Lecture 13

Lecture 13 - EE 555 Broadband Network Architectures...

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EE 555 Broadband Network Architectures 2.5 Packet/Network Layer Technologies Prof. John Silvester Wide Area Network Architecture Options IP IP IP IP IP HDLC ATM PPP Ethernet Ethernet (MAC) MPLS? (WAN-PHY) 802.1q; PBB? Digital Service (e.g. SONET OC-X SONET/SDH OC-X SONET/SDH OC-192 Ethernet (10G LAN-PHY) T1, T3) OC X OC X OC 192 (10G LAN PHY) Wire/Optical Optical λ Optical λ Optical λ Optical λ Traditiona IP over ATM POS (Packet IP over IP over Etherne Traditional POS (Packet over SONET) IP over Ethernet over SONET IP over Ethernet 2 usc-den-ee555-spring2009
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Virtual Circuit Functionality • VC to better manage flows and provide more VC to better manage flows and provide more predictable performance •A TM – designed to supported voice and other traffic types • MPLS – coming out of frame relay, to support both ATM and IP. Became the dominate solution • PBB – Provider based bridges for Ethernet Switching in the (wide-area) Backbone 3 usc-den-ee555-spring2009 Basic ATM Structure (Fast) Packet Switching using fixed length packets (called cells). Faster packer processing and buffer management Cell switch can Faster packer processing and buffer management. Cell switch can be implemented largely in hardware Virtual circuit (split into virtual path and virtual channel) Error detection on header only (to prevent inserting a cell into the wrong stream which could cause all kinds of problems) No HBH error detection or recovery on payload Small header since minimal functionality (this is necessary due to small packet size necessitated by voice small packet size necessitated by voice) Various types of traffic defined – CBR: continuous bit rate – VBR: variable bit rate – ABR: available bit rate (best effort) 4 usc-den-ee555-spring2009
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ATM Protocol Architecture 5 usc-den-ee555-spring2009 Packet (Cell) Size for ATM • Needed to satisfy the voice demands of low Needed to satisfy the voice demands of low latency (<50ms) •D e l a y components – Packetization delay (time to fill a packet) – Transmission delay (time to transmit the packet) – Store and Forward delay (time to store and forward the packet) (per hop) – Propagation delay (ETE) – Processing delay (per hop) – Queueing delay (per hop Queueing delay (per hop) 6 usc-den-ee555-spring2009
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Voice -Example Voice Example Processing delay (per hop) – small to negligible for virtual circuit Queueing delay (per hop) – small to negligible for fixed bit rate virtual circuit Propagation delay (ETE) – about 15ms for LA-NY Transmission delay (time to transmit the packet) – Link Transmission delay (time to transmit the packet) Link Capacity/Packet Length. Basically negligible for fast links and small packets. For Capacity of 50 Mbps and 10,000 bit packet this is less than 1ms Store and Forward delay (time to store and forward the packet) (per Store and Forward delay (time to store and forward the packet) (per hop) – same as transmission delay (for a single packet) Packetization delay (time to fill a packet) An 8-bit voice sample is generated every 125 μ s (8,000 samples per second). For a 10,000
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Lecture 13 - EE 555 Broadband Network Architectures...

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