to other active component links
in minimal disruptive manner. When a composite link can't recover
some impacted flows, it notifies control plane about the flows. When
a composite link is not able to transport all flows, it preempts
some flows based upon local management configuration and informs the
control plane on these preempted flows. This action ensures the
remaining traffic is transported properly.
The composite link functions provide component link fault
notification and composite link fault notification. Component link
fault notification is sent to the management plane. Composite link
fault notification is sent to the control plane and management
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plane. Composite link allows operator to trace which component link
a LSP is assigned to.
6. Security Considerations
For further study.
7. IANA Considerations
IANA actions to provide solutions are for further study.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan, G.
Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels," December
2001
[RFC4201] Kompella, K., "Link Bundle in MPLS Traffic Engineering",
RFC 4201, March 2005.
[RFC5036] Andersson, L., "LDP Specification", RFC 5036 , October
2007.
8.2. Informative References
[CL-REQ] Villamizar, C. and McDysan, D, "Requirements for MPLS Over
Composite Link", Oct. 2010, Work in Progress
[Entropy Label] Kompella, K. and S. Amante, "The Use of Entropy
Labels in MPLS Forwarding", November 2008, Work in Progress
[FAT-PW] Bryan, S., et. Al, "Flow Aware Transport of Pseudowire over
an MPLS PSN", draft-ietf-pwe3-fat-pw-04, Work in progress
[MLSP] Kompella, K. "Multi-path Label Switched Paths Signaled Using
RSVP-TE", draft-kompella-mpls-rsvp-ecmp-00.txt, July 2010, Work in
Progress
9. Acknowledgments
Authors would like to thank Adrian Farrel for his extensive comments
and suggestions, Ron Bonica, Nabil Bitar, Eric Gray, Lou Berger, and
Kireeti Kompella for their reviews and great suggestions.
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Authors' Addresses
So Ning
Verizon
2400 N. Glem Ave.,
Richerdson, TX 75082
Phone: +1 972-729-7905
Email: ning.so@verizonbusiness.com
Andrew Malis
Verizon
117 West St.
Waltham, MA 02451
Phone: +1 781-466-2362
Email: andrew.g.malis@verizon.com
Dave McDysan
Verizon
22001 Loudoun County PKWY
Ashburn, VA 20147
Email: dave.mcdysan@verizon.com
Lucy Yong
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 469-229-5387
Email: lucyyong@huawei.com
Frederic Jounay
France Telecom
2, avenue Pierre-Marzin
22307 Lannion Cedex,
FRANCE
Email: frederic.jounay@orange-ftgroup.com
Yuji Kamite
NTT Communications Corporation
Granpark Tower
3-4-1 Shibaura, Minato-ku
Tokyo 108-8118
Japan
Email: y.kamite@ntt.com
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