Outlines Received due 13 March 30 %

NO CLASS Week of March (Spring Break)

MID-TERM  1 Hour 15 minute Test  Work 4 of 5 pages  Know the last midterm  Memory Dump in the space provided  Closed Book & Notes  Calculators are NOT allowed...Set up numerical problem for full credit

Term Paper  Due by COB 12 April 2000  Remember to probe further  Any statements not ‘common knowledge’ should be cited in the body of your paper  Don’t ask what I want to see, ask what you want to see

Voice (Video) on LAN (WAN)  More complex system than circuit switched voice  Packet Assembler  Transmitter Buffer  Receiver Buffer  End-to-End Delays > Circuit Switch TDM  Delay Variability > Circuit Switch TDM

Switched Network Carrying Capacity  Line Speed: Traffic injection speed  Efficiency: Ability to use that Line Speed  Carrying Capacity: Ability to usefully use the Line Speed  Accounts for packet overhead  Accounts for inability to fully load StatMux trunk lines & have a usable connection  Accounts for inability to fully load TDM trunk lines with random, bursty traffic

Switched Network Carrying Capacity: Queue Length  100,000,000 bps output trunk  100,000,001 bps average input  Average Input rate > Output rate  Queue Length builds up (without bound, in theory)  Delays go to infinity, Nothing gets dropped

Infinite Length Queue (Classical StatMux Theory) 0% 100% Trunk Offered Load Probability of dropped packets Average Delay for delivered packets

Finite Length Queue (Real World) 0% 100% Trunk Offered Load Probability of dropped packets Average Delay for delivered packets

Finite Length Queue (Real World StatMux) 0% 100% Trunk Offered Load Probability of dropped packets Average Delay for delivered packets Classical Self-Similar

Packet Switch StatMux Trunking (Pure Internet Model) Router SONET OC-N Time Sensitive Traffic Bursty Data Traffic Assumptions: All Time Sensitive Traffic (mainly voice) is packetized. All traffic is Statistically Multiplexed onto the trunk BW.

Cell Switched StatMux Trunking (ATM Model) ATM Switch SONET OC-N Time Sensitive Traffic Bursty Data Traffic Assumptions: CBR traffic gets near-TDM like service. Data Traffic is StatMuxed onto the remaining trunk BW.

Circuit Switch TDM Trunking (Old ‘Private Line’ Network Model) TDM Switch SONET OC-N Time Sensitive Traffic Bursty Data Traffic Assumptions: All Time Sensitive Traffic (mainly voice) is Fixed Rate. Bursty Data Traffic channels (from any data source) receive dedicated trunk BW based on peak (line) rates.

Hybrid TDM Trunking (Network Model for older Carriers) Assumptions: All Time Sensitive Traffic (mainly voice) is Fixed Rate. Bursty Data Traffic is all StatMuxed onto a common fabric (such as Frame Relay). Aggregate streams are TDM cross connected onto SONET. TDM Switch SONET OC-N Time Sensitive Bursty Data Packet Switch

Switched Network Carrying Capacities TST = 8 kbps Fixed Rate Voice SONET OC-3 Trunk 0% Data 100% Data 100% TST 0% TST Offered Load Carrying Capacity Circuit Switch TDM Packet Switch StatMux Cell Switch StatMux Hybrid

Switched Network Carrying Capacities 8 Kbps VBR-rt VoIP over ATM SONET OC-3 Trunks 0% Data 100% Data 100% TST 0% TST Offered Load Carrying Capacity Circuit Switch TDM Packet Switch StatMux Cell Switch StatMux Hybrid

Switched Network Carrying Capacities 8 Kbps VBR-rt Native ATM SONET OC-3 Trunks 0% Data 100% Data 100% TST 0% TST Offered Load Carrying Capacity Circuit Switch TDM Packet Switch StatMux Cell Switch StatMux Hybrid

Carrying Capacity...  Got bursty data traffic to move? A packet switched system using statistical multiplexing will allow you to service the most users given a fixed chunk of bandwidth.  Got time sensitive fixed rate traffic to move? A circuit switched system will allow you to potentially service the most customers given a fixed chunk of bandwidth.

Internet Voice Capacity looks bad... or does it?  Circuit Switched TDM (POTS) somewhat locked into 64 Kbps 15.6 simplex calls per Mbps deployed bandwidth  8 Kbps G.729 compressed voice has about same quality as 64 Kbps G.711  ATM 8 Kbps simplex calls per Mbps deployed bandwidth

Voice Quality vs. Bit Rate Bit Rate (Kbps) Quality G.728 G.711 G G.729 G.723.1

Variable Rate Voice Coders  8 Kbps G.729 using Silence Suppression  Active 40% of time at 8 Kbps  Silent 60% of time at 0 Kbps  3.2 Kbps average rate for a simplex conversation  Up to 125 calls per Mbps deployed bandwidth for VoIP  Up to 113 calls per Mbps deployed bandwidth for VoIP over ATM  Up to 188 calls per Mbps deployed bandwidth for native VBR ATM