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OrientationOrientation (2-89-90)(2-89-90) 1-1-11
Orientation
Computer NetworksComputer Networks
OrientationOrientation (2-89-90)(2-89-90) 1-1-22
Chapter 1: OrientationChapter 1: Orientation
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-33
Distributed Software Application (will be discussed): WEB, email, 3-tier appl., … Database Directory
Resource Sharing File, Software, Data, … (Network File System, File
Transfer, …) CPU, Memory, Peripherals, …
Communication Email, Chat, TV, Radio, Video Conference,
Telephone, . Virtual Terminal (Remote Login)
Why Networking !Why Networking !
OrientationOrientation (2-89-90)(2-89-90) 1-1-44
Platform (OS + Hardware)
Application Program Interface (API)
Application Software
Platform (OS + Hardware)
Application Program Interface (API)
Application process
Application process
Application process
Application process
Inter-process Communication
Platform Services Graphics Data Interchange Data Management User Interface Software Engineering Communication
Services
Application AgentApplication Agent
Application SoftwareApplication Software
OrientationOrientation (2-89-90)(2-89-90) 1-1-55
Distributed Applications or Network Application: Distributed Applications or Network Application: Client/ServerClient/Server
Application Software (Client Part)
Application Software (Client Part)
Networking Software & HardwareNetworking Software & Hardware
Application Software (Server Part)
Application Software (Server Part)
Client (user) AgentClient (user) Agent Server AgentServer Agent
CommunicationCommunicationNetworkNetwork
Client Agents Examples: Internet Explorer, Opera MS’s Outlook + SMTP,
Netscape’s Messenger + SMTP, Eudora + SMTP
… next slide
Application Program Interface (API) Application Program Interface (API)Syste
mA
pplica
tion
Platform (OS + Hardware)Platform (OS + Hardware)
OrientationOrientation (2-89-90)(2-89-90) 1-1-66
Application process
Application process
Client/Server ApplicationsClient/Server Applications
Application Program Interface (API) Application Program Interface (API)
Networking Software & HardwareNetworking Software & Hardware
CommunicationCommunicationNetworkNetwork
Platform (OS + Hardware) Platform (OS + Hardware)
Application Process(Client Side)
Application Process(Client Side)
Application Process(Server Side)
Application Process(Server Side)
Server Agents Examples: Internet Information Sever,
Appachi SQL query engines
Networking (Communication) Software Examples: TCP, UDP; IP…
OrientationOrientation (2-89-90)(2-89-90) 1-1-77
Communicating EntitiesCommunicating Entities
Do the computers communicate? Do the users communicate? Do the processes communicate?
CommunicationCommunicationNetworkNetwork
user
user
Web server processWeb client process
user
Mail client process
Mail server process
Mail client process
OrientationOrientation (2-89-90)(2-89-90) 1-1-88
Application Software
Presentation
User Interface
Business (Application Logic)
Data (Database Access)
Layered Application ModelLayered Application Model
Client Part
Server Parts
OrientationOrientation (2-89-90)(2-89-90) 1-1-99
Presentation: The client agent remains focused
on presenting information to or receiving
input from the user.
User Interface: User’s access to the application
logic via client agent. It can be dynamic and
configured by user. It is build on the top of the
user interface control. Dynamic User Interface:
• Customizing the look (example: www.cstore.com
• Customizing the content ( examples:
my.yahoo.com , www.exite.com )
Client PartClient Part
OrientationOrientation (2-89-90)(2-89-90) 1-1-1010
Business Rules (Application Logic) Units of processing or algorithms that
represents concept of importance to the organization using database.
Data (Database Access) Logic to connect to database; access/manipulate data
held within databases.
Server PartsServer Parts
OrientationOrientation (2-89-90)(2-89-90) 1-1-1111
User InterfaceUser Interface
Presentation Presentation Business
(Application Logic)
Business (Application
Logic)
Database
Layered Application: Layered Application: 3-Tier Client/Server Model3-Tier Client/Server Model
Client Workstation(rich client)
Application Sever
Data (Data Access and Storage)
Data (Data Access and Storage)
CommunicationCommunicationNetworkNetwork
Mobile ClientWorkstation (thin client)
User InterfaceUser Interface
Presentation Presentation
Data Server
Run by Client AgentRuns by Application
Server Agent
Runs by Database Server Agent
Run by Client Agent
user
user
OrientationOrientation (2-89-90)(2-89-90) 1-1-1212
““Logical Tiers vs Physical TiersLogical Tiers vs Physical Tiers
Application Model Logical Tiers
• Presentation• User Interface• Business• Data
Physical Tiers• Client workstation• Application server• Data Base
Application Model Logical Tiers
• Presentation• User Interface• Business• Data
Physical Tiers• Client workstation• Application server• Data Base
PresentationClient WorkstationUser Interface
Business (Application Logic)
Application Server
Data (Database Access)
Database
OrientationOrientation (2-89-90)(2-89-90) 1-1-1313
Chapter 1 OutlineChapter 1 Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-1414
Local ISP (LAN)Local ISP (LAN)
Repeater hub
Client
Printer
Server
Client
LAN Switch
Client
Remote Access ServerModem pools
TelephoneLines
Router
External Link
Serversmodem
modem
Client
modem
modem External LinkRouter
OrientationOrientation (2-89-90)(2-89-90) 1-1-1515
internet: network of networksinternet: network of networks
router
server
modem
Base Station
links
Stelite
Home network
Mobile network
Regional ISP
Company network
Global ISP
mobile station
workstation
OrientationOrientation (2-89-90)(2-89-90) 1-1-1616
InternetInternet
millions of connected computing devices: hosts, end-systems PCs workstations, servers, … Personal Data Assistances, phones, … running network apps
communication links fiber, copper, radio, satellite transmission rate = bandwidth
routers: forward packets
Networking Hardware and Software Protocols, Hubs, LAN Switches, Repeaters,
OrientationOrientation (2-89-90)(2-89-90) 1-1-1717
protocols control sending, receiving of messages e.g., TCP, IP, HTTP, FTP, PPP, …
Internet: “network of networks” loosely hierarchical public Internet versus private intranet
Internet standards (IAB) RFC: Request for comments IETF: Internet Engineering Task Force
InternetInternet
OrientationOrientation (2-89-90)(2-89-90) 1-1-1818
E-mail The Web Instant Messaging Login into a remote computer (Telnet, Virtual
Terminal, SSH) P2P file sharing File Transfer Multi-User Networked games Stored Video/Audio Real time Video/Audio Internet Telephone
Secure Shell or SSH is a set of standards and an associated network protocol that allows establishing a secure channel between a local and a remote computer.
Popular Internet ApplicationsPopular Internet Applications
OrientationOrientation (2-89-90)(2-89-90) 1-1-1919
Examples? Search Engines (Google) Email (Yahoo, Hotmail) Shopping (Amazon) Auctions (eBay) Instance Massaging (AOL, Yahoo) P2P file sharing (Gnutella) E-learning Games …
Goals? Fast service (low latency) Service all users (scalability) Always available (fault tolerance)
Internet ServicesInternet Services
OrientationOrientation (2-89-90)(2-89-90) 1-1-2020
the Internetthe Internetintranet
router
Intranet: access is denied from outside
firewall
A private corporate network consisting of hosts, routers, and networks that use TCP/IP technology. An intranet may or may not connect to the global Internet.
intranetintranet
OrientationOrientation (2-89-90)(2-89-90) 1-1-2121
Extranet: an internet of networkseach of which is belong to
individual company or organization
Company 1
Company 2
Company 3
extranetextranet
OrientationOrientation (2-89-90)(2-89-90) 1-1-2222
IP addressing: ICANNIP addressing: ICANN
Q: How does an ISP get block of addresses and Names?
A: ICANN: (Internet Corporation For Assigned Names and Numbers) The organization that took over the IANA
duties after Postel’s death. IANA: (Internet Assigned Number Authority)
Essentially one individual (Jon Postel). IANA was originally responsible for assigning IP addresses and the constants used in TCP/IP protocols. Replaced by ICANN in 1999.
Q: How does an ISP get block of addresses and Names?
A: ICANN: (Internet Corporation For Assigned Names and Numbers) The organization that took over the IANA
duties after Postel’s death. IANA: (Internet Assigned Number Authority)
Essentially one individual (Jon Postel). IANA was originally responsible for assigning IP addresses and the constants used in TCP/IP protocols. Replaced by ICANN in 1999.
OrientationOrientation (2-89-90)(2-89-90) 1-1-2323
IP addressing: ICANNIP addressing: ICANN
ICANN coordinates the assignment of identifiers that must be globally unique for the Internet to function. allocates addresses manages DNS assigns domain names, resolves disputes assigns default port numbers sets protocol parameter
OrientationOrientation (2-89-90)(2-89-90) 1-1-2424
(b)(b) USC-ISI Marina del Rey, CA
(l)(l) ICANN Marina del Rey, CA
(e) (e) NASA Mt View, CA(f)(f) Internet Software C. Palo Alto, CA
(i)(i) NORDUnet Stockholm, Sweden
(k)(k) RIPE London, UK
(m)(m) WIDE Tokyo, Japan
(a)(a) NSI Herndon, VA(c)(c) PSInet Herndon, VA
(d)(d) U Maryland College Park, MD(g)(g) DISA Vienna, VA
(h)(h) ARL Aberdeen, MD(j)(j) NSI (TBD) Herndon, VA
DNS Root ServersDNS Root Servers
OrientationOrientation (2-89-90)(2-89-90) 1-1-2525
communication infrastructure enables distributed applications: Web, email, games,
e-commerce, database., file (MP3) sharing
communication services provided to apps: connectionless connection-oriented
What’s the Internet: a service viewWhat’s the Internet: a service view
Home network
Mobile network
Regional ISP
Company network
Global ISP
OrientationOrientation (2-89-90)(2-89-90) 1-1-2626
Chapter 1: OutlineChapter 1: Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edgeNetwork coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-2727
Network StructureNetwork Structure
network edge: 1- applications
2- hosts (end-systems) network core:
1- routers
2- links between routers access networks,
physical media:1- communication links2- modems
Home network
Mobile network
Regional ISP
Company network
Global ISP
OrientationOrientation (2-89-90)(2-89-90) 1-1-2828
The network edge:The network edge:✓
end systems (hosts): run application programs e.g. Web, email at “edge of network”
client/server model client host requests, receives
service from always-on server e.g. Web browser/server;
email client/server
peer-peer model: minimal (or no) use of
dedicated servers e.g. Skyp, Bit Torent
Home network
Mobile network
Regional ISP
Company network
Global ISP
✓ ✓
✓
✓
✓ ✓
✓
✓
✓ ✓
✓✓
✓
✓
OrientationOrientation (2-89-90)(2-89-90) 1-1-2929
ApplicationsApplications
1. Client-ServerClient Side SoftwareServer Side Software
2. Peer-to-Peer ! (chapter 2)
✓ ✓
✓
✓
✓ ✓
✓
✓
✓ ✓
✓✓
✓
✓
Server SideSoftware
Peer Side
Client SideSoftware
Peer Side
OrientationOrientation (2-89-90)(2-89-90) 1-1-3030
Server TypesServer Types
Web server File Server (example: Network File System) Database Server Application Server Groupware Server Software Server Object Server Proxy Server DNS Server
OrientationOrientation (2-89-90)(2-89-90) 1-1-3131
Network edge: connection-oriented serviceNetwork edge: connection-oriented service
Goal: data transfer between end systems handshaking: setup (prepare for) data transfer
ahead of time set up “state” in two communicating hosts
OrientationOrientation (2-89-90)(2-89-90) 1-1-3232
Network edge: connectionless serviceNetwork edge: connectionless service
Goal: data transfer between end systems No handshaking: No setup (no preparation
for) data transfer ahead of time. Data transfer without any notice.
OrientationOrientation (2-89-90)(2-89-90) 1-1-3333
Chapter 1 OutlineChapter 1 Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-3434
The Network Core: The Network Core: ✓✓
mesh of interconnected routers
the fundamental question: how is data transferred through net? circuit switching:
dedicated circuit per call: telephone net
packet-switching: data sent thru net in discrete “chunks”
Home network
Mobile network
Regional ISP
Company network
Global ISP
✓
✓✓
✓
✓✓✓
✓✓
✓
✓ ✓
✓✓✓
✓
✓
✓
✓
✓
✓
✓✓
✓
✓
OrientationOrientation (2-89-90)(2-89-90) 1-1-3535
Network Core: Circuit SwitchingNetwork Core: Circuit Switching
End-end resources reserved for “call”
link bandwidth, switch capacity
dedicated resources: no sharing
circuit-like (guaranteed) performance
call setup required
Home network
Mobile network
Regional ISP
Company network
Global ISP
OrientationOrientation (2-89-90)(2-89-90) 1-1-3636
Network Core: Circuit SwitchingNetwork Core: Circuit Switching
network resources (e.g., bandwidth) divided into “pieces”
pieces allocated to calls
resource piece idle if not used by owning call (no sharing)
dividing link bandwidth into “pieces” frequency division time division
OrientationOrientation (2-89-90)(2-89-90) 1-1-3737
Packet Switching: Statistical MultiplexingPacket Switching: Statistical Multiplexing
Sequence of A & B packets does not have fixed pattern statistical multiplexing.
In TDM each host gets same slot in revolving TDM frame.
Sequence of A & B packets does not have fixed pattern statistical multiplexing.
In TDM each host gets same slot in revolving TDM frame.
A
B
C10 MbsEthernet
1.5 Mbs
D E
statistical multiplexing
queue of packetswaiting for output
link
emptybuffer
OrientationOrientation (2-89-90)(2-89-90) 1-1-3838
Packet switching versus circuit switchingPacket switching versus circuit switching
Each user: sends 100 kbps when
“active” is active p =10% of time
Each user: sends 100 kbps when
“active” is active p =10% of time
Packet switching allows more users to use network!Packet switching allows more users to use network!
User: 1
1 Mbps link
User: N
Switch
OrientationOrientation (2-89-90)(2-89-90) 1-1-3939
How many Users?How many Users?
binomial distributionThe probability that k users be active together:
9983.00017.01)10k(P
0017.0)1.0,35;k(P)10k(P35
11k
Packet-Switch connect all users.
Example: if N=35 users, for active users ≤ 10
probability > 0.9983
for active users > 10 probability < 0.0017
No Blocking for 11th and after. There is queue instead.
)!kN(!k
!N
k
N: whichin
)p1(pk
N)p,N;k(P kNk
Circuit-Switch connect up to 10 simultaneous users.11th and beyond be blocked!
Circuit-Switch connect up to 10 simultaneous users.11th and beyond be blocked!
OrientationOrientation (2-89-90)(2-89-90) 1-1-4040
Packet Switching UsersPacket Switching Users
Switch supports 35 simultaneous users (connections) Up to 10 users be active: no queue, packet
switching has almost the same delay performance as circuit switching.
More than 10 users be active: output queue begin to grow and the connections experience queuing delay.
Because the probability of having 11 or more simultaneous active users is 0.0017,almost the same delay performance as circuit switching.
Packet switching allows more than 3 times the number of users.
OrientationOrientation (2-89-90)(2-89-90) 1-1-4141
Packet switching versus circuit switchingPacket switching versus circuit switching
Great for bursty trafic resource sharing simpler no call setup
Excessive congestion: packet delay and loss protocols needed for reliable data transfer,
congestion control Q: How to provide circuit-like behavior?
bandwidth guarantees needed for audio/video applications.
OrientationOrientation (2-89-90)(2-89-90) 1-1-4242
Traffic ProfilesTraffic Profiles
Constant-bit-rate traffic
Variable-bit-rate traffic
Bursty traffic
OrientationOrientation (2-89-90)(2-89-90) 1-1-4343
Packet-switching: store-and-forwardPacket-switching: store-and-forward
Takes L/R seconds to transmit (push out) packet of L bits on to link or R bps
Entire packet must arrive at router before it can be transmitted on next link: store and forward
delay = 3L/R
Example: L = 7.5 Mbits;
message size R = 1.5 Mbps; link
bandwidth message
transmission time = L/R = 5 sec
delay = 3L/R = 15 sec
R R R
L
OrientationOrientation (2-89-90)(2-89-90) 1-1-4444
Packet Switching: Message SegmentingPacket Switching: Message Segmenting
Now break up the message into 5000 packets
Each packet 1,500 bits
1 msec to transmit packet on one link
pipelining: each link works in parallel
Delay reduced from 15 sec to 5.002 sec
L
OrientationOrientation (2-89-90)(2-89-90) 1-1-4545
Packet-switched networks: forwardingPacket-switched networks: forwarding
Goal: move packets through routers from source to destination we’ll study several path selection (i.e.
routing)algorithms (chapter 4) datagram network:
destination address in packet determines next hop routes may change during session
virtual circuit network: each packet carries tag (virtual circuit ID), tag
determines next hop fixed path determined at call setup time, remains fixed
thru call routers maintain per-call state
OrientationOrientation (2-89-90)(2-89-90) 1-1-4646
Network TaxonomyNetwork Taxonomy
Telecommunicationnetworks
Telecommunicationnetworks
Circuit-switchednetworks
Circuit-switchednetworks
FDMFDM TDMTDM
Packet-switchednetworks
Packet-switchednetworks
Networkswith VCsNetworkswith VCs
DatagramNetworksDatagramNetworks
Internet is a Datagram network and provides both connection-oriented (TCP) and connectionless services (UDP) to applications.
OrientationOrientation (2-89-90)(2-89-90) 1-1-4747
Chapter 1 OutlineChapter 1 Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-4848
Access networks and physical mediaAccess networks and physical media
Q: How to connection end systems to edge router?
residential access nets institutional access
networks (school, company)
mobile access networks
Keep in mind: bandwidth (bits per
second) of access network?
shared or dedicated?
Regional ISP
Company network
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓ ✓
✓
✓
✓
✓
✓
✓✓
OrientationOrientation (2-89-90)(2-89-90) 1-1-4949
Residential access: point to point Residential access: point to point accessaccess
Dialup via modem up to 56Kbps direct access
to router (often less) Can’t surf and phone at
same time: can’t be “always on”
ADSL: asymmetric digital subscriber line up to 1 Mbps upstream (today typically < 256
kbps) up to 8 Mbps downstream (today typically < 1
Mbps) FDM: 50 kHz - 1 MHz for downstream 4 kHz - 50 kHz for upstream 0 kHz - 4 kHz for ordinary telephone
modem
modem
OrientationOrientation (2-89-90)(2-89-90) 1-1-5050
Company access: local area networksCompany access: local area networks
company/univ local area network (LAN) connects end system to edge router
Ethernet: shared or dedicated
link connects end system and router
10 Mbs, 100Mbps, Gigabit Ethernet
deployment: institutions, home LANs happening now
LANs: chapter 5
modem
modem
OrientationOrientation (2-89-90)(2-89-90) 1-1-5151
Wireless access networksWireless access networks
shared wireless access network connects end system to router via base station aka
“access point” wireless LANs:
802.11b (WiFi): 11 Mbps wider-area wireless
access provided by telco operator 3G ~ 384 kbps
• Will it happen?? WAP/GPRS in Europe
shared wireless access network connects end system to router via base station aka
“access point” wireless LANs:
802.11b (WiFi): 11 Mbps wider-area wireless
access provided by telco operator 3G ~ 384 kbps
• Will it happen?? WAP/GPRS in Europe
basestation
mobilestations (hosts)
router
OrientationOrientation (2-89-90)(2-89-90) 1-1-5252
Home networksHome networks
Typical home network components: ADSL or cable modem router/firewall/NAT Ethernet wireless access point
wireless access point
wirelesslaptops
router/Firewall/NATrouter/Firewall/NAT
cable modem
to/fromInternet
Ethernet (switched)
(Network Address Translation) A technology that allows hosts with private addresses to communicate with an outside network such as the global Internet.
(Network Address Translation) A technology that allows hosts with private addresses to communicate with an outside network such as the global Internet.
OrientationOrientation (2-89-90)(2-89-90) 1-1-5353
Physical (Transmission) Media-LinkPhysical (Transmission) Media-Link
Physical Media (link) : what lies between transmitter & receiver.Physical Media (link) : what lies between transmitter & receiver.
OrientationOrientation (2-89-90)(2-89-90) 1-1-5454
Twisted PairTwisted Pair
Twisted Pair (TP) Unshielded/Shielded UTP/STP
Category 3: traditional phone wires, 10 Mbps Ethernet
Category 5 TP: 100Mbps Ethernet
…
OrientationOrientation (2-89-90)(2-89-90) 1-1-5555
Physical Media: coax, fiberPhysical Media: coax, fiber
Coaxial cable: two concentric copper
conductors bidirectional baseband:
single channel on cable legacy Ethernet
broadband: multiple channel on
cable HFC
Fiber optic cable: glass fiber carrying
light pulses, each pulse a bit
high-speed operation: high-speed point-to-point
transmission (e.g., 5 Gps) low error rate:
repeaters spaced far apart ; immune to electromagnetic noise
OrientationOrientation (2-89-90)(2-89-90) 1-1-5656
CablesCables
LAN Twisted-Pair Cables
Fiber Optic and Patch Cords
OrientationOrientation (2-89-90)(2-89-90) 1-1-5757
Physical media: radioPhysical media: radio
signal carried in electromagnetic spectrum
no physical “wire” bidirectional propagation
environment effects: reflection obstruction by objects interference
Radio link types: terrestrial microwave
e.g. up to 45 Mbps channels
LAN (WLAN) 2Mbps, 11Mbps
wide-area 3G: hundreds of kbps WiMAX
satellite up to 50Mbps channel (or
multiple smaller channels)
270 msec end-end delay geosynchronous versus
LEOS
OrientationOrientation (2-89-90)(2-89-90) 1-1-5858
IEEE Standards View of Wireless Network IEEE Standards View of Wireless Network TechnologiesTechnologies
WWAN<15 km
802.20 (proposed)
MAN<5 km
70 Mbit/s
802.16a/e
WiMAXStandard forFixed broadbandWireless.
WLAN<100 m
11-54 Mbit/s
802.11a/b, e, g, h
Wi-Fi®Includes 802.11a/b/g.
PAN<10 m
~1 Mbit/s
802.15.1 (Bluetooth)
802.15.3 (UWB) *
802.15.4 (ZigBee)**
OrientationOrientation (2-89-90)(2-89-90) 1-1-5959
LAN, MAN, WANLAN, MAN, WAN
Source:http://www.crema.unimi.it/didattica/Labsistemi/matagg/Tutorial%20Networking.htm
OrientationOrientation (2-89-90)(2-89-90) 1-1-6060
WIMAX: WIMAX: WWorldwideorldwide IInteroperability for nteroperability for MMicrowaveicrowave AAccessccess
Goal of WIMAX: Provide high-speed Internet access to home and business subscribers, without wires.
Frequency range: 10-66 GHz and sub 11 GHz Supports:
Legacy voice systems Voice over IP TCP/IP Applications with
different QoS requirements.
OrientationOrientation (2-89-90)(2-89-90) 1-1-6161
Chapter 1 OutlineChapter 1 Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-6262
Tier Definition-Tier 1Tier Definition-Tier 1
Tier 1 providers make settlement-free interconnection arrangements with other Tier 1 providers, in which the two networks agree to carry each other's traffic (so-called "peering" with one another) at no cost.
No Tier 1 carriers have to pay for IP transit to any other Tier 1, and in general all other ISPs directly or indirectly pay the Tier 1s for access to their networks.
Tier 1 providers own the physical medium over which information is carried, as well as the network equipment which manages that information.
OrientationOrientation (2-89-90)(2-89-90) 1-1-6363
Tier 1 IPv4 ISPsTier 1 IPv4 ISPs
The following are believed to be the only Tier 1 ISPs worldwide:1. AOL Transit Data Network (ATDN)-AS 1668 2. AT&T-AS 70183. Global Crossing (GX)-AS 3549 4. Level 3-AS 3356 5. Verizon Business (UUnet)-AS 7016. Nippon Telegraph and Telephone Corp. (NTT)-AS 2914 7. Qwest-AS 209
8. SAVVIS (Cable & Wireless America)-AS 3561
9. Sprint Nextel Corporation-AS 1239 • In the Internet, an autonomous system (AS) is a collection of IP
networks and routers under the control of one entity (or sometimes more) that presents a common routing policy to the Internet. See RFC 1930 for additional detail on this updated definition.
OrientationOrientation (2-89-90)(2-89-90) 1-1-6464
Tier-1 ISPs InterconnectionTier-1 ISPs Interconnection
9
11
22
33
4
Links Data Rates: 622Mbps, 2.5-10Gbps
▪▪▪
▪▪▪
▪▪▪
▪▪▪
▪▪▪
POPs
POPs
POPs
POPs
POPs
NA
P:
Netw
ork
Acc
ess
Poin
t
Tier-2 ISPsTier-2 ISPs
NAPNAP
PO
P:
Poin
t O
f Pre
sen
ce (
a g
roup
of
route
rs)
Private “peering” agreements between two backbone companies often bypass NAP
OrientationOrientation (2-89-90)(2-89-90) 1-1-6565
AT&T Global NetworkAT&T Global Network
OrientationOrientation (2-89-90)(2-89-90) 1-1-6666
Seattle
Atlanta
Chicago
Roachdale
Stockton
San Jose
Anaheim
Fort Worth
Orlando
Kansas City
CheyenneNew York
PennsaukenRelay
Wash. DC
Tacoma
DS3 (45 Mbps)OC3 (155 Mbps)OC12 (622 Mbps)OC48 (2.4 Gbps)
…
to/from customers
peering
to/from backbone
….
………POP: point-of-presence
Sprint US backbone network
OrientationOrientation (2-89-90)(2-89-90) 1-1-6767
UUNET US backbone networkUUNET US backbone network
OrientationOrientation (2-89-90)(2-89-90) 1-1-6868
Tier Definition-Tier 2, 3Tier Definition-Tier 2, 3
There is no formal interconnection hierarchy, lower-tier companies are divided into two categories: Tier 2 - A network who peers with other networks,
but still pays for transit to reach some portion of the Internet.
Tier 3 - A network who solely purchases transit from other networks to reach the Internet.
Many of Tier 2 and 3 companies are very large Internet providers, but since they purchase IP transit from other networks they are not considered Tier 1.
OrientationOrientation (2-89-90)(2-89-90) 1-1-6969
▪▪▪▪POPs
Tier-2 Tier-2 ISPISP Tier-2 Tier-2
ISPISP
Tier-1 Tier-1 ISPISP
Access ISP
Access ISP
Servers modem
Com3
RAS+
Modem Pool
modem
Tier-2 ISPs / Access ISPsTier-2 ISPs / Access ISPs
Remote Clients
Clients
▪▪▪ To Tier-1 ISP
OrientationOrientation (2-89-90)(2-89-90) 1-1-7070
Internet structure: network of Internet structure: network of networksnetworks
roughly hierarchical at center: “tier-1” ISPs (e.g., UUNet, BBN/Genuity,
Sprint, AT&T), national/international coverage treat each other as equals
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Tier-1 providers interconnect (peer) privately
NAP
Tier-1 providers also interconnect at public network access points (NAPs)
OrientationOrientation (2-89-90)(2-89-90) 1-1-7171
Internet structure: network of Internet structure: network of networksnetworks
“Tier-2” ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISPTier-2 ISP
Tier-2 ISP
Tier-2 ISP
Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet tier-2 ISP is customer oftier-1 provider
Tier-2 ISPs also peer privately with each other, interconnect at NAP
Tier-2 ISP
OrientationOrientation (2-89-90)(2-89-90) 1-1-7272
Internet structure: network of Internet structure: network of networksnetworks
“Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems)
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISPTier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
localISPlocal
ISPlocalISP
localISP
localISP Tier 3
ISP
localISP
localISP
localISP
Local and tier- 3 ISPs are customers ofhigher tier ISPsconnecting them to rest of Internet
Internet Internet Connection Connection Providers Providers (ICPs)(ICPs)For local ISPsFor local ISPs
OrientationOrientation (2-89-90)(2-89-90) 1-1-7373
End to End CommunicationEnd to End Communication
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISPTier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
AccessISPAccess
ISPAccess
ISP
AccessISP
AccessISP Tier 3
ISP
AccessISP
AccessISP
AccessISP
a packet passes through many networks!
OrientationOrientation (2-89-90)(2-89-90) 1-1-7474
Chapter 1 OutlineChapter 1 Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-7575
How do loss and delay occur?How do loss and delay occur?
packets queue in router buffers packet arrival rate to link exceeds output link capacity packets queue, wait for turn
A
B
packet being transmitted (delay)
packets queue (delay)
free (available) buffers: arriving packets dropped (loss) if no free buffers
OrientationOrientation (2-89-90)(2-89-90) 1-1-7676
Four sources of packet delayFour sources of packet delay
1. nodal processing: check bit errors determine output link
A
B
propagation
transmission
nodalprocessing queue
2. queueing time waiting at output
link for transmission depends on
congestion level of router
OrientationOrientation (2-89-90)(2-89-90) 1-1-7777
Delay in packet-switched networksDelay in packet-switched networks
3. Transmission delay: R=link bandwidth (bps) F =number of bits in
packet (bits) time to send bits into
link = F/R
4. Propagation delay: d = length of physical
link s = propagation speed
in medium (~2x108 m/sec)
propagation delay = d/s
A
B
propagation
transmission
nodalprocessing queue
Note: s and R are verydifferent quantities!
Note: s and R are verydifferent quantities!
bit length: s/R [m]packet length: Fs/R
[m]
bit length: s/R [m]packet length: Fs/R
[m]
OrientationOrientation (2-89-90)(2-89-90) 1-1-7878
Caravan analogyCaravan analogy
car=bit caravan = packet cars speed (km/hr) = propagation speed (m/sec) service rate at toll booth (car/sec) = bandwidth
(bit/sec)
ten-car caravan 120
km
toll booth2233101011 toll booth
OrientationOrientation (2-89-90)(2-89-90) 1-1-7979
Caravan AnalogyCaravan Analogy..
cars speed = 120 km/hr = 2km/mintoll booth takes 12 sec to service a car ( car/sec)
Q: How long until caravan is lined up before 2nd toll booth?
Time to “push” entire caravan through toll booth onto highway = 12*10 = 120sec = 2min
Time for last car to propagate from 1st to 2nd toll both: 120km/(120km/hr)= 1 hr
A: 62 minutes
121
120 km
toll booth22331010
11toll booth
4km
OrientationOrientation (2-89-90)(2-89-90) 1-1-8080
Caravan AnalogyCaravan Analogy....
Q: Will cars arrive to 2nd booth before all cars serviced at 1st booth?
After (1+6) min, 1st car at 2nd booth and 3 cars still at 1st booth.
1st bit of packet can arrive at 2nd router before packet is fully transmitted at 1st router!
cars speed = 1200 km/hr = 20km/mintoll booth takes 1min to service a car ( 1
car/min)
120 km 2233
1010
11toll booth7799 88
toll booth
20km20km
OrientationOrientation (2-89-90)(2-89-90) 1-1-8181
Bit LengthBit Length
bit length = s/R Packet length = Fs/R
s = propagation speed of energy in the link (medium) [m/sec]
R = link bandwidth [bps] F = number of bits in packet [bits]
Example : s= 200m/µs; R=10Mbps [Tbit =0.1 µs]; F= 500 Byte = 4000 bit
20m
linksource destination
Propagation direction
40
00 3
99
9 1234
20×4000 m
OrientationOrientation (2-89-90)(2-89-90) 1-1-8282
Delay Latency for propagating data along the link Corresponds to the “length” of the link Typically measured in seconds
Bandwidth (Capacity) Amount of data sent (or received) per unit time Corresponds to the “capacity” of the link Typically measured in bits per second
Bandwidth(Bps)
Delay(sec)
delay x bandwidth(bit)
Links: Delay and BandwidthLinks: Delay and Bandwidth
OrientationOrientation (2-89-90)(2-89-90) 1-1-8383
R bits per second (bps)
T seconds
F bits
time
Transmission time = F/RT
Propagation delay =T = Link Length/speed1/speed = 3.3 nanosec/m in free space 4 nanosec/m in copper 5 nanosec/m in fiber
Transmission and Propagation DelaysTransmission and Propagation Delays
OrientationOrientation (2-89-90)(2-89-90) 1-1-8484
F = 1 KbyteR = 1 Gbps100 Km, fiber =>T = 500 μsec F/R = 8 μsec
F = 1 KbyteR = 100 Mbps1 Km, fiber => T = 5 μsec F/R = 80 μsec
T
F/R
time
time
T
F/R
T >> F/R
T << F/R
Transmission and Propagation ExamplesTransmission and Propagation Examples
OrientationOrientation (2-89-90)(2-89-90) 1-1-8585
The queue has Q bits when packet arrives. Packet has to wait for the queue to drain before being transmitted.
F bits
time
F/R
T
Q bits
Queueing Delay = Q/R
Capacity = R bpsPropagation delay = T sec
Queuing DelayQueuing Delay
OrientationOrientation (2-89-90)(2-89-90) 1-1-8686
Queuing delay.Queuing delay.
R=link bandwidth (bps) F=packet length (bits) a=average packet
arrival rate
I=traffic intensity = Fa/Rout
I ~ 0: average queuing delay small I —> 1: delays become large I > 1: more “work” arriving than can be
serviced, average delay infinite!
I
Avera
ge q
ueuin
g d
ela
y
1
a
Rin Rout
OrientationOrientation (2-89-90)(2-89-90) 1-1-8787
Total dTotal delayelay
dprocess = nodal processing delay typically a few msecs or less
dqueue = queuing delay depends on congestion
dtrans = transmission delay = F/R, significant for low-speed links
dprop = propagation delay d/s, a few microsecs to hundreds of msecs
prop.trans.queueprocess dddddelay
OrientationOrientation (2-89-90)(2-89-90) 1-1-8888
Switching: Store and ForwardSwitching: Store and Forward
A packet is stored (queued) before being forwarded (sent)
Sender Receiver10 Mbps 5 Mbps 100 Mbps 10 Mbps
time
F/10Mbps
F/5Mbps
F/100Mbps
F/10Mbps
T
Throughput = F/T bps
OrientationOrientation (2-89-90)(2-89-90) 1-1-8989
Store and Forward: Two Packets ExampleStore and Forward: Two Packets Example
time
Sender Receiver10 Mbps 5 Mbps 100 Mbps 10 Mbps
T
Throughput = 2F/T bps
OrientationOrientation (2-89-90)(2-89-90) 1-1-9090
Network ThroughputNetwork Throughput
Sender Receiver10 Mbps 5 Mbps 100 Mbps 10 Mbps
Sender ReceiverR= 2F/T
Equivalent
Throughput: rate (bits/time unit) at which bits transferred between sender/receiver instantaneous: rate at given point in time average: rate over longer period of time
OrientationOrientation (2-89-90)(2-89-90) 1-1-9191
““Real” Internet delays and routesReal” Internet delays and routes
What do “real” Internet delay & loss look like? Traceroute program: provides delay
measurement from source to router along end-end Internet path towards destination. For all i: sends three packets that will reach router i on path
towards destination router i will return packets to sender sender times interval between transmission and reply.
3 probes
3 probes
3 probes
OrientationOrientation (2-89-90)(2-89-90) 1-1-9292
““Real” Internet delays and routesReal” Internet delays and routes
1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms 6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms17 * * *18 * * *19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms
traceroute: gaia.cs.umass.edu to www.eurecom.frThree delay measements from gaia.cs.umass.edu to cs-gw.cs.umass.edu
* means no reponse (probe lost, router not replying)
trans-oceaniclink
OrientationOrientation (2-89-90)(2-89-90) 1-1-9393
Packet LossPacket Loss
Queue ( buffer) preceding a link in buffer has finite capacity
When packet arrives and find a full queue, packet is dropped (lost)
Fraction of lost packets increases as the traffic intensity increases
Performance at a node is often measured not only in terms of delay, but also in terms of the probability of packet loss.
Lost packet may be retransmitted by previous node, by source end system, or not retransmitted at all
OrientationOrientation (2-89-90)(2-89-90) 1-1-9494
Chapter 1 OutlineChapter 1 Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-9595
Network ModelsNetwork Models
The network model is defined in 3-D space.
App. Software (User) Plane: Data Communication.
Control Plane: Connection setup and
connection Maintenance, Resources access control and
access level control. Management Plane:
Measurement and management of network performance.
App. SoftwareApp. Software(User)(User)PlanePlane
Network Model.
We study this part only!We study this part only!
OrientationOrientation (2-89-90)(2-89-90) 1-1-9696
Breaks up a complex system into smaller manageable sub-systems, can compose simple service to provide complex ones
Abstraction of implementation details, separation of implementation and specification, can change implementation as long as service
interface is maintained, Can reuse functionality,
upper layers can share lower layer functionality.
Complex Systems and LayeringComplex Systems and Layering
OrientationOrientation (2-89-90)(2-89-90) 1-1-9797
Breaking a Complex SystemBreaking a Complex System
Entity4
Entity3
Entity2
Entity1
Entity5
ProcessProcess
Services
Services
Services
Services
Services
Entity4
Entity3
Entity2
Entity1
Entity5
ProcessProcess
Services
Services
Services
Services
Servicescommunications
Networking software and hardware is a complex system. Complex system is organized into layers. Organization is hierarchical:
Lower layer entity provide service(s) to upper layer entity. Peer entities communicate based on a protocol.
OrientationOrientation (2-89-90)(2-89-90) 1-1-9898
Some TerminologiesSome Terminologies
Service access point (SAP) (port number, e.g. 80 for http) interface between an upper layer and a lower layer
Protocol data unit (PDU) packets exchanged between peer entities
Service data units (SDU) packets handed to a layer by an upper layer
PDUn = SDUn + header or trailer
Layern Entity Layern Entity
Layern+1 Entity Layern+1 Entity
PDUnPDUn
PDUn+1PDUn+1
SAPn
SDUnSDUnSDUnSDUn
SAPnLayers n & n+1 Service Interface
OrientationOrientation (2-89-90)(2-89-90) 1-1-9999
Layering: A Modular ApproachLayering: A Modular Approach
Sub-divide the problem Each layer relies on services from layer below Each layer exports services to layer above
Interface between layers defines interaction Hides implementation details Layers can change without disturbing other layers
Link hardware
Host-to-host connectivity
Application-to-application channels
Application
OrientationOrientation (2-89-90)(2-89-90) 1-1-100100
A protocol is: a set of rules and formats
that govern the communication between communicating peers,
a set of valid meaning full messages that exchanged between communicating peers.
A protocol is necessary for any function that requires cooperation between peers
ProtocolsProtocols
OrientationOrientation (2-89-90)(2-89-90) 1-1-101101
Syntax of a message what fields does it contain? in what format?
Semantics of a message what does a message mean? for example, not-OK message means
receiver got a corrupted file Actions to take on receipt of a message
for example, on receiving not-OK message, retransmit the entire file
Protocol Messages and ActionsProtocol Messages and Actions
OrientationOrientation (2-89-90)(2-89-90) 1-1-102102
protocol = agreed upon conventions (for communication)
architecture = method or style of building
So “protocol architecture” is the common “design style” for: set of related network protocols.
protocol = agreed upon conventions (for communication)
architecture = method or style of building
So “protocol architecture” is the common “design style” for: set of related network protocols.
Protocol ArchitectureProtocol Architecture
OrientationOrientation (2-89-90)(2-89-90) 1-1-103103
A set of protocols is open if protocol details are publicly available changes are managed by an organization whose
membership and transactions are open to the public A system that implements open protocols is
called an open system International Organization for Standards (ISO)
prescribes a standard to connect open systems open system interconnect (OSI)
Has greatly influenced thinking on protocol stacks
ISO OSI reference modelISO OSI reference model
OrientationOrientation (2-89-90)(2-89-90) 1-1-104104
Reference model formally defines what is meant by a layer, a service
etc. Service architecture
describes the services provided by each layer and the service access point
Protocol architecture set of protocols that implement the service
architecture compliant service architectures may still use non-
compliant protocol architectures
ISO OSIISO OSI
OrientationOrientation (2-89-90)(2-89-90) 1-1-105105
Network
Data Link
Physical
End system 1 (host)
End system 2 (host)
Intermediate systems (Routers)
OSI Seven LayersOSI Seven Layers
Presentation
Application
Session
Transport
Network
Data Link
Physical
Peer-layer communication (protocol)
layer-to-layer communication (services)
Presentation
Application
Session
Transport
Network
Data Link
Physical
Network
Data Link
Physical
Physical link
OrientationOrientation (2-89-90)(2-89-90) 1-1-106106
Application Programs Services
Process-to-Process Channels (end to end
actions) Host-to-Host Connectivity (hop by hop actions)
Five LayersFive Layers
Link Management(hop to hop delivery)
(hides physical network from upper layers)
Hardware (physical interface)
OrientationOrientation (2-89-90)(2-89-90) 1-1-107107
Internet LayersInternet Layers
Network
Link
Transport
Application
Presentation
Session
Transport
Network
Link
Physical
The 7-layer OSI Model The 4-layer Internet model
Applicationftp, http, …
ASCII/Binary
IP
TCP
Ethernet
OrientationOrientation (2-89-90)(2-89-90) 1-1-108108
OSI model vs TCP/IP modelOSI model vs TCP/IP model
application
transport
network
link
physical
application
transport
network
networkinterface
application
presentation
Session
transport
network
Link
physical
TC
P/IP
(Inte
rnet) P
roto
col
OrientationOrientation (2-89-90)(2-89-90) 1-1-109109
Data manipulation (touching / moving) Move to/from net Error detection Buffering for retransmission Encryption Moving to/from app address space Presentation formatting
Protocol Functions -1Protocol Functions -1
OrientationOrientation (2-89-90)(2-89-90) 1-1-110110
Control transfer Flow / congestion control Detecting network transmission problems:
loss, duplication, re-ordering Acknowledgement Multiplexing Time stamping Framing
Protocol Functions - 2Protocol Functions - 2
OrientationOrientation (2-89-90)(2-89-90) 1-1-111111
Summary of layersSummary of layers
OrientationOrientation (2-89-90)(2-89-90) 1-1-112112
Proprietary ProtocolsProprietary Protocols
AppleTalk [Apple Computer Inc.]
DECnet [Digital Equipment Corporation]
IPX/SPX (netware) [Novell Communications]
Server Message Block (SMB) and Common Internet File System (CIFS) [Microsoft]
Systems Network Architecture (SNA) [IBM] …
OrientationOrientation (2-89-90)(2-89-90) 1-1-113113
Need a top and a bottom ( 2 layers ) Need to hide physical link, so need datalink
( 1 layer ) Need both end-to-end and hop-by-hop actions;
so need at least the network and transport layers ( 2 layers )
Session and presentation layers are not so important, and are often ignored
So, we need at least 5, and 7 seems to be excessive
Note that we can place functions in different layers
Need a top and a bottom ( 2 layers ) Need to hide physical link, so need datalink
( 1 layer ) Need both end-to-end and hop-by-hop actions;
so need at least the network and transport layers ( 2 layers )
Session and presentation layers are not so important, and are often ignored
So, we need at least 5, and 7 seems to be excessive
Note that we can place functions in different layers
Why seven layers?Why seven layers?
OrientationOrientation (2-89-90)(2-89-90) 1-1-121121
Protocol Scalability- 1Protocol Scalability- 1
Computer networks will grow in 4 respects: size (number of devices connected and number of
routers), speed (bandwidth of the physical layer), type of service (integrated
data/multimedia/computing/… networks), growth of wireless and mobile connections.
For a network protocol to be scalable, it must work over a wide range of growth in these 4 areas.
OrientationOrientation (2-89-90)(2-89-90) 1-1-122122
Protocol Scalability- 2Protocol Scalability- 2
For size it must supports: Orders of magnitude growth in the address space, Additional demands upon the routing protocols used
to deliver packets to a destination.
For speed: Orders of magnitude increases in bandwidth (hence
data rate) dramatically change the relative importance of transmission time and latency (which is essentially fixed) in the calculations used in flow/congestion control algorithms.
OrientationOrientation (2-89-90)(2-89-90) 1-1-123123
Protocol Scalability- 3Protocol Scalability- 3
For type of service: New services challenge the “best effort” delivery
philosophy of the original network design. Quality Of Service parameters is changing when new
services and applications introduced.
For wireless and mobile: Access, Handovers and Air-Capacities are the issues
behind the growth of wireless nodes.
OrientationOrientation (2-89-90)(2-89-90) 1-1-124124
Layers and AddressesLayers and Addresses
Application Layer domain name e.g. www.iust.ac.ir
Transport Layer the identity of the application in the
destination host Port number: 2 bytes e.g. 80
Network Layer the network identity of the destination
host IP address: 4 bytes for IPv4 e.g. 202.156.1.78
Link Layer the identity of network interface card MAC address (physical address): 6 bytes e.g. 00-04-23-5E-6A-93
Application Layer domain name e.g. www.iust.ac.ir
Transport Layer the identity of the application in the
destination host Port number: 2 bytes e.g. 80
Network Layer the network identity of the destination
host IP address: 4 bytes for IPv4 e.g. 202.156.1.78
Link Layer the identity of network interface card MAC address (physical address): 6 bytes e.g. 00-04-23-5E-6A-93
application
transport
network
link
physical
OrientationOrientation (2-89-90)(2-89-90) 1-1-125125
Layering and Data-1Layering and Data-1
Each layer takes data from above adds header information to create new data unit passes new data unit to layer below
PDUs: frame, datagram (packet), segment, messagePDUs: frame, datagram (packet), segment, message
applicationtransportnetwork
linkphysical
Source process
applicationtransportnetwork
linkphysical
Destination process
message
segment
datagram
frame
M
M HtHnHl Tl
M HtHn
M Ht
M
M HtHnHl Tl
M HtHn
M Ht
OrientationOrientation (2-89-90)(2-89-90) 1-1-126126
Layering and Data-2Layering and Data-2
Different devices switch different things Physical layer: electrical signals (repeaters and
hubs) Link layer: frames (bridges and switches) Network layer: packets (routers)
Application gateway
Transport gateway
Router
Bridge, switch
Repeater, hub
Frameheader
Packetheader
TCPheader
User Data+App. header
OrientationOrientation (2-89-90)(2-89-90) 1-1-127127
Layering and ProtocolLayering and Protocol
Appl. Soft. Appl. Soft.
App. Layer Protocols(ftp, http, SMTP, …)
Transport LayerProtocol (TCP, UDP)
Network LayerProtocols (IP, OSPF, RSVP)
Link LayerProtocols (Ethernet, FDDI, …)
application
transport
network
link
physical
application
transport
network
link
physicalPhysical Layer
Protocols (Ethernet, FDDI, …)
Physical Communication Channel
NETWORKNETWORK
OrientationOrientation (2-89-90)(2-89-90) 1-1-128128
Protocol layering and dataProtocol layering and data
Ht
Message App. ProcessApp. Process
applicationHa
Message
transport Ht Ht
Ht
network
App. Process decides to send a message to its counterpart
App. Layer adds its header, sends the message to transport layer
Transport layer breaks down the message into several parts, add its header to each part And makes segments.It sends one-by-one segments to network layer
OrientationOrientation (2-89-90)(2-89-90) 1-1-129129
sourceapplicatio
ntransportnetwork
linkphysical
HtHn M
segment Ht
datagram
destination
application
transportnetwork
linkphysical
HtHnHl M
HtHn M
Ht M
M
networklink
physical
linkphysical
HtHnHl M
HtHn M
HtHn M
HtHnHl M
router
switch
message M
Ht M
Hn
frame
Encapsulation1Encapsulation1
OrientationOrientation (2-89-90)(2-89-90) 1-1-130130
sourceapplicatio
ntransportnetwork
linkphysical
destination
application
transportnetwork
linkphysical
HtHnHl M
HtHn M
Ht M
M
networklink
physical
linkphysical
router
switch
segment
datagram
message
frame
Encapsulation2Encapsulation2
OrientationOrientation (2-89-90)(2-89-90) 1-1-131131
Protocol Layer Data [throughput] UnitsProtocol Layer Data [throughput] Units
message[mes/sec]
Segment[seg/sec]
Datagram[Packet/sec]
Frame[frame/sec]
application
transport
network
link
physical
Appl. Soft.
application
transport
network
link
physical
Appl. Soft.[tps], [HTTPops/s],[NFS IOPS]
1st layer PDU(physical frame)
[bps]
Physical Communication Channel[Baud], [Hz]
Bau
d =
ch
an
ges
in s
ign
al/se
cB
au
d =
ch
an
ges
in s
ign
al/se
c
OrientationOrientation (2-89-90)(2-89-90) 1-1-132132
Network Network BandwidthBandwidth, , ThroughputThroughput and and GoodputGoodput
Application Layer
Transport Layer
Network Layer
Link Layer
Physical layer
Bandwidth Throughput Goodput
Tps, HTTPops/s,
…
Segmant/s
Packet/s Frame/s
Bit/s
Bandwidth: The rate at which the data units can be transmitted.
Throughput: The rate at which the data units are delivered to the receiver computer.
It is a function of load. Its upper-band is Bandwidth.
Goodput: The rate at which the data units are delivered to the receiver application.
Its upper-band is the Throughput.
Bandwidth: The rate at which the data units can be transmitted.
Throughput: The rate at which the data units are delivered to the receiver computer.
It is a function of load. Its upper-band is Bandwidth.
Goodput: The rate at which the data units are delivered to the receiver application.
Its upper-band is the Throughput.
OrientationOrientation (2-89-90)(2-89-90) 1-1-133133
Throughput, Goodput vs LoadThroughput, Goodput vs Load
Goodput
ThroughputSystemCapacity
Load
OrientationOrientation (2-89-90)(2-89-90) 1-1-134134
Example: Network Layer GoodputExample: Network Layer Goodput
Goodput:
Efficiency:
link. congestion-no and packet, corupted-no packet, loss-no
:of condition in goodput goodput Optimum
[bps] goodput optimum
[bps] goodputEfficiency
[sec] duration time recieving
[bit] packet per length payloadreplica) recieved - packets recievedsbGoodput
100
(]/[
OrientationOrientation (2-89-90)(2-89-90) 1-1-135135
Protocols/ServicesProtocols/Services
application
transport
network
link
physical
Transport Services
Application Program Services
Hop-to-Hopprotocols
End-to-Endprotocols
OrientationOrientation (2-89-90)(2-89-90) 1-1-136136
Data loss some apps (e.g., audio)
can tolerate some loss other apps (e.g., file
transfer, telnet) require 100% reliable data transfer
Timing some apps (e.g.,
Internet telephony, interactive games) require low delay to be “effective”
Throughput some apps (e.g.,
multimedia) require minimum amount of bandwidth to be “effective”
other apps (“elastic apps”) make use of whatever bandwidth they get
What Transport Service does an App Need?
OrientationOrientation (2-89-90)(2-89-90) 1-1-137137
Application Data loss
Throughput Time Sensitive
file transfer no loss elastic no
e-mail no loss elastic no
web documents
no loss elastic (few kbps) no
real-time audio/video
loss-tolerant
audio: few kbps-1Mbps
video:10kbps-5Mbps
yes, 100s of msec
stored audio/video
loss-tolerant
same as above no
interactive games
loss-tolerant
few kbps-10kbps yes, 100s of msec
instant messaging
no loss elastic yes and no
Requirements of Selected Network Requirements of Selected Network ApplicationsApplications
OrientationOrientation (2-89-90)(2-89-90) 1-1-138138
From Application ViewpointFrom Application Viewpoint
Application Program Interface (API)
Communication Software & HardwarePlatform (OS + Hardware)
Application SoftwareApplication Software
APIAPI
App. SoftwareApp. Software
transportnetwork
linkphysical
application
Controlledby OS
Controlledby App. Soft.
OrientationOrientation (2-89-90)(2-89-90) 1-1-139139
Layering: Physical Communication Layering: Physical Communication
applicationtransportnetwork
linkphysical
modem
modem
networklink
physical
applicationtransportnetwork
linkphysical
applicationtransportnetwork
linkphysical
applicationtransportnetwork
linkphysical
data
data
Host A
Host B
Router R
OrientationOrientation (2-89-90)(2-89-90) 1-1-140140
Layering: Logical Communication-1 Layering: Logical Communication-1
Each layer: distributed “entities”
implement layer functions at each node
entities perform actions, exchange messages with peers
applicationtransportnetwork
linkphysical
modem
modem
networklink
physical
applicationtransportnetwork
linkphysical
applicationtransportnetwork
linkphysical
applicationtransportnetwork
linkphysical
OrientationOrientation (2-89-90)(2-89-90) 1-1-141141
Layering: LogicalLayering: Logical Communication Communication
E.g.: transport take data from
app add addressing,
reliability check info to form “datagram”
send datagram to peer
wait for peer to ack receipt
analogy: post office
applicationtransportnetwork
linkphysical
modem
modem
networklink
physical
applicationtransportnetwork
linkphysical
applicationtransportnetwork
linkphysical
applicationtransportnetwork
linkphysical
data
data
transport
data
transport
ack
OrientationOrientation (2-89-90)(2-89-90) 1-1-142142
TCP/IP protocol stackTCP/IP protocol stack
mimemime
ftpftp httphttp smtpsmtp telnettelnet snmpsnmp tftptftp rtprtp dnsdns ……
Transmission Control Pr. (TCP)
Transmission Control Pr. (TCP)
User Datagram Pr. (UDP)User Datagram Pr. (UDP)
icmpicmp ospfospfrsvprsvp igmpigmp
Ethernet, Wireless, token ring, FDDI, ATM, Frame relay, SNA, X25
Ethernet, Wireless, token ring, FDDI, ATM, Frame relay, SNA, X25
domain name service
real time pr.trival file transfer pr.
simple network management pr.
ftp: file transfer protocolhttp; hypertext transfer protocolSmtp: simple mail transfer protocolMime: multipurose Internet mail extensionstelnet=virtual terminal
icmp: Internet control message protocolospf: open shortest path first protocolrsvp: resource reservation protocoligmp: Internet group management protocol
arparp rarprarpInternet Protocol (IP)Internet Protocol (IP)
arp: address resolution protocolrarp: reverse address resolution protocol
OrientationOrientation (2-89-90)(2-89-90) 1-1-143143
IP IP HHourourGGlasslass
IP
TCP UDP
Applications
Token
radio, copper, fiber
802.11 PPPEth.
IP
TCP UDP
Applications
Token
radio, copper, fiber
802.11 PPPEth.
diffserv
intservmcastmobile
NAT IPSEC
IP “hourglass” Middle-age IP “hourglass” ?
middle age: a narrowing mind, a widening waist
OrientationOrientation (2-89-90)(2-89-90) 1-1-144144
IP
TCP UDP
Applications
Token
radio, copper, fiber
802.11 PPPEth.
IP
TCP UDP
overlay services
Token
radio, copper, fiber
802.11 PPPEth.
client server apps
application overlays
IP IP HHourourGGlasslass
Modern: a expanding mind, a slim waist
IP “hourglass” Modern IP “hourglass” ?
OrientationOrientation (2-89-90)(2-89-90) 1-1-145145
Chapter 1 OutlineChapter 1 Outline
1.0 Why Networking1.1 What is the Internet?1.2 Network Structure
Network edge
Network coreNetwork access and physical media
1.3 Internet structure and ISPs 1.4 Delay & loss in packet-switched networks1.5 Protocol layers, service models1.6 History
OrientationOrientation (2-89-90)(2-89-90) 1-1-146146
brick (dumb)
brain (smart)
lock (you can’t get in)
Common View of the TelCommon View of the Telphonephone NetworkNetwork
OrientationOrientation (2-89-90)(2-89-90) 1-1-147147
Common View of the IP NetworkCommon View of the IP Network
OrientationOrientation (2-89-90)(2-89-90) 1-1-148148
OrientationOrientation (2-89-90)(2-89-90) 1-1-149149
OrientationOrientation (2-89-90)(2-89-90) 1-1-150150
http://en.wikipedia.org/wiki/Image:Internet_map_1024.jpghttp://en.wikipedia.org/wiki/Image:Internet_map_1024.jpg
OrientationOrientation (2-89-90)(2-89-90) 1-1-151151
Internet Host CountInternet Host Count
Internet Systems Consortium, Inc. (ISC) is a nonprofit corporation
dedicated to supporting the infrastructure of the universal connected self-organizing Internet and
has autonomy to participates by developing and maintaining core production quality software, protocols, and operations.
Internet Systems Consortium, Inc. (ISC) is a nonprofit corporation
dedicated to supporting the infrastructure of the universal connected self-organizing Internet and
has autonomy to participates by developing and maintaining core production quality software, protocols, and operations.
OrientationOrientation (2-89-90)(2-89-90) 1-1-152152
Internet Standard: RFCsInternet Standard: RFCs
Introduction Year
RF
C N
umbe
rs
ftp://ftp.rfc-editor.org/in-notes/rfc-editor/tutorial.latest.pdf
OrientationOrientation (2-89-90)(2-89-90) 1-1-153153
Internet HistoryInternet History
1961: Kleinrock - queueing theory shows effectiveness of packet-switching
1964: Baran - packet-switching in military nets
1967: ARPAnet conceived by Advanced Research Projects Agency
1969: first ARPAnet node operational
1972: ARPAnet
demonstrated publicly
NCP (Network Control Protocol) first host-host protocol
first e-mail program ARPAnet has 15
nodes
1961-1972: Early packet-switching principles1961-1972: Early packet-switching principles
OrientationOrientation (2-89-90)(2-89-90) 1-1-154154
Internet HistoryInternet History
1970: ALOHAnet satellite network in Hawaii
1973: Metcalfe’s PhD thesis proposes Ethernet
1974: Cerf and Kahn - architecture for interconnecting networks
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 required to interconnect networks
best effort service model
stateless routers decentralized control
define today’s Internet architecture
1972-1980: Internetworking, new and proprietary nets1972-1980: Internetworking, new and proprietary nets
OrientationOrientation (2-89-90)(2-89-90) 1-1-155155
Internet HistoryInternet 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
1988: TCP congestion control
new national networks: Csnet, BITnet, NSFnet, Minitel
100,000 hosts connected to confederation of networks
new national networks: Csnet, BITnet, NSFnet, Minitel
100,000 hosts connected to confederation of networks
1980-1990: new protocols, a proliferation of networks1980-1990: new protocols, a proliferation of networks
OrientationOrientation (2-89-90)(2-89-90) 1-1-156156
Internet HistoryInternet History
Early 1990’s: ARPAnet decommissioned
1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)
early 1990s: Web hypertext [Bush 1945,
Nelson 1960’s] HTML, HTTP: Berners-Lee 1994: Mosaic, later
Netscape late 1990’s:
commercialization of the Web
Late 1990’s – 2000’s:
more killer apps: instant messaging, peer2peer file sharing (e.g., Naptser)
network security to forefront
est. 50 million host, 100 million+ users
backbone links running at Gbps
1990, 2000’s: commercialization, the Web, new apps1990, 2000’s: commercialization, the Web, new apps
OrientationOrientation (2-89-90)(2-89-90) 1-1-157157
References & LinksReferences & Links
Complimentary Hyperlinks This part provides hyperlinks to interesting
(and hopefully useful) computer-networking resources. Most of these resources provide complimentary information to the material in chapter 1. If you're asked to write a paper pertaining to a specialized topic in computer networking, these resources should serve as a good starting point for your research.
References and Hyperlinks
OrientationOrientation (2-89-90)(2-89-90) 1-1-158158
ComplimentaryComplimentary Hyperlinks 1 Hyperlinks 1
IEEE History Center http://www.ieee.org/organizations/history_center/oral_histories/comsoc_oh.html.
Oral Histories that have been collected to commemorate the 50th Anniversary of the IEEE Communications Society. A number of interesting interviews with pioneers in the field.
International Engineering Consortium: Web ProForum Tutorials http://www.iec.org/online/tutorials/
More than 150 tutorials on communications and networking topics, with a focus on cutting edge technology. The tutorials vary in terms of their technical depth, but many are outstanding, and all are extremely well-written and very readable. This is the first place we look when looking for an on-line survey or tutorial.
OrientationOrientation (2-89-90)(2-89-90) 1-1-159159
Broadband: Bringing home the bits http://www.nap.edu/html/broadband Extensive report on the importance and future of
residential broadband access from the Computer Science And Telecommunications Board, National Research Council, January 2002
Webopedia http://www.pcwebopaedia.com/ Online dictionary for computer and Internet
technology
Internet Economics http://china.si.umich.edu/telecom/net-economics.html Comprehensive index for resources relating to
Internet economics, including regulation and pricing.
Complimentary Hyperlinks 2Complimentary Hyperlinks 2
OrientationOrientation (2-89-90)(2-89-90) 1-1-160160
traceroute.org http://www.traceroute.org/ As discussed in Section 1.6, Traceroute provides routes and packet
delays between pairs of hosts in the Internet. This site gives you direct access to hundreds of source hosts from which you can trace routes to arbitrary destination hosts. Choose a country, a source host in that country, and any destination host -- then see how the packets weave their way through the Internet.
Internet Engineering Task Force (IETF) http://www.ietf.org/
The IETF is an open international community concerned with the development and operation of the Internet and its architecture. The IETF was formally established by the Internet Architecture Board (IAB), http://www.isi.edu/iab, in 1986. The IETF meets three times a year; much of its ongoing work is conducted via mailing lists by working groups. Typically, based upon previous IETF proceedings, working groups will convene at meetings to discuss the work of the IETF working groups. The IETF is administered by the Internet Society, http://www.isoc.org/, whose Web site contains lots of high-quality, Internet-related material.
Complimentary Hyperlinks 3Complimentary Hyperlinks 3
OrientationOrientation (2-89-90)(2-89-90) 1-1-161161
Henning Schulzrinne's Internet Technical Resources http://www.cs.columbia.edu/~hgs/internet Henning Schulzrinne has an extensive - although not
always current - index of online resources for the Internet.
The Association for Computing Machinery (ACM) http://www.acm.org/ A major international professional society that has
technical conferences, magazines, and journals in the networking area. The ACM Special Interest Group in Data Communications (SIGCOMM), http://www.acm.org/sigcomm, is the group within this body whose efforts are most closely related to networking
Complimentary Hyperlinks 4Complimentary Hyperlinks 4
OrientationOrientation (2-89-90)(2-89-90) 1-1-162162
The Institute of Electrical and Electronics Engineers (IEEE) http://www.ieee.org/
The other major international professional society that has technical conferences, magazines, and journals in the networking area. The IEEE Communications Society, http://www.comsoc.org/, and the IEEE Computer Society, http://www.computer.org/, are the groups within this body whose efforts are most closely related to networking.
The SETI@home Project http://setiathome.ssl.berkeley.edu/ As discussed in Section 1.2, the SETI@home project is a scientific
experiment that uses Internet-connected computers to search for extraterrestrial intelligence. You can download the SETI program directly from this site.
Nerds 2.0.1 A Brief History of the Internet http://www.pbs.org/opb/nerds2.0.1
This is the Web site for the highly entertaining and informative PBS video on the history of the Internet. The PBS video, Triumph of the Nerds, about the history of personal computers, is also recommended.
Complimentary Hyperlinks 5Complimentary Hyperlinks 5
OrientationOrientation (2-89-90)(2-89-90) 1-1-163163
Leonard Kleinrock's Personal History of the Internet http://www.lk.cs.ucla.edu/LK/Inet/birth.html
Professor Leonard Kleinrock made numerous important contributions to Internet technology and to the field of computer networking. This page provides his own interesting and highly entertaining description of the early history of the Internet.
The DSL Forum http://www.dslforum.org/ DSL Forum is a consortium of nearly 250 leading industry players
covering telecommunications, equipment, computing, networking and service provider companies. The site is rich in information about developments in digital subscriber loop and broadband access to the home.
Cable-modems.org http://www.cable-modems.org/ This site has many tutorials on cable modems, hybrid fiber-coax,
and related topics. Also includes reviews of cable modem products.
Complimentary Hyperlinks 6Complimentary Hyperlinks 6
OrientationOrientation (2-89-90)(2-89-90) 1-1-164164
A note on Internet Request for Comments (RFCs): Copies of Internet RFCs are maintained at multiple sites. The RFC URLs below all point into the RFC archive at the Information Sciences Institute (ISI), maintained the the RFC Editor of the Internet Society (the body that oversees the RFCs). Other RFC sites include http://www.faqs.org/rfc, http://www.pasteur.fr/other/computer/RFC (located in France), and http://www.csl.sony.co.jp/rfc/ (located in Japan).
Internet RFCs can be updated or obsoleted by later RFCs. We encourage you to check the sites listed above for the most up-to-date information. The RFC search facility at ISI, http://www.rfc-editor.org/rfcsearch.html, will allow you to search for an RFC and show updates to that RFC.
Complimentary Hyperlinks 7Complimentary Hyperlinks 7
OrientationOrientation (2-89-90)(2-89-90) 1-1-165165
References and Hyperlinks 1References and Hyperlinks 1
[@Home 1998] @Home, "Frequently Asked Questions," http://www.home.com/qa.html.
[Abramson 1970] N. Abramson, "The Aloha System--Another Alternative for Computer Communications," Proceedings of Fall Joint Computer Conference, AFIPS Conference, p. 37, 1970.
[ADSL 1998] ADSL Forum, "ADSL Tutorial," http://www.adsl.com/adsl_tutorial.html
[Almanac 1998] Computer Industry Almanac, http://www.c-i-a.com/
OrientationOrientation (2-89-90)(2-89-90) 1-1-166166
References and Hyperlinks 2References and Hyperlinks 2
[AT&T Apps 1998] AT&T, "Killer Apps," http://www.att.com/technology/forstudents/brainspin/networks/killerapps.html
[AT&T Bandwidth 1999] AT&T, "Bandwidth: The Need for Speed," http://www.att.com/technology/forstudents/brainspin/networks/bandwidth/game.html
[AT&T Optics 1999] AT&T, "What are fiber optics?," http://www.att.com/technology/forstudents/brainspin/fiberoptics/
[Baran 1964] P. Baran, "On Distributed Communication Networks," IEEE Transactions on Communication Systems, Mar. 1964. Rand Corporation Technical report with the same title (Memorandum RM-3420-PR, 1964). http://www.rand.org/publications/RM/RM3420/
OrientationOrientation (2-89-90)(2-89-90) 1-1-167167
References and Hyperlinks 3References and Hyperlinks 3
[Berners-Lee 1989] T. Berners-Lee, CERN, "Information Management: A Proposal," Mar. 1989, May 1990. http://www.w3.org/History/1989/proposal.html
[Bertsekas 1991] D. Bertsekas and R. Gallagher, Data Networks, 2nd Ed. , Prentice Hall, Englewood Cliffs, NJ, 1991.
[Bush 1945] V. Bush, "As We May Think," The Atlantic Monthly, July 1945. http://www.theatlantic.com/unbound/flashbks/computer/bushf.htm
[Cable 1998] Cable Data News, "Overview of Cable Modem Technology and Services," 1998. http://www.cabledatacomnews.com/cmic/cmic1.html
OrientationOrientation (2-89-90)(2-89-90) 1-1-168168
References and Hyperlinks 4References and Hyperlinks 4
[Cerf 1974] V. Cerf and R. Kahn, "A Protocol for Packet Network Interconnection," IEEE Transactions on Communications Technology, Vol. COM-22, No. 5, pp. 627-641.
[Cisco LAN 1998] Cisco Systems Inc., "Designing Switched LAN Internetworks," http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2012.htm
[Clark 1988] D. Clark, " The Design Philosophy of the DARPA Internet Protocols, Proceedings of ACM SIGCOMM'88, (Stanford, CA), Aug. 1988, Vol. 18, No. 4, http://www.acm.org/sigcomm/ccr/archive/1995/jan95/ccr-9501-clark.html
[Cusumano 1998] M.A. Cusumano and D.B. Toffle, Competing on Internet Time: Lessons from Netscape and its Battle with Microsoft, Free Press, 1998
OrientationOrientation (2-89-90)(2-89-90) 1-1-169169
References and Hyperlinks 5References and Hyperlinks 5
[Daigle 1991] J. N. Daigle, Queuing Theory for Telecommunications, Addison-Wesley, Reading, MA, 1991.
[DEC 1990] Digital Equipment Corporation, "In Memoriam: J. C. R. Licklider 1915-1990," SRC Research Report 61, Aug. 1990. http://gatekeeper.dec.com/pub/DEC/SRC/research-reports/abstracts/src-rr-061.html
[Dertouzos 1999] M. Dertouzos, "The Future of Computing," Scientific American, August 1999, pp.52-55.
[Fraser 1983] A. G. Fraser, "Towards a Universal Data Transport System," IEEE Journal on Selected Areas in Communications, Vol. SAC-1, No 5, pp. 803-816.
OrientationOrientation (2-89-90)(2-89-90) 1-1-170170
References and Hyperlinks 6References and Hyperlinks 6
[Fraser 1993] A. G. Fraser (1993). "Early Experiments with Asynchronous Time Division Networks," IEEE Network Magazine, Vol. 7, No. 1, pp. 12-27.
[Goodman 1997] D. Goodman (Chair), The Evolution of Untethered Communications, National Academy Press, Washington DC, Dec. 1997. http://www.nap.edu/readingroom/books/evolution/index.html
[Green 1992] P. Green, Fiber Optics Networks, Prentice Hall, 1992
[Greenberg 1997] I. Greenberg, "The Future of the Living Room." http://www.cnet.com/Content/Features/Dlife/Living/index.html
OrientationOrientation (2-89-90)(2-89-90) 1-1-171171
References and Hyperlinks 7References and Hyperlinks 7
[Haynal 1999] R. Haynal, "Internet Backbones," http://navigators.com/isp.html
[Huston 1999a] G. Huston, "Interconnection, Peering, and Settlements - Part I," The Internet Protocol Journal, Vol. 2, No. 1, (June 1999). http://www.cisco.com/warp/public/759/ipj_2-1/ipj_2-1_ps1.html
[Huston 1999b] G. Huston, "Interconnecting, Peering, and Settlements - Part II," The Internet Protocol Journal, Vol. 2, No. 2 (June 1999). http://www.cisco.com/warp/public/759/ipj_2-2/ipj_2-2_ps1.html
[Iren 1999] S. Iren, P. Amer, P. Conrad, "The Transport Layer: Tutorial and Survey," ACM Computing Surveys, Vol 31, No 4, (Dec 1999). http://www.cis.udel.edu/~amer/PEL/survey/
[Jacobson 1988] V. Jacobson, "Congestion Avoidance and Control," Proceedings of ACM SIGCOMM '88, pp. (Stanford, CA, Aug. 1988), 314-329, ftp://ftp.ee.lbl.gov/papers/congavoid.ps.Z
OrientationOrientation (2-89-90)(2-89-90) 1-1-172172
References and Hyperlinks 8References and Hyperlinks 8
[Kegel 1999] Dan Kegel's ISDN Page, http://alumni.caltech.edu/~dank/isdn/
[Kleinrock 1961] L. Kleinrock, "Information Flow in Large Communication Networks," RLE Quarterly Progress Report, July 1961.
[Kleinrock 1964] L. Kleinrock, 1964 Communication Nets: Stochastic Message Flow and Delay, McGraw-Hill, NY, NY, 1964.
[Kleinrock 1975] L. Kleinrock, Queuing Systems, Vol. 1, John Wiley, New York, 1975.
[Kleinrock 1976] L. Kleinrock, Queuing Systems, Vol. 2, John Wiley, New York, 1976.
[Kleinrock 1998] L. Kleinrock, "The Birth of the Internet," http://www.lk.cs.ucla.edu/LK/Inet/birth.html
[Leiner 1998] B. Leiner, V. Cerf, D. Clark, R. Kahn, L. Kleinrock, D. Lynch, J. Postel, L. Roberts, and S. Woolf, "A Brief History of the Internet," http://www.isoc.org/internet/history/brief.html
[List 1999] "The List: The Definitive ISP Buyer's Guide," http://thelist.internet.com/
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References and Hyperlinks 9References and Hyperlinks 9
[Lucky 1997] R. Lucky, "New Communication Services - What Do People Want?", Proceedings of the IEEE, Oct. 1997, pp 1536-1543.
[Metcalfe 1976] R. M. Metcalfe and D. R. Boggs. "Ethernet: Distributed Packet Switching for Local Computer Networks," Communications of the Association for Computing Machinery, Vol. 19, No. 7, (July 1976), pp. 395 - 404. http://www.acm.org/classics/apr96/
[Mills 1998] S. Mills, "TV set-tops set to take off," CNET News.com, Oct. 1998. http://news.cnet.com/news/0-1006-200-334433.html
[NAS 1995] National Academy of Sciences, The Unpredictable Certainty: Information Infrastructure Through 2000, National Academy of Sciences Press, 1995. http://www.nap.edu/readingroom/books/unpredictable/chap4.html
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References and Hyperlinks 10References and Hyperlinks 10
[Network 1996] Network Wizards, "Internet Domain Survey", July 1996, http://www.nw.com/zone/WWW-9607/report.html
[Network 1999] Network Wizards, "Internet Domain Survey," Jan. 1999, http://www.isc.org/ds/
[Pacific Bell 1998] Pacific Bell, "ISDN Users Guide," http://www.pacbell.com/Products_Services/Residential/ISDNuserguide/0,1078,20,00.html
[Perkins 1994] A. Perkins, "Networking with Bob Metcalfe," The Red Herring Magazine, Nov. 1994. http://www.herring.com/mag/issue15/bob.html
[Quittner 1998] J. Quittner, M. Slatalla, Speeding the Net: The Inside Story of Netscape and How it Challenged Microsoft, Atlantic Monthly Press, 1998.
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References and Hyperlinks 11References and Hyperlinks 11
[Ramaswami 1998] R. Ramaswami, K. Sivarajan, Optical Networks: A Practical Perspective, Morgan Kaufman Publishers, 1998
[RFC 001] S. Crocker, "Host Software," RFC 001 (the very first RFC!).
[RFC 793] J. Postel, "Transmission Control Protocol," RFC 793, Sept. 1981. http://www.rfc-editor.org/rfc/rfc793.txt
[RFC 801] J. Postel, "NCP/TCP Transition Plan," RFC 801 Nov. 1981. http://www.rfc-editor.org/rfc/rfc801.txt
[RFC 1034] P. V. Mockapetris, "Domain Names--Concepts and Facilities," RFC 1034, Nov. 1987. http://www.rfc-editor.org/rfc/rfc1034.txt
[Roberts 1967] L. Roberts, T. Merril, "Toward a Cooperative Network of Time-Shared Computers," AFIPS Fall Conference, Oct. 1966.
[Ross 1995] K. W. Ross, Multiservice Loss Models for Broadband Telecommunication Networks, Springer, Berlin, 1995.
[Segaller 1998] S. Segaller, Nerds 2.0.1, A Brief History of the Internet, TV Books, New York, 1998.
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References and Hyperlinks 12References and Hyperlinks 12
[Thinplanet 2000] Thinplanet homepage, http://www.thinplanet.com/
[Turner 1986] J. Turner, "New Directions in Communications (or Which Way to the Information Age?)," Proceedings of the Zürich Seminar on Digital Communication, (Zurich, Switzerland, Mar. 1986), pp. 25-32,.
[W3C 1995] The World Wide Web Consortium, "A Little History of the World Wide Web," 1995. http://www.w3.org/History.html
[Wakeman 1992] Ian Wakeman, Jon Crowcroft, Zheng Wang, and Dejan Sirovica, "Layering Considered Harmful," IEEE Network, Jan. 1992, p. 20-24.
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References and Hyperlinks 13References and Hyperlinks 13
[Waung 1998] W. Waung, "Wireless Mobile Data Networking The CDPD Approach," Wireless Data Forum, 1998. http://www2.wirelessdata.org/public/whatis/whatis.html
[Wireless 1998] Wireless Data Forum, "CDPD System Specification Release 1.1," 1998. http://www2.wirelessdata.org/public/specification/index.html
[Wood 1999] L. Wood, "Lloyds Satellites Constellations," http://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/iridium.html
[Ziff-Davis 1998] Ziff-Davis Publishing, "Ted Nelson: Hypertext pioneer," 1998. http://www.zdnet.com/zdtv/screensavers_story/0,3656,2127396-2102293,00.html© 2000-2001 by Addison Wesley Longman A division of Pearson Education.