© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM III – 1 ETH Zürich Part III: Overview of Technologies, ATM, and IP Overview of Networking

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM III – 1 ETH Zürich

Part III: Overview of Technologies, ATM, and IP

• Overview of Networking Technologies– Developments– High-speed Characteristics– Switching Techniques

• ATM (Asynchronous Transfer Mode) – Principles of Cell Switching – ATM Connection Management– ATM Layer and Adaptation Layer

• IP (Internet Protocol)– Key Elements– Protocol Stack


Networks

Networks provide an infrastructure for:• Interconnecting machines or services (connectivity),• Making available scarce resources (resource sharing),• Equalizing traffic volumes (load balancing), and• Providing alternative fallbacks (reliability).

Structuring networks according to dimensions:• Expansion (LAN, MAN, WAN),• Topology (star, ring, bus, meshed),• Performance (low-speed, high-speed, real-time),• Administration (public, private), and• Task (internet or physical net, intranet or virtual net).


Inventions in Telecommunications

Oscillating needle telegraph experimentsEarly telegraphy (Morse code dots and dashes)

Printing telegraph systemsBaudot multiplex telegraph (6 machines on one line)

First telephone channels constructed

First carrier telephonyCarrier telephony carries 12 voice channels on wire

60 voice channels over coaxial cable

600 voice channels over cable (T3) and microwave

3600 voice channels over cable and microwave

32000 voice channels over cable108000 voice channels over cable

Multimode optical fiber 45 Mbit/s

Multimode optical fiber 140 Mbit/s

Monomode optical fiber 565 Mbit/s

Monomode optical fiber 16 Gbit/s

18

50

18

60

18

70

18

80

18

90

19

00

19

10

19

20

19

30

19

40

19

50

19

60

19

70

19

80

19

90

20

00

Year

1800 voice channels over cable and microwave

1012

1011

1010

109

108

107

106

105

104

103

102

10

1Bandwidth

bit/s


Transmission Media

Fiber optical media:• Low error rates, long distances, low attenuation.

Attenuation[dB/km]

10 0 10 1 10 2 10 3

10 0

10 1

Frequency[MHz]

10 2

Copper(UTP)

Copper(Coaxial)

Fiber(Multimode)

Fiber(Monomode)

Fiber(Gradient)


Last MileProblem:• Connection

between thehome and thebackboneis serious.

• Requires ahuge capitalinvestment.

• Fiber ignoresthe lastmile problem.

Evolution of Bandwidth

Bandwidth[kbit/s]

1975

10 0

10 1

Time[year]

10 2

10 3

10 4

10 5

10 6

10 7

1980 1985 1990 1995 2000 2005

POTS

WAN

LAN

LANPOTSWAN

Local Area NetworkPlain Old Telephone ServiceWide Area Network


High Speed Networks – Overview (1)

High Speed Local Area Networks (LAN):• Fast Ethernet: 100 Mbit/s• Gigabit Ethernet: 1.0 Gbit/s• HIPPI: 800 Mbit/s• Fiber Channel: 100, 200, 400, or 800 Mbit/s• High Speed Token Ring: 100 Mbit/s (1 Gbit/s)

High Speed Metropolitan Area Networks (MAN):• FDDI: 100 Mbit/s• FDDI-II: 100 Mbit/s (incl. isochronous channels)• DQDB: 34 Mbit/s, 155 Mbit/s, or 622 Mbit/s

High Speed Wide Area Networks (WAN):• ATM-based B-ISDN: e.g., 2, 34, 155, 622, or 2,400 Mbit/s



Carrier support (physical layer):• Plesiochronous Digital Hierarchy (PDH):

– e.g., DS-0: 0.064 Mbit/s (= 1 voice channel)

– T-1 (USA): 1.544 Mbit/s ( 24 voice channels) (also called DS-1)

– E-1 (Europe): 2.048 Mbit/s

– E-3 (Europe): 34.368 Mbit/s

– T-3 (USA): 44.736 Mbit/s (also called DS-3)

• Synchronous Digital Hierarchy (SDH) orSynchronous Optical Network (SONET):

– e.g., STS/OC-1: 51.84 MBit/s

– STS/OC-3: 155.52 MBit/s ( STM-1)

DS: Digital Signal

T: Telephone Line

OC: Optical Carrier

STS: Synchronous Transfer Signal Level



Carrier support (physical layer) continued: • Wavelength Division Multiplexing (WDM)

Access technologies:• Cable TV• Frame Relay (FR)• xDSL (Digital Subscriber Line)• Satellite networks and wireless local loop

Service technologies:• Switched Multimegabit Data Service (SMDS)


HSTRFast EthernetxDSL

Token RingEthernet

FDDI,DQDB,CRMA

X.25 N-ISDN

STMATM LAN

Network Dimensions

System Bus 1980/90

1980 1990

10 -1

Transmissionrate

[Mbit/s]

10 -3 10 -2 10 0 10 1 10 2 10 3 10 4

10 -3

10 -2

10 -1

10 0

10 1

10 2

Distance[km]

10 3

Wide AreaNetwork 2000

2000

1985

Local Area Network 1995

MetropolitanArea

Network 1995

HIPPI 1990 ATM-based B-ISDN


Protocol Layer Architecture – Examples

SDH/SONETWDM

ADSL: Asymmetric Digital Subscriber LoopATM: Asynchronous Transfer ModeHDLC: High Data Link Control

IP: Internet Protocol PPP: Point-to-Point Protocol WDM: Wavelength Division Multiplexing

SDH/SONETADSL

TransmissionConvergence

Voice HDLCVideo

ATM PPP

IPVoice IP ... ...

Voice telnet...


Characteristics of High Speed Networks

Characteristics of high speed networks:• Low bit error rate (fiber optical media),• Higher packet error rate (buffer overflow),• Existing Jitter (different buffer lengths),• Small transmission units (cells), • Many connections (context data),• High bandwidth (fiber optical media), and• Extreme bandwidth-delay product.

Protocols have to deal with these issues to alleviate influences of delayed, corrupted, or lost data.


File Transfer Example

File size: 1 Mbyte

Link: San Diego – Boston

Signal delay: 25 ms

64 kbit/s channel:• 64 kbit/s * 25 ms = 1,600 bit• 0.02 % of file on link

2 Mbit/s channel:• 2 Mbit/s * 25 ms = 50,000 bit• 0.6 % of file on link

1 Gbit/s channel:• 1 Gbit/s * 25 ms = 25,000,000 bit• 8 ms for transmission, 17 ms idle

SAN BOS

SAN

BOS

1,600 bit

50,000 bit

25,000,000 bit

5000 km

Bits are smaller – not faster !


Effects on Data in Transit

Signal delay is dominating the transmission delay.• This grows worse for high transmission rates.

Buffer overflows dominate occurring errors.• The effect grows worse for fast and real-time traffic.

Error recovery has to be a trade-off between a waste of bandwidth or extending delays.• Bandwidth is much cheaper than tolerating high delays.• Multimedia applications normally don´t like delays.

A huge amount of data is in transit within high speed and long distance networks Path Capacity PC: PC = B * Dsignal

B: Bandwidth, Dsignal: Signal delay.


Switching Techniques – Overview

Switching Techniques:• Based on circuits, cells, frames, or packets.

Circuit switching suffers from fixed bandwidth constraints for bursty traffic.

Packet switching allows for variable bandwidth.

CircuitSwitching

(STM)

FastCircuit

SwitchingATM

FrameRelay

PacketSwitching

Fixed Behavior of Bandwidth Variable

MultirateCircuit

Switching

FastPacket

Switching

FrameSwitching

IntricacySimple Complex


Circuit information are stored during establishment times in a translation table.• Delay is determined by the

propagation delay and theprocessing in switches.

• Bounded to 450s by ITU-T. • Bit error rates are caused

by single bit errors (switch-ing malfunction) or bursts(loss of synchronization).

Inflexible, e.g., G.703 PCM.• Fixed bandwidth.

Circuit Switching

l1

l2

lm

IncomingLink

TimeSlot

OutgoingLink

TimeSlot

12…m12…m12…m

O1

O2

O3

…O1

O2

O3

…O1

O2

O3

…

32…142…m1m…1


Packet Switching

Based on user data that are encapsulated in packets. Concept is based on technology available in the 60s:

• Erroneous links:– Link-based error control in complex protocols.

• Low bandwidth links:– High delays (due to retransmissions) and low speed

(due to protocol processing) – Lacking support of real-time and multimedia traffic

• Software-based protocol implementations:– Variable sized packets require a complex buffering.

X.25 is the oldest example of packet switching nets.


Frame Relay (1)

Frame Relay supports connection-oriented services. Subscriber Network Interface (SNI) defined between

customer (router) and PTO equipment.• Support of pure data, not particularly voice etc.• Multiplexes flows of data being divided in data blocks.• Flows are carried in virtual channels which may exceed

their bandwidth as other channels are idle.• Frame Relay may carry X.25 packets/frames.

Performance:• Different implementation approaches exist, however,

2 Mbit/s access speeds are common.• Insufficient guarantees on bandwidth and delay variation.

PTO: Public Telecommunication Operator


Frame Relay (2)

Physical and data link layer specifications available. The data link layer is based on LAPD (ISDN):

• Data link services: addressing (DLCI, local significance).• Error control is left out as an end-to-end function.• Core LAPD frame:

DLCI: Data Link Connection IdentifierC/R: not usedEA: Extended Address

FECN: Forward Error Congestion NotificationBECN: Backward Error Congestion NotificationDE: Discard Eligibility

Flag Address Payload FCS Flag

1 2 variable 2 1Byte

DLCI C/R EA DLCI FECNBECN DE EA

6bit 1 1 4 1 1 1 1

01111110 01111110


Frame Relay (3)

Frame Relay DLCI assignments:

A simple sample Frame Relay network:

User B

User C

User A

Permanent Virtual Circuits16

1007

1451007

16, 145, 1007: DLCI

0 Reserved for Call Control Signaling1-15 Reserved16-1007 Assigned to Permanent Virtual Circuits (PVC)1008-1022 Reserved1023 Local Management Interface

Frame Relay Interface




Comparison

Summary of important functional differences:

Connection-orientedConnectionlessFrame BoundariesBit StuffingCRCError-Control ARQFlow-ControlMultiplexing of log. Channels

X.25–

FrameSwitching

or –

FrameRelay––––

Light weightHeavy weight

Technology

CRC: Cyclic Redundancy Check


Part II: Overview of Technologies, ATM, and IP





Cell-based Switching

Integration of a variety of services:• Bursts are smoothened.• Isochronous data are delivered according to their jitter.• Data may be multiplexed statistically, if the overall

bandwidth is sufficient. Efficiency: statistical multiplexing gain.

Delay problems occur in case of sending packets of different length. Extremely long blocking can be avoided, if cells of fixed-size are used. If the overall cell length is too big, a similar problem appears.


Handling Cells – Segmentation/Reassembly

To sent packets over cell-based networks, packets have to be segmented and reassembled again.

The segmentation and reassembly (SAR) functionality is placed right above the cell level.

Packet PacketCells

HLP

User Data

User Data

SAR HLP UD

User Data Cell UDSAR HLP Cell SAR User Data Cell SAR

User Data SAR User Data SAR

Cell Header

SAR Header. . .

. . . HLP Higher Layer Protocol Header

Total Cell LengthCell Payload Length


Structure of an ATM-based B-ISDN Network

Customer Premises Equipment

ATM-Switch

NNI

NNI

NNI

UNI

UNI

UNI

ATM-connectedMM-Workstation

ATM-connectedMM-Workstation

ATM: Asynchronous Transfer ModeMM: MultimediaNNI: Network Node InterfaceUNI: User Network Interface

ATM-Switch

ATM-Switch

ATM-Switch NNI

NNI

ATM-Switch

Core ATM-Switch

Edge ATM-Switch

ATM-Switch


B-ISDN Reference Model – I.321

Modeling communication systems is done in a logically hierarchical structure, e.g., ISO/OSI BRM.

Relation between OSI and B-ISDN/ATM undefined. The plane approach has been used within B-ISDN.

Physical Layer

ATM Layer

ATM Adaptation Layer

Higher Layer Protocols

Management Plane

Control P. User P.

Pla

ne M

anag

emen

t L

ayer

Man

agem

ent

P.: Plane


ATM Connections (1)

Connections, links, ATM equipment, and identifiers:

ATMEnd-system

ATMEnd-system

ATMCross-connect

ATMSwitch

ATMCross-connect

ATMSwitch

VCC 1

VPC 1 VPC 2 VPC 3

VCI 1 VCI 2 VCI 3

VPI 1 VPI 3 VPI 5VPI 2 VPI 4

VPL 1 VPL 3 VPL 5VPL 2 VPL 4

VC: Virtual Channel, VP: Virtual Path, L: Link, I: Identifier, C: Connection

Link

sE

quip

men

tId

entif

iers

“Con

nect

ions

”


ATM Connections (2)

Hierarchical connection concept includes:• Virtual Connections are identified by two identifiers, which

are significant only locally per link in the virtual connection.– Error-control is done end-to-end only, if required.

High quality links and a good call acceptance control.

– Flow-control is not provided. High bandwidth delay product.

• Virtual Channel (VC) is a uni-directional channel, identified by the Virtual Channel Identifier (VCI).

– Dynamically allocatable connections.• Virtual Path (VP) contains a group of VCs, identified by the

Virtual Path Identifier (VPI).– Statically allocatable connections.


ATM Connections (3)

Simultaneous support of many thousands of VCs requires the ATM cell to carry the VCI field.

Supporting many semi-permanent connections between endpoints, carrying many grouped VPs requires the ATM cell to carry the VPI field.

LinkVPI1

VPIk

VCIn

VCIm

VCI1

VCI2

VPI Virtual Path IdentifierVCI Virtual Channel Identifier

Pre-assigned VPI/VCI values:0/0 Unassigned, idle0/1 Meta-signaling0/3 Segment flow (between

VP end-points, F4)0/4 End-to-end F4 flow0/5 Signaling0/15 SMDS0/16 ILMI

ILMI: Integrated Layer Management InterfaceSMDS: Switched Multimegabit Data Service


ATM Switching (1)

Two types of switching may be performed. VP switching (ATM Cross-connect):

• Switching between VPs,• No evaluation and change of VCIs,• Change of VPIs, and• Variable number of VCs per VP possible.

VC/VP switching (ATM Switch):• Switching in close cooperation between VCs and VPs,• Evaluation of VCI and VPI in an intermediate system,• Change of VCI and VPI if necessary, and• Incoming VCs of one VP may be distributed between many

outgoing VPs.


ATM Switching (2)

Use of VPI in a B-ISDN network (cross-connect).

ATM

PHY

B-ISDN Network

ATM

PHY

ATM

PHY

VPIin VPIout

7 59 7

VPI = 7VCI = 1, 2, 3

VPI = 3VCI = 3, 4

VPI = 9VCI = 3, 4

VPI = 7VCI = 1, 2, 3

VPI = 5VCI = 1, 2, 3

VPI = 7VCI = 3, 4

VPIin VPIout

5 7

VPIin VPIout

7 3A

B

C

1

2

3


ATM Switching (3)

Use of VPI-VCI in a B-ISDN network (ATM switch).

ATM

PHY

B-ISDN Network

ATM

PHY

ATM

PHY

VPI-VCIin VPI-VCIout

7.1 5.17.2 7.37.3 5.29.3 7.49.4 5.3

VPI = 7VCI = 1, 2, 3

VPI = 3VCI = 3, 4

VPI = 9VCI = 3, 4

VPI = 7VCI = 1, 2, 3

VPI = 5VCI = 1, 2, 3

VPI = 7VCI = 3, 4


5.1 7.25.2 7.15.3 7.3


7.3 3.47.4 3.3A

B

C

1

2

3


ATM Layer – UNI Cell Format

GFC: Generic Flow-Controlused at the service interface.

PT: Payload Type definescontents of a cell:• User data congested,• User data non-congested,• Operation And Maintenance

(OAM) cells, and• Resource management cells.

CLP: Cell Loss Priority to identify low/high priority cells.

HEC: Header Error Control.

GFC

VPI

VCI

VCI

HEC

VPI

VCI

PT CLP

1

2

3

4

5

1 2 3 4 5 6 7 8bit

Byte

Header Payload

5 Byte 48 Byte

UNI: User-Network Interface


ATM Layer – NNI Cell Format

VPI: Virtual Path Identifiercomprises of 12 bit length.

PT: Payload Type definescontents of a cell:• User data congested,• User data non-congested,• Operation And Maintenance

(OAM) cells, and• Resource management cells.

CLP: Cell Loss Priority to identify low/high priority cells.

HEC: Header Error Control.

VPI

VCI

VPI

VCI

HEC

VCI

PT CLP

1

2

3

4

5

1 2 3 4 5 6 7 8bit

Byte

Header Payload

5 Byte 48 Byte

NNI: Network-Network Interface


Structure of the AAL

AAL includes sublayers:• Segmentation and

Reassembly (SAR) between packets/cells.

• Convergence sublayer(CS) for service-dependent adaptation:

– Common Part Con-vergence Sublayer(CPCS) and

– Service Specific Con-vergence Sublayer(SSCS).

• Layers may be empty.

CS-1

SAR-1

AAL 1

SSCS-2

CPCS-2

SAR-2

AAL 2

SSCS-3/4

CPCS-3/4

SAR-3/4

AAL 3/4

SSCS-5

CPCS-5

SAR-5

AAL 5

ATM Adaptation Layer

ATM Layer

Class A Class B Class C/D Class C/D


AAL Comparison

AAL 1

AAL Service ClassMessage Delimiter

Advanced Buffer AllocationMultiplexingCS Padding

CS Protocol OverheadCS ChecksumSAR Payload

SAR Protocol OverheadSAR Checksum

Criteria AAL 3/4 AAL 5AAL 2

Anonono00

no46/47 Byte

1/2 Byteno

Bnonoyes

0/46 Byte2 Byte

no1/47 Byte

3 Byteno

C/DBTAG

yesyes

4 Byte8 Byte

no44 Byte4 Byte10 bit

C/DBit in PTI

nono

0/47 Byte8 Byte32 bit

48 Byte0

no

PTI: Payload Type Information


ATM Functions per Layer – Summary

LayerAAL

ATM

PHY

Subl.CS

SAR

TC

PM

FunctionHandles transmission errorsHandles lost and misinserted cell conditionsHandles timing between source and destinationHandles cell delay variationSegments higher-layer information into 48 Byte fieldsReassembles cell payload in higher layer informationMultiplexes cells from different ATM channelsGenerates cell header (first four bytes)Performs payload type discriminationPerforms traffic shaping and flow controlRoutes and switches cells as neededIndicates cell loss priority and selects cells for discardingHEC header sequence generation and verificationCell delineationTransmission frame generation and recoveryBit timing


Part II: Overview of Technologies, ATM, and IP





IP Technology

Key elements of the technology used in the Internet:• Packet switching, using datagrams• No connection-dependent state information in the network• Distributed management• Many physical subnetwork technologies• One network protocol• Two transport protocols• Infrastructure for hundreds of different distributed

applications• Scalability: to accommodate exponential growth


IP Protocol Stack

Phys. Networklayer

Internetlayer

Applicationlayer

Ethernet DECnetATM

HTTP DNSFTP

IP

TCP UDPTransport

layer

Routing


Internet Protocol (IP)

IPv4 shows addressing problems:• Nearly exhausted Class B addresses. Classless Inter-

domain Routing (CIDR) provides short-term solution only.• Routing tables grow extremely fast .• IP unicast address space will run out due to radipdly, e.g.,

increasing Internet hosts and low-end Internet devices.

Next Generation Internet, IPv6, delivers solutions:• Extended addressing: 128 bit addresses.• Address hierarchy levels (hierarchy: subscriber, subnet, ...)• Anycast addresses to reach the “nearest” node of a group

(in terms of the routing metric).• Simplified IP header, including a flow label.


Internet Network Model

International ISP“Backbone”

RegionalISP B

LargeEnterprise

SmallEnterprise

ISP: Internet Service Provider SOHO: Small Office and Home

SOHO


Example – Backbone ISP: UUNET

http://www.caida.org/Tools/Mapnet/Backbones/


Example – Regional ISP: Switch

http://www.switch.ch


Switch – UUNET Interconnection

http://www.switch.ch


Co-location Model

Extensions broadens the model by other services: • More than a pure routing and traffic exchange role.• Content provider supported, e.g., with high volumes,

selection of non-local transit providers.• E.g., Multicast, Web, DNS, policy-based route services.

Router

Router Router

RouterRouter Router

RouterRouter

Router

RouterRouter

Router Multicast Router

Route Server

WebServer

DNSServer


Services Integrated Internet

QoS Guarantees

Configuration

Zone

State

Information

Required

Protocols

Status

Best-effort IntServ DiffServ

no

none

entire

network

none

none

operational

per data stream

per session

(dynamic)

end-to-end

data stream

per data stream,

in router

signaling

(RSVP)

matured

aggregated

log-term

(static)

domain-

oriented

(none, in

BB, in edge

router)

bit fields

(BB, COPS)

worked on

IntServ: Integrated Services, DiffServ: Differentiated Services, QoS: Quality-of-ServiceRSVP: Resource Reservation Protocol, BB: Bandwidth Broker, COPS: Common Open Policy Service


IntServ Implementation

Integrated Services Architecture (IntServ) supports best-effort and guaranteed services.

Traffic control functions:• Admission control,• Packet classifier, and• Packet scheduler.• Optional: Policy

control (COPS).

Protocol support:• Resource reservation,

E.g., RSVP (Resource Reservation Protocol).

Host and router require similar functionality.

PolicyControl

ResourceReservation

Application

AdmissionControl

PacketClassifier

PacketScheduler

Control

Data


The DiffServ Approach

Requirements for Differentiated Services proposals:• Aggregated bandwidth allocation without the need of

per-session signaling and complex router state,• Aggregated QoS guarantees with edge-complexity,• Long-term service contracts within a single domain,• Integrated and simplified accounting,• Better traffic isolation for performance predictability, and• Better services for users willing to pay more.

A set of new proposals for DiffServ:• Expedited Forwarding (EF) and• Assured Forwarding (AF).


DiffServ Implementation


References (1)

• F. Fluckiger: Understanding Networked Multimedia; Prentice Hall, London, England, 1995, ISBN 0–13–190992–4.

• R. Steinmetz: Multimedia Technologie; Springer Verlag, Bonn, Germany, 1999, ISBN 3-540-62060-5.

• M. de Prycker: Asynchronous Transfer Mode – Solution for Broadband ISDN; 3rd Edition, Prentice Hall, Englewood Cliffs, New Jersey, U.S.A., 1995, ISBN 0–13–342171–6.

• ITU-T – Maintenance Principles: Frame Relay Operation and Maintenance Principles and Functions; I.620, October 1996.


References (2)

• R. J. Vetter: ATM Concepts, Architectures, and Protocols; Communications of the ACM, Vol. 38, No. 2, February 1995, pp 30 – 38.

• B. G. Kim, P. Wang: ATM Network: Goals and Challenges; Com. of the ACM, Vol. 38, No. 2, February 1995, pp 39 – 44.

• M. de Prycker: Asynchronous Transfer Mode – Solution for Broadband ISDN; 3rd Edition, Prentice Hall, Engle-wood Cliffs, New Jersey, U.S.A., 1995, ISBN 0–13–342171–6.

• T. Braun: Die Internet-Protokollfamilie der nächsten Generation; Praxis der Informationsverarbeitung und Kommunikation, Vol. 19, No. 2, 1996, pp 94 – 102.

• X. Xiao, L. M. Ni: Internet QoS: A Big Picture; IEEE Network Magazine, Vol. 13, March/April 1999, pp 8 – 18.

Documents

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM III – 1 ETH Zürich Part III: Overview of Technologies, ATM, and IP Overview of Networking