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High-Speed Internet Switches and Routers COMP 680E Mounir Hamdi Professor, Computer Science Director, MSc-IT Hong Kong University of Science and Technology Goals of the Course Understand the architecture, operation, and evolution of the Internet IP, ATM, Optical

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Slide1 l.jpg

High-Speed Internet Switches and Routers

COMP 680E

Mounir Hamdi

Professor, Computer Science

Director, MSc-IT

Hong Kong University of Science and Technology


Goals of the course l.jpg
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


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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 KEY building blocks of the Internet, and as a result, the capability of the Internet in all its aspects depends on the capability of its switches and routers.

  • 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.


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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


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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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Grading

  • Homework 20%

  • Midterm 30%

  • Project 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:

    • 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

  • 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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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


Internet history l.jpg

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

Internet History

1961-1972: Early packet-switching principles


Internet history21 l.jpg

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

Internet History

1972-1980: Internetworking, new and proprietary nets


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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


Internet history23 l.jpg

1983: deployment of TCP/IP

1982: SMTP e-mail protocol defined

1983: DNS defined for name-to-IP-address translation

1985: ftp protocol defined (first version: 1972)

1988: TCP congestion control

New national networks: CSnet, BITnet, NSFnet, Minitel

100,000 hosts connected to confederation of networks

Internet History

1980-1990: new protocols, a proliferation of networks


Internet history24 l.jpg

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

Internet History

1990’s: commercialization, the WWW


Growth of the internet l.jpg
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


Internet global statistics l.jpg

1997

22.5 Million Hosts

50 Million Users

2005

350 Million Hosts

1,018 Million Users

Internet - Global Statistics

(approx. 2.4 Billion Telephone Terminations, 660 Million PCs and 1.6B mobile phones)


Internet penetration december 2006 l.jpg
Internet Penetration December 2006

(Source www.internetstats.com)


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Top 10: % Internet Use (Dec 2006)

www.internetworldstats.com



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Who is Who on the Internet ?

  • Internet Engineering Task Force (IETF):The IETF is the protocol engineering and development arm of the Internet. Subdivided into many working groups, which specify Request For Comments or RFCs.

  • IRTF (Internet Research Task Force):The Internet Research Task Force is composed of a number of focused, long-term and small Research Groups.

  • 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


Commercial internet after 1994 l.jpg

local

ISP

local

ISP

regional ISP

NBP B

NBP A

regional ISP

NAP

NAP

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


Internet organization l.jpg

ISP

ISP

NAP

BSP

NAP

BSP

NAP

BSP

POP

POP

POP

POP

POP

POP

POP

ISP

CN

CN

CN

CN

CN

CN

CN

CN

Internet Organization

ISP = Internet Service Provider

BSP = Backbone Service Provider

NAP = Network Access Point

POP = Point of Presence

CN = Customer Network


Commercial internet after 199439 l.jpg
Commercial Internet after 1994

Joe's Company

Berkeley

Stanford

Regional ISP

Campus Network

Bartnet

Xerox Parc

SprintNet

America On Line

UUnet

NSF Network

IBM

NSF Network

Modem

Internet MCI

IBM



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Basic Architecture: NAPs and National ISPs

  • The Internet has a hierarchical structure.

  • At the highest level are largenationalInternet 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.


Slide43 l.jpg

pop

pop

pop

pop


The hierarchical nature of the internet l.jpg

Node

Node

Node

Node

The Hierarchical Nature of the Internet

Metro Network

Long Distance Network

Central

Office

Central

Office

San Francisco

New York

Major

City

-

Regional

Center

Major

City

-

Regional

Center

Central

Office

Central

Office

Central

Office

Central

Office


Points of presence pops l.jpg

POP3

POP2

POP1

D

POP4

A

B

E

POP5

POP6

C

POP7

POP8

F

Points of Presence (POPs)




Hop by hop behavior l.jpg
Hop-by-Hop Behavior

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)

Within HK

Los Angeles

Qwest

(Backbone)

Stanford


Nap based architecture l.jpg

CHI

NAP

SF

NAP

NY

NAP

Sprint Net

MAE

West

QWest

MCI

WDC

NAP

UUNET

NAP-Based Architecture


Basic architecture maes and local isps l.jpg
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.


Internet packet exchange charges peering l.jpg
Internet Packet Exchange ChargesPeering

  • 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 modempool, 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.


Ds telephone carrier data rates l.jpg
DS (telephone carrier) Data Rates

Designation

Number of

Voice Circuits

Bandwidth

DS0

1

64 kb/s

DS1 (T1)

24

1.544 Mb/s

96

6.312 Mb/s

DS2 (T2)

DS3 (T3)

672

44.736 Mb/s


Sonet data rates l.jpg
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 LevelLine 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


Isps and backbones l.jpg
ISPs and Backbones

POP: connection with POP of the same ISP or different ISPs

POP: Connection with customers

T1 Lines to

Customers

T3 Lines to

Other POPs

Line

Server

Dialup Lines

to Customers

OC-3

Line

T3 Line

ATM

Switch

Core

Router

Router

Ethernet

OC-3

Lines

to Other

ATM Switches

Point of Presence (POP)


Slide58 l.jpg

ISP Point-of-Presence

ISP POP

Individual

Dial-up Customers

Modem Pool

ISP POP

Corporate

T1 Customer

T1 CSU/DSU

ATM

Switch

ATM

Switch

ISP POP

Corporate

T3 Customer

T3 CSU/DSU

Remote

Access

Server

Corporate

OC-3 Customer

ATM Switch

NAP/MAE



From the isp to the nap mae l.jpg
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.


Slide62 l.jpg

Inside an Internet Network Access Point

ISP A

ISP D

Router

Router

ATM

Switch

ISP B

ISP E

Router

ATM Switch

ISP C

Route

Server

ISP F

Router

ATM Switch




Isps and backbones65 l.jpg
ISPs and Backbones

POP

POP

POP

POP

POP

POP

ATM/SONET

Core

POP

POP

POP

Router Core

POP

Access Network

POP

POP

POP




Uunet l.jpg
UUNET

  • Mixed OC-12 – OC-48 – OC 192 backbone

  • 1000s miles of fiber

  • 3000 POPs

  • 2,000,000 dial-in ports



Qwest l.jpg
Qwest

  • OC-192 backbone

  • 25,000 miles of fiber

  • 635 POPs

  • 85,000 dial-in ports


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AT&T

  • OC-192 backbone

  • 53,000 miles of fiber

  • 2000 POPs

  • 0 dial-in ports


Internet backbones in 2006 l.jpg
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.


Links for long haul transmission l.jpg
Links for Long Haul Transmission

  • Possibilities

    • IP over SONET

    • IP over ATM

    • IP over Frame Relay

    • IP over WDM


User services core transport l.jpg

OC-3

OC-3

OC-12

STS-1

STS-1

STS-1

User Services & Core Transport

EDGE

CORE

Frame Relay

Frame

Relay

IP

Router

IP

ATM

Switch

ATM

Sonet

ADM

Lease Lines

TDM

Switch

Users

Services

Service Provider

Networks

Transport Provider

Networks


Typical but not all ip backbone late 1990 s l.jpg

Core

Router

Core

Router

ATM

Switch

ATM

Switch

MUX

MUX

SONET/SDH

ADM

SONET/SDH

ADM

SONET/SDH

DCS

SONET/SDH

DCS

SONET/SDH

ADM

SONET/SDH

ADM

MUX

MUX

ATM

Switch

ATM

Switch

Core

Router

Core

Router

Typical (BUT NOT ALL) IP Backbone (Late 1990’s)

  • Data piggybacked over traditional voice/TDM transport


Ip backbone evolution one version l.jpg

Removal of ATM Layer

Next generation routers provide trunk speeds and SONET interfaces

Multi-protocol Label Switching (MPLS) on routers provides traffic engineering

Core

Router

(IP/MPLS)

SONET/SDH

DWDM

IP Backbone Evolution (One version)

Core

Router

(IP/MPLS)

FR/ATM Switch

MUX

SONET/SDH

DWDM

(Maybe)


Hierarchy of routers and switches l.jpg

FR/ATM Switch

SONET/SDH

Hierarchy of Routers and Switches

Core

IP Router

  • 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


Customer network l.jpg
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


Customer network79 l.jpg
Customer Network

Clients

LAN

Ethernet

10 Mb/s

Servers

Router

T1 Link

1.54 Mb/s

WAN



Internet access technologies81 l.jpg
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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DSL Architecture

Customer Premises

Local Carrier End Office

DSL Modem

Line Splitter

Main

Distribution

Frame

Voice

Telephone

Network

Local Loop

Hub

Telephone

ISP POP

ATM Switch

Computer

DSL Access

Multiplexer

Computer

ISP POP

Customer

Premises

ISP POP

ISP POP

Customer

Premises


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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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Cable Company

Fiber Node

Customer Premises

Cable Company Distribution Hub

TV Video

Network

Cable Modem

Cable Splitter

Downstream

Combiner

Optical/Electrical

Converter

Upstream

Hub

TV

Router

Shared

Coax

Cable

System

Cable

Company

Fiber Node

Cable Modem

Termination

System

Computer

Computer

ISP POP

Customer

Premises

Customer

Premises

Cable Modem Architecture


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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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Fixed Wireless Architecture

Customer Premises

Individual Premise

Main

Distribution

Frame

Voice

Telephone

Network

DSL Modem

Line Splitter

Hub

Individual

Premise

Telephone

Wireless

Transceiver

DSL Access

Multiplexer

Individual

Premise

Computer

Computer

Wireless Access Office

Customer

Premises

Wireless

Transceiver

Router

Customer

Premises

ISP POP



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Communication Network

SwitchedCommunication Network

BroadcastCommunication Network

Packet-SwitchedCommunication Network

Circuit-SwitchedCommunication Network

Virtual Circuit Network

Datagram Network

A Taxonomy of Communication Networks

  • Communication networks can be classified based on the way in which the nodes exchange information:


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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

    • circuit establishment

    • data transfer

    • circuit termination

  • If circuit is not available: “Busy signal”

  • Examples

    • Telephone networks

    • ISDN (Integrated Services Digital Networks)

    • Optical Backbone Internet (going in this direction)


  • Timing in circuit switching l.jpg

    Circuit Establishment

    Data Transmission

    Circuit Termination

    Timing in Circuit Switching

    Host 1

    Host 2

    Node 1

    Node 2

    DATA

    processing delay at Node 1

    propagation delay

    between Host 1

    and Node 1

    propagation delay

    between Host 2

    and Node 1


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    Circuit Switching

    • A node (switch) in a circuit switching network

    Node

    incoming links

    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 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

    Header

    Data

    Trailer


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    Packet Switching

    • A node in a packet switching network

    Node

    incoming links

    outgoing links

    Memory


    Packet switching multiplexing demultiplexing l.jpg
    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


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    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


    Timing of datagram packet switching l.jpg

    Packet 1

    Packet 1

    Packet 1

    Packet 2

    Packet 2

    Packet 2

    Packet 3

    Packet 3

    Packet 3

    Timing of Datagram Packet Switching

    Host 1

    Host 2

    Node 1

    Node 2

    propagation

    delay between

    Host 1 and

    Node 2

    transmission

    time of Packet 1

    at Host 1

    processing delay of Packet 1 at Node 2


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    Datagram Packet Switching

    Host C

    Host D

    Host A

    Node 1

    Node 2

    Node 3

    Node 5

    Host B

    Host E

    Node 7

    Node 6

    Node 4


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    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

      • VC establishment

      • data transfer

      • VC disconnect

    • Note: packet headers don’t need to contain the full destination address of the packet (One key to this idea)


    Timing of vc packet switching l.jpg

    Packet 1

    Packet 1

    Packet 1

    Packet 2

    Packet 2

    Packet 2

    Packet 3

    Packet 3

    Packet 3

    Timing of VC Packet Switching

    Host 1

    Host 2

    Node 1

    Node 2

    propagation delay

    between Host 1

    and Node 1

    VC

    establishment

    Data

    transfer

    VC

    termination


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    VC Packet Switching

    Host C

    Host D

    Host A

    Node 1

    Node 2

    Node 3

    Node 5

    Host B

    Host E

    Node 7

    Node 6

    Node 4


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    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



    Packet switches l.jpg

    A

    A

    A

    B

    B

    B

    Packet Switches

    Routing

    Table

    Destination

    Address

    Connectionless

    Packet Switch

    Possibly different paths through switch

    Connection

    Identifier

    Always same path through switch

    Connection-Oriented

    Packet Switch

    Connec-

    tion

    Table


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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”



    Internet protocols112 l.jpg
    Internet Protocols

    Application

    Application

    Transport

    Transport

    Network

    Network

    Network

    Link

    Link

    Link

    Link

    Host

    Router

    Host


    Ip protocol stack l.jpg
    IP Protocol Stack

    Ping

    Telnet

    FTP

    H.323

    SIP

    RTSP

    RSVP

    S/MGCP/

    NCS

    User

    application

    TCP

    UDP

    OSPF

    ARP

    ICMP

    IP

    IGMP

    RARP

    Link Layer


    Demultiplexing l.jpg

    Application

    Application

    Application

    Application

    Application

    Transport

    TCP

    UDP

    ICMP

    IGMP

    Network

    IP

    ARP

    RARP

    Link

    Ethernet

    Driver

    incoming frame

    Demultiplexing


    Link protocols l.jpg
    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


    Additional link protocols l.jpg
    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




    Transport protocols l.jpg
    Transport Protocols

    • Transmission Control Protocol (TCP)

    • User Datagram Protocol (UDP)


    Application protocols l.jpg
    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.


    The internet network layer the glue of all networks l.jpg

    • IP protocol

    • addressing conventions

    • datagram format

    • packet handling conventions

    • Routing protocols

    • path selection

    • RIP, OSPF, BGP

    routing

    table

    The Internet Network layer: The Glue of all Networks

    Transport layer: TCP, UDP

    Network

    layer

    Link layer

    physical layer


    Demultiplexing details l.jpg

    User process

    User process

    User process

    User process

    

    

    

    

    

    

    hdr

    cksum

    dest

    addr

    source

    addr

    data

    protocol type

    IP header

    

    

    

    

    Demultiplexing Details

    echo

    server

    1024-5000

    7

    FTP

    server

    telnet

    server

    discard

    server

    21

    23

    9

    TCP src port

    TCP dest port

    data

    header

    17

    UDP

    TCP

    TCP

    ICMP

    6

    1

    IGMP

    2

    ARP

    x0806

    Others

    x8035

    IP

    RARP

    Novell

    IP

    x0800

    AppleTalk

    dest

    addr

    source

    addr

    data

    Ethernet frame type

    CRC

    (Ethernet frame types in hex, others in decimal)


    Ip features l.jpg
    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” servicesError and control messages generated by Internet Control Message Protocol (ICMP)


    What ip does not provide l.jpg
    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)


    Internet protocol ip l.jpg
    Internet Protocol (IP)

    • Two versions

      • IPv4

      • IPv6

    • IPv4 dominates today’s Internet

    • IPv6 is used sporadically

      • 6Bone, Internet 2


    Ipv4 header l.jpg
    IPv4 Header

    0

    15

    31

    Ver

    HLen

    TOS

    Length

    Ident

    Flags

    Offset

    TTL

    Protocol

    Checksum

    SrcAddr

    DestAddr

    Options

    Pad


    Ipv4 header fields 1 l.jpg
    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


    Ipv4 header fields 2 l.jpg
    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


    Fragmentation example l.jpg
    Fragmentation Example

    20-byte optionless

    IP headers

    Id = x

    0

    0

    1

    0

    492 data bytes

    Id = x

    0

    0

    0

    0

    Id = x

    0

    0

    1

    492

    1400 data bytes

    492 data bytes

    Id = x

    0

    0

    0

    984

    416 data bytes


    Ipv4 header fields 3 l.jpg
    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


    Ipv4 header fields 4 l.jpg
    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


    Slide132 l.jpg
    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” of several replicated servers

    • IPv6 datagram format:

      • fixed-length 40 byte header

      • no fragmentation allowed (done only by source host)


    Ipv6 differences from ipv4 l.jpg
    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


  • Ipv6 headers l.jpg
    IPv6 Headers

    0

    15

    31

    Ver

    Pri

    Flow Label

    Payload Length

    Next Header

    Hop Limit

    Source Address

    Destination Address


    Ipv6 header fields 1 l.jpg
    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


    Ipv6 header fields 2 l.jpg
    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


    Ipv6 header fields 3 l.jpg
    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


    Addressing modes in ipv6 l.jpg
    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


    Migration from ipv4 to ipv6 l.jpg
    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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