Integrated networking

Columbia University ELE6905, Spring 2004  Thursdays 10:00-12:30, Mudd Building rm. 545

Instructor Stephen Weinstein (Dept. of Elect. Eng.), sbw@cttcgroup.com

Office hours: Thursdays 1:30-3, or by appointment.Lecture notes and references posting: http://www.cvn.columbia.edu/courses/Spring2004/ELENE6905.html

Class #8March 11, 2004

Today, class #6

Wired Access Networks

xDSL, cable data, PON

But first, a bit more discussion of token/leaky buckettraffic smoothing

- Token bucket imposes an average rate constraint, leaky bucket a peak rate constraint. Both offer some control of the duration of a high-speed burst from the source.

- Can be used to police a DiffServ Service Level Specification (part of an SLA) between two network domains, specifying how traffic crossing the boundary of the two domains is to be treated. In particular, how each other’s traffic is conditioned (limited and smoothed) at the boundary, and how packets can be labeled or relabeled for different treatments.

Token bucket (limits average rate)Periodic token deposit, Rav tokens/sec (independent of packet arrivals)

Bucket capacity C tokens

Serverqueue

One token withdrawn to serve a packet whenever a packet is present

Arriving trafficrate r packets/sec

Shaped output traffic

Leaky bucket (limits peak rate)One token deposited each time a packet arrives

Bucket capacity C tokens

Serverqueue

Tokens "leak" out at periodic rate Rp

Arriving trafficrate r packets/sec

Shaped output traffic

Burst length analysis of token bucket

Bucket size C.Tokens deposited in bucket at constant rate Rav.Token removed from bucket each time a packet is served.Packets arrive at a rate r packets/sec.

Assume token bucket initially full (C) after a period of little activity. High-speed burst of packets arrives at rate r > Rav and is immediately serviced, passing through at rate r, until the bucket empties (after which service is at Rav rate).

Tb = maximum burst length time until the bucket empties. C + RavTb = no. of tokens already in bucket or added over Tb.rTb = ni, of tokens withdrawn over Tb.

0 = C + RavTb - rTb, or Tb = C/(r-Rav)

Digital access networksThe communications facilities used between local/personal networksand metropolitan/core networks.

UWB(Ultra Wideband) LEOS, direct satellite

IEEE 802.16

xDSL(and ISDN)

Cellular mobile

Cable data

T-carrierservices

AccessnetworksPON

Wireless MAN

Powerline communications

Where is access networking heading?

The generic goal: An IP-oriented optical/electrical and optical/optical convergence architecture

Optical node

Optical metropolitanand core networks

optical fiber

Access network(optical, wireless, coax, twisted pair- it doesn't matter much)

Subscriber

IP servicesoverlay

Ethernet frames?

End-to-end Ethernet: A new communicationsparadigm, or just a fad?

Optical metropolitanand core networks

Access network

Ethernet frames

Ethernet card

Ethernet switch

LAN

Ethernetbridge(IEEE802.1D)

IP stack

IP on Ethernet

Optical framer

OXC

Ethernet switch

Access network

Ethernetbridge

Ethernet switch Ethernet switch

Ethernet bridge

Why are there many more cable data than ADSLsubscribers in the U.S.?

-Cable systems 15 years ago began major upgrades to HFC (hybrid fiber-coax) to reduce maintenance costs and improve transmission performance, before digital services came along. They were better prepared for digital services.

Headend

Runs of up to 20 amplifiers contributedto noise, distortion, frequent failures

-Cable systems have monopolies, but local telephone companies must lease facilities to competitors, discouraging major capital investment in access by telcos.

-Cable operators began with a broadband services perspective, while telcos were associated with (and thought like) telephone companies.

-ISDN was too little, too late.

Is any access system free from congestionproblems?

Basically no. All access systems have capacitybottlenecks because no carrier wishes to overinvestin excess capacity. Most capacity bottlenecks canbe relieved with additional investment in facilities.

xDSL (Digital Subscriber Line)

- Uses the telephone subscriber twisted pair, bypassing the voice switches with their 4KHz channel filters.

- Supports (in some versions) normal analog telephone in addition to data services.

- Comes in various symmetric and asymmetric versions (next page).

- Performance, especially maximum dependable data rate, is dependent on distance from Central Office (or fiber node) and on crosstalk between twisted pairs in the same bundle.

Digital Subscriber Line Types (24-26AWG twisted pair)(POTS: Plain Old (analog) Telephone Service)

Name Rates down/up POTS Distance ISDN (Basic Rate) 144kbps/144kbps no 18KftADSL (Asymmetric 1.5-8 Mbps/128-640Kbps yes 6.5-24Kft Digital Subscriber Line)G.lite (ITU-T G.992.2) 0.78-4Mbps/<512Kbps yes <24Kf "splitterless"SHDSL (or just HDSL) 0.768Mbps each way no <18Kft (Symmetric High Speed DSL)G.shdsl (ITU-T G.91.2) 0.144-2.32Mbps each way no 12-20Kft "Multi-rate and extended reach" [http://www.cisco.com/warp/public/cc/so/neso/dsso/global/shdsl_wp.htm]

VDSL 26-55Mbps/2Mbps no ~1Kft (Very High Speed Digital Subscriber Line)

ADSL standard: T1.413-1998, "Network to Customer Installation Interfaces - Asymmetric Digital Subscriber Line (ADSL) Metallic Interface: November, 1998"available for $350 at www.atis.org/atis/docstore/doc_display.asp?ID=159

ADSL can operate much faster than a telephonemodem because the data signal bypasses thevoiceband filters of telephone switches

PSTNvoice carriersystem

PSTNswitch

ISP

3KHz voiceband filter

a) Dialup Modem

Line concentrator(the bottleneck)

Data network(s)

ISP

DSLAM

voice carriersystem

b) ADSL

ADSL modem with data passband filter

Line concentrator(voice bottleneck)

Voiceband filters

PSTN

Data bottleneck

trunk(s)Router

ADSL subscribertermination

Digital Subscriber Line Access Multiplexer

...

Typically an ATM switch

Commercial ref. for a DSLAM: http://www.adtran.com/static/docs/DOC000965.pdf

"G.lite" (G.992.2)Subscriber ADSL modem plugs into computer, just like a voiceband modem. So-called "Splitterless" system. Lower rate,smaller BW (512KHz upper edge).

Convenient installation, but unreliable inside wiringusually degrades performance

ADSL subscribertermination

To DSLAM

Commercial example: www.hellosoft.com/products/hdsl/hdsl.htm

ADSL modulation formats

- Primary standard: DMT (discrete multitone) Generate with Discrete Fourier Transform, as described previously.

138KHz 1.1MHz

Different data rates and amounts of transmitted power can be allocatedto different subbands, in accordance with transmission rate requirementand quality of channel at different frequencies.

May use QAM signal constellations of different sizesin different subbands.

sinc(f) spectrum (magnitude shown here) has nulls at carrierfrequencies of adjacent subbands, eliminating interbandinterference (in a system with no channel distortion).

~20KHz

Upstream

4KHz(POTS)

DMT/OFDM performance costs to maintainorthogonality of subbands

- Overhead from cyclic extension (extending blocks beyond multipath dispersion)

- Virtual (unused) subbands on the edges of the total band to avoid interference with other bands.

138KHz 1.1MHz

Filtered MultiTone (FMT)

A variation on DMT applied in VDSL. Mitigates DMT/OFDMperformance costs."With FMT, orthogonality between subchannels is ensured by usingnon-overlapping spectral characteristics instead of overlappingsinc(f) type spectra. Since the linear transmission medium doesnot destroy orthogonality achieved in this manner, cyclic prefixing isnot needed".

Ref: I. Berenguer & I. Wassell, "FMT Modulation: Receiver filter bank definition forthe derivation of an efficient implementation"www-lce.eng.cam.ac.uk/~ib226/papers/fmt_modulation.pdf

IDFTParalleldata

Bandpass versionsof a standard low-pass filter

Parallel/serial

Line signal

- Secondary standard: CAP (Carrierless Amplitude-Phase Modulation) Essentially the same as QAM (quadrature amplitude modulation), generated by direct inband digital techniques.

Store of inbanddigitally modulatedsignal sequences

Information streamPassband signalsamples

D/A Linesignal

By proper design, can generatesignals for an infinite variety ofinformation streams from a finiteset of stored inband digital segments

ADSL modem

Receivingfilter

ADSL modu-lator/filter

Telephonefilter

Data fromcomputer

Subscriber line

RJ-11 jack

Ethernet

Demodulation/equalization/detection

Pulseshaper

Coder/decoder

.138 1.1

0.3 3.3

Hybridcoupler

KHz

MHz

26 138KHz

Splitter

ADSL protocol stack

TCP/UDP

Computer(or appliance)

ADSL terminal

DSLAMData networkterminal

IP

PPPEthernet

Ethernet

ADSL

ATM(optional)

ADSL

ATM(optional)

SONET

ATM(optional)

IP IP

ISP (InternetService Provider)

SONET

ATM(optional)

IPPPP

TCP/UDP Protocol servicessuch as DHCP

Exchange office Subscriber

The future of xDSL?

-Existing full-length subscriber line ADSL doesn’t work (at any attractive rate) on a significant percentage (30%?) of subscriber lines. VHDSL will develop as fiber nodes come closer to subscribers.

-Requires capital investment in metropolitan data networking to alleviate congestion as subscriber population grows.

Telcos want exclusive right to offer xDSL on their subscriber lines; enthusiastic deployment and performance advances depends on that. [They object to unbundling rules.]

-Unbundling rules (carriers required to "unbundle" their facilities and lease the pieces to service competitors at reasonable rates)

Telcos may be holding back on broadband access (especially VHDSL) until their monopoly is comparable with cable's.

Central Office Telco ADSL

Co-located competitor ADSL?

Telco-built subscriber lines

Cable Data System

DOCSIS: Data-Over-Cable Service Interface Specifications: Radio Frequency Interface Specification SP-RFIv1.1-I06-001215, Cable Laboratories, December 15, 2000

Main DOCSIS Technical SpecificationsModulation Bandwidth (MHz) Data Rate(Mbps)

Down 64 or 256 QAM 6 27 or 36 Up QPSK or 16-QAM 0.2-3.2 0.32-10

In both directions: MPEG-2 framing, Reed-Solomon forward errorcorrection coding, DES encryption.

Upstream Medium Access Control: Packet-based, contention and reservation slots, QoS capabilities.

Management: SNMP, with MIB definitions.

Residential network interface: 10BT Ethernet (USB and IEEE 1394 planned).

Business network interfaces: 10/100BaseT, ATM, FDDI

Spectrum utilization (within the cable)

5 42 50 8606MHz channelizationMHz

Upstream (0.2-3.2MHz channels in usable parts of this noisy spectrum)

Downstream

Each downstream channel can be used for:-One analog TV signal, or-Six-seven 4Mbps MPEG-2 digital TV signals, or-One 19Mbps HDTV signal plus two digital TV signals, or-Data (e.g. Internet downloads) at 30Mbps.

64-QAM or 256-QAM used downstream for high spectral efficiency.

................................

Coaxial cabledistribution network

Cable Headend

...

E/OO/E

Backbone network

Cable ModemTermination System (CMTS)

...

Combiner (mux)

Analog headend term

Analog signal modulators(6MHz channels)

Digital satelliteprogramming

Analogsatelliteprogramming

Single-modeoptical fibersOC3-OC12

125-500subscri-bers

Ethernet

Digital or Analog TV

QAM receiver

Cable modem:QAM receiver,QPSK transmitter

MPEG, control functions

T T

Splitter

R ... ...

Switch or network adaptor

Network termination

To PSTN

Set-top box

Telco return accessconcentrator (TRAC)

Local server facility

Operations Support

Security &AccessController

R T T

Fiber node(O/E, E/O)

Contention in shared coaxial cable tree

Remote server facility

T T T T

Contention for (upstream) bandwidth in theDOCSIS MAC (medium access control)

Resources are allocated as "minislots" of upstream transmission time.

Client sources

Medium

Mediator

Requests

Alloc.

Mapping MAC frame into minislots

Example MAC frame

Minislots 6.25μsGrant: 4 x 6.25μs 6.25μs 6.25μs

fragmentation

Later grant for remainder of request

In the upstream direction, transmission time is slotted into minislots for TDMA (time division multiple access). The time duration of a packet transmission is a power of two multiple of 6.25s minislot increments. If grant isn’t sufficient, MAC frame is fragmented andpart is sent later.

Used by others

Medium Access Protocol management message

Requests

CMTS

Slots not yet mapped

Maintenance

Cable modem transmit opportunity

Requestcontentionarea

Slots previouslymapped

Information elements assign slots to different modems

Minislot allocation for upstream traffic

(Cable Modem Termination System)

Request contention resolved through backoff algorithm.

The future of cable data and the comparisonwith xDSL?

-Cable operators (at least in U.S.) are advanced in broadband digital services (entertainment as well as Internet access) and with further innovations may continue in lead.

-Congestion on shared coaxial cable tree can be resolved by splitting the fiber node (making two nodes, each of which takes half the lower distribution tree). (This requires capital investment!)

Fiber node(O/E, E/O)

400 subscribers

Fiber node(O/E, E/O)

200 subs

Fiber node(O/E, E/O)

200 subs

(more)

-Modern cable plants can offer high-speed data service to almost all of their customers, unlike ADSL that can only be offered to about 70%.

-Telcos still ahead in quality of plant engineering and maintenance.

-Telcos may catch up and pass cable operators when and if the investment cable operators made in fiber nodes is matched by telco investment in fiber nodes (to implement VHDSL).

-Both systems have capacity bottlenecks, but cable's may be more expensive to resolve.

-xDSL and cable data likely converge to a common "fiber to the neighborhood" architecture with a variety of "last mile" transmission media.

PON (Passive Optical Network)

A passive splitter in the field reduces cost and makesfiber to the home/business more practical. May replaceT-carrier access systems and services.

Passive splitter

Metropolitan/core networks

Telco servingoffice

COterminal

Up to 64 broadcast drops

ATM or (newer)Ethernet basedtransmissions

ONU

PON interfaces

Tutorial ref: www.iec.org/online/tutorials/epon/topic04.html?Next.x=37&Next.y=14

COterminal

DS-1DS-3OC-3OC-12

IP router

ATM switch

DS-1DS-3

POTS

PBX

ONUEnet

Dedicated wavelength

Layers 2/3 switching & routingData provisioning in 64kbps increments up to 1 Gbps

EPON (Ethernet PON)

Objectives:

- Point-to-multipoint, low-cost architecture using single-mode fiber.

- Access network distances (at least 10km)

- Standard Ethernet frames, no contention

- Standard 1 Gigabit Ethernet rate

- Minimum 1:16 split

- Replacement for earlier ATM PON

Ref (brief tutorial): www.ieee802.org/3/efm/public/jul01/tutorial/pesavento_1_0701.pdf

EPON (Ethernet PON)

Downstream:

OLT

Optical lineterminal

21 13

ONU1

splitter

Users

ONU2

ONU3

1

2

3

21 13

211

3

21 13

11

2

3

All packets broadcast to all ONUs, where Ethernet frames for particularusers are separated on the basis of the MAC (medium access control)addresses.

Headend (e.g. CO terminal)

Optical network unit

Ethernet packet

Header

Data field (up to 1500 bytes for 10Mbps)

Preamble(7 bytes)

Start of frame delimiter (1 byte)

Type, or length of data field (2 bytes)

Pad (0-46 bytes)

Checksum (2 bytes)

Destination address (2 or 6 bytes)Source address (2 or 6 bytes)

Example of MAC address: 00-50-DA-CE-E2-76

6 bytes (each hexadecimal pair is one byte)

EPON

Upstream:

OLT

Optical lineterminal

211 3

ONU1

splitter

Users

ONU2

ONU3

1

2

3

2

1

3

1

2

3

Synchronized system does upstream time slicing, so there are no collisionsand no need for packet fragmentation.

"MAC uses existing PAUSE control frame or other control messages."

11

33

3 3

3 3

EPON optical aspects

OLT

ONU11:N opticalsplitter

ONU2

ONU3

λ1Mediumaccesslogic

λ2

R

TWDM

MediumaccesslogicR

TWDM

Full duplex operation using separate wavelengths. (example: 1550nm/1310nm)

Headend permits only one subscriber at a time to transmit.

End users see only traffic from headend, not from each other.

Data

Review for the midterm exam

Sampling theorem:For x(t) bandlimited to (-W, W) Hz,

Analog to digital conversion

x(t) = x(n/2W)sin[2W(t-n/2W)]/[2W(t-n/2W)]n

Interpolation function (what is itsfrequency spectrum?)

T= 1/2W

T 2T3T 4T

5Ttime (sec)

Reconstruction formula above realized in a low-pass filter limited to what frequencies?What are advantages of digitized media?Does a digitized media stream necessarily use less bandwidth than the original analog media signal?

LEOS, direct satelliteIEEE 802.16

IR

Wireless LAN(IEEE 802.11) Subscriber

line

Local areanetworks(LANs)

Cellular mobile

Infrastructure network types

Cable data

Switched Ethernet T-carrier

services

Accessnetworks

SONET ring,RPR

Metropolitanarea networks(MANs)

Core (or long haul)networks

1-10GbpsEthernet

Optical Core Network(DWDM)

Satellitetransport,broadcasting

Personal Area NetworksBluetooth

PON

Resilient Packet Ring

Wireless local loop("wireless MAN")

UWB

request transport

Application

Transport

Network

Link, Phys

request link access & physical commun.

Application

Transport

Network

Link, Phys

Packet transfer

Transport data package transfer

Information unit transfer

request packet forwarding

Physical network

Protocol layers offering services to higher layersand peer-to-peer interaction across networks

Virtual Circuits, e.g. in ATM

Pools of capacity for different services

CBRVBRABR

guaranteed peak capacityguaranteed average capacity

whatever is left over

CBRVBRABR

CBR: Continuous bit rateVBR: Variable bit rateABR: Available bit rateUBR: unrestricted bit rate, best effort service

Public Internet(or any data network)

Destin.host

Enterprise networksegment

Enterprise networksegment(or individualremote host)

Encrypted end-end packet

Firewallrouter

Encapsulating "tunnel" packetaddressed to firewall

Virtual Private Network

VoIP (general concepts of Internet-PSTN interworking)

codecMikeSpkr

UDP/IP/Phys

RTP

Echo canceler

Internet

IP telephone (H.323 compliant)

Peer-to-peerIP communication

Internet/PSTNGatewayPSTN

Addr. Dir.

PSTNtelephone

Mediagatewaycontroller

H.248

Signaling (e.g. SIP)

IP address xxx.xx.xxx.xx

bufbuf

Tel number (212) 854-xxxx

IP tel.

Telephony ApplicationPort zz

Spectrum policy (e.g. renting spectrum in bandwidthand time) and applications of software-defined radio

- Multiple air interfaces.

- Agility to move between available time/bandwidth slots rather than stick to fixed assignments.

Frequency

Time

Infrastructure and ad-hoc modes

AccessPoint Ad-hoc mode

(peer to peer relay)

Infrastructure mode

AccessPoint

Backbone network,wired or wireless

Network interoperability at PHY/MAC levels vs.network interoperability at network level (IP) Challenges for PHY/MAC interoperability:- Matching different protocol implementations of different operators- Matching rate offerings in the digital hierarchy- Coordinating operations and management functions (protection/restoration, traffic engineering, comparable service features and performance, ...)

At network level: How does IP avoid these complexity problems? What kinds of agreements are still needed?

Network vulnerabilities- Physical damage and congestion.- Congestion.- Cyber attacks.- Cascading failures.Everyday restoration mechanisms, such as SONET ring, and breaksthat cannot be managed by everyday restoration mechanisms.

Add/drop multiplexer

Normalpath

X

Restorationpath

Damaged conduit

e.g. efficient use of capacity from statistical multiplexing of different sources (What is the difference from a circuit-switched network?) and resilience (why?)

packetizer

packetizer

packetizer

Aggregated traffic

silent

silent

talking

Packet networking advantages

Router functions

Transfer

Lookuptable

Classifier

Destinationaddress

IP packet

Schedulingalgorithm(what kinds ofservice disciplines?)

Scheduler

Input port 1Queue 1

State

Output port 1

to output port 1, toppriority

to outputport m,top priority

RoutingAlgorithm(what is OSPF?)

Link states fromneighboring nodes

Transfer

Classifier

Server

Queue n

Scheduler

Queue 1State

Output port m

Server

Queue nto outputport m,lowest priority

Input port m

MPLSMulti-Protocol Label Switching

ApplicationRTP, RTP

TransportTCP, UDP

NetworkIP, DiffServ, SLA, traffic smoothing & policing

Link or MACLink-level framing, circuit switching,medium contention resolution

Packet transfer(IP addresses)

Transport data package transfer (port numbers)

Information unit transfer(stream IDs)

Physical networkPhysicalPlug interfaces, modulation

SessionHTTP

Client-server requests/responses

HTMLSIP

JAVA, CORBA,SOAP

IP protocol stacks

Successive encapsulation

UDP protocol unit IP packet IP header

UDP header

Application-level information unit (e.g. mediaencapsulation)

AIUheader

Ethernet frame

IPv4 address classes A,B,C – How the 32 bitsare used

0 1 8 16 24 31 Network ID

CLASS A Bit number

0 Host ID

Fraction of alladdresses

1/8

For the relatively small number of networks supporting a verylarge number of hosts computers.

Can address up to 27 = 128 networks, each with up to224 = 16,777,216 host computers.

What is the address depletion problem addressed by IPv6, and whatare the major differences between IPv4 and IPv6? How can addresstranslation mitigate the address depletion problem?

TCP and UDP

Provide an end to end (application to application) transport service.

TCP (transport control protocol): Reliable, connection- oriented service.

UDP (user datagram protocol): Unreliable datagram service (but no delays for retransmissions!)

What are the major similarities and differences between TCP andUDP? What is sliding window flow control in TCP?

Internet

ApplicationRTP1

UDPIP

Physical

Stream DataControl messages

RTP2

Session 1 (audio) port x

Session 2 (video) port y

RTP Audio and Video Sessions

ApplicationRTP1

UDPIP

Physical

RTP2

Internet QoS with DiffServ, SLA, MPLS

DSCP (Differentiated Services CodePoint) marking(for class of traffic).Possible traffic smoothing.

Clientnetwork

ISP network with DiffServ-capable routers

Traffic conditioning part of SLA regulatesvolume of submitted traffic for each DSCP

DiffServ PHBs invokedby DSCP markings

Traffic-engineered links using MPLS

ISP ingress router

Policing of submitted traffic

Direction of traffic

Clientnetwork

DiffServ Classes

EF (expedited forwarding): Specified PIR (peak information rate) and bounded delay (e.g. for voice). The EF PHB implements a pass-through service with no queueing delays or delay jitter .

AF1-AF4 (assured forwarding): Preferred forwarding at routers to minimize packet losses. Each level has a specified CIR (committed information rate) and PIR.

BE (best effort): Packets utilize whatever capacity is left after preferred classes are accommodated.

What is a DiffServ codepoint? What is an SLA? What is "colormarking"? What are token and leaky buckets?

Traffic conditioning in a network router

classifier

PacketsMeter/shaper

profile

conforming

drop-per

passed

dropped

Non-con-forming

DiffServ class marker(if not already marked)

To PHB scheduler

Best effortOther AF classes

EF

AF1

Conformance marker

conforming

drop-per

passed

dropped

Non-con-forming

To PHB scheduler

Meter/shaper

profile

Meter measures conformance with SLAShaper smooths traffic to conform with SLA

What are IntServ and DiffServ?

IntServ DiffServNo. of service classes 2 6 (incl AF1-4)Session state maintained Yes No (only preferred in network? service discipline)

Advance resource Yes (e.g. by No (SLA by customer

reservation? RSVP) and class)

Where would they tend to be used in networks? What are the IntServ and DiffServ classes?How can IntServ and DiffServ work together (at least be interfaced)

MPLS - what is it and what is it good for?

Paths for forwarding equivalence classes

San Francisco

New York

Chicago

St. Louis

Denver

NY to SFExpedited Forwarding traffic

NY to SFAll other traffic

What is "label swapping"?

Connectionless and Connection-Oriented

Datagrams

Connection-orientedstream

What is a virtual circuit?What is the difference between a switch and a router?

Cell switching (ATM)

-"Asynchronous" because cells need not arrive at a switch at fixed times.

-Resource reservation setup in advance through signaling.

-Offers quality of service (bandwidth/delay guarantees) in broadband networks.

Why a 53-byte cell?What is VCI swapping?What are the service types?What is a Virtual Path?What is an adaptation layer?

Synchronous, asynchronous, isochronous,plesiochronous

Synchronous: Data stream synchronized to a clock

time

Data stream 1 (e.g. a tributary as on last slide)

Data stream 2

What are TDM and TDMA?

High-speed Ethernet switch(Metropolitan Area 1Gbps/10Gbps)

PSTN access and metropolitan network

Terabitrouter

DWDM core network

PBX, LANOXC2

Lightpath shown with two redlinks and one green link

Framing (SONETand/or OTN) (Transp.)

(Opaque)

λ1 λ2

λ2

λ2

λ1

OXC3

OXC4

OXC1

λ1

SONETring

ADM

λ3

O/E E/O

(Opaque)

Optical networks: Metropolitan/core network integration

OTN: Optical Transport Network, ITU-T G.709

EthernetLAN

LightpathsWhat are WDM and DWDM?What are opaque and transparent optical switching?What is hierarchical optical switching?

cross-connect

opticalfibers

RepeaterOne fiber

Routing and wavelength assignment through an optical corenetwork continues to be a research topic

SONET framing (155.52Mbps SONET/SDH frame)

........................

........................

........................

........................

........................

........................

........................

........................

........................

9 rows

270 columns

First bytein frame

Last bytein frame

Transport overhead(section and line)

t=0

t=125μs(entire frame)

PayloadVirtual container (including path overhead)

Pointer to start ofvirtual container

What is GFP?

Fiber access systemsWhat are FTTC, FTTH, PON? What is VDSL?

SONETBroadband network(OC-3 to OC-48)

Telco servingoffice

VDSL on twisted pair, < 1000ft Up to 50Mbps (asymmetric)

TV

COterminal

ONU (fiber node)

Example product for either FTTH or FTTC:40-870MHz band downstreamon 1310nm and 1550nmcarriers, carrying "a full complement of analog and digital signals"[http://www.synchronous.net]

Fiber with subcarrier-multiplexedVDSL signal

What is modulation?Baseband/passband, PCM and PAM (M-level), Fourier transform (spectrum), spectral efficiency, PSK, QAM, CDMA, DMT/OFDM,signal constellations, noise immunity, UWB

Modulated transmissionsignal

signallevelsencoder

modulator

Carrier waveformBaseband information signal

Next week (March 18): Spring Break

Next class (March 25)

Midterm exam