Internet%20Infrastructure:%20Switches%20and%20Routers

1

• Internet Infrastructure Switches and Routers
• Mounir Hamdi
• Head Professor, Computer Science and
  Engineering
• Hong Kong University of Science and Technology

2
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

3
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.

4
Outline of the Course

• Introduction
• 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

5
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, shared memory contention, etc.)
• Emulation of output-queueing switches by more
  practical switches
• State-of-the-art commercial products

6
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

7
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

8
Outline of the Course

• Internet Wireless Access
• WLANs and 802.11
• WiMAX and 802.16
• Cellular mobile networks
• Performance Evaluation
• Simulations
• Modeling

9
Grading

• Homework 20
• Midterm 40
• Project 40

10
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

11
Course Project

• Ill 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

12
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/seminal papers to choose from
• Report contains
• Description of the paper
• Goals and problems solved in the paper
• What did you like/dislike about the paper
• How the paper affected the advances in networking
  (if any)
• Recommendations for improvements or extension of
  the work

13
How to Contact Me

• Instructor Mounir Hamdi, hamdi_at_cse.ust.hk
• TA Mr. Lin Dong, ldcse_at_cse.ust.hk
• Office Hours
• You can come any time just email me ahead of
  time
• I would like to work closely with each student

14
Overview and History of the Internet
15
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 ...

16
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...

17
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

18
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

19
The Internet

• Global scale, general purpose, heterogeneous-techn
  ologies, 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

20
Internet History
1961-1972 Early packet-switching principles

• 1961 Kleinrock - queueing theory shows
  effectiveness
• of packet-switching
• 1964 Baran Introduced first Distributed
  packet-switching Communication networks
• 1967 ARPAnet conceived and sponsored by Advanced
  Research Projects Agency Larry Roberts
• 1969 first ARPAnet node operational at UCLA.
  Then Stanford, Utah, and UCSB

• 1972
• ARPAnet demonstrated publicly
• NCP (Network Control Protocol) first host-host
  protocol (equivalent to TCP/IP)
• First e-mail program to operate across networks
• ARPAnet has 15 nodes and connected 26 hosts

21
Internet History
1972-1980 Internetworking, new and proprietary
nets

• 1970 ALOHAnet satellite network in Hawaii
• 1973 Metcalfes PhD thesis proposes Ethernet
• 1974 Cerf and Kahn - architecture for
  interconnecting networks (TCP)
• late70s proprietary architectures DECnet, SNA,
  XNA
• late 70s switching fixed length packets (ATM
  precursor)
• 1979 ARPAnet has 200 nodes

• Cerf and Kahns internetworking principles
• minimalism, autonomy - no internal changes is
  required to interconnect networks
• best effort service model
• stateless routers
• decentralized control
• define todays Internet architecture

22
1971-1973 Arpanet Growing

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

23
Internet History
1980-1990 new protocols, a proliferation of
networks

• 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

24
Internet History
1990s commercialization, the WWW

• Early 1990s ARPAnet decomissioned
• 1991 NSF lifts restrictions on commercial use of
  NSFnet (decommissioned, 1995)
• early 1990s WWW
• hypertext Bush 1945, Nelson 1960s
• HTML, http Berners-Lee
• 1994 Mosaic, later Netscape
• late 1990s commercialization of the WWW

• Late 1990s
• est. 50 million computers on Internet
• est. 100 million users in 160 countries
• backbone links running at 1 Gbps
• 2000s
• VoIP, Video on demand, IPTV, Internet business
• RSS, Web 2.0
• Social networking

25
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)
26
Internet Users by World Region
27
Internet Domain Survey Host Count
28
Internet Penetration 2008
29
Top 20 Internet Use (2008)
Country or Region Penetration(Population) Internet UsersLatest Data Population( 2008 Est. ) Population( 2008 Est. ) Source and Dateof Latest Data
1 Greenland 92.3 52,000 56,326 ITU - Mar/08 ITU - Mar/08
2 Netherlands 90.1 15,000,000 16,645,313 ITU - Mar/08 ITU - Mar/08
3 Norway 87.7 4,074,100 4,644,457 ITU - Aug/07 ITU - Aug/07
4 Antigua Barbuda 85.9 60,000 69,842 ITU - Mar/08 ITU - Mar/08
5 Iceland 84.8 258,000 304,367 ITU - Sept/06 ITU - Sept/06
6 Canada 84.3 28,000,000 33,212,696 ITU - Mar/08 ITU - Mar/08
7 New Zealand 80.5 3,360,000 4,173,460 ITU - Mar/08 ITU - Mar/08
8 Australia 79.4 16,355,388 20,600,856 Nielsen//NR - Mar/08 Nielsen//NR - Mar/08
9 Sweden 77.4 7,000,000 9,045,389 ITU - Mar/08 ITU - Mar/08
10 Falkland Islands 76.5 1,900 2,483 CIA - Dec/02 CIA - Dec/02
11 Japan 73.8 94,000,000 127,288,419 ITU - Mar/08 ITU - Mar/08
12 Portugal 72.9 7,782,760 10,676,910 IWS - Mar/08 IWS - Mar/08
13 United States 72.3 220,141,969 303,824,646 Nielsen//NR - June/08 Nielsen//NR - June/08
14 Bermuda 72.1 48,000 66,536 ITU - Mar/08 ITU - Mar/08
15 Luxembourg 71.0 345,000 486,006 ITU - Mar/08 ITU - Mar/08
16 Korea, South 70.7 34,820,000 49,232,844 ITU - Mar/08 ITU - Mar/08
17 Faroe Islands 69.9 34,000 48,668 ITU - Aug/07 ITU - Aug/07
18 Hong Kong 69.5 4,878,713 7,018,636 N//NR - Feb/05 N//NR - Feb/05
19 Switzerland 69.0 5,230,351 7,581,520 Nielsen//NR - May/08 Nielsen//NR - May/08
20 Denmark 68.6 3,762,500 5,484,723 ITU - Sept/05 ITU - Sept/05
30
Languages of Internet Users
31
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.

32
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.

33
Services Provided by the Internet

• Shared access to computing resources
• telnet (1970s)
• Shared access to data/files
• FTP, NFS, AFS (1980s)
• Communication medium over which people interact
• email (1980s), on-line chat rooms, instant
  messaging (1990s)
• audio, video (1990s)
• replacing telephone network?
• A medium for information dissemination
• USENET (1980s)
• WWW (1990s)
• replacing newspaper, magazine?
• audio, video (1990s)
• replacing radio, CD, TV?

34
Todays 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

35
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
  nos
• Electronic Crimes
• hacker can bring the whole world to its knee

36
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

37
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

38
Commercial Internet after 1994

• Roughly hierarchical
• National/international backbone providers (NBPs)
• e.g., Sprint, ATT, 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

39
Internet Organization
ISP Internet Service Provider BSP Backbone
Service Provider NAP Network Access Point POP
Point of Presence CN Customer Network
40
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
41
Topology of CERNET
42
The Role of Hong Kong Internet Exchange
Global Internet
HK ISP-B
HK ISP-A
HKIX
Downstream Customers
Downstream Customers
43
(No Transcript)
44
HKIX Infrastructure
Internet
Internet
Internet
ISP 2
ISP 3
ISP 1
HKIX - AS4635
HKIX2
HKIX1
2 x 10Gbps links
ISP 5
ISP 6
ISP 4
Internet
Internet
Internet
45
(No Transcript)
46
HARNET/Internet
47
Internet Architecture
48
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).

49
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.

50
(No Transcript)
51
The Hierarchical Nature of the Internet
Long Distance Network
Metro 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
52
Points of Presence (POPs)
53
A Birds View of the Internet
54
A Birds View of the Internet
55
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.r
each.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
56
NAP-Based Architecture
57
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.

58
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.

59
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.

60
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 ISPs modem
  pool, after which a remote access server (RAS)
  checks the userid and password.

61
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 ISPs 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.

62
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
63
SONET Data Rates
A small set of fixed data transmission rates is
defined for SONET. All of these rates are
multiples of 51.84 Mb/s, which is referred to as
Optical Carrier Level 1 (on the fiber) or
Synchronous Transport Signal Level 1 (when
converted to electrical signals)
Optical Level Line Rate, Mb/s
OC-1 OC-3 OC-9 OC-12 OC-18 OC-24 OC-36 OC-48 OC-96
OC-192 OC-768
51.840 155.520 466.560 622.080 933.120 1244.160 18
66.240 2488.320 4976.640 9953.280 39813.120
64
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
Router
Core Router
Ethernet
OC-3 Lines to Other ATM Switches
Point of Presence (POP)
65
Sprint
Abilene
UUNet
CANet 3
Verio
DREN
WSU
Router
Boeing
Router
Router
Microsoft
U Idaho
Switch
Switch
Router
Router
Montana State U
HSCC
High-speed Router
High-speed Router
Router
ATT
U Montana
Router
Switch
Switch
SCCD
Router
Sprint
U Alaska
U Wash
OC-48 OC-12 T-3
Portland POP
Inside the Pacific/Northwest Gigapop
66
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 ISPs 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.

67
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.

68
Network Access Point
69
ISPs and Backbones
POP
POP
POP
POP
POP
POP
ATM/SONET Core
POP
POP
POP
Router Core
POP
Access Network
POP
POP
POP
70
Three national ISPs in North America
71
Backbone Map of UUNET - USA
72
UUNET

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

73
Backbone Map of UUNET - World
74
Qwest

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

75
ATT

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

76
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.

77
Links for Long Haul Transmission

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

78
User Services Core Transport
CORE
EDGE
Frame Relay
Frame Relay
IP Router
IP
ATM Switch
ATM
Sonet ADM
Lease Lines
TDM Switch
Transport Provider Networks
Service Provider Networks
Users Services
79
Typical (BUT NOT ALL) IP Backbone (Late 1990s)

• Data piggybacked over traditional voice/TDM
  transport

80
IP Backbone Evolution (One version)
Core Router (IP/MPLS)

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

FR/ATM Switch
MUX
SONET/SDH
DWDM (Maybe)
81
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

82
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

83
Customer Network
http//www.ust.hk/itsc/network/
Clients
LAN
Ethernet 10 Mb/s
Servers
Router
T1 Link 1.54 Mb/s
WAN
84
Internet Access Technologies
85
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)

86
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.

87
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 carriers end office. It also includes
  an analog channel for voice transmissions.

88
Customer Premises
Local Carrier End Office
DSL Architecture
Line Splitter
DSL Modem
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
89
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.

90
Cable Company Fiber Node
Customer Premises
Cable Company Distribution Hub
TV Video Network
Cable Splitter
Cable Modem
Combiner
Downstream
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
91
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 ISPs wireless access
  office.

92
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
93
Classifying Computer Networks
94
A Taxonomy of Communication Networks

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

95
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

96
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)

97
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
98
Circuit Switching

• A node (switch) in a circuit switching network

Node
incoming links
outgoing links
99
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

100
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
101
Packet Switching

• A node in a packet switching network

Node
incoming links
outgoing links
Memory
102
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

103
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

104
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
105
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
106
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

107
Virtual-Circuit Packet Switching

• Communication using virtual circuits takes place
  in three phases
• VC establishment
• data transfer
• VC disconnect
• Note packet headers dont need to contain the
  full destination address of the packet (One key
  to this idea)

108
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
109
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
110
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 31 for audio, and 151 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

111
Fixed-Rate versus Bursty Data
112
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
113
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)

114
Link Diversity

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

115
Internet Protocols
116
Internet Protocols
Application
Application
Transport
Transport
Network
Network
Network
Link
Link
Link
Link
Host
Host
Router
117
IP Protocol Stack
Telnet
FTP
SIP
RTSP
RSVP
S/MGCP/ NCS
User application
H.323
Ping
UDP
TCP
OSPF
RARP
IGMP
IP
ICMP
ARP
Link Layer
118
Demultiplexing
119
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

120
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

121
ARP Protocol
122
Sending an IP Packet over a LAN
123
Transport Protocols

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

124
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.

125
The Internet Network layer The Glue of all
Networks
Transport layer TCP, UDP
Network layer
Link layer
physical layer
126
Demultiplexing Details
echo server
1024-5000
7
FTP server
telnet server
discard server
21
23
9
data
TCP src port
TCP dest port
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)
127
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)

128
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)

129
Internet Protocol (IP)

• Two versions
• IPv4
• IPv6
• IPv4 dominates todays Internet
• IPv6 is used sporadically
• 6Bone, Internet 2

130
IPv4 Header
0
31
15
Length
TOS
HLen
Ver
Ident
Flags
Offset
Checksum
TTL
Protocol
SrcAddr
DestAddr
Options
Pad
131
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 gt 5
• TOS type of service
• Packet precedence (3 bits)
• Delay/throughput/reliability specification
• Rarely used

132
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

133
Fragmentation Example
20-byte optionless IP headers
Id x
0
0
0
1
492 data bytes
Id x
0
0
0
0
Id x
492
0
0
1
1400 data bytes
492 data bytes
Id x
984
0
0
0
416 data bytes
134
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

135
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

136
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)

137
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

138
IPv6 Headers
0
31
15
Flow Label
Pri
Ver
Payload Length
Hop Limit
Next Header
Source Address
Destination Address
139
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

140
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 gt 6, UDP gt 17, ICMP gt 58, IP 4, none gt
  59
• Hop Limit time to live

141
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
• FEDCBA9876543210FEDCBA9876543210

142
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

143
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