Computer Networks
Chapter 1:Introduction
Computer Networking:
A Top Down Approach ,
4th edition.
Jim Kurose, Keith Ross
Today’s Lecture

 Layered Architecture
 Brief description of Five Layers
Protocol Layers
Networks are complex!
• many “pieces”:
– hosts
– routers
– links of various
media
– applications
– protoco...
Layering of Airline Functionality
ticket (purchase)

ticket (complain)

ticket

baggage (check)

baggage (claim

baggage

...
Why layering?
Dealing with complex systems:
Discuss a well defined, specific part of a
large and complex system
Modulari...
Internet Protocol Stack
 To provide structure to design of
network
protocols,
network
designers organize protocols in
lay...
Internet Protocol Stack
 To provide structure to design of
network
protocols,
network
designers organize protocols in
lay...
Internet Protocol Stack
• Application Layer:
 Network applications and their application layer protocols
reside.
 Provid...
Internet Protocol Stack
• Transport Layer:
 Transports application-layer messages between application
end points.
 Trans...
Internet Protocol Stack
• Network Layer:
Responsible for moving network layer packets
known as datagrams from one host to...
Internet Protocol Stack
• Link Layer:
Moves a packet from one node (host or router)
to the next node in the route.
Divid...
Internet Protocol Stack
• Physical Layer:
The job of this layer is to move the individual
bits with in frames from one no...
Internet Protocol Stack
 Application: Provides user interfaces and
support for services such as e-mail, file
transfer etc...
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Week2 lec1-bscs1

  1. 1. Computer Networks Chapter 1:Introduction Computer Networking: A Top Down Approach , 4th edition. Jim Kurose, Keith Ross
  2. 2. Today’s Lecture  Layered Architecture  Brief description of Five Layers
  3. 3. Protocol Layers Networks are complex! • many “pieces”: – hosts – routers – links of various media – applications – protocols – hardware, software Question: Is there any way of organizing network architecture? Answer: Yes possible with a layered architecture
  4. 4. Layering of Airline Functionality ticket (purchase) ticket (complain) ticket baggage (check) baggage (claim baggage gates (load) gates (unload) gate runway (takeoff) runway (land) takeoff/landing airplane routing airplane routing airplane routing departure airport airplane routing airplane routing intermediate air-traffic control centers arrival airport Airline functionality can be divided into layers, providing a frame work in which we can discuss air travel. • At the ticketing layer and below – Airline-counter-to-airline-counter transfer of a person. • At the gate layer – Departure-gate –to-arrival-gate transfer of a person is accomplished Layers: each layer implements a service – via its own internal-layer actions – Combined with the services directly below it •
  5. 5. Why layering? Dealing with complex systems: Discuss a well defined, specific part of a large and complex system Modularization eases maintenance, updating of system Change of implementation of layer’s service transparent to rest of system e.g. change in gate procedure doesn’t affect rest of system
  6. 6. Internet Protocol Stack  To provide structure to design of network protocols, network designers organize protocols in layers  Service – says what a layer does  Protocol – says how the service is implemented  Advantages  Drawbacks  When taken together the protocols of various layers are called the Protocol Stack.  Internet Protocol Stack consists of Five layers  Physical, Link, Network, Transport and Application layers .  Organization of Book
  7. 7. Internet Protocol Stack  To provide structure to design of network protocols, network designers organize protocols in layers  Service – says what a layer does  Protocol – says how the service is implemented  Advantages  Drawbacks  When taken together the protocols of various layers are called the Protocol Stack.  Internet Protocol Stack consists of Five layers  Physical, Link, Network, Transport and Application layers .  Organization of Book
  8. 8. Internet Protocol Stack • Application Layer:  Network applications and their application layer protocols reside.  Provides user interfaces and support for services such as email, file transfer etc. Hyper Text Transfer Protocol (HTTP) File Transfer Protocol (FTP) Session Initiation Protocol (SIP)  An application layer protocol is distributed over multiple end systems  The packets of information at the application layer is called as a message.
  9. 9. Internet Protocol Stack • Transport Layer:  Transports application-layer messages between application end points.  Transport layer packet is called as a segment  Breaks long messages into shorter segments  There are two Transport Layer Protocols  Transmission Control Protocol (TCP)  Connection Oriented service  Guaranteed delivery of application layer messages  Flow control  Congestion Control  User Datagram Protocol (UDP)  Connectionless service  No reliability, flow control and congestion control
  10. 10. Internet Protocol Stack • Network Layer: Responsible for moving network layer packets known as datagrams from one host to another. Transport layer passes a transport layer segment and a destination address to the network layer. Network layer includes IP Protocol Defines the fields in the datagram as well as how end systems and routers act on these fields Commonly referred as IP layer. Different routing protocols. Determine the route that datagrams take between source and destination
  11. 11. Internet Protocol Stack • Link Layer: Moves a packet from one node (host or router) to the next node in the route. Divide the stream of bits received from the network layer into manageable data units called frames. Transforms a raw transmission facility to a reliable link. Mechanism to detect and retransmit damaged or lost frames Example of link layer protocols include WiFi, Ethernet etc.
  12. 12. Internet Protocol Stack • Physical Layer: The job of this layer is to move the individual bits with in frames from one node to next. Representation of bits Physical Layer data consists of a stream of bits (0 or 1) To be transmitted bits must be encoded into signals. The physical layer defines the type of encoding. The protocol in this layer depend on the actual transmission medium of the link.
  13. 13. Internet Protocol Stack  Application: Provides user interfaces and support for services such as e-mail, file transfer etc.  FTP, HTTP  Transport: Transports application-layer messages between application end points.   Segmentation and reassembly TCP, UDP  Network: Routing of Datagrams from source to destination  IP, routing protocols  Link: Move a packet from one node (host or router) to the next node in the route.  Ethernet, WiFi  Physical: Move the individual bits with in frames from one node to next Application Transport Network Link Physical

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