CSIT560 by M. Hamdi 1 Internet Infrastructure: Switches and Routers Mounir Hamdi Head & Professor,...
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Transcript of CSIT560 by M. Hamdi 1 Internet Infrastructure: Switches and Routers Mounir Hamdi Head & Professor,...
1CSIT560 by M. Hamdi
Internet Infrastructure: Internet Infrastructure: Switches and RoutersSwitches and Routers
Mounir HamdiMounir HamdiHead & Professor, Computer Science and EngineeringHead & Professor, Computer Science and Engineering
Hong Kong University of Science and TechnologyHong Kong University of Science and Technology
2CSIT560 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
• Evaluate various Internet access methods (including wireless)• Performance Evaluation• Appreciate what is a good project
– Task selection and aim– Survey & conclusion & research methodology– Presentation
3CSIT560 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 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 (hardware and software).
• The goal of the course is to provide a basis for understanding, appreciating, and performing research/survey and development in networking with a special emphasis on switches and routers.
4CSIT560 by M. Hamdi
Outline of the Course
• IntroductionIntroduction– Evolution of the Internet (Architecture, Protocols
and Applications) – Evolution of packet switches and routers, basic
architectural components, some example architectures
– Network Processors and Packet Processing (IPv4 and IPv6)
– Architecture and operation of “optical” circuit-switched switches/routers
5CSIT560 by M. Hamdi
Outline of the Course
• High-Performance Packet Switches/RoutersHigh-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, shared memory contention, etc.)– Emulation of output-queueing switches by more
practical switches– State-of-the-art commercial products
6CSIT560 by M. Hamdi
Outline of the Course
• Quality-of-Service Provision in the Internet – QoS paradigms (IntServ, DiffServ, Controlled load,
etc.)– Flow-based QoS frameworks: Hardware and
software solutions – Stateless QoS frameworks: RED, WRED,
congestion control, and Active queue management– MPLS/GMPLS– State-of-the-art commercial products
7CSIT560 by M. Hamdi
Outline of the Course
• Optical NetworksOptical 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
8CSIT560 by M. Hamdi
Outline of the Course
• Internet Wireless AccessInternet Wireless Access– WLANs and 802.11
– WiMAX and 802.16
– Cellular mobile networks
• Performance EvaluationPerformance Evaluation– Simulations
– Modeling
9CSIT560 by M. Hamdi
Grading
• Homework 20%
• Midterm 40%
• Project 40%
10CSIT560 by M. Hamdi
Course project
• Investigate and survey 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
11CSIT560 by M. Hamdi
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
• Final project presentation (20-25 minutes) • Submit project reports
12CSIT560 by M. Hamdi
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/seminal” papers to choose from
• Report contains:
1. Description of the paper
2. Goals and problems solved in the paper
3. What did you like/dislike about the paper
4. How the paper affected the advances in networking (if any)
5. Recommendations for improvements or extension of the work
13CSIT560 by M. Hamdi
How to Contact Me
• Instructor: Mounir Hamdi, [email protected]
• TA: Mr. Lin Dong, [email protected]
• Office Hours– You can come any time – just email me ahead of
time– I would like to work closely with each student
14CSIT560 by M. Hamdi
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 ...
16CSIT560 by M. Hamdi
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...
17CSIT560 by M. Hamdi
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
18CSIT560 by M. Hamdi
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
19CSIT560 by M. Hamdi
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: 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
1961-1972: Early packet-switching principles
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Internet History
• 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
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
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Internet History
• 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
1980-1990: new protocols, a proliferation of networks
24CSIT560 by M. Hamdi
Internet History
• 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,
IPTV, Internet business• RSS, Web 2.0• Social networking
1990’s: commercialization, the WWW
CSIT560 by M. Hamdi
Internet - Global Statistics
1998
• 32.5 Million Hosts
• 80 Million Users
2008• 550 Million Hosts • 1,463 Million
Users
(approx. 2.6 Billion Telephone Terminations, 760 Million PCs and 1.9B mobile phones, as of 2008)
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Internet Users by World Region
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Internet Domain Survey Host Count
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Internet Penetration 2008
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Top 20: % Internet Use (2008)# Country or Region
Penetration(%Population)
Internet UsersLatest Data
Population( 2008 Est. )
Source and Dateof Latest Data
1 Greenland 92.3 % 52,000 56,326 ITU - Mar/08
2 Netherlands 90.1 % 15,000,000 16,645,313 ITU - Mar/08
3 Norway 87.7 % 4,074,100 4,644,457 ITU - Aug/07
4 Antigua & Barbuda 85.9 % 60,000 69,842 ITU - Mar/08
5 Iceland 84.8 % 258,000 304,367 ITU - Sept/06
6 Canada 84.3 % 28,000,000 33,212,696 ITU - Mar/08
7 New Zealand 80.5 % 3,360,000 4,173,460 ITU - Mar/08
8 Australia 79.4 % 16,355,388 20,600,856 Nielsen//NR - Mar/08
9 Sweden 77.4 % 7,000,000 9,045,389 ITU - Mar/08
10 Falkland Islands 76.5 % 1,900 2,483 CIA - Dec/02
11 Japan 73.8 % 94,000,000 127,288,419 ITU - Mar/08
12 Portugal 72.9 % 7,782,760 10,676,910 IWS - Mar/08
13 United States 72.3 % 220,141,969 303,824,646 Nielsen//NR - June/08
14 Bermuda 72.1 % 48,000 66,536 ITU - Mar/08
15 Luxembourg 71.0 % 345,000 486,006 ITU - Mar/08
16 Korea, South 70.7 % 34,820,000 49,232,844 ITU - Mar/08
17 Faroe Islands 69.9 % 34,000 48,668 ITU - Aug/07
18 Hong Kong 69.5 % 4,878,713 7,018,636 N//NR - Feb/05
19 Switzerland 69.0 % 5,230,351 7,581,520 Nielsen//NR - May/08
20 Denmark 68.6 % 3,762,500 5,484,723 ITU - Sept/05
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Languages of Internet Users
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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.
32CSIT560 by M. Hamdi
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.”
33CSIT560 by M. Hamdi
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?
34CSIT560 by M. Hamdi
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, voter
35CSIT560 by M. Hamdi
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
36CSIT560 by M. Hamdi
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
37CSIT560 by M. Hamdi
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
38CSIT560 by M. Hamdi
Commercial Internet after 1994
NBP A
NBP B
NAP NAP
regional ISP
regional ISP
localISP
localISP
• 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
39CSIT560 by M. Hamdi
Internet Organization
ISP = Internet Service ProviderBSP = Backbone Service ProviderNAP = Network Access PointPOP = Point of PresenceCN = Customer Network
NAP
NAP
NAP
BSP
ISP
ISP
POP
POP
POP
ISPPOP
BSP
BSPPOP
POP
CN
CN
CN
CNCN
CN
CN
CN
POP
40CSIT560 by M. Hamdi
Commercial Internet after 1994
NSF Network
Regional ISP
America On Line
IBM
BartnetCampus Network
Joe's CompanyStanford
Xerox Parc
Berkeley
NSF Network
Internet MCI
UUnet
SprintNet
Modem
IBM
41CSIT560 by M. Hamdi
Topology of CERNET
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The Role of Hong Kong Internet Exchange
Global Internet
HK ISP-A HK ISP-B
HKIX
Downstream CustomersDownstream Customers
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HKIX Infrastructure
HKIX - AS4635
ISP 4 ISP 5 ISP 6
ISP 1 ISP 2 ISP 3
InternetInternet Internet
Internet Internet Internet
HKIX2 HKIX1
2 x 10Gbps links
45CSIT560 by M. Hamdi
46CSIT560 by M. Hamdi
HARNET/Internet
CityU
LU
HKUCUHK
PolyU
HKBU
HKIEdHKUST
54M/108M5M/10M
22M/44M11M/22M 10M/20M
54M/108M6M/12M54M/108M
6M/12M
54M/108M6M/12M
PCCWATM
NETWORK
35M/70M25M/50M 24M/48M
6M/12M24M/48M6M/12M
Internet2Internet2STARTAPSTARTAP
Commodity Commodity InternetInternet
HKIXHKIX
CERNET/ CERNET/ TANETTANET
45M IPLC45M IPLC
EQUANTINTERNETBACKBONE
PCCW Data Centre
Equant Data Centre
96M IP96M IP
45M/90M45M/90M24M/48M24M/48M8 8
2 2 50M/100M50M/100M
2 M2 M
10M10M
47CSIT560 by M. Hamdi
Internet Architecture
48CSIT560 by M. Hamdi
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).
49CSIT560 by M. Hamdi
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 po
p
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Long Distance Network
Central
Office
Central
Office
The Hierarchical Nature of the InternetThe Hierarchical Nature of the Internet
Central
Office
Central
Office
Central
Office
Central
Office
Central
Office
Central
Office
Central
Office
Central
Office
Central
Office
Central
Office
Major
City
-
Regional
Center
Major
City
-
Regional
Center
Major
City
-
Regional
Center
Major
City
-
Regional
Center
Node
Node
Node
Node
San FranciscoSan Francisco New YorkNew York
Metro Network
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Points of Presence (POPs)
A
B
C
POP1
POP3POP2
POP4 D
E
F
POP5
POP6 POP7POP8
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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
From traceroute.pacific.net.hk to cs.stanford.edutraceroute 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
Qwest(Backbone)
Stanford
Los Angeles
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NAP-Based Architecture
UUNET
NYNAP
CHINAP
WDCNAP
SFNAP
MCI
QWest
Sprint Net
MAEWest
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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 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 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
DesignationNumber of
Voice CircuitsBandwidth
DS0 1 64 kb/s
DS1 (T1) 24 1.544 Mb/s
DS2 (T2) 96 6.312 Mb/s
DS3 (T3) 672 44.736 Mb/s
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SONET Data RatesA 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)
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/sOptical 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
LineServer
Dialup Linesto Customers
Ethernet
Router
T1 Lines toCustomers
CoreRouter
Point of Presence (POP)
T3 Line
T3 Lines toOther POPs
ATMSwitch
OC-3Line
OC-3Lines
to OtherATM Switches
POP: Connection with customers
POP: connection with POP of the same ISP or different
ISPs
65CSIT560 by M. HamdiInside the Pacific/Northwest Gigapop
Router
High-speedRouter
Abilene
DREN
WSU
Boeing
U Idaho
High-speedRouter
Router
Router
Montana State U
U Montana
U Alaska
Portland POP
Microsoft
Router Router
Switch
U Wash
Router
Switch Switch
CA*Net 3Sprint UUNet Verio
Router
AT&T
Sprint
Router
OC-48OC-12T-3
HSCC
Switch
SCCD
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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.
67CSIT560 by M. Hamdi
• 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.
From the ISP to the NAP/MAE
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Network Access Point
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ISPs and Backbones
ATM/SONETCore
Router Core
Access Network
POP
POP
POP
POPPOP
POP
POP
POP
POP
POPPOPPOP
POP
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Three national ISPs in North America
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Backbone Map of UUNET - USA
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UUNET
• Mixed OC-12 – OC-48 – OC 192 backbone
• 1000s miles of fiber
• 3000 POPs• 2,000,000 dial-in
ports
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Backbone Map of UUNET - World
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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
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Internet Backbones after 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 converted to OC-192 (10 Gbps) by the end of 2005.
• Many 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 100 Tbps by 2010.
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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
ATMSwitch
SonetADM
IPRouter
TDMSwitch
Transport ProviderNetworks
Service ProviderNetworks
OC-3
OC-3
OC-12
STS-1STS-1STS-1
FrameRelay
UsersServices
Frame Relay
IP
ATM
Lease Lines
COREEDGE
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Typical (BUT NOT ALL) IP Backbone (Late 1990’s)
• Data piggybacked over traditional voice/TDM transport
SONET/SDHDCS
SONET/SDHDCS
CoreRouter
ATMSwitch
MUX
SONET/SDHADM
CoreRouter
ATMSwitch
MUX
CoreRouter
ATMSwitch
MUX
CoreRouter
ATMSwitch
MUX
SONET/SDHADM
SONET/SDHADM
SONET/SDHADM
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SONET/SDH
DWDM
CoreRouter(IP/MPLS)
IP Backbone Evolution (One version)
• Removal of ATM Layer– Next generation routers
provide trunk speeds and SONET interfaces
– Multi-protocol Label Switching (MPLS) on routers provides traffic engineering
CoreRouter(IP/MPLS)
MUX
SONET/SDH
DWDM(Maybe)
FR/ATM Switch
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Hierarchy of Routers and Switches
SONET/SDHCoreIP Router
FR/ATM Switch
•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
Servers
LAN
WAN
Ethernet10 Mb/s
T1 Link1.54 Mb/s
Router
http://www.ust.hk/itsc/network/
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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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DSL Architecture
Local Carrier End Office
Line Splitter
Customer Premises
Telephone
DSL Modem
Hub
Computer Computer
Local Loop
MainDistribution
Frame
CustomerPremises
CustomerPremises
VoiceTelephoneNetwork
DSL AccessMultiplexer
ATM Switch
ISP POP
ISP POP
ISP POP
ISP POP
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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 Modem Architecture
Cable Company Distribution Hub
Cable Splitter
Customer Premises
TV
Cable Modem
Hub
Computer Computer
SharedCoaxCable
System
Combiner
CustomerPremises
CustomerPremises
TV VideoNetwork
Cable ModemTermination
System
ISP POP
Cable CompanyFiber Node
Optical/ElectricalConverter
Downstream
Upstream
Router
Cable Company
Fiber Node
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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
Wireless Access Office
WirelessTransceiver
Customer Premises
Telephone
DSL Modem
Hub
Computer Computer
CustomerPremises
CustomerPremises
MainDistribution
Frame
VoiceTelephoneNetwork
DSL AccessMultiplexer
WirelessTransceiver
Router
Line Splitter
Individual Premise
IndividualPremise
IndividualPremise
ISP POP
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Classifying Computer Networks
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• Communication networks can be classified based on the way in which the nodes exchange information:
A Taxonomy of Communication Networks
Communication Network
SwitchedCommunication
Network
BroadcastCommunication
Network
Circuit-Switched
Communication Network
Packet-Switched
Communication Network
Datagram Network
Virtual Circuit Network
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• 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
Broadcast vs. Switched Communication Networks
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Circuit Switching
• Three phases1. 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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Timing in Circuit Switching
DATA
Circuit Establishment
Data Transmission
Circuit Termination
Host 1 Host 2Node 1 Node 2
propagation delay between Host 1 and Node 1
propagation delay between Host 2 and Node 1
processing delay at Node 1
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Circuit Switching
• A node (switch) in a circuit switching network
incoming links outgoing linksNode
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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
incoming links outgoing linksNode
Memory
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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
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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
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Packet 1
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
Timing of Datagram Packet Switching
Packet 1
Packet 2
Packet 3
processing delay of Packet 1 at Node 2
Host 1 Host 2Node
1Node
2
propagationdelay betweenHost 1 and Node 2
transmission time of Packet 1at Host 1
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Datagram Packet Switching
Host A
Host BHost E
Host D
Host C
Node 1 Node 2
Node 3
Node 4
Node 5
Node 6 Node 7
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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 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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Packet 1
Packet 2
Packet 3
Packet 1
Packet 2
Packet 3
Timing of VC Packet Switching
Packet 1
Packet 2
Packet 3
Host 1 Host 2Node
1Node
2
propagation delay between Host 1 and Node 1VC
establishment
VCtermination
Datatransfer
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VC Packet Switching
Host A
Host BHost E
Host D
Host C
Node 1 Node 2
Node 3
Node 4
Node 5
Node 6 Node 7
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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
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Fixed-Rate versus Bursty Data
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Connec-tion
Table
RoutingTable
Packet Switches
DestinationAddress
ConnectionIdentifier
A
B
A
A
B B
Possibly different paths through switch
Always same path through switch
ConnectionlessPacket Switch
Connection-OrientedPacket 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
Network
Link
Transport
Application
Network
Link
Transport
Application
Network
Link Link
Host HostRouter
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IP Protocol Stack
Link Layer
RARP
Telnet FTP
OSPF
SIP RTSP RSVPS/MGCP/
NCSUser
application
UDP
H.323
IGMPIP
TCP
ICMP
Ping
ARP
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Demultiplexing
incoming frame
RARPARP
UDP
Application Application
TCP
Application Application
IGMPICMP
EthernetDriver
IP
Application
Transport
Network
Link
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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
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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
routingtable
Routing protocols•path selection•RIP, OSPF, BGP
IP protocol•addressing conventions•datagram format•packet handling conventions
ICMP protocol•error reporting•router “signaling”
Transport layer: TCP, UDP
Link layer
physical layer
Networklayer
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Demultiplexing Details
(Ethernet frame types in hex, others in decimal)
destaddr
sourceaddr
Ethernet frame type data CRC
destaddr
sourceaddr
dataprotocol type
IP header
hdrcksum
ARP
RARPNovell
IP
Others
AppleTalk
dataTCP src port
headerTCP dest port
FTPserver
telnetserver
echoserver
discardserver
23
7
9
21User process
User processUser process
User process
1024-5000
UDP 17
6
IGMP
ICMP 1
2
TCP
IPIP
TCPTCP
x0800
x8035
x0806
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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
Length
Ident
Checksum
SrcAddr
DestAddr
Options
0 3115
TOS
TTL
HLenVer
Flags Offset
Protocol
Pad
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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
Id = x
1400 data bytes
00 0 0
Id = x
492 data bytes
00 0 1
Id = x
492 data bytes
4920 0 1
Id = x
416 data bytes
9840 0 0
20-byte optionlessIP headers
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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” of several replicated servers
• 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
Flow Label
Payload Length
Source Address
PriVer
Hop LimitNext Header
Destination Address
0 3115
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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