Multi-Protocol Lambda Switching: The Role of IP Technologies in Controlling and Managing Future...

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Multi-Protocol Multi-Protocol Switching: The Role of Switching: The Role of IP Technologies in IP Technologies in Controlling and Managing Controlling and Managing Future Optical Networks Future Optical Networks Dr. Vishal Sharma Dr. Vishal Sharma [email protected] [email protected] †A version of this seminar appeared in the First On-line Symposium for Electronics Engineers (OSEE), 9 January 2001

description

This is an early short tutorial from back in 2001 that focuses on the control of dynamic (or agile) optical networks. We begin by highlighting the motivation for such networks, their basic requirements, and the advantages of agility. We examine the functionality needed for routing and connection establishment in such dynamic networks, and compare possible candidates for the design of such a...

Transcript of Multi-Protocol Lambda Switching: The Role of IP Technologies in Controlling and Managing Future...

Page 1: Multi-Protocol Lambda Switching: The Role of IP Technologies in Controlling and Managing Future Optical Networks

Multi-Protocol Multi-Protocol Switching: Switching: The Role of IP Technologies in The Role of IP Technologies in

Controlling and Managing Controlling and Managing Future Optical NetworksFuture Optical Networks††

Dr. Vishal SharmaDr. Vishal [email protected]@ieee.org

†A version of this seminar appeared in the First On-line Symposium for

Electronics Engineers (OSEE), 9 January 2001

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Organization of the TalkOrganization of the Talk

Agile (or dynamic) optical networks Motivation

Analysis of basic requirements for agility

Advantages of having dynamic optical networks

Control Plane Possible candidates for the control plane

Motivation for adopting/re-using an MPLS-based control plane

What enhancements does this reuse/integration entail?

Implementation choices for the control plane

Architectural considerations in deployment

Some open issues: path characterization, link management, survivability

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Motivation for agile optical networksMotivation for agile optical networks

Reduce expense and complexity of network provisioning

Growth in fibers and s complicates path provisioning

Shift from manual configuration to automatic signaled setup

Increase responsiveness of optical transport network (OTN)

Reduce provisioning time: weeks/months to hrs/minutes or less

Facilitate deployment of new services that require quick setup

Limit electronic termination and processing

Today, higher aggregate link speeds (esp. with WDM), but limited electronic processing

switch and route at optical channel level (not on a per-packet level)

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Basic requirements for agile optical networksBasic requirements for agile optical networks

Topology/resource discovery

Distributed routing

Dissemination of network state information

Path selection

Traffic engineering based on resource/policy constraints.

Signaling

Connection establishment and path management

Survivability mechanisms

OXCs

1. Resource Discovery

2. Routing

3. Path Selection

4. Signaling

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Advantages of dynamic optical networksAdvantages of dynamic optical networks

Flexible connectivity via timely virtual topology reconfiguration

Simplifies higher-layer routing

Allows wider range of services

Enables interworking of: DCSs, OXCs, DWDM gear, routers

Eases management & control

Router Network

Optical Transport Network

R1

R2

R3

R4

Optical light-paths

Initial virtual links between routers

Final virtual topology

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Required components for agile optical networksRequired components for agile optical networks

Addressing/naming scheme

Routing protocols

Path computation and selection algorithms

Signaling protocols

Protection and restoration schemes

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Drawbacks of the traditional “control plane”: a.k.a. network managementDrawbacks of the traditional “control plane”: a.k.a. network management

Slow convergence following failure Except for pre-provisioned, dedicated protection channels

No instantaneous service provisioning

Complicates interworking of equipment from different manufacturers Incompatible EMSs cause integration problems

Complicates inter-network provisioning Lack of EDI between operator NMSs causes significant

operator intervention

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So what are likely options for the control plane?So what are likely options for the control plane?

Devise new routing and signaling protocols for the optical layer

Increased operation and maintenance cost

Significant interoperability concerns

Need careful coordination with higher layer restoration mechanisms

Modify network management to make it “dynamic”

Adapt existing protocols from data networks. For example, protocols from IP-based networks

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Issues in modifying a network management systemIssues in modifying a network management system Lacks hop-by-hop signaling

Multiple messages between NMS and network elements

No common NMS for multi-vendor equipment

NMSNMSSetup

Request

EMS

1

3

2

5

4

6

7

8

9

10

11

12

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Issues in modifying a network management systemIssues in modifying a network management system

Channel recovery & associated signaling can be complex

NMS network topology and resilience is itself an issue

NMS subject to vagaries of device architectures

Agreement on stds. complex

NMSNMSSetup

Request

EMS

NMS

Original path

Recovery path

2. Failure Indication

3. Recovery path configuration

1. Failure

4. Switchover

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Issues in having a distributed control planeIssues in having a distributed control plane

Allows easier end-point initiated channel setup

Standardization of signaling and routing is not subject to debate

Control plane protocols are being worked on in standards bodies (IETF, OIF, ITU)

Control Plane

Element in service control plane is in use

Control message traffic is limited

1

2 4 6

5

7

8

9

Signaling messages between elements

Signal to program switching element

3

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Basic Concept of MPLS

Routing fills routing table.

Signaling fills label forwarding table.

DA Next hoprouter

N/wInt.

129.89.10.x 198.168.7.6 1

179.69.x.x 198.168.7.6 1

128.89.10.x

1

179.69.x.x

21

128.89.10.12

179.69.42.3

198.168.7.6

Inlabel

Outlabel

Address Prefix N/wInt.

Advertises binding<5, 128.89.10.x>

Advertises binding<7, 179.69.x.x>

128.89.10.x 5 1

179.69.x.x 7 2

Advertises bindings<3, 128.89.10.x> <4, 179.69.x.x>

128.89.10.x 3 1

179.69.x.x 4 1

3

4

X

X

DA Next hoprouter

N/wInt.

129.89.10.x 129.89.10.1 1

179.69.x.x 179.69.42.3 2

Routing Table

Inlabel

Outlabel

Address Prefix N/wInt. Label

ForwardingTable

R1 R2

R3

R4

Step 1

Step 2

Step 3

Step 4

Step 5

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Basic Concept of MPLS

At ingress, unlabeled packets are prepended with label

At egress, labels are removed and packets are routed

128.89.10.x

1

179.69.x.x

21

128.89.10.12

179.69.42.3

198.168.7.6

Inlabel

Outlabel

Address Prefix N/wInt.

Inlabel

Outlabel

Address Prefix N/wInt.

128.89.10.x 5 1

179.69.x.x 7 2128.89.10.x 3 1

179.69.x.x 4 1

3

4

X

X

3

5

Packet arrives DA=128.89.10.25

3Push Label

5Pop label

Forward packet

553

Swap Label

R1 R2

R3

R4

Step 1

Step 2

Step 3

Step 4

Step 5

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Elements of MPLSElements of MPLS Label Forwarding:

Use data link addressing. E.g. ATM VPI/VCI, FR DLCI

Put “shim” header between data link and IP header

Label Creation and Binding.

Label Assignment and Distribution:

Ride piggyback on routing protocols, where possible (BGP).

Use separate label distrn. protocol:RSVP-TE, LDP/CR-LDP

Variable

L2 header L3 IP header MPLS “shim” header

Higher Layers

4 bytes 20 bytes

Label CoS TTL S

20 bits 3 bits 8 bits

Data Plane

Control Plane

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Motivation for MPLS control plane: Similarities between LSRs and OXCsMotivation for MPLS control plane: Similarities between LSRs and OXCs

Analogous data plane processing

De-couple control plane from data plane

Path is setup using control plane

Data is forwarded using data plane

LSR uses label swapping to transfer labeled pkt. from I/P to O/P

OXC uses switching matrix to connect channel from I/P to O/P

Controller

Switching Matrix

LSR OXC

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Motivation for MPLS control plane: Similarities between LSRs and OXCsMotivation for MPLS control plane: Similarities between LSRs and OXCs

Data plane relationships

Controller

Switching Matrix

1

2

1

2

<1, label > <2, label >

OXC: <in_port, in_channel> <out_port, out_channel>

LSR: <in_port, in_label> <out_port, out_label>

<1, > <2, >

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Motivation for MPLS control plane: Similarities between LSPs and channelsMotivation for MPLS control plane: Similarities between LSPs and channels

Point-to-point, virtual path connection abstractions

Induce a virtual graph on the underlying topology

Payload is transparent to intermediate nodes

Constraint-based routing (CBR) used to select paths

IP Routers OXCs

LSPs Optical Channels

Induced virtual graph Induced virtual graph

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Similarities between the MPLS and optical network control planesSimilarities between the MPLS and optical network control planes

The two control planes have nearly identical functions:Addressing

Resource discovery

Routing

Signaling/connection management

Constructs from MPLS-TE can be adapted for OXCs

Local adaptation can be used to tailor the control plane to specific OXC implementations with different hardware capabilities

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What adaptations does this reuse entail?Enhancements to signaling and routingWhat adaptations does this reuse entail?Enhancements to signaling and routing

Termination incapable

Fiber switch capable

Termination capable

SONET capable

Handle links with different capabilities

OXC

Router

OC-48

OC-48

Router

OC-48

OC-48

Fiber

2

Wavelength 1

1

OC-48 SONET frames

Wavelength switch capable Packet switch capable

SXC

OC-192SXC

OC-192

OC-192 SONET frame

OC-192 SONET frame

R1

R2

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What adaptations does this reuse entail?Enhancements to signaling and routingWhat adaptations does this reuse entail?Enhancements to signaling and routing

Bind the control and data (bearer) channels Activate/deactivate bearer channels

Assign bearer channels to optical paths

De-multiplex control traffic for different bearer channels

Handle links with disparate bandwidth granularities Fiber, wavelength, and SONET channels

Have routing protocol distribute info. on available b/w resources

Enhance routing to carry info. about physical fiber plant diversity

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What adaptations does this reuse entail?Enhancements to optical elementsWhat adaptations does this reuse entail?Enhancements to optical elements

Mechanism to exchange control information

Out-of-band

Via an optical supervisory channel (OSC)

In-band

Via overhead in “digital wrapper” or SONET overhead bytes

Via a separate IP network Via sub-carrier modulation (SCM) on the optical channel

Control Plane

OSC

Separate network

Digital wrapper or SONET overhead bytes

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Implementation choices for the control channel: Out-of-band signalingImplementation choices for the control channel: Out-of-band signaling

Use a separate as an OSC

Possible when the wavelength count is large

Use physically separate control network

O-EMPLS

signalingControl wavelength

Data wavelengths

Wavelength switchingIncoming

fiber

Outgoing fiber

E-O

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Implementation choices for the control channel: In-band signalingImplementation choices for the control channel: In-band signaling

Use overhead in “digital wrapper” or SONET frame

Assumes all O-E-O devices

Use sub-carrier modulation

Gives control channel with Mb/s of bandwidth

Reserve part of bandwidth of a for MPLS signaling

Useful when count is small

Assumes O-E-O at node Outgoing fiber

Control wavelength

Incoming fiber

O-E E-O

MPLS signaling

Label Processing

Control Packets

MPLS signaling

SubcarrierExtraction

SubcarrierInsertion

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Architectural considerations in deployment: Overlay modelArchitectural considerations in deployment: Overlay model

Use different instances of the control plane in the OTN and IP domains

IP domain a client of optical domain

OTN provides p2p optical channels between IP network elements

Gives maximal control isolation

IP Router Network

Optical Transport Network

Overlay Model

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Architectural considerations in deployment: Peer modelArchitectural considerations in deployment: Peer model

Use single instance of control plane in optical and IP domain

Both domains run common signaling and routing protocol stacks

IP reachability info. is passed around within optical domain

IP Router Network

Optical TransportNetwork

Peer Model

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Advantages of a uniform control infrastructureAdvantages of a uniform control infrastructure

Provides a framework for: Optical bandwidth management

Real-time optical channel provisioning

Allows uniform semantics for network management and operational control in both transport and data networks

Enables inter-working of network elements from different vendors

Simplifies inter-network provisioning

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Some control plane issues currently under developmentSome control plane issues currently under development

Setting up of symmetric, bi-directional channels (e.g. SONET or GbE)

Current signaling does not allow a bi-directional path to be setup in a single reservation round.

Optical path descriptor

Describes the characteristics of the channel (a fiber,, or SONET channel) to be established

Useful to verify that all links along the the path can support the descriptor (compatibility check)

E.g. OC-48 channel reservation wishing to cross an OC-192 link will be successful if the link supports OC-48 multiplexing

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Some control plane issues currently under developmentSome control plane issues currently under development

Need protocols for link provisioning and fault isolation

Discovery of OXC adjacency and port interconnections

Negotiation of acceptable label ranges btwn. neighbors

Setting up of port map tables (consulted during setting up and tearing down channels)

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Unresolved issues in control plane developmentUnresolved issues in control plane development

Need to extend protocols for high-reliability

Require diverse routing, associated path computation algorithms

Fault detection/isolation is an issue, esp. in pure OXCs

Need characteristics and performance of paths for dynamic bandwidth provisioning

Digital overhead bits do not give channel performance data

Identifying causes of degradation is difficult

Setting appropriate threshold values for alarms is difficult

Alarm correlation is imp. For e.g., a failed could trigger alarms from all downstream OXCs.

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SummarySummary

Explored the need for agile optical networks.

Examined components needed for agility.

Analyzed drawbacks of existing network management systems for providing dynamic control.

Motivated choice of MPLS control plane as possible candidate for adoption in optical networks.

Examined optics-specific enhancements needed in MPLS control plane, and control enhancements needed in optical network elements.

Discussed implementation choices and architectural considerations

Overviewed some open and unresolved issues.