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Unit 1 Introduction to Internetworking

•    What did you learn in TDC 361 and 362?
•    What is a (communications) network?
• An interconnected structure that allows attached
  devices to communicate with each other
•     Client/Server Model
•     Network Protocols
•     Network Classifications LAN, MAN, WAN etc.
•     Internetwork
•        Internetworking devices
•        The Internet as an example
•        Brief history
•        Structure of the Internet
•        RFC (Request for Comments)
•     Network Architectures OSI and TCP/IP 
•     Internetworking devices revisited
•     Some Internet probing tools ping and
  traceroute / tracert
•     Conversion between different number systems
•     IP Classful Addresses

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Request Service
Provide Service

• Network Protocols
• agreed-upon ways in which computers exchange
  information
• Syntax structure or format of the data
• Semantics meanings
• Timing when data should be sent and how fast it
  can be sent.

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Internetwork Internetworking devices bridges,
routers, gateways etc.  
The Internet
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The Internet A collection of networks and
routers that span many countries and uses the
TCP/IP protocols to form a single, cooperative
virtual network.   Intranet connection of
different LANs within an organization.   Main
players in the Internet Started by U.S.
research/military organizations (D)ARPA
(Defense) Advanced Research Projects Agency
? funds technology with military
usefulness   DoD U.S. Department of Defense
? early adaptor of Internet
technology   NSF National Science Foundations
? funds university research
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Today National backbone providers (NBPs)
interconnected through exchange points NAPs
(Network Access Points) and MAEs (Metropolitan
Area Exchanges)   Regional ISPs connects to the
NBPs  
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Brief History of the Internet 1830
telegraph   1876 telephone (circuit-switching)  
Development of Early Packet Switching
Principles early 1960's concept of packet
switching (Paul Baran)   1965 MIT's Lincoln
Laboratory commissions Thomas Marill to study
computer networking   1968 ARPAnet contract
awarded to Bolt Beranek and Newman (BBN)   1969
ARPAnet has 4 nodes (UCLA, SRI, UCSB, U. Utah),
connected by IMPs (Interface message processors)
connected by 50 kbps lines   1971 15 nodes and
23 hosts
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Internetworking, and New and Proprietary
Networks 1973 TCP/IP design. First
satellite link from California to Hawaii
First international connections to the
ARPANETEngland and Norway   1979 ARPAnet had
about 100 nodes   1980s DARPA funded Berkeley
Unix, with TCP/IP   1980-81 BITNET (IBM
protocols) and CSNET (NSF-funded)   Early 1980's
split ARPnet (research), MILNET
(Military)   Proliferation of Networks 1984
Domain Name Services (Mapping Domain names into
IP addresses)   1986 NSFNET created (56kbps
backbone)   1989 Internet passes 100,000 nodes
First proposal for World Wide Web
NSFNET backbone upgraded to T1 (1.544 Mbps)
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Commercialization and the Web 1990 Original
ARPAnet disbanded Fall 1991 CSNET
discontinued 1991 Gopher released by University
of Minnesota   1992 NSFNET backbone upgraded to
T3 (44.736 Mbps) March 1992 First MBONE
(Multicast Backbone) video multicast November
1992 First MBONE video multicast   Februray
1993 1,776,000 hosts May 1993 NSF solicited for
bids and designated a series of NAPs (e.g.
Chicago NAP is run by Ameritech)   April 30,
1995 NSFNet backbone disbanded   (See
http//www.navigators.com/isp.html for excellent
information and links about the architecture of
the Internet)
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Internet growth from 1981 through 2000 plotted on
a log scale
Internet growth from 1981 through 2000
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Some Internet-related organizations ISOC
http//www.isoc.org The Internet SOCiety (ISOC)
is a professional membership society with more
than 150 organizational and 6,000 individual
members in over 100 countries. It provides
leadership in addressing issues that confront the
future of the Internet, and is the organization
home for the groups responsible for Internet
infrastructure standards, including the Internet
Engineering Task Force (IETF) and the Internet
Architecture Board (IAB). IAB
http//www.iab.org The IAB (Internet
Architecture Board) is the Internet Society
overseer of the technical evolution of the
Internet. The IAB supervises the Internet
Engineering Task Force (IETF), which oversees the
evolution of TCP/IP, and the Internet Research
Task Force (IRTF), which works on network
technology. IETF http//www.ietf.org The
Internet Engineering Task Force (IETF) is a large
open international community of network
designers, operators, vendors, and researchers
concerned with the evolution of the Internet
architecture and the smooth operation of the
Internet. It is open to any interested
individual. Responsible for RFCs (Request for
Comments, Internet Standards/drafts) which can be
located at http//www.ietf.org/rfc.html   ICANN
http//www.icann.org The Internet Corporation for
Assigned Names and Numbers (ICANN) is the
non-profit corporation that was formed to assume
responsibility for the IP address space
allocation, protocol parameter assignment, domain
name system management, and root server system
management function previously performed under
U.S. Government contract by IANA (Internet
Assigned Numbers Authority) and other entities.
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Analogy Application boss Transport
secretary Network Access post office
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ISO OSI Model (ISO International Standard
Organization, OSI Open Systems Interconnection)
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OSI Layers
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An exchange using the OSI model Encapsulation
and Decapsulation
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TCP/IP and OSI Model
Connection-oriented
Connectionless
IP Internet Protocol TCP Transmission Control
Protocol UDP User Datagram Protocol
Connection-oriented a connection must be set up
first. Data go in sequence Connectionless no
need to set up a connection. Data may arrive out
of sequence.
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Figure 2-13 Relationship of layers and addresses
in TCP/IP
Example web browser implementing HTTP
Eg. TCP port 80 for web server
Interface. Eg. WINSOCK on PCs
Implemented in TCP and UDP software.
HTTP uses TCP.
Eg. 140.192.33.37 (32- bit)
Implemented in IP software
Eg. Ethernet Medium Access Control (MAC)
implemented in NIC card (Network Interface Card)
and driver software
Eg. Ethernet address (48-bit)
Eg. Ethernet PHY layer. Implemented in NIC card
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Figure 2-14 Physical addresses identify and
interface card (Link address, MAC address) Eg.
Ethernet a broadcast network.
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Figure 2-15 IP addresses (A logical address
necessary for universal communication over the
internet, and is independent of the underlying
physical networks)
Note We commonly uses names such as
www.cs.depaul.edu (called Domain Names). To
translate from names to IP addresses, needs to
use DNS (Domain Name Service) implemented at the
Application level.
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• Internetworking devices
• Bridges interconnect LANs at Layer 2
• Connected LANs assigned a single network number
  (a single extended LAN)
• Routers interconnect at Layer 3
• Each network assigned a different network number
• Gateway many kind of devices
• Interconnect at Layer 4 and above
• Note Routers are used to (and sometimes still)
  be called gateways

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A host is assigned a host number unique within a
network
A router assigned an IP address per interface
Each network assigned an IP network number
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Dotted Decimal Notation
Class A Large networks Class B Medium
networks Class C Small networks Hostid with all
0s or all 1s are special.
Classful IP Addresses
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Range of addresses in each class
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Multihomed devices have different addresses for
each interface