High-Speed Internet Switches and Routers COMP 680E Mounir Hamdi

Transcript High-Speed Internet Switches and Routers COMP 680E Mounir Hamdi

High-Speed Internet Switches and Routers

COMP 680E

Mounir Hamdi Professor, Computer Science Director, MSc-IT Hong Kong University of Science and Technology COMP680E by M. Hamdi

Goals of the Course

• Understand the architecture, operation, and evolution of the Internet – IP, ATM, Optical • Understand how to design, implement and evaluate Internet routers and switches (Telecom Equipment) – Both hardware and software solutions • Get familiar with current Internet switches/routers research and development efforts • Appreciate what is a good project – Task selection and aim – Survey & solution & research methodology – Presentation • Apply what you learned in a small class project

COMP680E by M. Hamdi

Outline of the Course

• The focus of the course is on the design and analysis of high-performance electronic/optical switches/routers needed to support the development and delivery of advanced network services over high speed Internet. • The switches and routers are the its switches and routers.

KEY

building blocks of the Internet, and as a result, the capability of the Internet in all its aspects depends on the capability of • The goal of the course is to provide a basis for understanding, appreciating, and performing research and development in networking with a special emphasis on switches and routers.

COMP680E by M. Hamdi

Outline of the Course

•

Introduction

– Definition and History of Networking/Internet – Evolution and Trends in the Internet – Architecture of The Internet – Classification and Evolution of Internet Equipment – Review and Evolution of Internet Protocols – Different technologies of the Internet

COMP680E by M. Hamdi

Outline of the Course

•

Network Processors: Table Lookup and Packet Classification

– Internet addressing and CIDR – Table Lookup: Exact matches, longest prefix matches, performance metrics, hardware and software solutions. – Packet classifiers for firewalls, QoS, and policy-based routing; graphical description and examples of 2-D classification, examples of classifiers, theoretical and practical considerations – State-of-the-art commercial products

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Outline of the Course

•

High-Performance Packet Switches/Routers

– Architectures of packet switches/routers (IQ, OQ, VOQ, CIOQ, SM, Buffered Crossbars) – Design and analysis of switch fabrics (Crossbar, Clos, shared memory, etc.) – Design and analysis of scheduling algorithms (arbitration, Maximum/maximal matching, shared memory contention, etc.) – Emulation of output-queueing switches by more practical switches – State-of-the-art commercial products

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Outline of the Course

•

Quality-of-Service Provision in the Internet

– QoS paradigms (IntServ, DiffServ, Controlled load, etc.) – MPLS/GMPLS – Flow-based QoS frameworks: Hardware and software solutions – Stateless QoS frameworks: RED, WRED, congestion control, and Active queue management – State-of-the-art commercial products

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Outline of the Course

•

Optical Networks

– Optical technology used for the design of switches/routers as well as transmission links – Dense Wavelength Division Multiplexing – Optical Circuit Switches: Architectural alternatives and performance evaluation – Optical Burst switches – Optical Packet Switches – Design, management, and operation of DWDM networks – State-of-the-art commercial products

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• • • Homework Midterm Project

Grading

20% 30% 50%

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Course project

• Investigate existing advances and/or new ideas and solutions – related to Internet Switches and Routers - in a small scale project (To be given or chosen on your own) – define the problem – execute the survey and/or research – work with your partner – write up and present your finding

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Course Project

• I’ll post on the class web page a list of projects – you can either choose one of these projects or come up with your own • Choose your project, partner (s), and submit a one page proposal describing: – the problem you are investigating – your plan of project with milestones and dates – any special resources you may need • Final project presentation (~ 30 minutes) • Submit project papers

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Homework

• • • Goals: 1.

Synthesize main ideas and concepts from very important research or development work I will post in the class web page a list of “well-known” papers to choose from 1.

Report contains: Description of the papers Goals and problems solved in the papers What did you like/dislike about the paper Recommendations for improvements or extension of the work

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How to Contact Me

• Instructor: Mounir Hamdi [email protected]

• Office Hours – You can come any time – just email me ahead of time – I would like to work closely with each student

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Overview and History of the Internet

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What is a Communication Network?

(from an end system point of view)

• A network offers a service: move information – Messenger, telegraph, telephone, Internet … – another example, transportation service: move objects • horse, train, truck, airplane ...

• What distinguishes different types of networks?

– The services they provide • What distinguish the services?

– latency – bandwidth – loss rate – number of end systems – Reliability, unicast vs. multicast, real-time, message vs. byte ...

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What is a Communication Network?

Infrastructure Centric View

• Hardware – Electrons and photons as communication data – Links: fiber, copper, satellite, … – Switches: mechanical/electronic/optical, • Software – Protocols: TCP/IP, ATM, MPLS, SONET, Ethernet, PPP, X.25, Frame Relay, AppleTalk, IPX, SNA – Functionalities: routing, error control, congestion control, Quality of Service (QoS), … – Applications: FTP, WEB, X windows, VOIP, IPTV...

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Types of Networks

• Geographical distance – Personal Areas Networks (PAN) – Local Area Networks (LAN): Ethernet, Token ring, FDDI – Metropolitan Area Networks (MAN): DQDB, SMDS (Switched Multi-gigabit Data Service) – Wide Area Networks (WAN): IP, ATM, Frame relay • Information type – data networks vs. telecommunication networks • Application type – special purpose networks: airline reservation network, banking network, credit card network, telephony – general purpose network: Internet

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Types of Networks

• Right to use – private: enterprise networks – public: telephony network, Internet • Ownership of protocols – proprietary: SNA – open: IP • Technologies – terrestrial vs. satellite – wired vs. wireless • Protocols – IP, AppleTalk, SNA

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The Internet

• Global scale, general purpose, heterogeneous technologies, public, computer network • Internet Protocol – Open standard: Internet Engineering Task Force (IETF) as standard body – Technical basis for other types of networks • Intranet: enterprise IP network • Developed by the research community

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Internet History

1961-1972: Early packet-switching principles

• 1961: Kleinrock - queueing theory shows effectiveness of packet-switching • 1964: Baran – Introduced first Distributed packet-switching Communication networks • 1967 : ARPAnet conceived and sponsored by Advanced Research Projects Agency – Larry Roberts • 1969: first ARPAnet node operational at UCLA. Then Stanford, Utah, and UCSB • 1972: – ARPAnet demonstrated publicly – NCP (Network Control Protocol) first host-host protocol (equivalent to TCP/IP) – First e-mail program to operate across networks – ARPAnet has 15 nodes and connected 26 hosts

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Internet History

1972-1980: Internetworking, new and proprietary nets

• 1970: ALOHAnet satellite network in Hawaii • 1973: Metcalfe’s PhD thesis proposes Ethernet • 1974: Cerf and Kahn - architecture for interconnecting networks (TCP) • late70’s: proprietary architectures: DECnet, SNA, XNA • late 70’s: switching fixed length packets (ATM precursor) • 1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles: – minimalism, autonomy - no internal changes is required to interconnect networks – best effort service model – stateless routers – decentralized control define today’s Internet architecture

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1971-1973: Arpanet Growing

• 1970 - First 2 cross-country link, UCLA-BBN and MIT Utah, installed by AT&T at 56kbps

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Internet History

1980-1990: new protocols, a proliferation of networks

• 1983: TCP/IP • 1982: protocol defined • 1983: deployment of SMTP e-mail DNS defined for name-to-IP-address translation • 1985: ftp protocol defined (first version: 1972) • 1988 : control TCP congestion • New national networks: CSnet, BITnet, NSFnet, Minitel • 100,000 hosts connected to confederation of networks

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Internet History

1990’s: commercialization, the WWW

• Early 1990’s: ARPAnet decomissioned • 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) • early 1990s: WWW – hypertext [Bush 1945, Nelson 1960’s] – HTML, http: Berners-Lee – 1994: Mosaic, later Netscape – late 1990’s: commercialization of the WWW Late 1990’s : • est. 50 million computers on Internet • est. 100 million+ users in 160 countries • backbone links running at 1 Gbps+ 2000’s • VoIP, Video on demand, Internet business • RSS, Web 2.0

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Growth of the Internet

•

Number of Hosts on the Internet:

Aug. 1981 213 Oct. 1984 1,024 Dec. 1987 28,174 Oct. 1990 313,000 Oct. 1993 2,056,000 Apr. 1995 5,706,000 Jan. 1997 16,146,000 Jan. 1999 56,218,000 Jan. 2001 109,374,000 Jan. 2003 171,638,297 Jul 2004 285,139,107 Jul 2005 353,284,187 Today ~ 440,000,000 Source: http://www.isc.org/index.pl?/ops/ds/host-count history.php

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Internet - Global Statistics

1997 2005

• 22.5 Million Hosts • 50 Million Users • 350 Million Hosts • 1,018 Million Users (approx. 2.4 Billion Telephone Terminations, 660 Million PCs and 1.6B mobile phones)

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Internet Penetration December 2006

(Source www.internetstats.com)

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Top 10: % Internet Use (Dec 2006)

Country or Region 1 2 3 4 5 6 7 8 9 10 Penetration (% Population) Iceland New Zealand Sweden Portugal Australia United States Falkland Islands Denmark Hong Kong (China) Luxembourgh % Internet Users 86.3 % 74.9 % 74.7 % 73.8 % 70.2 % 69.6 % 69.4 % 69.2 % 68.2 % 68.0 %

www.internetworldstats.com

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Languages of Internet Users

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Who is Who on the Internet ?

• • • •

Internet Engineering Task Force (IETF):

Request For Comments or RFCs .

The IETF is the protocol engineering and development arm of the Internet. Subdivided into many working groups, which specify

IRTF (Internet Research Task Force):

Research Task Force is composed of a number of focused, long-term and small Research Groups.

The Internet

Internet Architecture Board (IAB)

: The IAB is responsible for defining the overall architecture of the Internet, providing guidance and broad direction to the IETF.

The Internet Engineering Steering Group (IESG)

: The IESG is responsible for technical management of IETF activities and the Internet standards process. Composed of the Area Directors of the IETF working groups.

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Internet Standardization Process

• All standards of the Internet are published as RFC (Request for Comments). But not all RFCs are Internet Standards !

– available: http://www.ietf.org • A typical (but not only) way of standardization is: – Internet Drafts – RFC – Proposed Standard – Draft Standard (requires 2 working implementation) – Internet Standard (declared by IAB) • David Clark, MIT, 1992: "We reject: kings, presidents, and voting. We believe in: rough consensus and running code.”

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Services Provided by the Internet

• Shared access to computing resources – telnet (1970’s) • Shared access to data/files – FTP, NFS, AFS (1980’s) • Communication medium over which people interact – email (1980’s), on-line chat rooms, instant messaging (1990’s) – audio, video (1990’s) • replacing telephone network?

• A medium for information dissemination – USENET (1980’s) – WWW (1990’s) • replacing newspaper, magazine?

– audio, video (1990’s) • replacing radio, CD, TV? – 2000s: peer-to-peer systems – triple play bundles

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Today’s Vision

• Everything is digital: voice, video, music, pictures, live events, … • Everything is on-line: bank statement, medical record, books, airline schedule, weather, highway traffic, … • Everyone is connected: doctor, teacher, broker, mother, son, friends, enemies

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What is Next? – many of it already here

• Electronic commerce – virtual enterprise • Internet entertainment – interactive sitcom • World as a small village – community organized according to interests – enhanced understanding among diverse groups • Electronic democracy – little people can voice their opinions to the whole world – little people can coordinate their actions – bridge the gap between information haves and have no’s • Electronic Crimes – hacker can bring the whole world to its knee

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Industrial Players

• Telephone companies – own long-haul and access communication links, customers • Cable companies – own access links • Wireless/Satellite companies – alternative communication links • Utility companies: power, water, railway – own right of way to lay down more wires • Medium companies – own content • Internet Service Providers • Equipment companies – switches/routers, chips, optics, computers • Software companies

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What is the Internet?

• The collection of hosts and routers that are mutually reachable at any given instant • All run the Internet Protocol (IP) – Version 4 (IPv4) is the dominant protocol – Version 6 (IPv6) is the future protocol • Lots of protocols below and above IP, but only one IP – Common layer

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Commercial Internet after 1994

• Roughly hierarchical • National/international backbone providers (NBPs) – e.g., Sprint, AT&T, UUNet – interconnect (peer) with each other privately, or at public Network Access Point (NAPs) • regional ISPs – connect into NBPs • local ISP , company – connect into regional ISPs local ISP regional ISP NBP B NAP NBP A regional ISP local ISP NAP

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Internet Organization

NAP

POP

ISP

CN CN CN

POP BSP POP

CN CN

NAP

POP

ISP POP BSP POP

BSP ISP NAP

POP CN

ISP = Internet Service Provider BSP = Backbone Service Provider NAP = Network Access Point POP = Point of Presence 38

Commercial Internet after 1994

Joe's Company Campus Network Regional ISP Stanford Bartnet Berkeley Xerox Parc SprintNet America On Line IBM Modem NSF Network Internet MCI IBM

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Internet Architecture

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Basic Architecture: NAPs and National ISPs

• The Internet has a hierarchical structure.

• At the highest level are large

national

Internet Service Providers

that interconnect through

Network Access Points (NAPs)

• There are about a dozen NAPs in the U.S., run by common carriers such as Sprint and Ameritech, and many more around the world (Many of these are traditional telephone companies, others are pure data network companies).

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The real story…

•

Regional

ISPs

interconnect with

national

ISPs

and provide services to their customers and sell access to

local

ISPs

who, in turn, sell access to individuals and companies.

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pop pop pop pop COMP680E by M. Hamdi

The Hierarchical Nature of the Internet Metro Network Long Distance Network

Central Office Central Office

San Francisco New York

Central Office Major City Regional Center Major City Regional Center Central Office Central Office

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Central Office 44

A B C

Points of Presence (POPs)

POP1 POP2 POP3 POP4 POP6 POP7 POP5 POP8

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F 45 D E

A Bird’s View of the Internet

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A Bird’s View of the Internet

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Hop-by-Hop Behavior

Within HK Los Angeles Qwest (Backbone) Stanford From traceroute.pacific.net.hk to cs.stanford.edu

traceroute to cs.stanford.edu (171.64.64.64) from lamtin.pacific.net.hk (202.14.67.228), rsm-vl1.pacific.net.hk (202.14.67.5) gw2.hk.super.net (202.14.67.2) 3 wtcr7002.pacific.net.hk (202.64.22.254) 4 atm3-0-33.hsipaccess2.hkg1.net.reach.com (210.57.26.1) 5 ge-0-3-0.mpls1.hkg1.net.reach.com (210.57.2.129) 6 so-4-2-0.tap2.LosAngeles1.net.reach.com (210.57.0.249) 7 unknown.Level3.net (209.0.227.42) 8 lax-core-01.inet.qwest.net (205.171.19.37) 9 sjo-core-03.inet.qwest.net (205.171.5.155) 10 sjo-core-01.inet.qwest.net (205.171.22.10) 11 svl-core-01.inet.qwest.net (205.171.5.97) 12 svl-edge-09.inet.qwest.net (205.171.14.94) 13 65.113.32.210 (65.113.32.210) 14 sunet-gateway.Stanford.EDU (171.66.1.13) 15 CS.Stanford.EDU (171.64.64.64)

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MAE West SF NAP

NAP-Based Architecture

CHI NAP

Sprint Net QWest MCI UUNET COMP680E by M. Hamdi

NY NAP WDC NAP 49

Basic Architecture: MAEs and local ISPs

• As the number of ISPs has grown, a

new type

of network access point, called a

metropolitan area exchange (MAE)

has arisen.

• There are about 50 such MAEs around the U.S. today.

• Sometimes large regional and local ISPs (AOL) also have access directly to NAPs.

• It has to be approved by the other networks already connected to the NAPs – generally it is a business decision.

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Internet Packet Exchange Charges Peering

• ISPs at the

same level

usually do not charge each other for exchanging messages.

• They update their routing tables with each other customers or pop.

• This is called

peering

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Charges: Non-Peering

• Higher level ISPs, however, charge lower level ones (national ISPs charge regional ISPs which in turn charge local ISPs) for carrying Internet traffic.

• Local ISPs, of course, charge individuals and corporate users for access.

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Connecting to an ISP

• ISPs provide access to the Internet through a

Point of Presence (POP)

• Individual users access the POP through a dial-up line using the

PPP protocol .

• The call connects the user to the ISP’s

modem pool

, after which a

remote access server (RAS)

checks the userid and password.

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More on connecting

• Once logged in, the user can send TCP/IP/[PPP] packets over the telephone line which are then sent out over the Internet through the ISP’s POP (point of presence) • Corporate users might access the POP using a T-1, T-3 or ATM OC-3 connections, for example, provided by a common carrier.

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DS (telephone carrier) Data Rates

Designation DS0 DS1 (T1) DS2 (T2) DS3 (T3) Number of Voice Circuits 1 24 96 672 Bandwidth 64 kb/s 1.544 Mb/s 6.312 Mb/s 44.736 Mb/s COMP680E by M. Hamdi

SONET Data Rates

A small set of fixed data transmission rates is defined for SONET. All of these rates are multiples of 51.84 Mb/s, which is referred to as Optical Carrier Level 1 (on the fiber) or Synchronous Transport Signal Level 1 (when converted to electrical signals)

Optical Level Line Rate, Mb/s

OC-1 OC-3

OC-9

OC-12

OC-18 OC-24 OC-36

OC-48

OC-96

OC-192 OC-768 51.840

155.520

466.560

622.080

933.120

1244.160

1866.240

2488.320

4976.640

9953.280

39813.120

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ISPs and Backbones

POP: Connection with customers Line Server Dialup Lines to Customers T1 Lines to Customers T3 Line POP: connection with POP of the same ISP or different ISPs T3 Lines to Other POPs Ethernet Router Point of Presence (POP) OC-3 Core Router Line ATM Switch OC-3 Lines to Other ATM Switches COMP680E by M. Hamdi

Individual Dial-up Customers Corporate T1 Customer Corporate T3 Customer Corporate OC-3 Customer ISP Point-of-Presence Modem Pool ISP POP T1 CSU/DSU T3 CSU/DSU ATM Switch ATM Switch Remote Access Server ATM Switch COMP680E by M. Hamdi ISP POP ISP POP NAP/MAE

HK Major Internet Exchange (HK –NAP/ MAE) COMP680E by M. Hamdi

From the ISP to the NAP/MAE

• Each ISP acts as an autonomous system, with is own interior and exterior routing protocols.

• Messages destined for locations within the same ISP are routed through the ISP’s own network.

• Since most messages are destined for other networks, they are sent to the nearest MAE or NAP where they get routed to the appropriate “next hop” network.

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From the ISP to the NAP/MAE

• Next is the connection from the local ISP to the NAP. From there packets are routed to the next higher level of ISP.

• Actual connections can be complex and packets sometimes travel long distances. Each local ISP might connect a different regional ISP, causing packets to flow between cities, even though their destination is to another local ISP within the same city.

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ISP A

Inside an Internet Network Access Point

Router ATM Switch ISP D Router ISP B Router ISP E ATM Switch ISP C Router Route Server COMP680E by M. Hamdi ISP F ATM Switch

Inside an Internet Network Access Point COMP680E by M. Hamdi

Network Access Point

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ISPs and Backbones

POP POP POP POP ATM/SONET Core POP POP Router Core POP Access Network POP COMP680E by M. Hamdi POP POP POP POP POP

Three national ISPs in North America

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Backbone Map of UUNET - USA

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• Mixed OC-12 – OC-48 – OC 192 backbone • 1000s miles of fiber • 3000 POPs • 2,000,000 dial-in ports

UUNET

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Backbone Map of UUNET - World

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• OC-192 backbone • 25,000 miles of fiber • 635 POPs • 85,000 dial-in ports

Qwest

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• OC-192 backbone • 53,000 miles of fiber • 2000 POPs • 0 dial-in ports

AT&T

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Internet Backbones in 2006

• As of mid-2001, most backbone circuits for national ISPs in the US are 622 Mbps ATM OC-12 lines.

• The largest national ISPs are planning to convert to OC-192 (10 Gbps) by the end of 2003.

• A few are now experimenting with OC-768 (40 Gbps) and some are planning to use OC-3072 (160 Gbps).

• Aggregate Internet traffic reached 2.5 Terabits per second (Tbps) by mid-2001. It is expected to reach 35 Tbps by 2007.

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Links for Long Haul Transmission

• Possibilities – IP over SONET – IP over ATM – IP over Frame Relay – IP over WDM

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User Services & Core Transport

EDGE CORE

Frame Relay IP ATM Lease Lines

Users Services IP Router TDM Switch Frame Relay

OC-3 OC-3

ATM Switch

OC-12

Sonet ADM

STS-1 STS-1 STS-1

Service Provider Networks Transport Provider Networks

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Typical (BUT NOT ALL) 1990’s) IP Backbone (Late Core Router ATM Switch MUX SONET/SDH ADM SONET/SDH ADM MUX Core Router ATM Switch SONET/SDH DCS SONET/SDH DCS MUX ATM Switch Core Router SONET/SDH ADM SONET/SDH ADM MUX ATM Switch Core Router

• Data piggybacked over traditional voice/TDM transport

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IP Backbone Evolution (One version)

Core Router (IP/MPLS) FR/ATM Switch MUX SONET/SDH

• Removal of ATM Layer – Next generation routers provide trunk speeds and SONET interfaces – Multi-protocol Label Switching (MPLS) on routers provides traffic engineering

DWDM (Maybe) COMP680E by M. Hamdi Core Router (IP/MPLS) SONET/ SDH DWDM

Hierarchy of Routers and Switches

Core IP Router FR/ATM Switch SONET/SDH

•IP Router (datagram packet switching) • Deals directly with IP addresses; • Slow

– typically no interface to SONET equipment

• Expensive • Efficient (No header overhead and alternative routing) •ATM Switch (VC packet switching) • Label based switching • Fast (Hardware forwarding) • Header Tax •SONET OXC (Circuit switching) • Extremely fast

– Optical technology

• Inexpensive

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Customer Network

• All hosts owned by a single enterprise or business • Common case – Lots of PCs – Some servers – Routers – Ethernet 10/100/1000-Mb/s LAN – T1/T3 1.54/45-Mb/s wide area network (WAN) connection

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Customer Network

Clients LAN Servers Ethernet 10 Mb/s Router WAN T1 Link 1.54 Mb/s COMP680E by M. Hamdi

Internet Access Technologies

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Internet Access Technologies

• Previously, most people use 56K dial-up lines to access the Internet, but a number of new access technologies are now being offered. • The main new access technologies are: – Digital Subscriber Line/ADSL – Cable Modems – Fixed Wireless (including satellite access) – Mobile Wireless (WAP)

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Digital Subscriber Line

• Digital Subscriber Line (DSL) is one of the most used technologies now being implemented to significantly increase the data rates over traditional telephone lines. • Historically, voice telephone circuits have had only a limited capacity for data communications because they were constrained by the 4 kHz bandwidth voice channel.

• Most local loop telephone lines actually have a much higher bandwidth and can therefore carry data at much higher rates.

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Digital Subscriber Line

• DSL services are relatively new and not all common carriers offer them.

• Two general categories of DSL services have emerged in the marketplace. –

Symmetric DSL

(SDSL) provides the same transmission rates (up to 128 Kbps) in both directions on the circuits.

–

Asymmetric DSL

(ADSL) provides different data rates to (up to 640 Kbps) and from (up to 6.144 Mbps) the carrier’s end office. It also includes an analog channel for voice transmissions.

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Customer Premises DSL Modem Line Splitter Local Loop Local Carrier End Office Main Distribution Frame Voice Telephone Network DSL Architecture Hub Telephone ATM Switch ISP POP Computer Computer DSL Access Multiplexer Customer Premises ISP POP ISP POP ISP POP Customer Premises COMP680E by M. Hamdi

Cable Modems

• One potential competitor to DSL is the “cable modem” a digital service offered by cable television companies which offers an upstream rate of 1.5-10 Mbps and a downstream rate of 2-30 Mbps. • A few cable companies offer downstream services only, with upstream communications using regular telephone lines.

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Customer Premises Cable Modem Cable Splitter Cable Company Fiber Node Downstream Cable Company Distribution Hub TV Video Network Combiner Optical/Electrical Converter Upstream Hub TV Router Computer Computer Customer Premises Customer Premises Shared Coax Cable System Cable Company Fiber Node Cable Modem Termination System ISP POP Cable Modem Architecture COMP680E by M. Hamdi

Fixed Wireless

• Fixed Wireless is another “dish-based” microwave transmission technology. • It requires “line of sight” access between transmitters.

• Data access speeds range from 1.5 to 11 Mbps depending on the vendor.

• Transmissions travel between transceivers at the customer premises and ISP’s wireless access office.

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Customer Premises Fixed Wireless Architecture Individual Premise DSL Modem Line Splitter Hub Telephone Individual Premise Main Distribution Frame Voice Telephone Network Wireless Transceiver DSL Access Multiplexer Individual Premise Computer Computer Customer Premises Customer Premises COMP680E by M. Hamdi Wireless Access Office Wireless Transceiver Router ISP POP

Classifying Computer Networks

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A Taxonomy of Communication Networks

• Communication networks can be classified based on the way in which the nodes exchange information: Communication Network Switched Communication Network Broadcast Communication Network Circuit-Switched Communication Network Packet-Switched Communication Network Datagram Network Virtual Circuit Network

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Broadcast vs. Switched Communication Networks

• Broadcast communication networks – information transmitted by any node is received by every other node in the network • examples: usually in LANs (Ethernet, Wavelan) – Problem: coordinate the access of all nodes to the shared communication medium (Multiple Access Problem) • Switched communication networks – information is transmitted to a sub-set of designated nodes • examples: WANs (Telephony Network, Internet) – Problem: how to forward information to intended node(s) • this is done by special nodes (e.g., routers, switches) running routing protocols

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Circuit Switching

• Three phases 1. circuit establishment 2. data transfer 3. circuit termination • If circuit is not available: “Busy signal” • Examples    Telephone networks ISDN (Integrated Services Digital Networks) Optical Backbone Internet (going in this direction)

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Host 1 Circuit Establishment Data Transmission Circuit Termination

Timing in Circuit Switching

Node 1 Node 2 processing delay at Node 1 Host 2 propagation delay between Host 1 and Node 1 propagation delay between Host 2 and Node 1

DATA

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Circuit Switching

• A node (switch) in a circuit switching network incoming links Node outgoing links

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Circuit Switching: Multiplexing/Demultiplexing

• Time divided in frames and frames divided in slots • Relative slot position inside a frame determines which conversation the data belongs to • If a slot is not used, it is wasted • There is no statistical gain

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Packet Switching

• Data are sent as formatted bit-sequences, so-called packets.

• Packets have the following structure: Header Data Trailer • Header and Trailer carry control information (e.g., destination address, check sum) • Each packet is passed through the network from node to node along some path (

Routing

) • At each node the entire packet is received, stored briefly, and then forwarded to the next node (

Store-and-Forward Networks

) • Typically no capacity is allocated for packets

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Packet Switching

• A node in a packet switching network incoming links Node Memory outgoing links

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Packet Switching: Multiplexing/Demultiplexing

• Data from any conversation can be transmitted at any given time • How to tell them apart?

– use meta-data (header) to describe data

COMP680E by M. Hamdi

Datagram Packet Switching

• Each packet is independently switched – each packet header contains destination address • No resources are pre-allocated (reserved) in advance • Example: IP networks

COMP680E by M. Hamdi

Timing of Datagram Packet Switching

Host 1 Host 2 Node 1 Node 2 transmission time of Packet 1 at Host 1 Packet 1 Packet 2 Packet 3 propagation delay between Host 1 and Node 2 Packet 1 Packet 2 Packet 3

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processing delay of Packet 1 at Node 2 Packet 1 Packet 2 Packet 3 100

Datagram Packet Switching

Host A Node 1 Host C Node 2 Node 5 Host B Node 4 Node 6

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Node 7 Node 3 Host D Host E 101

Virtual-Circuit Packet Switching

• Hybrid of circuit switching and packet switching – data is transmitted as packets – all packets from one packet stream are sent along a pre-established path (=virtual circuit) • • Guarantees in-sequence delivery of packets

However

: Packets from different virtual circuits may be interleaved • Example: ATM networks

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Virtual-Circuit Packet Switching

• Communication using virtual circuits takes place in three phases 1. VC establishment 2. data transfer 3. VC disconnect • Note: packet headers don’t need to contain the full destination address of the packet (One key to this idea)

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Host 1

Timing of VC Packet Switching

VC establishment Node 1 Node 2 Host 2 propagation delay between Host 1 and Node 1 Data transfer VC termination Packet 1 Packet 2 Packet 3 Packet 1 Packet 2 Packet 3

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Packet 1 Packet 2 Packet 3 104

VC Packet Switching

Host A Node 1 Host C Node 2 Node 5 Host B Node 4 Node 6

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Node 7 Node 3 Host D Host E 105

Packet-Switching vs. Circuit-Switching

• Most important advantage of packet-switching over circuit switching: Ability to exploit statistical multiplexing: – efficient bandwidth usage; ratio between peek and average rate is 3:1 for audio, and 15:1 for data traffic • However, packet-switching needs to deal with congestion: – more complex routers – harder to provide good network services (e.g., delay and bandwidth guarantees) • In practice they are combined – IP over SONET, IP over Frame Relay

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Fixed-Rate versus Bursty Data COMP680E by M. Hamdi

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Destination Address A Connection Identifier B

Packet Switches

Routing Table Connectionless Packet Switch

A Possibly different paths through switch A

Connec tion Table

B B Always same path through switch

Connection-Oriented Packet Switch

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Store-and-Forward Operation

• Packet entering switch or router is stored in a queue until it can be forwarded – Queueing – Header processing – Routing-table lookup of destination address – Forwarding to next hop • Queueing time variation can result in non deterministic delay behavior (maximum delay and delay jitter) • Packets might overflow finite buffers (Network congestion)

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Link Diversity

• Internet meant to accommodate many different link technologies – Ethernet – ATM – SONET – ISDN – Modem • The list continues to grow • “IP on Everything”

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Internet Protocols

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Internet Protocols

Application Transport Network Link Host Network Link Link Router COMP680E by M. Hamdi Application Transport Network Link Host

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IP Protocol Stack

Ping Telnet FTP

H.323

SIP RTSP RSVP S/MGCP/ NCS User application

ARP

TCP

ICMP

Link Layer

UDP

IGMP OSPF RARP

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Demultiplexing Application

Application Application Application Application

Transport

ICMP IGMP TCP UDP

Network

ARP

Link

IP RARP Ethernet Driver incoming frame

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Link Protocols

• Numerous link protocols – Ethernet + LLC (Logical Link Control) – T1/DS1 + HDLC (High-level Data Link Control) – T3/DS3 + HDLC – Dialup + PPP (Point-to-Point Protocol) – ATM/SONET + AAL (ATM Adaptation Layer) – ISDN + LAPD (Link Access Protocol) + PPP – FDDI + LLC

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Additional Link Protocols

• ARP (Address Resolution Protocol) is a protocol for mapping an IP address to a physical machine address that is recognized in the local network. Most commonly, this is used to associate IP addresses (32-bits long) with Ethernet MAC addresses (48-bits long).

• RARP is the reverse of ARP

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ARP Protocol COMP680E by M. Hamdi

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Sending an IP Packet over a LAN

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Transport Protocols

• Transmission Control Protocol (TCP) • User Datagram Protocol (UDP)

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Application Protocols

• • File Transfer Protocol (FTP) • Simple Mail Transfer Protocol (SMTP) • Telnet • Hypertext Transfer Protocol (HTTP) • Simple Network Management Protocol (SNMP) • Remote Procedure Call (RPC)

DNS:

The Domain Name System service provides TCP/IP host name to IP address resolution.

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The Internet Network layer: The Glue of all Networks

Network layer Transport layer: TCP, UDP Routing protocols •path selection •RIP, OSPF, BGP IP protocol •addressing conventions •datagram format •packet handling conventions routing table ICMP protocol •error reporting •router “signaling” Link layer physical layer

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Demultiplexing Details 1024-5000

User process User process User process User process FTP server TCP src port

21 23

telnet server

TCP dest port

 header  echo server

7 TCP 9

 data  discard server ICMP UDP

1 17

TCP

IGMP

2 ARP x0806

 IP header 

Others x8035 RARP Novell IP x0800 protocol type AppleTalk

dest addr source addr hdr cksum

dest addr source addr  data 

Ethernet frame type

 data  (Ethernet frame types in hex, others in decimal)

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IP Features

• Connectionless service • Addressing • Data forwarding • Fragmentation and reassembly • Supports variable size datagrams • Best-effort delivery: Delay, out-of-order, corruption, and loss possible. Higher layers should handle these.

• Provides only “Send” and “Delivery” services Error and control messages generated by Internet Control Message Protocol (ICMP)

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What IP does NOT provide

• End-to-end data reliability & flow control (done by TCP or application layer protocols) • Sequencing of packets (like TCP) • Error detection in payload (TCP, UDP or other transport layers) • Error reporting (ICMP) • Setting up route tables (RIP, OSPF, BGP etc) • Connection setup (it is connectionless) • Address/Name resolution (ARP, RARP, DNS) • Configuration (BOOTP, DHCP) • Multicast (IGMP, MBONE)

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Internet Protocol (IP)

• Two versions – IPv4 – IPv6 • IPv4 dominates today’s Internet • IPv6 is used sporadically – 6Bone, Internet 2

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IPv4 Header

0 15 Ver HLen TTL Ident TOS Protocol Flags Length Offset Checksum SrcAddr DestAddr Options Pad 31 COMP680E by M. Hamdi

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IPv4 Header Fields (1)

• Ver: version of protocol – First thing to be determined – IPv4  4, IPv6  6 • Hlen: header length (in 32-bit words) – Usually has a value of 5 – When options are present, the value is > 5 • TOS: type of service – Packet precedence (3 bits) – Delay/throughput/reliability specification – Rarely used

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IPv4 Header Fields (2)

• Length: length of the datagram in bytes – Maximum datagram size of 65,535 bytes • Ident: identifies fragments of the datagram (Ethernet 1500 Bytes max., FDDI: 4900 Bytes Max., etc.) • Flag: indicates whether more fragments follow • Offset: number of bytes payload is from start of original user data

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Fragmentation Example

20-byte optionless IP headers Id = x 0 0 1 492 data bytes 0 Id = x 0 0 0 1400 data bytes 0 Id = x 0 0 1 492 data bytes 492 Id = x 0 0 0 416 data bytes COMP680E by M. Hamdi 984

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IPv4 Header Fields (3)

• TTL: time to live gives the maximum number of hops for the datagram • Protocol: protocol used above IP in the datagram – TCP  6, UDP  17, • Checksum: covers IP header

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IPv4 Header Fields (4)

• SrcAddr: 32-bit source address • DestAddr: 32-bit destination address • Options: variable list of options – Security: government-style markings – Loose source routing: combination of source and table routing – Strict source routing: specified by source – Record route: where the datagram has been – Options rarely used

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IPv6

• Initial motivation: 32-bit address space completely allocated by 2008. • Additional motivation: – header format helps speed processing/forwarding – header changes to facilitate QoS – new “ anycast ” address: route to “ best ” servers of several replicated • IPv6 datagram format: – fixed-length 40 byte header – no fragmentation allowed (done only by source host)

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IPv6: Differences from IPv4

Flow label – Intended to support quality of service (QoS) • 128-bit network addresses • No header checksum – reduce processing time • Fragmentation only by source host • Extension headers – Handles options (but outside the header, indicated by “Next Header” field

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IPv6 Headers

0 Ver Pri Payload Length 15 Flow Label Next Header Hop Limit 31 Source Address Destination Address COMP680E by M. Hamdi

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IPv6 Header Fields (1)

• Ver: version of protocol • Pri: priority of datagram – 0 = none, 1 = background traffic, 2 = unattended data transfer – 4 = attended bulk transfer, 6 = interactive traffic, 7 = control traffic • Flow Label – Identifies an end-to-end flow – IP “label switching” – Experimental

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IPv6 Header Fields (2)

• Payload Length: total length of the datagram less that of the basic IP header • Next Header – Identifies the protocol header that follows the basic IP header – TCP => 6, UDP => 17, ICMP => 58, IP = 4, none => 59 • Hop Limit: time to live

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IPv6 Header Fields (3)

• Source/Destination Address – 128-bit address space – Embed world-unique link address in the lower 64 bits – Address “colon” format with hexadecimal – FEDC:BA98:7654:3210:FEDC:BA98:7654:3210

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Addressing Modes in IPv6

• Unicast – Send a datagram to a single host • Multicast – Send copies a datagram to a group of hosts • Anycast – Send a datagram to the nearest in a group of hosts

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Migration from IPv4 to IPv6

• Interoperability with IPv4 is necessary for gradual deployment.

• Two mechanisms: – dual stack operation: IPv6 nodes support both address types – tunneling: tunnel IPv6 packets through IPv4 clouds • Unfortunately there is little motivation for any one organization to move to IPv6.

– the challenge is the existing hosts (using IPv4 addresses) – little benefit unless one can consistently use IPv6 • can no longer talk to IPv4 nodes – stretching address space through address translation seems to work reasonably well

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