© 2000 b. stiller, b. plattner ethz-tik, d. bauer ibm research cm i – 1 eth zürich prof. dr....

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

Prof. Dr. Bernhard Plattner, Prof. Dr. Burkhard StillerInstitut für Technische Informatik und Kommunikationsnetze

Fachgruppe Kommunikationssysteme, ETH ZürichGloriastrasse 35

CH-8092 Zürich, Switzerland

Phone: +41 1 [632 7000 | 632 7016], FAX: +41 1 632 1035E-Mail: [ plattner | stiller ]@tik.ee.ethz.ch

in cooperation with Dr. Daniel BauerIBM Research Division, Zürich Laboratories

Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland

High Speed Networks– Technology and Applicatios –

Manno, January 9, 2001


Course Outline

Part I: Introduction, Quality-of-Service, Internet Basics andRouting in Networks

Part II: LAN Technologies and Internetworking

Part III: Overview of Networking Technologies, ATM, and IP

Part IV: Carrier Technologies,Traffic Management, and Trends


Part I: Introduction, QoS, and Routing

• Introduction– Applications– Multimedia Systems

• Quality of Service (QoS) – Concept and Definitions– Example

• Routing– Internet Basics– Switching and Forwarding– Routers and the Big Picture– Routing Protocols


Introduction

Why are High Speed Networks an issue? Increasing dependency of business processes

on availability of various computing resources (servers, distributed applications, interpersonal communication facilities).

Ever increasing processing speeds of PCs, workstations and servers.

Technology push: High Speed Network Technology is available.

User pull: New distributed multimedia applications need faster networks and new kinds of services.


Traditional Applications

Client/server networking (e.g., Novell, Windows 95/NT).

Document exchange (directly between users or with a server as an intermediary).

Electronic mail services (proprietary technologies, or vendor independent standards like X.400 or Internet mail).

10 Mbit/s LAN technologies have generally been sufficient for these applications


Changing Picture

Percentage of employees really using computers has increased (cf. visions of LAN use of the 70s!)• 20/80% rule changes to 80/20% rule.

Graphical user interfaces tend to cause more traffic (X-Window System, UI design trends).

Graphical visualization of information has become popular (World Wide Web, Internet -> Intranet).

High-speed backup systems.

> Need for flexibility and extensibility of network infrastructure:• Universal cable plants, bridges, routers, LAN switches

• 100 Mbit/s LAN technology as a logical step


Emerging Applications

New types of applications:• Digitized analog applications: E.g., video/audio broad-

casting, picture phone, HDTV, conferencing, FAX• Digital applications per se: E.g., network management,

secure messaging, virtual reality.• Examples: Netmeeting or MBone tools (A/V conferencing)

or Marimba (Software Updates) Distributed applications:

• Collaborative work (CSCW)• Support for virtual enterprises• New technolgies in education, tele-teaching for life-long

learning• Entertainment (distributed games, Napster, Gnutella, ...)


Why do we need more bandwidth?

Text and graphics based applications will gradually give way to distributed multimedia applications:

Medium Data rate of representation

Speech, telephone quality (PCM) 64 kbit/sCD quality audio 172.3 kBytes/sCompressed audio 4:1, 37'800 Hzsampling

43 kBytes/s

MPEG-1 video target rate: 1.2 Mbit/s

MPEG-2 video (digital video studiostandard quality)

target rate: 40 Mbit/s

Motion JPEG as used at ETH(Telepoly)

~8 Mbit/s for one audio/videochannel


Future Developments

Ubiquitous computers Virtual reality Distributed simulation systems:

• “World models” or• Battlefield simulation -> virtual reality

Multiparty applications Mobile (multimedia) systems Active networks


Definition of a “Multimedia System”

Simple quantitative definition: A system supporting more than one medium (text, graphics, sound, video, tactile feelings, smell, ...).

Qualitative definition: A system supporting a combination of discrete and continuous media.

Additional properties:• Independence of the various media and• Computer-supported integration of media

(programmability, controllable timing, synchronization).

High speed networks should be capable of supporting distributed multimedia systems.


Components of a Multimedia System

Input/output devices

• Camera• Audio I/O• Mouse• Screen

Multimedia Workstation:• Standard processor• Memory and secondary

storage• Special purpose processors

(optional)• Graphics, audio and video

adapters• Communications adapters• Multimedia operating system

Multimedia servers

High- speed

integrated services network

Multimedia applications

Communication Middleware


Requirements (1)

Multimedia workstation: General state of the art high

performance hardware platform.

Operating system with support for continuous media:• Soft real-time support for

timely delivery of data,• Direct paths between data

sources and sinks,• Non-real time control

functions, and• Suitable device drivers.

High speed network: Basic properties: high

throughput, low delay, low delay jitter, low intrinsic error rate, and low loss.

Integrated services support:• Multiple service classes,• Quality-of-Service (QoS)

guarantees,• Facilities for the reservation of

resources, and• Implication: control path

separated from data path.


Requirements (2)

Multimedia applications: User interface for

controlling multimedia streams and applications semantics.

Accepts Quality-of-Service requests form the user.

Maps the user’s QoS wishes to lower level QoS requirements.

Capability for requesting the quality of service for continuous media streams.

Communication middleware: Offers an easy-to-use

communication service as an application pro-grammer’s interface (API).

Accepts QoS requirements from the application.

Maps QoS requirements to network QoS parameters and resource reservations.

Manages streams between sources and sinks.





• Routing– Switching and Forwarding– Routers and the Big Picture– Routing Protocols


Quality-of-Service (QoS)

What does QoS stand for?• Quality-of-Service: the grade, excellence, or goodness of a

service; in the considered case, communication services.

What is QoS?• A concept for qualitative and quantitative specification of

service requirements and properties, • Complemented with a set of rules and mechanisms for

aquiring requested QoS

Why QoS?• Basis of a „contract“ between a service user and a service

provider (e.g. in a service level agreement)


Quality-of-Service

A concept to describe service requirements is needed.• Examples for service characteristics comprise:

– Throughput,– Delay,– Jitter,– Error rates (reliability),– Ordered delivery,– Multicasting, and– Data unit size.


Different components of the communication architecture require distinct parameters.

QoS – An Example

Application

Middleware

Network

OperatingSystem

User

Communication qualities:Throughput, delay, error rates, jitter

Abstract qualities:High, medium, low

Media qualities:Frames/second, synchronization

System qualities:Thread duration, priority,scheduling method


Types of Service

There exist two basic types of service:• Best effort service and• Guaranteed service.

Best Effort Service:• Service type that does not give any guarantees for QoS

(no commitment).• No reservation of resources within the end-system or the

network.• Often QoS cannot be monitored, as no monitoring

mechanisms are defined; adaptive applications have to do their own monitoring.

• Specification of QoS parameters is not necessary.


Type-of-Service (2)

Two different guarantees are possible:• Statistical (stochastical) guarantees – weak:

– Requested QoS is provided with some (high) probability

– Utilization of network can be maximized (multiplexing).– Reserving resources for an “average” case necessary.

• Deterministic guarantees – strong:– Requested QoS is fully guaranteed.– Resource reservations are required for the worst case.

ToS is sometimes called “QoS semantics” as well.


Examples

For a file transfer application:• Best effort service concerning timing and delay:

– No values can be specified or reserved.• Guaranteed service (deterministic) concerning reliability:

– Bit error rate is zero for received data (retransmission).– However, service may be aborted due to slow links.

For video transmission:• Statistically Guaranteed service concerning frame delay:

– p percent of delayed frames may exceed the maximum bounded delay D.

– “Flickering” pictures (black outs) may occur due to frames arriving late.





• Routing– Internet Basics– Switching and Forwarding– Routers and the Big Picture– Routing Protocols


Internet (IP) Technology

Key elements of the technology used in the Internet:• Internet: Network of (sub)networks• 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


Interconnection of Heterogeneous Networks

HostHost

Host

HostHost

Host

Host

Host

Host

DECnet

Router

Token RingR

R

R

REthernet


Model of a Router

RoutingAgent

ManagementAgent

IPPackets

OutputDrivers

Forwarding table

Forwardingengine

IPPackets


IP Protocol Stack

Phys. Networklayer

Internetlayer

Applicationlayer

Ethernet DECnetATM

HTTP DNSFTP

IP

TCP UDPTransport

layer

Routing


Forwarding with A/B/C Address Classes

Forwarding is based on network id Simple and efficient

Net ID Host ID0

Net ID Host ID10

Net ID Host ID110

A

B

C

8 32160 24

A P

AA P

BA P

C


Step 1: Subnetting

Subnetting provides flexibility for network-internal addressing of subnetworks

Network administrators have the freedom to structure their own A/B/C address space into a few or many subnetworks

Class B 10 Net ID Host ID

Subnet 10 Net ID Subnet ID Host ID

0 1 2 3 4 8 16 24 31

16 Bits n Bits 16-n Bits

Subnet mask

Example: Net 129.132.0.0, Mask 255.255.255.192 = 10 Bit Subnet


Motivation for Hierarchical Routing

Large networks (> 10’000 sub-networks) are no longer tractable by a flat routing architecture.• The topology database becomes very large.

• Link state packets consume a lot of the available bandwidth.

• Path computation time grows with n2.

Administration and management becomes increasingly difficult as the network grows.• Administration has to be centralized.

• All routers need to run the same code, which makes updating difficult.


Hierarchical routing

Routing Domain 1

Routing Domain 2

Routing Domain 3

Routing Backbone

Intra-Domain-Router

Inter-Domain-Router

Routing Domain: Anaggregate of networks

or subnetworks that usea common internal

routing protocol andcommunicate to otherrouting domains via anInter-domain routing

protocol


Hierarchical Routing Principles

Address Aggregation(Address Summary)

Grouping of routes based onnetwork addresses.

A

C

B

A.1 A.2

C.2

C.1

C.3

B.2

B.3

B.2.4

A.2.5

A.2.3


Topology View of Node B.2.4

A

C

B.3

B.2.4B.1

B.2.3

B.2.2B.2.1

Summary Addresses(Address Prefixes)


Step 2: Classless Inter-Domain Routing

For efficient address allocation and routing, the distinction between A, B and C address classes is eliminated

Address registries may• allocate part of a A/B/C address space to a client• allocate several “adjacent” C networks to one client

The addresses belonging to one client may be identified by an address prefix of up to 32 bits (typical 8-30)

Inter-domain routing is done only on the prefix Intra-domain routing is done on the local network numbers Prefix length is not encoded into the address


Flexible Address Structure

Inter-domain (backbone) routers only need to know and look at the address prefixes of addresses

Intra-domain routers only look at local network Id Hosts Ids have subnetwork-local significance

Address prefix used forinter-domain routing

Host IdNetwork Id

with intra-domainrouting significance


Hierarchical Routing in the Internet

Inter-domain (backbone) routingA

B

C205.244.*/16

D129.132.66.*/26

E

Intra-domainrouting

129.132.*/16

/Prefix

129.132.66.44/32

129.132/16 ABC205.244/16D

Examples:129.132.72.15 is forwarded to A129.132.66.48 is forwarded to B129.132.66.68 is forwarded to A


Detailed Explanation

Sample forwarding table of backbone router:

Sample destination addresses to be matched against forwarding table:

Prefix (decimal) Prefix (binary) Next hop129.132/16 10000001 10000100 * A129.132.66/26 10000001 10000100 01000010 00* B129.132.66.44/32 10000001 10000100 01000010 00101100 C205.244/16 11001101 11110100 * D

Address (decimal) Address (binary) Next hop found129.132.72.15 10000001 10000100 01001000 00001111 A129.132.66.48 10000001 10000100 01000010 00110000 B129.132.66.68 10000001 10000100 01000010 01000100 A


The State of the Art for Forwarding Lookups

Patricia tries


Trie-based Forwarding Lookup

Forwarding table

1* A11* B111* C1000* D10001* E100011* F1000111* G1110111* H

A

B

C

H

D

E

F

G

1

1

1

1

1

1

0

0

0

0

1

1

1

Root


The State of the Art for Forwarding Lookups

Protocol based solutions (“label switching”)• small integer labels packets that take the same route• label may be used as an index into forwarding table• IP Switching, Tag Switching, ...

Caching (using CAMs for fast operation)

Patricia tries Hardware solutions - Content Addressable

Memories (CAM)


Fast Forwarding is a Difficult Problem ...

Performance• 10 Gbit/s throughput @ packet size 128 bytes -> 10

million packets/s -> 100 ns per packet• Trie lookups are too slow: O(W) memory accesses in the

worst case; only a few memory lookups can be allowed

Scalability• Trie lookups have large memory requirements, worst

case performance is linear to the prefix length

Cost• CAM solutions are expensive• Caching needs associative memory (CAMs) for good

performance


… and was solved only recently

M. Waldvogel, G. Varghese, J. Turner, and B. Plattner: Scalable High Speed IP Routing LookupsProc. ACM SIGCOMM '97 Conference (in: Computer Communication Review, Volume 27, Number 4, October 1997)

Needs 2-3 memory accesses for finding the best matching prefix

Achieved with a novel application of a binary search strategy with hash tables


Router Architecture

Single-CPU/Shared Bus Router


Router with one Card per Port


Today: Switch-based Router

Durchschaltenetz(switch fabric)

Steuerung

Paketverarbeitung

Steuerung

Paketverarbeitung

Steuerung

Paketverarbeitung

Steuerung

Paketverarbeitung

Steuerung

Paketverarbeitung

Steuerung

Paketverarbeitung

Steuerung

Paketverarbeitung

Steuerung

Paketverarbeitung

Router & Switchcontrol

Line if cards Line if cards


Tasks of a Routing Protocol

Routing involves two activities:• Determining optimal (shortest) routing paths.• Transporting packets through an internetwork.

Routing protocols calculate optimal routing paths based on a distributed routing algorithm.

Path calculation is split into two tasks:• Collecting topology information (“get a view of the

network”).• Constructing optimal routing paths based on the collected

topology information.


Link Metrics

Paths are computed based on “metrics”. Static Metrics

• Assigned by network administrator.• Examples: hop-count, distance, link capacity, weight, etc.

Dynamic Metrics• Measured or computed by routers.• Examples: available bandwidth, current delay, etc.

Additive Metrics (hop-count, delay, weight)•

Restrictive Metrics (available bandwidth)•

)linkmetric()path(metric i

))link(metric()path(metric iMin


Static Routing

Routing tables configures by administrator. Most stable “routing protocol”. Only applicable in very small and simple networks.

C

A B

D1

2

Forwarding Table Node C

Dest Port Distance A 1 1 D 2 1 B 1 2 B 2 2


Distance Vector Routing

Distributed variant of the “Bellman-Ford” algorithm. Distributes reachability and metric information.

A

B

C

D

13

3

1

1

Dest. Port/CostA A/3C -/0D D/1

Dest. Port/CostA A/3B A/4C A/6D A/4C -/0D D/1

Dest. Port/CostA A/3B A/4C -/0D D/1

Dest. Port/CostA A/3B A/4C -/0A D/2B D/3C D/2D D/1

Dest. Port/CostA D/2B D/3C -/0D D/1


Link State Routing

Routers distribute their local view (the “link-state”) to all other routers. The local view consists of:• Nodal information describing routers.• Link information describing links.• Reachability information describing reachable hosts.• Metric information as attributes for links and reachabilities.

Each router maintains a complete view of the topology in the topology database.

Dijkstra’s “shortest path first” algorithm is used to calculate paths to all reachabilities.


Link State Routing: Pro and Con

Link state routing converges faster than distance vector routing and thus is more scalable.

It provides more functionality:• Each router knows the full topology, which makes it easier

to debug.• Powerful source routing schemes can be implemented.

Link state routing is more robust since the topology is described with some redundancy.

It is more complex to implement and requires more memory, CPU power and bandwidth.


Routing in the Internet

Autonomous Systems:• Administered by a single authority.• Implements a single routing policy.• Has a unique identifier (AS number).

Interior Gateway Protocols (IGP),OSPF, RIP, ...

Exterior GatewayProtocols (EGP),BGP4


ATM Routing: Schematic Overview

Callee

Caller

Setup

Setup

Connect

Connect

Routing decision


Signaling and Interfaces

PublicATM

PrivateATM

PublicATM

PrivateATM

Private NNI(B-ICI)

PublicUNI

PrivateUNI

Public UNI

PrivateNNI

ILMI

ILMI

NNI Network Node InterfaceUNI User Network InterfaceILMI Integrated Local Management InterfaceB-ICI Broadband-Inter Carrier Interface


Summary Routing Protocols

The Internet uses hierarchical routing based on interior and exterior gateway protocols.

OSPF, the recommended IGP, is a link state routing protocol that uses static metrics.

BGP is the EGP of choice. It is a path vector protocol supporting various routing policies.

The current IP routing protocols do not support dynamic metrics such as available bandwidth.

In ATM, PNNI provides hierarchical routing using link state routing.

PNNI supports dynamic metrics.


References

• F. Fluckiger: Understanding Networked Multimedia; Prentice Hall, London, England, 1995, ISBN 3–13–190992–4.

• K. Nahrstedt, R. Steinmetz: Multimedia: Computing, Communications, and Applications; Prentice Hall, Upper Saddle River, New Jersey, U.S.A., 1995, ISBN 0-13-324435-0.

• B. Stiller: Quality-of-Service; International Thomson Publishing, Bonn, Germany, 1996, ISBN 3–8266–0171–8.

• G. Malkin: RIP Version 2; RFC 2453, November 1998.• J. Moy: OSPF Version 2, RFC 2328, April 1998• ATM Forum: Private Network-Network Interface Specification

1.0 (PNNI 1.0), af-pnni-0055.000, March 1996• Y. Rekhter, T. Li: A Border Gateway Protocol 4, RFC 1771,

March 1995

© 2000 b. stiller, b. plattner ethz-tik, d. bauer ibm research cm i – 1 eth zürich prof. dr....

Documents

plattner stiller

plattner ethztik

eth zrich introduction

o user

eth zrich gloriastrasse

o technology push

distributed applications

eth zrich course outline