Introduction to TCPIP

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COURSE
LECTURE 3
COMS 525 TCPIP
TOPIC
TRANSMISSION CONTROL PROTOCOL / INTERNET
PROTOCOL(TCP/IP)
K. PALANIVEL Systems Analyst, Computer
Centre Pondicherry University, Puducherry
605014.
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Topics to be covered

• TCPIP
• Layered Architecture
• Functions
• Layered Communications
• Different Views of Layers
• Encapsulation and Demultiplexing
• Summary

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Why TCP/IP is so popular?

• TCP/IP was developed very early
• Technologies were widely discussed and circulated
  in documents called Request for Comments (RFC)
  free of charge
• Supported by UNIX operating system

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TCP/IP Model

• Because TCP/IP was developed earlier than the OSI
  7-layer mode, it does not have 7 layers but only
  4 layers

OSI 7-layer
TCP/IP Protocol Suite
FTP, SMTP, Telnet, HTTP,
TCP, UDP
IP, ARP, ICMP
Network Interface
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TCP/IP Model
Application Layer Application programs using the
network
Transport Layer (TCP/UDP) Management of
end-to-end message transmission, error detection
and error correction
Network Layer (IP) Handling of datagrams
routing and congestion
Data Link Layer Management of cost effective and
reliable data delivery, access to physical
networks
Physical Layer Physical Media
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Application Layer Protocols

• Application layer protocols define the rules when
  implementing specific network applications
• Rely on the underlying layers to provide accurate
  and efficient data delivery
• Typical protocols
• FTP File Transfer Protocol
• For file transfer
• Telnet Remote terminal protocol
• For remote login on any other computer on the
  network
• SMTP Simple Mail Transfer Protocol
• For mail transfer
• HTTP Hypertext Transfer Protocol
• For Web browsing

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Transport Layer Protocols

• TCP/IP is built on connectionless technology,
  each datagram finds its own way to its
  destination
• Transport Layer protocols define the rules of
• Dividing a chunk of data into segments
• Reassemble segments into the original chunk
• Typical protocols
• TCP Transmission Control Protocol
• Provide further the functions such as reordering
  and data resend
• UDP User Datagram Service
• Use when the message to be sent fit exactly into
  a datagram
• Use also when a more simplified data format is
  required

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Network Layer Protocols

• Network layer protocols define the rules of how
  to find the routes for a packet to the
  destination
• It only gives best effort delivery. Packets can
  be delayed, corrupted, lost, duplicated,
  out-of-order
• Typical protocols
• IP Internet Protocol
• Provide packet delivery
• ARP Address Resolution Protocol
• Define the procedures of network address / MAC
  address translation
• ICMP Internet Control Message Protocol
• Define the procedures of error message transfer

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Encapsulation and Demultiplexing
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TCP/IP Protocol Suite

• The TCP/IP protocol suite is the protocol
  architecture of the Internet
• The TCP/IP suite has four layers Application,
  Transport, Network, and Data Link Layer
• End systems (hosts) implement all four layers.
  Gateways (Routers) only have the bottom two
  layers.

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Functions of the Layers

• Data Link Layer
• Service Reliable transfer of frames over a
  link Media Access Control on a LAN
• Functions Framing, media access control, error
  checking
• Network Layer
• Service Move packets from source host to
  destination host
• Functions Routing, addressing
• Transport Layer
• Service Delivery of data between hosts
• Functions Connection establishment/termination,
  error control, flow control
• Application Layer
• Service Application specific (delivery of
  email, retrieval of HTML documents, reliable
  transfer of file)
• Functions Application specific

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TCP/IP Suite and OSI Reference Model
The TCP/IP protocol stack does not define the
lower layers of a complete protocol stack
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Assignment of Protocols to Layers
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Layered Communications

• An entity of a particular layer can only
  communicate with
• a peer layer entity using a common protocol (Peer
  Protocol)
• adjacent layers to provide services and to
  receive services

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Layered Communications

• A layer N1 entity sees the lower layers only as
  a service provider

N1 LayerEntity
N1 LayerEntity
Service Provider
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Service Access Points

• A service user accesses services of the service
  provider at Service Access Points (SAPs)
• A SAP has an address that uniquely identifies
  where the service can be accessed

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Exchange of Data

• The unit of data send between peer entities is
  called a Protocol Data Unit (PDU)
• For now, let us think of a PDU as a single packet
• Scenario Layer-N at A sends a layer-N PDU to
  layer-N at B
• What actually happens
• As layer-N passes the PDU to one the SAPs at
  layer-N-1
• Layer-N-1 entity at A constructs its own
  (layer-N-1) PDU which it sends to the layer-N-1
  entity at B
• PDU at layer-N-1 layer-N-1 Header layer N
  PDU

A
B
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Exchange of Data
Exchange of Data
A
B
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Layers in the Example
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Layers in the Example
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Layers and Services

• Service provided by TCP to HTTP
• reliable transmission of data over a logical
  connection
• Service provided by IP to TCP
• unreliable transmission of IP datagrams across an
  IP network
• Service provided by Ethernet to IP
• transmission of a frame across an Ethernet
  segment
• Other services
• DNS translation between domain names and IP
  addresses
• ARP Translation between IP addresses and MAC
  addresses

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Encapsulation and Demultiplexing
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Encapsulation and Demultiplexing

• As data is moving down the protocol stack, each
  protocol is adding layer-specific control
  information

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Encapsulation and Demultiplexing

• Let us look in detail at the Ethernet frame
  between Argon and the Router, which contains the
  TCP connection request to Neon.
• This is the frame in hexadecimal notation.
• 00e0 f923 a820 00a0 2471 e444 0800 4500 002c
  9d08 4000 8006 8bff 808f 8990 808f 4715 065b 0050
  0009 465b 0000 0000 6002 2000 598e 0000 0204 05b4

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Parsing the information in the frame
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Encapsulation and Demultiplexing Ethernet Header
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Encapsulation and Demultiplexing Ethernet Header
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Encapsulation and Demultiplexing IP Header
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Encapsulation and Demultiplexing Ethernet Header
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Encapsulation and Demultiplexing TCP Header
Option maximum segment size
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Encapsulation and Demultiplexing Ethernet Header
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Encapsulation and Demultiplexing Application Data
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Different Views of Networking
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Different Views of Networking

• Different Layers of the protocol stack have a
  different view of the network. This is HTTPs and
  TCPs view of the network.

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Network View of IP Protocol
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Network View of Ethernet

• Ethernets view of the network

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• Questions?