IP over WDM network

Chia sẻ: Nguyendanh Son | Ngày: | Loại File: PPT | Số trang:23

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Outline: History of WDM networks. Current Internet: Multilayer protocol stack between IP and WDM layers. Future: IP directly over WDM Challenge: Virtual Topology Reconfiguration, Multilayer routing, One proposal: Optical Burst Switching technologies.

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Nội dung Text: IP over WDM network

IP over WDM network Fang Yu 294 Class Presentation
Outline  History of WDM networks  Current Internet: Multilayer protocol stack between IP and WDM layers  Future: IP directly over WDM  Challenge  Virtual Topology Reconfiguration  Multilayer routing  One proposal: Optical Burst Switching technologies
History  In the late 70s  First fiber based optical transmission system  Before 1995  Mostly a single highspeed optical channel  All multiplexing done in electrical domain(TDM)  50Mb/s to 10Gb/s data services  After 1995  WDM allows simultaneously transmitting multiple highspeed channels on different frequencies (Up to 160 wavelengths today)  40G per λ (OC768)  Total link capacity = 160 λ *40G =6.4 Tbps
Current Typical Protocol Stacks IP N e tw o rk D a ta lin k ATM N e tw o rk D a ta lin k IP SONET N e tw o rk ATM D a ta lin k SONET WDM P h y s ic a l WDM
Transport Layer Model “Packet” 1/0 DCS 4E 4E “Packet” 1/0 DCS Service CHCG Layers “Packet” “Packet” 1/0 DCS 1/0 DCS LA 4E 4E DS1 (1.5 Mb/s) ATM/IP ATM/IP DS3 LA 3/1 DCS 3/1 DCS 3/1 DCS (45 Mb/s) Layer ATM/IP ATM/IP 3/1 DCS 3/1 DCS CHCG Core ATM/IP DACS III DACS III Layers CHCG LA DACS III DACS III 3/3 DCS DS3 Layer (DACS III) (45 Mb/s) PHNX SONET ADM LA ADM ADM ADM ADM CHCG Layer ADM ADM ADM OC48+ Wavelength Path (2.5+ Gb/s) Hard- LA OTS OTS OTS OTS OTS OTS Crossconnect Wired PHNX CHCG Optical Transport (OTS: System) Proprietary (20-400 Gb/s) Wavelength Mux Section CHCG Crossconnect LA PHNX Fiber Conduit/ Media Sheath Layer
Disadvantage of Current Multi layer Protocol Stack  Inefficient  In IP over ATM over SONET over WDM network, 22% bandwidth used for protocol overhead  Layers often do not work in concert  Every layer now runs at its own speed. So, low speed devices cannot fill the wavelength bandwidth.  When detecting of failure, different layers compete for protection  Optical layer detects failure almost immediately, restores error in 2us to 60ms  SONET layer detects failure in 2.3–100 us, restores error in 60 ms
Disadvantage of Current Multi layer Protocol Stack (Cont)  Functional overlap: So many layers are doing the same thing  Routing  Protections  Slow speed  Electronic devices can not catch the transmission speed available at optical layer  Latencies of connection
Historical Reason for Multilayer  SONET over WDM  Conventional WDM deployment is using SONET as standard interface to higher layers  IP over ATM  IP packets need to be mapped into ATM cells before transporting over WDM using SONET frame  OEO conversions at every node is easier to build than all optical switch Electronic Electronic O/E/O Network E/O O/E/O E/O Network O/E/O O/E/O O/E/O O/E/O E/O E/O Electronic Electronic Network Network Optical Core
Simplified Protocol Stacks? IP IP Frame Relay WDMaware Electronic layer ATM SONET WDM WDM Current Typical Protocol Stack Simplified Protocol Stack
IP Directly Over WDM?  Establish highspeed optical layer connections (lightpaths)  IP routers connected through lightpaths rather than fiber IP ro u te r B C E W a v e le n g th c ro ssco n n e c t L ig h tp a th s A D
Challenge for IP over WDM network  WDMaware Electronic layer  Reconfiguration and load balancing  Protection and restoration  Optical flow switching  Network management/control  Crosslayer optimization  Reconfigurable (within milliseconds) OXC  Wavelength Converters 2 3 3 2 WC No λ converters With λ converters 1 New request 1 New request 1 3 1 3
Virtual Topology Reconfiguration  Physical topology  Seen by optical layer  Virtual topology: a set of nodes interconnected by lightpaths (wavelength)  Seen by electronic layer  Reconfigure of lightpaths in WDM network by  Changing the light path connectivity between electronic switches  Tuning of the transmitter wavelength and the frequencyselective switches A B A B C D C D
Virtual Topology Reconfiguration(Cont.)  Enable network to dynamically response to changing of traffic pattern  Load balancing Fixed Blocking Probability 0.1 Routing  Efficiency Reconfigurable X6 Routing 0.01 WDM ring, 20 nodes one transceiver/node call BW = 1 wavelength 0.001  Issues: 0.01 0.02 0.03 Call arrival rate 0.04 0.05  Time scale of changes  Triggered by what mechanisms  IP routing properties (e. g. stability)
Multilayer Routing  IP layer routing is the bottleneck of present Internet  Solution: Routing long duration flows at lower layers User 1 Network control User 2 ... ... Router 1 Router 2 Router 3 WDM layer • Conventional packet routing • Optical bypass of intermediate routers for high volume traffic LIDS • End-to end (user-to-user) flow of entire file bypassing routers
Multilayer Routing(Cont.)  Routing in higher layer  No bandwidth reservation needed  More knowledge of application requirements  Routing in lower layer  Faster routing  Faster error detection and restoration
Switching all the packets in optical layer?  Requires intelligence in the optical layer  Need to store packet during header processing  Optical buffers are extremely hard to implement  1 pkt = 12 kbits @ 10 Gbps requires 1.2 µs of delay => 360 m of fiber)  Optical Packet Switch still has a long way to go………………………
Various Optical Switching Technologies
Optical Burst Packet Switching  Retrospect the goal of IP over WDM:  Avoid electronic bottlenecks  Decrease the cost by simplifying the multiple layer architecture  OBS is one proposal of how to realize such a network
Optical Burst Switching  Resources are allocated using one way reservation  Sender sends a request  Sender sends burst without waiting for an acknowledgement of its reservation request  Switch does preparation for the burst when getting the request  Bursts can have variable lengths  Burst switching does not necessarily require buffering
Various OBSs  The schemes differ in the way bandwidth release is triggered.  Inbandterminator (IBT) – header carries the routing information, then the payload followed by silence (needs to be done optically).  Tellandgo (TAG) – a control packet is sent out to reserve resources and then the burst is sent without waiting for acknowledgement. Refresh packets are sent to keep the path alive.