Title: Internet Infrastructure: Switches and Routers
1- Internet Infrastructure Switches and Routers
- Mounir Hamdi
- Head Chair Professor, Computer Science and
Engineering - Hong Kong University of Science and Technology
2Goals of the Course
- Understand the architecture, operation, and
evolution of the Internet - IP, Optical, Openflow
- Understand how to design, implement and evaluate
Internet routers and switches (Telecom Equipment) - Understand the implementation of network services
(e.g., QoS) on switches and routers - Introduction to Network-on-Chip (NoC),
Communication Performance, Organizational
Structure, Interconnection Topologies, Trade-offs
in Network Topology, and Routing - Evaluate various Internet access methods
(including wireless) - Build solid learning skills for investigating a
good project - Task selection and aim
- Survey conclusion research methodology
- Presentation
3Outline 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) - Understand the evaluate the evolution of the
Internet infrastructure (e.g., NoC, Wireless,
etc.) - 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.
4Outline of the Course
- Introduction
- Evolution of the Internet (Architecture,
Protocols and Applications) - Evolution of packet switches and routers, basic
architectural components, and some example
architectures - Network Processors and Packet Processing (IPv4
and IPv6) - Architecture and operation of optical
circuit-switched switches/routers
5Outline 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
6Outline of the Course
- Network-on-chip (NoC) Design and Applications
- Introduction to NoC
- Communication Performance, Organizational
Structure, Interconnection Topologies, Trade-offs
in Network Topology, and Routing - Applications of NoC in network Equipment
- Future trends of this paradigm
7Outline of the Course
- Quality-of-Service Provision in the Internet
- Internet Congestion Control
- 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
- Openflow
- State-of-the-art commercial products
8Outline 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
9Outline of the Course
- Internet Wireless Access
- WLANs and 802.11
- WiMAX and 802.16
- Cellular mobile networks
- Performance Evaluation
- Simulations
- Modeling
10Grading
- Homework 20
- Midterm 40
- Project 40
11Course project
- Investigate and survey existing advances and/or
new ideas and solutions related to Internet
Infrastrcuture - 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
12Course 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
13Independent Projects
- If you want to go deeper in a topic related to
Internet Infrastructures (e.g., Wireless,
Internet Routers, Data centers, Cloud Computing,
Optical, QoS, NoC, Applications, etc.), then you
might want to opt for an Independent Project - You can come and talk to me
14Homework
- 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
15How 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
16Overview and History of the Internet
17What 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 ...
18What is a Communication Network?Infrastructure
Centric View
- Hardware
- Electrons and photons as communication data
- Links fiber, copper, satellite, WiFI,
- Switches mechanical/electronic/optical,
- Software
- Protocols TCP/IP, ATM, MPLS, SONET, Ethernet,
PPP, X.25, Frame Relay, AppleTalk, Openflow, SNA - Functionalities routing, error control,
congestion control, Quality of Service (QoS), - Applications FTP, WEB, X windows, VOIP, IPTV...
19Types of Networks
- Geographical distance
- Body Area Networks (BAN)
- Personal Areas Networks (PAN)
- Sensor Networks
- 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, sensor networks, banking network, credit
card network, telephony - general purpose network Internet
20Types 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
21The 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
22Internet 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
23Internet 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
241971-1973 Arpanet Growing
- 1970 - First 2 cross-country link, UCLA-BBN and
MIT-Utah, installed by ATT at 56kbps
25Internet 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
26Internet 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
27Internet - Global Statistics
- 1999
- 32.5 Million Hosts
- 80 Million Users
-
- 2010
- 800 Million Hosts
- 1966 Million Users
(approx. 4.6Billion mobile phone users, as of
2010)
28Internet Users by World Region
29Internet Domain Survey Host Count
30Internet Penetration 2010
31Top 20 Internet Use (2009)
Country or Region Penetration( Population) Internet UsersLatest Data Population( 2010 Est. ) Source and Dateof Latest Data
1 Falkland Islands 100.0 2,546 2,546 ITU - June/10
2 Iceland 97.6 301,600 308,910 ITU - June/10
3 Norway 94.8 4,431,100 4,676,305 ITU - June/10
4 Greenland 90.2 52,000 57,637 ITU - Mar/08
5 Sweden 92.5 8,397,900 9,074,055 ITU - June/10
6 Saint Kitts and Nevis 34.1 49,898 17,000 ITU - June/10
7 Netherlands 88.6 14,872,200 16,783,092 ITU - June/10
8 Denmark 86.1 4,750,500 5,515,575 ITU - June/10
9 Finland 85.3 4,480,900 5,255,695 ITU - June/10
10 New Zealand 85.4 3,600,000 4,213,418 ITU - June/10
11 Australia 80.1 17,033,826 21,262,641 N-O - AUG/09
12 Luxembourg 85.3 424,500 497,538 ITU - June/10
13 Korea 81.1 39,440,000 48,636,068 ITU - June/10
14 Faroe Islands 76.4 37,500 49,057 ITU - Nov/08
15 United Kingdom 82.5 51,442,100 62,348,447 ITU - June/10
16 United States 77.3 239,893,600 310,232,863 ITU - June/10
17 Antigua Barbuda 74.9 65,000 86,754 ITU - June/09
18 Switzerland 75.3 5,739,300 7,623,438 ITU - Sept/09
19 Japan 78.2 99,143,700 126,804,433 ITU - June/10
20 Germany 79.1 65,123,800 82,282,988 ITU - June/10
32Languages of Internet Users
33Who 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.
34Internet 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.
35Services 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?
36Todays 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
37What is Next? many of it already here
- E-Health, e-Govrnment, e-Banking, e-Business, .
- Internet of Things
- Social Networking (Facebook, Twitter)
- Already has huge impact (e.g., Tunisia, Egypt,
etc.) - Electronic democracy
- little people can voice their opinions to the
whole world - WikiLeaks
- bridge the gap between information haves and have
nos - Electronic Crimes
- hacker can bring the whole world to its knee
38Industrial 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
39What 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
40Commercial 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
41Internet Organization
ISP Internet Service Provider BSP Backbone
Service Provider NAP Network Access Point POP
Point of Presence CN Customer Network
42Commercial 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
43Topology of CERNET
44The Role of Hong Kong Internet Exchange
Global Internet
HK ISP-B
HK ISP-A
HKIX
Downstream Customers
Downstream Customers
45(No Transcript)
46HKIX 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
47(No Transcript)
48HARNET/Internet
49Internet Architecture
50Basic 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).
51The 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.
52(No Transcript)
53The 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
54Points of Presence (POPs)
55Router Market Share
56A Birds View of the Internet
57A Birds View of the Internet
58Hop-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
59NAP-Based Architecture
60Basic 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.
61Internet 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.
62Charges 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.
63Connecting 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 user-id and password.
64More 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.
65DS (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
66SONET 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
67ISPs 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)
68Sprint
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
69From 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.
70From 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.
71Network Access Point
72ISPs and Backbones
POP
POP
POP
POP
POP
POP
ATM/SONET Core
POP
POP
POP
Router Core
POP
Access Network
POP
POP
POP
73Three national ISPs in North America
74Backbone Map of UUNET - USA
75UUNET
- Mixed OC-12 OC-48 OC 192 backbone
- 1000s miles of fiber
- 3000 POPs
- 2,000,000 dial-in ports
76Backbone Map of UUNET - World
77Qwest
- OC-192 backbone
- 25,000 miles of fiber
- 635 POPs
- 85,000 dial-in ports
78ATT
- OC-192 backbone
- 53,000 miles of fiber
- 2000 POPs
- 0 dial-in ports
79Internet 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 2011.
80Data Centers
81Links for Long Haul Transmission
- Possibilities
- IP over SONET
- IP over ATM
- IP over Satellite
- IP over WDM
82User 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
83Typical (BUT NOT ALL) IP Backbone (Mid 2000s)
- Data piggybacked over traditional voice/TDM
transport
84IP 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)
85Hierarchy 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
86Customer 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
87Customer Network
http//www.ust.hk/itsc/network/
Clients
LAN
Ethernet 10 Mb/s
Servers
Router
T1 Link 1.54 Mb/s
WAN
88Internet Access Technologies
89Internet 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)
90Digital 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.
91Digital 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.
92Customer 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
93Cable 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.
94Cable 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
95Fixed 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.
96Fixed 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
97Classifying Computer Networks
98A Taxonomy of Communication Networks
- Communication networks can be classified based on
the way in which the nodes exchange information
Communication Network
SwitchedCommunication Network
BroadcastCommunication Network
Circuit-SwitchedCommunication Network
Packet-SwitchedCommunication Network
Virtual Circuit Network
Datagram Network
99Broadcast 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
100Circuit 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)
101Timing 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
102Circuit Switching
- A node (switch) in a circuit switching network
Node
incoming links
outgoing links
103Circuit 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
104Packet 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
105Packet Switching
- A node in a packet switching network
Node
incoming links
outgoing links
Memory
106Packet 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
107Datagram Packet Switching
- Each packet is independently switched
- each packet header contains destination address
- No resources are pre-allocated (reserved) in
advance - Example IP networks
108Timing 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
109Datagram 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
110Virtual-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
111Virtual-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)
112Timing 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
113VC 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
114Packet-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
115Fixed-Rate versus Bursty Data
116Packet 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
117Store-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)
118Link Diversity
- Internet meant to accommodate many different link
technologies - Ethernet
- ATM
- SONET
- ISDN
- Modem
- The list continues to grow
- IP on Everything
119Internet Protocols
120Internet Protocols
Application
Application
Transport
Transport
Network
Network
Network
Link
Link
Link
Link
Host
Host
Router
121IP 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
122Demultiplexing
123Link 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
124Additional 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
125ARP Protocol
126Sending an IP Packet over a LAN
127Transport Protocols
- Transmission Control Protocol (TCP)
- User Datagram Protocol (UDP)
128Application 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.
129The Internet Network layer The Glue of all
Networks
Transport layer TCP, UDP
Network layer
Link layer
physical layer
130Demultiplexing 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)
131IP 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)
132What 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)
133Internet Protocol (IP)
- Two versions
- IPv4
- IPv6
- IPv4 dominates todays Internet
- IPv6 is used sporadically
- 6Bone, Internet 2
134IPv4 Header
0
31
15
Length
TOS
HLen
Ver
Ident
Flags
Offset
Checksum
TTL
Protocol
SrcAddr
DestAddr
Options
Pad
135IPv4 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
136IPv4 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
137Fragmentation 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
138IPv4 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
139IPv4 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
140IPv6
- 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)
141IPv6 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
142IPv6 Headers
0
31
15
Flow Label
Pri
Ver
Payload Length
Hop Limit
Next Header
Source Address
Destination Address
143IPv6 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
144IPv6 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
145IPv6 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
146Addressing 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
147Migration 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