ECEN5553 Telecom Systems Week #9 Read [17a] "Rapidly Recovering from the Catastrophic Loss of a Major Telecom Office" [17b] "How IT Leaders Can Best Plan for Disaster" [18] "All Optical Networking" Outline: 12 October (Remote DL) Exam #2: 24 October (Live & Local DL) No Later than 31 October (Remote DL) No Class Friday, 14 October (Fall Break)

Outlines Received due 12 October (remote) 91 %

Network Used for Numerical Results to follow... OC-3 Access 2 Voice Switch/ Gateways 1 Routers B Voice Switch/ Gateways 3 4 OC-12 VoIP Backbone A G.729 Coders. MPLS could nail down paths. 20 msec end-to-end propagation delay

150 msec End-to-End Delay 1 Frame per packet Voice Coding Delay (.015) + Packet Assembly Delay (1*.010) + End-to-End Propagation Delay (.020) + Service Times + worst case Queuing Delays at the voice source and all intermediate packet switches + Receiver De-Jitter Buffer Delay + Voice Decoding Delay (.010) = 55 msec 95 msec to spend - trunks can be heavily loaded But most bits moved are overhead (47 out of 57B).

Gateway A to Gateway B Path Time Packet M Packet 1 Packet 4M M Packets Packet 4M Worst Case Delivery Packet M Packet 1 IAT Packet 1 Packet 1 Packet 1 Our Packet Distance GA R4 R3 R2 GB OC-3 OC-12 OC-12 OC-3

150 msec End-to-End Delay 5 Frames per packet Voice Coding Delay (.015) + Packet Assembly Delay (5*.010) + End-to-End Propagation Delay (.020) + Service Times + worst case Queuing Delays at the voice source and all intermediate packet switches + Receiver De-Jitter Buffer Delay + Voice Decoding Delay (.010) = 95 msec 55 msec to spend Optimal for this example.

150 msec End-to-End Delay 10 Frames per packet Voice Coding Delay (.015) + Packet Assembly Delay (10*.010) + End-to-End Propagation Delay (.020) + Service Times + worst case Queuing Delays at the voice source and all intermediate packet switches + Receiver De-Jitter Buffer Delay + Voice Decoding Delay (.010) = 145 msec 5 msec to spend - Trunks can't carry much traffic But traffic carried is 2/3 voice (100 out of 147B).

150 msec End-to-End Delay 11 Frames per packet Voice Coding Delay (.015) + Packet Assembly Delay (11*.010) + End-to-End Propagation Delay (.020) + Service Times + worst case Queuing Delays at the voice source and all intermediate packet switches + Receiver De-Jitter Buffer Delay + Voice Decoding Delay (.010) White Items = 155 msec 0 msec to spend Impossible to meet delivery specification.

Voice Calls Possible Over an OC-12 Trunk (G.729 Fixed Rate Coder) 40000 100 msec 150 msec 30000 Trunk Voice calls supportable 20000 POTS can support 8,192 calls on an OC-12 10000 1 2 3 4 5 6 7 8 9 10 11 Number of Frames per Packet

G.729 Variable Rate Coder with Silence Suppression On a typical interactive conversation… A Specific Voice is Active 40% of time Coder generates 8 Kbps Voice is Quiet 60% of time Transmit 0 Kbps Average of 3.2 Kbps generated per simplex call

4*3/2 = 6 Links for this example. Full Mesh CO CO CO CO N(N-1)/2 Links 4*3/2 = 6 Links for this example.

One connection per Central Office. Hierarchical CO CO TO CO CO One connection per Central Office.

CO Connectivity CO TO CO TO CO CO Hierarchical Direct Connect 2nd Parallel Hierarchical Minimum of two diverse routes out of Central Office.

POTS Connectivity Small Cities have a CO Big Cities have CO’s Hierarchical system, add High Usage Direct Lines between CO’s Tandem (Trunk-to-Trunk) Switches Minimum of two physically separate routes out of all switches desired Best compromise of cost & reliability

POTS Items in a typical wired phone: microphone & speaker hybrid dialing circuitry (DTMF) on/off hook switch ring circuitry Items in a typical CO: crosspoint switch hybrids A/D & D/A converters echo cancelers TDM or VoIP

Legacy Wired Phone Speaker Ring Circuitry On Hook Hybrid Off Hook Dialing Circuitry Wall Socket Microphone 4 Wire 2 Wire

Home Phone Speaker Inbound Audio Ring Circuitry On Hook Hybrid Off Dialing Circuitry Wall Socket Microphone 4 Wire 2 Wire

Home Phone Speaker Sidetone Ring On Circuitry Hook Outbound Audio Hybrid Outbound Audio Off Hook Dialing Circuitry Wall Socket Microphone 4 Wire 2 Wire

One Wire Speaker Microphone Earth Ground To get audio out of speaker, need a closed path to get a voltage drop across the speaker inputs Need two 'wires' to get a voltage drop across a speaker one wire can be an actual wire second 'wire' can be the earth Very Susceptible to static

Two Wires This configuration provides one-way commo Speaker Microphone Resistant to static Susceptible to EM interference over long distances Twisting the wires slashes interference Used widely after 1891 This configuration provides one-way commo Need another mic, speaker, & 2 more wires

Two Wires Speaker Hybrid Hybrid Hybrids allow Telco Two Wire lines to carry both outbound and inbound traffic short distances (local loop) Two wire local loops, instead of 4 wire saves $$ on cable plant

Four Wires Easier to amplify traffic moving one direction Microphone Speaker Amp Amp Speaker Microphone Easier to amplify traffic moving one direction Telco Four Wire lines 2, one-way, 2 wire connections Long distance

Dual Tone Multifrequency

POTS Connectivity (1920) Copper Local Loop Copper Local Loop Copper Long Haul CO CO Phone Phone 4 Wire 2 Wire 4 Wire 2 Wire 4 Wire Analog

POTS Connectivity (1970) Copper Local Loop Copper Local Loop Copper Long Haul CO CO Phone Phone 4 Wire 2 Wire 4 Wire 2 Wire 4 Wire Analog Digital TDM 64 Kbps Analog

POTS Connectivity (1990) Copper Local Loop Copper Local Loop Fiber Optic Trunk CO CO Phone Phone 4 Wire 2 Wire ‘4 Wire’ 2 Wire 4 Wire Analog Digital TDM 64 Kbps Analog

Simplified Central Office Switch Space Switch TDM deMux D/A Local Loops Echo Canceler Hybrid TDM Mux + A/D 2 Wire T1 Line 4 Wire Analog Digital

Simplified CO-to-CO connectivity Space Switch TDM deMux D/A Local Loops Echo Canceler Hybrid + A/D TDM Mux Space Switch TDM deMux D/A Local Loops Echo Canceler Hybrid + A/D TDM Mux

The Legacy Phone System... Parts are 4 wire (headset and long haul) 4 wire = two unidirectional simplex signals simplex signals make amplification a lot easier Parts are 2 wire (local loop) 2 wire = one bi-directional full duplex signal Turn-of-the-century decision to save $$$ and go 2 wire on local loops Parts are analog (phone & local loop) About 70% of U.S. Local Loops are copper all-the-way Parts are digital (long haul, most CO switches, some local loops) About 20-30% of U.S. Local Loops use Digital Loop Carriers