Introduction to Protection & Restoration for OBS Copyright, 2000, SUNY, Univ. at Buffalo Presented by Zaoyang Guo & Dahai Xu

Outline Basic Concepts of Protection & Restoration Review of OBS Protection & Restoration for OBS

Basic Concepts of Protection & Restoration What is protection & Restoration? Why we need Protection/Restoration? Protection Restoration Comparison between Protection & Restoration Protection/Restoration for Optical Network

What is protection & Restoration? Network is unreliable somehow Protection & Restoration are the mechanisms to recover from network failure Their difference will be discussed in the following parts

Why we need Protection/Restoration? To Recover from network failure To prevent a lot of data loss To provide reliable communication service

Protection Path Protection Link Protection Advantages & Disadvantages

Path Protection Use more than one path to guarantee the data be sent successfully

Path Protection (Continued) Dedicated Path Protection Shared Path Protection

Dedicated Path Protection 1+1 Protection Point-to-Point Protection & Mesh Network Protection

1+1 Protection

Mesh Network Protection

Shared Path Protection 1:1 Protection 1:N Protection

1:1 Protection

1:N Protection

Link Protection Use an alternate path if the link failed

Link Protection (Continued) Dedicated Link Protection: not practical Shared Link Protection: practical It may fail when a node fails

Dedicated Link Protection

Advantages & Disadvantages of Protection Simple Quick: Do not require much extra process time Usually can only recover from single link fault Inefficient usage of resource

Restoration Path Restoration Link Restoration Advantages & Disadvantages

Path Restoration The route can be computed after failure The resource is reserved and then used

Link Restoration The path is discovered at the end nodes of the failed link More practical than path restoration

Advantages & Disadvantages of Restoration Usually can recover from multiplex element faults More efficient usage of resource Complex Slow: require extra process time to setup path and reserve resource

Characteristic: Protection -- the resource are reserved before the failure, they may be not used; Restoration -- the resource are reserved and used after the failure route: Protection -- predetermined; Restoration -- can be dynamically computed Resource Efficiency: Protection -- Low; Restoration -- High Comparison between Protection & Restoration

Time used: Protection -- Short; Restoration -- Long Reliability: Protection -- mainly for single fault; Restoration -- can survive under multiplex faults Implementation: Protection -- Simple; Restoration -- Complex Comparison between Protection & Restoration (Continued)

Protection/Restoration for Optical Network Wavelength Path (WP) & Virtual Wavelength Path (VWP) FDL: to delay data Routing: central controlled or distributed controlled Resource Reservation: forward reservation / backward reservation

Wavelength Path (WP) & Virtual Wavelength Path (VWP) Wavelength Path (WP) / Lightpath (LP) : a wavelength and a physical path, no wavelength translation is used Virtual Wavelength Path (VWP) : wavelength translation may be employed Optical cross-connection

WP & VWP (Continued) Three types of network: no wavelength translation at all nodes; wavelength translation at all nodes; wavelength translation at some nodes

Review of OBS Main Advantages of OBS Requirement & Assumption

Main Advantages of OBS No buffer capacity is required at intermediate nodes: A lightpath/wavelength Path (WP) or Virtual Wavelength Path (VWP) must be setup Quick Setup: No acknowledgement from receiver (destination)

Main Advantages of OBS (Continued) Low Overhead: A control packet is sent and processed before the busty data transmission High efficient utilization of bandwidth: No acknowledgement from destination, low overhead

Requirement & Assumption Reliable Network: No ack. OBS is mainly used in backbone networks Every node knows sufficient information about the route or the topology of the whole network

Requirement & Assumption (Continued) If one element in the network fails, all the nodes will be notified in a short time Assume there will be only one element fail: If one element fails, the others will work correctly Generally only single link failure is considered

Protection & Restoration for OBS Protection/Restoration At The Source Node Protection/Restoration At Intermediate Node

Protection/Restoration At The Source Node Dedicated Path Protection: Send burst data to each path Shared Path Protection: Set a delay time to backup path Disadvantage: Not efficient usage of bandwidth

Protection/Restoration At Intermediate Node Assumption: The intermediate node found the next link is failed when it processes the control packet Method: Use alternate backup path to destination node or only to next node Use longer offset time: Need more intermediate nodes

Protection/Restoration At Intermediate Node (Continued) May need FDL to delay the data The route should be predetermined: No extra time to dynamically compute route VWP preferred: Easy to reserve resource (wavelength) successfully

MPLS Protection Overview MPLS Protection Principles An MPLS path Protection mechanism

Overview of MPLS Protection To deliver reliable service –LSP need protection –LSR provide protection

Motivation for MPLS Protection Layer 3 or IP rerouting is too slow Layer 0 or Layer 1 may be limited Layer 0 or Layer 1 mechanisms can not see higher layer operations Interoperability of protection mechanisms between multi-vendor LSRs in core MPLS networks.

MPLS Protection Principles MPLS protection switching Fast MPLS layer protection No assumptions about the underlying layer 1 or layer 2 transport mechanisms or their protection mechanism.

Objectives of MPLS Protection Fast recovery of the working traffic Should be specified for an LSP, PMTP(Protected MPLS Traffic Portion), or PMTG (Protected MPLS Traffic Group). Specified for traffic on an end-to- end LSP or for a segment of an LSP.

Objectives of MPLS Protection (Cont’) Not adversely effect other network operations. No interference among protection domains. Compatible with lower layers. Avoid Network layer violations.

Protection Configuration Dynamic Pre-negotiate

Protection Activation Global (end-to-end or centralized) Local (distributed)

Protection Span Link protection Path protection

Protection Modes Revertive Non-revertive

Protection Switching Options 1+1 Protection 1:1, 1:n, and n:m Protection

Failure Detection Loss of Signal:A signal is not detected at an interface Link Failure:Link probing mechanism fails Loss of Packets:Excessive discarding of packets at an LSR interface

An MPLS path recovery mechanism Liveness message to detect faults Special tree structure to distribute fault and/or recovery information Permit recovery mechanisms at different layers to coexist Lightweight notification mechanism Minimize delays of a recovery cycle

Core MPLS Path Protection Components Working Path Recovery Path Path Switch LSR (PSL) Path Merge LSR (PML) Intermediate LSR

Reverse Notification Tree (RNT) Can be established in association with the working path Only one RNT is required for all the working paths that merge Can be implemented either at Layer 3 or at Layer 2

Illustration of MPLS protection configuration

Protection Domain Definition:the set of LSRs which the working path and its corresponding recovery path are routed over LSPs merge

Relationship between protection domains with different RNTs –IndependentIndependent –OverlapOverlap with the same RNT

Multiple Faults

Configuration Establishing a Recovery/Protection Path Creating the RNT Engineering a Protection Domain

Establishing a Recovery/Protection Path working path and its corresponding recovery path would be specified during LSP setup –Path selection algorithm (running at a centralized location or at an ingress LSR) –Administrative configuration Inverse cross-connect table

Fault Detection Unidirectional Link Fault –Downlink Fault –Uplink Fault Bi-directional Link Fault or Node Fault

Fault Processing Fault Notification Switch Over Switch Back ----Finished----

Domains With different RNTs (Independent)

Domains With different RNTs (Overlap)

Domains With same RNT

Graph of Switch Over

Inverse cross-connect table

Reference "Survivable WDM Mesh Networks, Part I -Protection", S.Ramamurthy and B. Mukherjeee, IEEE INFOCOM'99, 1999 "Survivable WDM Mesh Networks, Part I -Restoration", S.Ramamurthy and B. Mukherjeee, IEEE INFOCOM'99, 1999 "Wavelength Requirements and Survivability in WDM Cross-Connected Networks", N. Wauters, ECOC'94 "Dynamic Routing of Bandwidth Guaranteed Tunnels with Restoration", Murali Kodialam (Bell Labs, Lucent Technologies), T. V. Lakshman (Bell Labs, Lucent Technologies) IEEE INFOCOM 2000 "Wavelength conversion in WDM networking", B. Ramamurthy and B. Mukherjee, IEEE Journal on Selected Areas in Communications, Sept. 1998, vol.16, (no.7): "Optical Burst Switching (OBS) - A New Paradigm for an Optical Internet", C.Qiao, in a special issue of J. High Speed Networks (JHSN) on WDM Networks, Vol. 8, No. 1, pp

Reference (Cont’) "Choices, Features and Issues in Optical Burst Switching", C.Qiao, to appear in Optical Networks. "MPLS Traffic Engineering : A Choice of Signaling Protocols "- White paper comparing RSVP and CR-LDP for label path distribution. By Data Connection "A Unified Approach to Network Survivability for Teletraffic Networks: Models, Algorithms and Analysis",D. Medhi, IEEE Trans. on Communications, Vol. 42, pp , "Multiprotocol Label Switching Architecture", "A Framework for Multiprotocol Label Switching", "Framework for MPLS Based Recovery", "Protection/Restoration of MPLS Networks", "A Path Protection/Restoration Mechanism for MPLS Networks",