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A Perspective on Photonic Multi-Protocol Label Switching

A Perspective on Photonic Multi-Protocol Label Switching. Masayuki Murata Cybermedia Center, Osaka University e-mail: murata@cmc.osaka-u.ac.jp http://www-ana.ics.es.osaka-u.ac.jp/. Contents. MP l S (MPLS based on WDM Lightpaths) Implementation Issues and Challenging Problems

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A Perspective on Photonic Multi-Protocol Label Switching

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  1. A Perspective on Photonic Multi-Protocol Label Switching Masayuki Murata Cybermedia Center, Osaka University e-mail: murata@cmc.osaka-u.ac.jp http://www-ana.ics.es.osaka-u.ac.jp/

  2. Contents MPlS (MPLS based on WDM Lightpaths) Implementation Issues and Challenging Problems OC-MPLS (MPLS based on Optical Code) Optical Implementations and Challenging Issues Perspectives on MPlS and OC-MPLS Advantages and Disadvantages

  3. Wavelength Demux Wavelength Mux Optical Switch Optical Crossconnect λ λ λ λ λ λ λ λ λ λ λ 1 1 1 2 2 1 1 2 2 2 1 Mapping from Generic MPLS to Lambda MPLS (or GMPLS) LSP (Label-Switched Path); Wavelength path (Lightpath) LSR (Label Switching Router); Optical crossconnect directly connecting input wavelength to output wavelength X X X Ingress LSR; Maps from IP address to lambda LDP (Label Distribution Protocol); Dimensioning by wavelength and routing assignment algorithm M. Murata

  4. Router X X X Optical Crossconnect Photonic Internet Architecture • Four Kinds of Architecture • WDM link network • Connects adjacent routers by WDM (multiple wavelengths increase the bandwidth) • WDM path network • Cut-through techniques for IP packets on established path provided by the underlying networks Router M. Murata

  5. Photonic Internet Architecture (Cont’d) • WDM Path Network • Lambda switching by MPLS technology(MPlS or GMPLS) • WDM Packet-switched Network • E.g., burst switching by routing and wavelength assignment (RWA) on demand basis Router X X X Optical Cross-Connect burst X X X M. Murata

  6. IP Router N N N N N N 4 3 2 3 4 2 Ingress LSR l-MPLS IP Router Ingress LSR l-MPLS Core LSR Core LSR Wavelength Demux Wavelength Mux l l l l l l l l l l l l l l l l l l l l l l l l l l l 1 1 2 2 1 1 2 2 1 1 1 2 1 2 2 1 2 2 1 1 1 1 2 2 2 1 2 Optical Switch N N N N N N N N N N 5 5 2 4 2 1 1 4 3 3 Optical Cross-Connect Logical Topology by Wavelength Routing • Physical Topology • Logical Topology M. Murata

  7. IP Router Logical View Provided to IP • Redundant Network with Large Degrees • Smaller number of hop-counts between end-nodes • Decrease load for packet forwarding at the router • Relief bottleneck at the router M. Murata

  8. Challenging Problems of MPlS • Logical Topology Design Issues • Past researches assume the traffic matrix is given • Objective is maximization of wavelength utilization or minimization of the required # of wavelengths • Optimization problem is then solved by LP or heuristics • Bottleneck at Ingress Nodes • Bottleneck is shifted to the Ingress Nodes requiring electronic processing • Survivability • IP and WDM Functional Partitioning or Integration M. Murata

  9. Incremental Capacity Dimensioning Approach • Initial Phase • Design Logical topology with given traffic demand • Incremental Phase • primary lightpath is incrementally setup • reconfigure backup lightpaths • Readjustment Phase • All of the lightpath (including primary lightpath) is reconfigured Initial Phase Incremental Phase Reconfigure backup lightpaths Readjustment Phase Reconfigure both primary and backup M. Murata

  10. l-MPLS Ingress LSR WDM Ring l l l l 3 1 1 2 Traffic Load Distribution by WDM Ring • Distribute the traffic load by WDM ring at the Ingress node M. Murata

  11. Logical Degree = 1024 512 128 Effects of Introducing WDM Ring 10+E5 Logical Degree = 8 1000 128 512 8 1024 10+E4 100 Required # of Wavelengths Required Processing Capability (Mpps) 10+E3 10 1 10+E2 0 5 10 15 20 0 5 10 15 20 The Number of Local Nodes LN The Number of Local Nodes LN Packet Processing Rate Required at Router Required Number of Wavelengths M. Murata

  12. Do We Need More “Intelligent” WDM Network? • WDM network itself has network control capabilities • Routing function • IP also has it! • Congestion control function • TCP also has it! • TCP over ATM (ABR service class) is difficult to work well Parameter tuning of control parameters in ABR is not easy • Connection establishment • IP is connectionless • Multimedia application does not require 10Gbps channel • Multi-layered Functionalities? • Important is reliability M. Murata

  13. Functional Partitioning between IP and WDM? • Reliability functionalities offered by two layers • IP Layer: Routing • WDM Layer: Path Protection and Restoration • WDM should provide its high-reliability mechanism to IP • Protection mechanism • link protection • dedicated-path protection • shared-path protection • Network dimensioning is important to properly acquire the required capacity of IP paths (traffic glooming) • Reconfiguration mechanism of logical topology by wavelength routing M. Murata

  14. WDM Protection • Immediately switch to backup path on failure of nodes/links • In the order of 10ms • 1:1 Protection vs. Many:1 Protection • Protection technique suitable to IP over WDM network? • IP has its own protection mechanism (i.e., routing) while it is slow • We want an effective usage of wavelengths • Many:1 protection is reasonable Primary Path Primary Path Backup Path 1:1 Protection Many:1 Protection M. Murata

  15. Cross-Connect, Switch and Router • Photonic switch within MPLS requires • packet forwarding based on “label” • queue management based on “label” • packet switching and buffering Photonic IP Router Photonic Packet Switch supported by GMPLS Routing Cross-Connect Forwarding Queue Management payload header Switching Buffering M. Murata

  16. 133.1.12.14 133.1.12.14 10 4 Label Swapping in MPLS Core LSR Egress LSR Ingress LSR M. Murata

  17. l1 OC- MPLSR#1 l1 l-DEMUX Output fiber 1 Input fiber 1 l1, l2, ..., lK l-DEMUX l1, l2, ..., lK MUX MUX MUX MUX MUX MUX MUX MUX l-DEMUX Input fiber N OC- MPLSR#N lK Output fiber N lK Optical switch Optical buffer Input packets Output packets Photonic label processor Photonic label swapper 1 bit time 0 p 0 p t OC-based photonic label Optical Code based MPLS • Photonic label based on optical codes OC-based Switching Node OC –based Switch M. Murata

  18. Input Replicas Address entries Output #1 t t t t t t Duplication Correlation t x x104 . . . . . . t # 104 t t Photonic Label Processing • Optical code by BPSK • Photonic label processing in optical domain • photonic label is tapped from packet header • optically dupilcated by optical amplification • power-splitted as many copies as the count of label entries in the table • optical correlations between the copies and the label entries is performed in parallel M. Murata

  19. DL1 DL2 Input packet Output packet 2x2 switch (a) Multi-stage switched delay line buffer EDFA:Erbium doped fiber amplifier PC: Polarization controller EDFA PC (b) Re-circulating loop buffer Implementations of Optical Buffers by Delay Lines M. Murata

  20. Photonic Packet Switch for Asynchronously Arriving Variable Packets • Buffer Scheduling • Delayed Line Buffer • Variable-Length Packets • Counter for Buffer State; bij for output line j on wavelength i • For each arrival of packet with length xFor each delay unit D • For asynchronous arriving • Introduce packet sequencer M. Murata

  21. Optical Switching Unit Optical Scheduling Unit Optical Buffering Unit Scheduler S1W Scheduler S11 b1W lW lW lW OC Decoder Photonic label processor l1 Photonic label processor l1 SC+Gate l1 l1 b11 b11 OC Encoder t0 t0 OC Decoder OC Decoder Header Photonic label processor Photonic label processor SC+Gate lW t1 t1 OC Encoder SC+Gate OC Decoder t0 t0 OC Decoder l1- lW Header l1- lW lW Optical SW SC+Gate OC Decoder t1 t1 Optical SW1 Time Synchronizer SC+Gate OC Decoder l-MUX t2 t2 OC Encoder O1 SC+Gate OC Decoder l-DEMUX Optical SW SC+Gate OC Decoder Optical SW1 t2 t2 l1 lW lW l1 OC Encoder OC Decoder l1 I1 SC+Gate OC Decoder l1 l1 lW OC Decoder Scheduler S2W Scheduler S21 lW lW lW b1W OC Decoder Photonic label processor l1 Photonic label processor l1 SC+Gate OC Encoder OC Decoder OC Decoder Header Photonic label processor Photonic label processor SC+Gate lW OC Encoder SC+Gate OC Decoder OC Decoder l1- lW Header l1- lW lW Optical SW SC+Gate OC Decoder Optical SW1 Time Synchronizer SC+Gate OC Decoder l-MUX OC Encoder O2 SC+Gate OC Decoder l-DEMUX Optical SW SC+Gate OC Decoder Optical SW1 l1 lW lW l1 OC Encoder OC Decoder l1 I2 SC+Gate OC Decoder l1 OC Decoder l1 lW Structure of OC-based Photonic Packet SwitchWithout Wavelength Conversion M. Murata

  22. Photonic label processor l1 Photonic label processor l1 b11 t0 SC+Gate SC+Gate Photonic label processor Photonic label processor t1 OC Encoder/ Decoder OC Encoder/ Decoder SC+Gate SC+Gate t0 Header Optical SW SC+Gate SC+Gate t1 Optical SW1 t2 Optical SW Optical SW1 SC+Gate SC+Gate t2 SC+Gate SC+Gate l1 l1 l1 l1 lW lW SC+Gate SC+Gate l1 b21 t0 t1 t0 t1 t2 t2 Structure of OC-based Photonic Packet SwitchWith Wavelength Conversion Optical Switching Unit Optical Scheduling Unit Optical Buffering Unit Scheduler S1 b1W lW lW lW l1 SC+Gate Header lW OC Encoder/ Decoder SC+Gate Time Synchronizer l1- lW l1- lW lW SC+Gate l-MUX O1 l-DEMUX SC+Gate l1 I1 l1 SC+Gate l1 lW SC+Gate Scheduler S2 b2W lW lW lW l1 l1 Photonic label processor Photonic label processor SC+Gate Header lW Photonic label processor Photonic label processor OC Encoder/ Decoder SC+Gate Time Synchronizer l1- lW Header Optical SW SC+Gate l1- lW lW l-MUX Optical SW1 O2 l-DEMUX Optical SW Optical SW1 SC+Gate l1 I2 l1 SC+Gate l1 lW SC+Gate M. Murata

  23. Performance of Proposed Switch 1 1E-02 1E-04 r = 0.85 1E-06 1E-08 Packet Loss Probability r = 0.8 1E-10 r = 0.75 1E-12 r = 0.7 1E-14 r = 0.65 1E-16 1E-18 5 10 15 20 The Number of Wavelengths W M. Murata

  24. Problems of MPlS • The incremental capacity dimensioning is infeasible in the current logical topology design approach • Network performance is heavily dependent on the logical topology design approach • Unit of Path Granularity is Wavelength Capacity • too large to accommodate the end-to-end traffic • The capacity increase per each wavelength does not alleviate the problem • The increase in the number of wavelengths may help it. However, it requires the large-scaled of, e.g., 1,000x1,000 optical cross-connect • Flow aggregation at the Core LSR cannot be expected • The label exchange within the network poses the wavelength change at an optical node M. Murata

  25. Advantages of OC-MPLS • The granularity is “packet” • Allows a flexible network structure • Simplified packet switching can offer large capacity in the optical domain • An ATM-based MPLS protocol suite can be applied • Traffic engineering developed for MPLS is also utilized. • OC-MPLS is capable of merging of packets by introducing optical buffering • Attains an ultimate bandwidth efficiency • MPlS is unable to realize it due to the coarse granularity. • The length of OC photonic label could be flexible • The longer label could be used as the network layer header of the packet • Can be used both to assigned multiple flows from IP prefix to application-level flow • Possible to offer QoS-enabled services • Optical codes are not only applicable to the exact match algorithm in the OC-MPLS but also applicable to the longest prefix match, and hence OC-based destination-based IP routing might be realizable. M. Murata

  26. Remaining Problems of Establishing OC-MPLS • The switch fabric, constructed with photonic space switch and photonic buffer, has to be optimized to achieve the desired performance • Statistical multiplexing would work well by very huge bandwidth provided by OC techniques even if the packet buffer capacity is not large. However, a further research on the traffic engineering approach of MPLS is necessary under the conditions that the bandwidth is very large, but the packet buffer size is small. M. Murata

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