Switching Architectures for Optical Networks CSIT 560 by M. Hamdi 1
Internet Reality Data Center SONET DWD M SONET Access Metro Long Haul CSIT 560 by M. Hamdi Metro Access 2
Hierarchies of Networks: IP / ATM / SONET / WDM CSIT 560 by M. Hamdi 3
Why Optical? • Enormous bandwidth made available – DWDM makes ~160 channels/ possible in a fiber – Each wavelength “potentially” carries about 40 Gbps – Hence Tbps speeds become a reality • Low bit error rates – 10 -9 as compared to 10 -5 for copper wires • Very large distance transmissions with very little amplification. CSIT 560 by M. Hamdi 4
Dense Wave Division Multiplexing (DWDM) 1 2 3 Long-haul fiber 4 Output fibers Multiple wavelength bands on each fiber Ø Transmit by combining multiple lasers @ different frequencies CSIT 560 by M. Hamdi 5
Anatomy of a DWDM System Terminal B Terminal A Transponder Interfaces M U X Post. Amp Line Amplifiers Direct Connections Pre. Amp D E M U X Transponder Interfaces Direct Connections Basic building blocks • Optical amplifiers • Optical multiplexers • Stable optical sources CSIT 560 by M. Hamdi
User Services & Core Transport EDGE Frame Relay IP IP Router CORE Frame Relay ATM Switch Lease Lines Sonet ADM Users Services TDM Switch OC-3 OC-12 STS-1 Service Provider Networks Transport Provider Networks CSIT 560 by M. Hamdi 7
• Provisioned SONET circuits. • Aggregated into Lamdbas. Core Transport Services Circuit Origin • Carried over Fiber optic cables. Circuit Destination OC-3 OC-12 STS-1 CSIT 560 by M. Hamdi 8
WDM Network: Wavelength View WDM link Edge Router Legacy Interfaces Legacy ( e. g. , Po. S, Gigabit Interfaces Ethernet, IP/ATM) Interfaces Legacy Interfaces Optical Switch CSIT 560 by M. Hamdi 9
Relationship of IP and Optical • Optical brings –Bandwidth multiplication –Network simplicity (removal of redundant layers) • IP brings –Scalable, mature control plane –Universal OS and application support –Global Internet • Collectively IP and Optical (IP+Optical) introduces a set of service-enabling technologies CSIT 560 by M. Hamdi 10
Typical Super POP Interconnectio n Network Core IP router DWDM + Metro Ring ADM Large Multi-service Aggregation Switch Voice Switch Core ATM Switch OXC CSIT 560 by M. Hamdi SONET Coupler & Opt. amp 11
Typical POP Voice Switch D W D M OXC D W D M SONET-XC CSIT 560 by M. Hamdi 12
What are the Challenges with Optical Networks? • Processing: Needs to be done with electronics – Network configuration and management – Packet processing and scheduling – Resource allocation, etc. • Traffic Buffering – Optics still not mature for this (use Delay Fiber Lines) – 1 pkt = 12 kbits @ 10 Gbps requires 1. 2 s of delay => 360 m of fiber) • Switch configuration – Relatively slow CSIT 560 by M. Hamdi 13
Optical Hardware • Optical Add-Drop Multiplexer (OADM) – Allows transit traffic to bypass node optically 1 2 3 1 OADM 2 ’ 3 3 ’ 3 Add and Drop DCS CSIT 560 by M. Hamdi 14
Wavelength Converters • Improve utilization of available wavelengths on links • All-optical WCs being developed • Greatly reduce blocking probabilities 3 2 WC No converters 1 New request 1 3 With converters 1 New request 1 3 CSIT 560 by M. Hamdi 15
Late 90 s: Backbone Nodes ADM ADM Digital Crossconnect DWDM Multiplexer & Demultiplexer IP Router ATM Switch CSIT 560 by M. Hamdi 16
Problems • About 80% traffic through each node is “passthrough” – No need to electronically process such traffic • 80 -channel DWDM requires 80 ADMs • Speed upgrade requires replacing all the ADMs in the node CSIT 560 by M. Hamdi 17
Today: Optical Cross Connect (OXC) Optical Crossconnect DWDM ATM Backbone Switch Digital Cross Connect Terabit IP Router Multiplexer & Demultiplexer IP Router ATM Switch CSIT 560 by M. Hamdi Source: JPMS 18
Wavelength Cross-Connects (WXCs) • A WDM network consists of wavelength cross-connects (WXCs) (OXC) interconnected by fiber links. • 2 Types of WXCs – Wavelength selective cross-connect (WSXC) • Route a message arriving at an incoming fiber on some wavelength to an outgoing fiber on the same wavelength. • Wavelength continuity constraint – Wavelength interchanging cross-connect (WIXC) • Wavelength conversion employed • Yield better performance • Expensive CSIT 560 by M. Hamdi 19
Wavelength Router Control Plane: Wavelength Routing Intelligence Data Plane: Optical Cross Connect Matrix Unidirectional DWDM Links to other Wavelength Routers Single Channel Links to IP Routers, SDH Muxes, . . . CSIT 560 by M. Hamdi Unidirectional DWDM Links to other Wavelength Routers 20
Optical Network Architecture UNI Mesh Optical Network UNI IP Network IP Router OXC Control unit Optical Cross Connect (OXC) Control Path Data Path CSIT 560 by M. Hamdi 21
OXC Control Unit • Each OXC has a control unit • Responsible for switch configuration • Communicates with adjacent OXCs or the client network through single-hop light paths – These are Control light paths – Use standard signaling protocol like GMPLS for control functions • Data light paths carry the data flow – Originate and terminate at client networks/edge routers and transparently traverse the core CSIT 560 by M. Hamdi 22
Optical Cross-connects (No wavelength conversion) l 2 l 4 All Optical Cross-connect (OXC) Also known as Photonic Cross-connect (PXC) l 1 l 3 Optical Switch Fabric l 3 l 4 l 1 l 2 CSIT 560 by M. Hamdi 23
Optical Cross-Connect with Full Wavelength Conversion Wavelength Converters l 2 l 1 l 2 ln l 1, l 2, . . . , ln 2. . . l 1, l 2, . . . , ln M Wavelength Demux l 1, l 2, . . . , ln l 1 ln 1 l 2 ln ln l 1 l 2 Optical Cross. Bar Switch l 1, l 2, . . . , ln 2. . . l 1, l 2, . . . , ln M Wavelength Mux • M demultiplexers at incoming side • M multiplexers at outgoing side • Mn x Mn optical switch has wavelength converters at switch outputs CSIT 560 by M. Hamdi 24
Wavelength Router with O/E and E/O Incoming Interface Incoming Wavelength Cross-Connect Outgoing Interface Outgoing Wavelength l 1 l 3 CSIT 560 by M. Hamdi 25
O-E-O Crossconnect Switch (OXC) Incoming fibers Demux 1 2 N WDM (many λs) Individual wavelengths O O O/E E/O E O/E E/O O/E O/E E/O E/O O/E O/E Outgoing fibers Mux 1 E/O E/O 2 N Switches information signal on a particular wavelength on an incoming fiber to (another) wavelength on an outgoing fiber. CSIT 560 by M. Hamdi 26
Optical core network Opaque (O-E-O) and transparent (O-O) sections Client signals E/O Transparent optical island O/E O O from other nodes O O O E E O O to other nodes E Opaque optical. CSIT 560 by M. Hamdi network O O 27
OEO vs. All-Optical Switches OEO All-Optical • Capable of status monitoring • Optical signal regenerated – improve signal-to-noise ratio • Traffic grooming at various levels • Less aggregated throughput • More expensive • More power consumption • Unable to monitor the contents of the data stream • Only optical amplification – signalto-noise ratio degraded with distance • No traffic grooming in subwavelength level • Higher aggregated throughput • ~10 X cost saving • ~10 X power saving CSIT 560 by M. Hamdi 28
Large customers buy “lightpaths” A lightpath is a series of wavelength links from end to end. optical fibers One fiber Repeater cross-connect CSIT 560 by M. Hamdi 29
Hierarchical switching: Node with switches of different granularities A. Entire fibers Fibers O O O Fibers B. Wavelength subsets O O O C. Individual wavelengths O E “Express trains” O CSIT 560 by M. Hamdi “Local trains” 30
Wide Area Network (WAN) GAN links WAN : Up to 200 -500 wavelengths 40 -160 Gbit/s/l wavebands (> 10 l) OXC: Optical Wavelength/Waveband Cross Connect CSIT 560 by M. Hamdi 31
Packet (a) vs. Burst (b) Switching CSIT 560 by M. Hamdi 32
MAN (Country / Region) IP packets optical burst formation CSIT 560 by M. Hamdi 33
Optical Switching Technologies • • MEMs – Micro. Electro. Mechanical Liquid Crystal Opto-Mechanical Bubble Technology Thermo-optic (Silica, Polymer) Electro-optic (Li. Nb 03, SOA, In. P) Acousto-optic Others… Maturity of technology, Switching speed, Scalability, Cost, Relaiability (moving components or not), etc. CSIT 560 by M. Hamdi 34
MEMS Switches for Optical Cross-Connect Proven technology, switching time (10 to 25 msec), moving mirrors is a reliability problem. CSIT 560 by M. Hamdi 35
WDM “transparent” transmission system (O-O nodes) Wavelengths disaggregator O Fibers Wavelengths aggregator O O O multiple λs O O Optical switching fabric (MEMS devices, etc. ) Incoming fiber Tiny mirrors CSIT 560 by M. Hamdi Outgoing fibers 36
Upcoming Optical Technologies • WDM routing is circuit switched – Resources are wasted if enough data is not sent – Wastage more prominent in optical networks • Techniques for eliminating resource wastage – Burst Switching – Packet Switching • Optical burst switching (OBS) is a new method to transmit data • A burst has an intermediate characteristics compared to the basic switching units in circuit and packet switching, which are a session and a packet, respectively CSIT 560 by M. Hamdi 37
Optical Burst Switching (OBS) • Group of packets a grouped in to ‘bursts’, which is the transmission unit • Before the transmission, a control packet is sent out – The control packet contains the information of burst arrival time, burst duration, and destination address • Resources are reserved for this burst along the switches along the way • The burst is then transmitted • Reservations are torn down after the burst CSIT 560 by M. Hamdi 38
Optical Burst Switching (OBS) CSIT 560 by M. Hamdi 39
Optical Packet Switching • Fully utilizes the advantages of statistical multiplexing • Optical switching and buffering • Packet has Header + Payload – Separated at an optical switch • Header sent to the electronic control unit, which configures the switch for packet forwarding • Payload remains in optical domain, and is recombined with the header at output interface CSIT 560 by M. Hamdi 40
Optical Packet Switch • Has – Input interface, Switching fabric, Output interface and control unit • Input interface separates payload and header • Control unit operates in electronic domain and configures the switch fabric • Output interface regenerates optical signals and inserts packet headers • Issues in optical packet switches – Synchronization – Contention resolution CSIT 560 by M. Hamdi 41
• Main operation in a switch: – – The header and the payload are separated. Header is processed electronically. Payload remains as an optical signal throughout the switch. Payload and header are re-combined at the output interface. hdr payload CPU hdr payload Wavelength i input port j Re-combined Wavelength i output port j Optical packet Optical switch CSIT 560 by M. Hamdi 42
Output port contention • Assuming a non-blocking switching matrix, more than one packet may arrive at the same output port at the same time. Input ports Optical Switch payloadhdr . . . payloadhdr CSIT 560 by M. Hamdi Output ports. . . 43
OPS Architecture: Synchronization Occurs in electronic switches – solved by input buffering Slotted networks • Fixed packet size • Synchronization stages required Sync. CSIT 560 by M. Hamdi 44
OPS Architecture: Synchronization Slotted networks • Fixed packet size • Synchronization stages required Sync. CSIT 560 by M. Hamdi 45
OPS Architecture: Synchronization Slotted networks • Fixed packet size • Synchronization stages required Sync. CSIT 560 by M. Hamdi 46
OPS Architecture: Synchronization Slotted networks • Fixed packet size • Synchronization stages required Sync. CSIT 560 by M. Hamdi 47
OPS Architecture: Synchronization Slotted networks • Fixed packet size • Synchronization stages required Sync. CSIT 560 by M. Hamdi 48
OPS Architecture: Synchronization Sync. CSIT 560 by M. Hamdi 49
OPS: Contention Resolution • More than one packet trying to go out of the same output port at the same time – Occurs in electronic switches too and is resolved by buffering the packets at the output – Optical buffering ? • Solutions for contention – Optical Buffering – Wavelength multiplexing – Deflection routing CSIT 560 by M. Hamdi 50
OPS Architecture Contention Resolutions 1 2 3 1 1 2 1 4 3 4 CSIT 560 by M. Hamdi 51
OPS: Contention Resolution • Optical Buffering – Should hold an optical signal • How? By delaying it using Optical Delay Lines (ODL) – ODLs are acceptable in prototypes, but not commercially viable – Can convert the signal to electronic domain, store, and reconvert the signal back to optical domain • Electronic memories too slow for optical networks CSIT 560 by M. Hamdi 52
OPS Architecture Contention Resolutions • Optical buffering 1 1 2 3 1 2 1 3 4 4 CSIT 560 by M. Hamdi 53
OPS Architecture Contention Resolutions • Optical buffering 1 1 2 2 3 3 4 4 CSIT 560 by M. Hamdi 54
OPS Architecture Contention Resolutions • Optical buffering 1 1 1 2 2 3 3 4 4 1 CSIT 560 by M. Hamdi 55
OPS: Contention Resolution • Wavelength multiplexing – Resolve contention by transmitting on different wavelengths – Requires wavelength converters - $$$ CSIT 560 by M. Hamdi 56
OPS Architecture Contention Resolutions • Wavelength conversion 1 1 2 2 CSIT 560 by M. Hamdi 57
OPS Architecture Contention Resolutions • Wavelength conversion 1 1 2 2 CSIT 560 by M. Hamdi 58
OPS Architecture Contention Resolutions • Wavelength conversion 1 1 2 2 CSIT 560 by M. Hamdi 59
OPS Architecture Contention Resolutions • Wavelength conversion 1 1 2 2 CSIT 560 by M. Hamdi 60
OPS Architecture Contention Resolutions • Wavelength conversion 1 1 2 2 CSIT 560 by M. Hamdi 61
Deflection routing • When there is a conflict between two optical packets, one will be routed to the correct output port, and the other will be routed to any other available output port. • A deflected optical packet may follow a longer path to its destination. In view of this: – The end-to-end delay for an optical packet may be unacceptably high. – Optical packets may have to be re-ordered at the destination CSIT 560 by M. Hamdi 62
Electronic Switches Using Optical Crossbars CSIT 560 by M. Hamdi 63
Scalable Multi-Rack Switch Architecture Optical links Line card rack Switch Core • Number of linecards is limited in a single rack – Limited power supplement, i. e. 10 KW – Physical consideration, i. e. temperature, humidity • Scaling to multiple racks – Fiber links and central fabrics CSIT 560 by M. Hamdi 64
Logical Architecture of Multi-rack Switches Scheduler Line Card Fiber I/O Local Framer Buffers Laser Line Card Laser Local Buffers Framer Fiber I/O Crossbar Line Card Fiber I/O Local Framer Buffers Line Card Laser Local Buffers Framer Fiber I/O Switch Fabric System • Optical I/O interfaces connected to WDM fibers • Electronic packet processing and buffering – Optical buffering, i. e. fiber delay lines, is costly and not mature • Optical interconnect – Higher bandwidth, lower latency and extended link length than copper twisted lines • Switch fabric: electronic? Optical? CSIT 560 by M. Hamdi 65
Optical Switch Fabric Scheduler Line Card Fiber I/O Local Framer Buffers Laser Line Card Laser Local Laser Buffers Framer Fiber I/O Crossbar Line Card Fiber I/O Local Framer Buffers Line Card Laser Local Buffers Framer Fiber I/O Switch Fabric System • Less optical-to-electrical conversion inside switch – Cheaper, physically smaller • Compare to electronic fabric, optical fabric brings advantages in – Low power requirement, Scalability, Port density, High capacity • Technologies that can be used – 2 D/3 D MEMS, liquid crystal, bubbles, thermo-optic, etc. • Hybrid architecture takes advantage of the strengths of both CSIT 560 by M. Hamdi electronics and optics 66
Electronic Vs. Optical Fabric Electronic Trans. Buffer Inter. Line connection Inter- Buffer Trans. connection Line Switching Fabric Optical Electronic E/O or O/E Conversion fa v Optical orr ed Trans. Buffer Inter. Line connection Inter- Buffer Trans. connection Line Switching Fabric CSIT 560 by M. Hamdi 67
Multi-rack Hybrid Packet Switch CSIT 560 by M. Hamdi 68
Features of Optical Fabric • Less E/O or O/E conversion • High capacity • Low power consumption • Less cost However, • Reconfiguration overhead (50 -100 ns) – Tuning of lasers (20 -30 ns) – System clock synchronization (10 -20 ns or higher) CSIT 560 by M. Hamdi 69
Scheduling Under Reconfiguration Overhead • Traditional slot-by-slot approach Scheduler Schedule Reconfigure Transfer Time Line • Low bandwidth usage CSIT 560 by M. Hamdi 70
Reduced Rate Scheduling Fabric setup (reconfigure) Traffic transfer Time slot Slot-by-slot Scheduling, zero fabric setup time Slot-by-slot Scheduling with reconfigure delay Reduced rate Scheduling, each schedule is held for some time • Challenge: fabric reconfiguration delay – • Traditional slot-by-slot scheduling brings lots of overhead Solution: slow down the scheduling frequency to compensate – • Each schedule will be held for some time Scheduling task 1. 2. Find out the matching Determine the holding time CSIT 560 by M. Hamdi 71
Scheduling Under Reconfiguration Overhead • Reduce the scheduling rate – Bandwidth Usage = Transfer/(Reconfigure+Transfer) Constant • Approaches – Batch scheduling: TSA-based – Single scheduling: Schedule + Hold CSIT 560 by M. Hamdi 72
Single Scheduling • Schedule + Hold – One schedule is generated each time – Each schedule is held for some time (holding time) – Holding time can be fixed or variable – Example: LQF+Hold CSIT 560 by M. Hamdi 73
Routing and Wavelength Assignment CSIT 560 by M. Hamdi 74
Optical Circuit Switching • An optical path established between two nodes • Created by allocation of a wavelength throughout the path. • Provides a ‘circuit switched’ interconnection between two nodes. – Path setup takes at least one RTT – No optical buffers since path is pre-set Desirable to establish light paths between every pair of nodes. • Limitations in WDM routing networks, – Number of wavelengths is limited. – Physical constraints: • limited number of optical transceivers limit the number of channels. CSIT 560 by M. Hamdi 75
Routing and Wavelength Assignment (RWA) • Light path establishment involves – Selecting a physical path between source and destination edge nodes – Assigning a wavelength for the light path • RWA is more complex than normal routing because – Wavelength continuity constraint • A light path must have same wavelength along all the links in the path – Distinct Wavelength Constraint • Light paths using the same link must have different wavelengths CSIT 560 by M. Hamdi 76
No Wavelength Converters WSXC Access Fiber Wavelength 1 POP Wavelength 2 Wavelength 3 CSIT 560 by M. Hamdi 77
With Wavelength Converters WIXC Access Fiber POP Wavelength 1 POP Wavelength 2 Wavelength 3 CSIT 560 by M. Hamdi 78
Routing and Wavelength Assignment (RWA) • RWA algorithms based on traffic assumptions: • Static Traffic – Set of connections for source and destination pairs are given • Dynamic Traffic – Connection requests arrive to and depart from network one by one in a random manner. – Performance metrics used fall under one of the following three categories: • Number of wavelengths required • Connection blocking probability: Ratio between number of blocked connections and total number of connections arrived CSIT 560 by M. Hamdi 79
Static and Dynamic RWA • Static RWA – Light path assignment when traffic is known well in advance – Arises in capacity planning and design of optical networks • Dynamic RWA – Light path assignment to be done when requests arrive in random fashion – Encountered during real-time network operation CSIT 560 by M. Hamdi 80
Static RWA • RWA is usually solved as an optimization problem with Integer Programming (IP) formulations • Objective functions – Minimize average weighted number of hops – Minimize average packet delay – Minimize the maximum congestion level – Minimize number of Wavelenghts CSIT 560 by M. Hamdi 81
Static RWA • Methodologies for solving Static RWA – Heuristics for solving the overall ILP sub-optimally – Algorithms that decompose the static RWA problem into a set of individual sub-problems, and solve a sub-set – http: //www. tct. hut. fi/~esa/java/wdm/ CSIT 560 by M. Hamdi 82
Solving Dynamic RWA • During network operation, requests for new lightpaths come randomly • These requests will have to be serviced based on the network state at that instant • As the problem is in real-time, dynamic RWA algorithms should be simple • The problem is broken down into two sub-problems – Routing problem – Wavelength assignment problem CSIT 560 by M. Hamdi 83
Optical Circuit Switching all the Way: End-to-End !!! Why might this be possible: • Huge CS bandwidth (large # of wavelength) – BW efficiency is not very crucial • Circuit switches have a much higher capacity than Packet switches, and Qo. S is trivial • Optical Technology is suited for CS CSIT 560 by M. Hamdi 84
How the Internet Looks Like Today The core of the Internet is already “predominantly” CS. Even a “large” portion of the access networks use CS (Modem, DSLs) CSIT 560 by M. Hamdi 85
How the Internet Really Looks Like Today SONET/SDH DWDM CSIT 560 by M. Hamdi 86
How the Internet Really Looks Like Today Modems, DSL CSIT 560 by M. Hamdi 87
Why Is the Internet Packet Switched in the First Place? • PS is bandwidth efficient “Statistical Multiplexing” • PS networks are robust Gallager: “Circuit switching is rarely used for data networks, . . . because of very inefficient use of the links” Tanenbaum: ”For high reliability, . . . [the Internet] was to be a datagram subnet, so if some lines and [routers] were destroyed, messages could be. . . rerouted” CSIT 560 by M. Hamdi 88
Are These Assumptions Valid Today? • • PS is bandwidth efficient • PS networks are robust • § § 10 -15% average link utilization in the backbone today. Similar story for access networks Routers/Switches are designed for <5 s down-time per year. They take >1 min to recover when they do (circuit switches must recover in <50 ms). CSIT 560 by M. Hamdi 89
How Can Circuit Switching Help the Internet? • Simple switches/routers: • • No buffering No per-packet processing (just per connection processing) Possible all-optical data path Peak allocation of BW • No delay jitter CSIT 560 by M. Hamdi Higher capacity switches Simple but strict Qo. S 90
Myth: Packet switching is simpler • A typical Internet router contains over 500 M gates, 32 CPUs and 10 Gbytes of memory. • A circuit switch of the same generation could run ten times faster with 1/10 th the gates and no memory. CSIT 560 by M. Hamdi 91
Instructions per arriving byte Packet Switch Capacity What we’d like: (more features) Qo. S, Multicast, Security, … What will happen: (fewer features) Or perhaps we’re doing something wrong? CSIT 560 by M. Hamdi time 92
What Is the Performance of Circuit Switching? End-to-End File = 10 Mbit 100 clients 1 Gb/s 1 server x 100 Circuit sw Packet sw Flow BW 1 Gb/s 10 Mb/s Avg latency 0. 505 s 1 s Worst latency 1 s 1 s CSIT 560 by M. Hamdi 99% of Circuits Finish Earlier 93
What Is the Performance of Circuit Switching? File = 10 Gbit/10 Mbit 100 clients 1 Gb/s 1 server x 99 Circuit sw Packet sw Flow BW 1 Gb/s 10 Mb/s+1 Gb/s Avg latency 10. 495 s 1. 099 sec Worst latency 10. 990 sec CSIT 560 by M. Hamdi A big file can kill CS if it blocks the link 94
What Is the Performance of Circuit Switching? File = 10 Gbit/10 Mbit 100 clients 1 Gb/s 1 server x 99 1 Mb/s Circuit sw Packet sw Flow BW 1 Mb/s Avg latency 109. 9 sec Worst latency 10, 000 sec CSIT 560 by M. Hamdi No difference between CS and PS in core 95
Possible Implementation TCP Switching • Create a separate circuit for each flow • IP controls circuits • Optimize for the most common case – TCP (85 -95% of traffic) – Data (8 -9 out of 10 pkts) CSIT 560 by M. Hamdi 96
TCP Switching Exposes Circuits to IP IP routers TCP Switches CSIT 560 by M. Hamdi 97
TCP “Creates” a Connection Source Router SYN Destination SYN+ACK DATA Packets CSIT 560 by M. Hamdi Packets 98
State Management Feasibility • Amount of state – Minimum circuit = 64 kb/s. – 156, 000 circuits for OC-192. • Update rate – About 50, 000 new entries per sec for OC-192. • Readily implemented in hardware or software. CSIT 560 by M. Hamdi 99
Software Implementation Results TCP Switching boundary router: • Kernel module in Linux 2. 4 1 GHz PC • Forwarding latency – Forward one packet: 21 s. – Compare to: 17 s for IP. – Compare to: 95 s for IP + Qo. S. • Time to create new circuit: 57 s. CSIT 560 by M. Hamdi 100
Скачать презентацию Switching Architectures for Optical Networks CSIT 560 by
d84bcacad9a5bc33103f6661ee193f4e.ppt