Computer Networks and Internet Protocols Introduction Quiz

COMPUTER NETWORKS AND INTERNET PROTOCOLS Introduction SOUMYA K GHOSH

SANDIP CHAKRABORTY

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

1

Objectives of the Course • • • •

Understand how two computers in the Internet talk to each other Go through the basic functionalities of the computer networks Learn how to program the network Learn the future of the computer network – Do we need any further changes in the design? Functionalities

Network Architecture

Protocols

So, What is Network Architecture? • A way to visualize how two remote computers talk to each other

Network Protocol Stack

What is Network Architecture? (contd…)

What is Network Architecture? (contd…)

Requirement: Convert digital data to analog signal and vice versa

Physical

What is Network Architecture? (contd…)

What is Network Architecture? (contd…)

L2 Switch

Data Link Requirement: Ensure proper scheduling in media access

Physical

What is Network Architecture? (contd…)

What is Network Architecture? (contd…) L3 Switch or Routers

Network Data Link Physical Requirement: Find out a suitable path to forward data

What is Network Architecture? (contd…)

What is Network Architecture? (contd…)

Transport Network Data Link Physical Requirement: End to end traffic control in the network

What is Network Architecture? (contd…)

Application

Network Protocol Stack

Transport Network Data Link Physical

Data Transfer between Two Remote Machines Source

Destination

Data Transfer between Two Remote Machines Application

Application

Transport

Transport

Network

Network

Network

Data Link

Data Link

Data Link

Data Link

Data Link

Physical

Physical

Physical

Physical

Physical

Protocols at Different Layers

Application

HTTP, FTP, SMTP

Transport

TCP, UDP, RTP

Network

IPv4, IPv6, MPLS

Data Link

Ethernet, WiFi, Bluetooth, UMTS, LTE

Physical

Network Management and Control – Cross Layer Protocols

Application

HTTP, FTP, SMTP

Transport

TCP, UDP, RTP

Network

IPv4, IPv6, MPLS

Data Link

Ethernet, WiFi, Bluetooth, UMTS, LTE

Physical

DNS SNMP ARP, DHCP

Two Ways to Learn Computer Networks

Application

Application

Transport

Transport

Network

Network

Data Link

Data Link

Physical

Physical

History of Computer Networks •

https://www.youtube.com/watch?v=9hIQjrMHTv4

https://www.internetsociety.org/internet/history-internet

History of Internet Year

Event

1836

Telegraph by Cooke and Wheatstone Revolutionized human (tele)communications. Morse Code a series of dots and dashes used to communicate between humans. This is similar to how computers communicate via (binary 0/1)

1858-1866

Transatlantic cable. Allowed direct instantaneous communication across the Atlantic. Today, cables connect all continents and are still a main hub of telecommunications.

1876

Telephone. Alexander Graham Bell Exhibits. Telephones exchanges provide the backbone of Internet connections today. Modems provide Digital to Audio conversions to allow computers to connect over the telephone network.

1957

The US forms the Advanced Research Projects Agency (ARPA) within the Department of Defense (DoD) to build US skills in computer technology. U.S.S.R. launches Sputnik.

1962

ARPA's contracts from the private sector to universities and laid the foundations for what would become the ARPANET.

History of Internet Year

Event

1962-1968

Packet-switching (PS) networks developed The Internet relies on packets to transfer data. Data is split into tiny packets that may take different routes to a destination.

1969

ARPANET commissioned by DoD for research into networking. Four (4) nodes: (i) Univ of California, Los Angeles (UCLA); (ii) Stanford Research Institute (SRI); (iii) Univ of California, Santa Barbara (UCSB); (iv) Univ of Utah

1971

Ray Tomlinson of invents Email program to send messages across a distributed network. 15 nodes (23 hosts) on ARPANET Global Networking becomes a reality. First international connections to the ARPANET: University College of London (England) and Royal Radar Establishment (Norway) Packets become mode of transfer Transmission Control Program (TCP) specified. Packet network Intercommunication -- the basis of Internet Communication. Telenet, a commercial version of ARPANET, opened -- the first public packet data service.

1973 1974

History of Internet Year

Event

1977

E-mail becomes a reality Hosts: 100+

1979

News Groups formed. USENET established using UUCP - A collection of discussions groups, news groups.

1982

establishes the Transmission Control Protocol (TCP) and Internet Protocol (IP), as the protocol suite, commonly known as TCP/IP, for ARPANET. TCP/IP defines future network communication.

1983

Name server developed.

1984

Domain Name Server (DNS) introduced. Hosts: 1,000+ NSFNET created - NSF establishes 5 super-computing centers to provide high-computing power for all -- This allows an explosion of connections, especially from universities.

1987

Commercialization of Internet. UUNET is founded with Usenix funds to provide commercial UUCP and Usenet access. Hosts: ~30,000.

History of Internet Year

Event

1989

First relays between a commercial electronic mail carrier and the Internet Hosts: 100,000+ WWW concept by Tim Berners-Lee

1990

First search-engine (Archie) 300,000 Hosts. 1,000 News groups ARPANET ceases to exist. First browser/editor program.

1991

User Friendly Interface to Internet established Gopher released by Paul Lindner and Mark P. McCahill from the U of Minnesota. Text based, menu-driven interface to access internet resources.

1992

Multimedia changes the face of the Internet Hosts: 1+ Million. News groups 4,000 The term "Surfing the Internet" is coined by Jean Armour Polly.

1993

The WWW Revolution truly begins Hosts: 2 Million. 600 WWW sites. The Mosaic Web browser is released on the Net

Web exploded… • • • • •

1994 – 3,2 million hosts and 3,000 websites 1995 – 6,4 million hosts and 25,000 websites 1997 – 19,5 million hosts and 1,2 million websites January 2001 – 110 million hosts and 30 million websites Expansion continues….

Some Facts • 1994 – Hotmail starts web based email • 1994 – World Wide Web Consortium (W3C) was founded • 1995 – JAVA source code was released • 1996 – Mirabilis (Israel) starts ICQ • 1998 – Google is founded

Books / Resources to Follow …

Application Transport Network Data Link Physical

Books / Resources to Follow …

Application Transport Network Data Link Physical

Books / Resources to Follow … (online)

Application Transport Network Data Link Physical

http://www.redbooks.ibm.com/abstracts/gg243376.html http://www.tcpipguide.com/

Internet Resources

29

COMPUTER NETWORKS AND INTERNET PROTOCOLS Protocol Stacks – OSI and TCP/IP SOUMYA K GHOSH

SANDIP CHAKRABORTY

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

1

History of Computer Networks •

https://www.youtube.com/watch?v=9hIQjrMHTv4

https://www.internetsociety.org/internet/history-internet

History of Internet Year

Event

1836

Telegraph by Cooke and Wheatstone Revolutionized human (tele)communications. Morse Code a series of dots and dashes used to communicate between humans. This is similar to how computers communicate via (binary 0/1)

1858-1866

Transatlantic cable. Allowed direct instantaneous communication across the Atlantic. Today, cables connect all continents and are still a main hub of telecommunications.

1876

Telephone. Alexander Graham Bell Exhibits. Telephones exchanges provide the backbone of Internet connections today. Modems provide Digital to Audio conversions to allow computers to connect over the telephone network.

1957

The US forms the Advanced Research Projects Agency (ARPA) within the Department of Defense (DoD) to build US skills in computer technology. U.S.S.R. launches Sputnik.

1962

ARPA's contracts from the private sector to universities and laid the foundations for what would become the ARPANET.

History of Internet Year

Event

1962-1968

Packet-switching (PS) networks developed The Internet relies on packets to transfer data. Data is split into tiny packets that may take different routes to a destination.

1969

ARPANET commissioned by DoD for research into networking. Four (4) nodes: (i) Univ of California, Los Angeles (UCLA); (ii) Stanford Research Institute (SRI); (iii) Univ of California, Santa Barbara (UCSB); (iv) Univ of Utah

1971

Ray Tomlinson of invents Email program to send messages across a distributed network. 15 nodes (23 hosts) on ARPANET

1973

Global Networking becomes a reality. First international connections to the ARPANET: University College of London (England) and Royal Radar Establishment (Norway)

1974

Packets become mode of transfer Transmission Control Program (TCP) specified. Packet network Intercommunication -- the basis of Internet Communication. Telenet, a commercial version of ARPANET, opened -- the first public packet data service.

History of Internet Year

Event

1977

E-mail becomes a reality Hosts: 100+

1979

News Groups formed. USENET established using UUCP - A collection of discussions groups, news groups.

1982

Transmission Control Protocol (TCP) and Internet Protocol (IP) are proposed, as the protocol suite, commonly known as TCP/IP, for ARPANET. TCP/IP defines future network communication.

1983

Name server developed.

1984

Domain Name Server (DNS) introduced. Hosts: 1,000+ NSFNET created - NSF establishes 5 super-computing centers to provide high-computing power for all -- This allows an explosion of connections, especially from universities.

1987

Commercialization of Internet. UUNET is founded with Usenix funds to provide commercial UUCP and Usenet access. Hosts: ~30,000.

History of Internet Year

Event

1989

First relays between a commercial electronic mail carrier and the Internet Hosts: 100,000+ WWW concept by Tim Berners-Lee

1990

First search-engine (Archie) 300,000 Hosts. 1,000 News groups ARPANET ceases to exist. First browser/editor program.

1991

User Friendly Interface to Internet established Gopher released by Paul Lindner and Mark P. McCahill from the U of Minnesota. Text based, menu-driven interface to access internet resources.

1992

Multimedia changes the face of the Internet Hosts: 1+ Million. News groups 4,000 The term "Surfing the Internet" is coined by Jean Armour Polly.

1993

The WWW Revolution truly begins Hosts: 2 Million. 600 WWW sites. The Mosaic Web browser is released on the Net

Network Management and Control – Cross Layer Protocols

Application

HTTP, FTP, SMTP

Transport

TCP, UDP, RTP

Network

IPv4, IPv6, MPLS

Data Link

Ethernet, WiFi, Bluetooth, UMTS, LTE

Physical

DNS SNMP ARP, DHCP

Web exploded… • • • • •

1994 – 3.2 million hosts and 3,000 websites 1995 – 6.4 million hosts and 25,000 websites 1997 – 19.5 million hosts and 1.2 million websites January 2001 – 110 million hosts and 30 million websites Expansion continues….

Some Facts • 1994 – Hotmail starts web based email • 1994 – World Wide Web Consortium (W3C) was founded • 1995 – JAVA source code was released • 1996 – Mirabilis (Israel) starts ICQ • 1998 – Google is founded

Protocols • Protocol is a controlled sequence of messages that is exchanged between two or more systems to accomplish a given task. • Protocol specifications define this sequence together with the format or layout of the messages that are exchanged.

OSI Model Layers OSI layer Application Presentation Session Transport Network Data Link Physical

Function provided Network applications such as file transfer and terminal emulation Data formatting and encryption Establishment and maintenance of sessions Provision for end-to-end reliable and unreliable delivery Delivery of packets of information, which includes routing Transfer of units of information, framing, and error checking Transmission of binary data of a medium

Transmission Control Protocol / Internet Protocol (TCP/IP)

• Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols has become the dominant standard for inter-networking. • TCP/IP represents a set of public standards that specify how packets of information are exchanged between computers over one or more networks.

OSI and TCP/IP

TCP/IP

OSI and TCP/IP

TCP/IP – Packet Encapsulation

Local Area Network (LAN) – Typical Components • • •

Clients – workstations Servers – usually have more computing resources Network devices – – – – – – –

Repeaters Hubs Transceivers NICs Bridges Switches Routers

Wide Area Networks • A WAN is a data communications network covering a large geographic area. • Unlike LANs , a WAN connection is generally rented from a service provider. • WANs connect various sites at different geographic locations so that information can be exchanged.

Evolution of LAN Devices •

NICs, Repeaters, & Hubs

•

Bridges

•

Switches

•

Routers

NIC Specifics •

NICs provide hosts with access to media by using a MAC address.

•

MAC stands for Media Access Control

•

NICs operate at Layer 2 !!

NICs, Repeaters, & Hubs

NIC

The First LAN

To connect two computers, you must... • Install a NIC card in each.

Attach computers using a crossover cable

NIC

NICs, Repeaters, & Hubs

NIC

Repeaters can be used to increase the distance

100 meters or approx. 300 feet Repeaters amplify and retime signals

NIC

NICs, Repeaters, & Hubs NIC

NIC

Using repeaters was fine as long as a business only needed two computers networked. What if a business wanted a third computer attached? NIC NIC Or a fourth? What device would they need?

NICs, Repeaters, & Hubs A multi-port repeater! Also called a... NIC

NIC

Hub

NIC

NIC

A Dilemma!

As businesses expanded their networks, they began to cascade hubs. NIC

NIC

NIC

NIC

What’s The Problem? 1) 2) 3)

Hubs share bandwidth between all attached devices. Hubs are stupid, Layer 1 devices. They cannot filter traffic. Most LANs use a “broadcast topology,” so every device sees every packet sent down the media.

Let’s take a look at how broadcasting works

Broadcasts

In this picture, all hubs forward all traffic to all devices.

Broadcasts

So, if Host 1 wants ping Host 2, all hosts see the ping. This is what we mean by a broadcast topology

1 2

The red arrows show that all hosts receive the ping request. Only Host 2 will respond.

What’s The Solution? •

We need a smarter hub!

•

What’s a “smarter hub” called?

•

A Bridge!

•

Bridges filter network traffic based on MAC addresses.

•

Let’s take a look at how this works.

Bridge To lessen the amount of LAN traffic, businesses began to uses bridges to filter frames based on MAC addresses.

Bridge Now, if Host 1 pings Host 2, only the hosts on that LAN segment see the ping. The bridges stop the ping.

1 2

Switch A switch (also know as a multi-port bridge), can effectively replace these four bridges.

Switch Another benefit of a switch is that each LAN segment gets dedicated bandwidth. 10 Mbps 10 Mbps

The Cloud

10 Mbps

10 Mbps

10 Mbps

Router Routers filter traffic based on IP addresses. The IP address tells the router which LAN segment the ping belongs to.

1

16

Devices Function at Layers

Know these!

Devices Function at Layers

Also know that each device not only works at its layer, but all layers below it.

Devices Function at Layers

For example, a router is a layer 3 device but also uses MAC addresses (layer 2) and repeats the signal (layer 1)

Hierarchical Design Model • • • • •

A layered model for network design Consists of 3 tiers Access layer - for end user connectivity Distribution layer - for policy based routing and access control Core layer- for switching packets as fast as possible across the internetwork.

Few points to note …. • • •

• •

Routers, by default, break up broadcast domain Broadcast domain – Set of all devices on a network segment that hear all the broadcasts sent on that segment Breaking-up of network broadcast is important – because when a host or server sends a network broadcast, every device on the network “must” read and process that broadcast. When a router’s interface receives this broadcast – it discards the broadcast without forwarding it on to other network Router also breaks up “collision domain” as well !

Few points to note …. (contd) • • • •

•

Switches aren’t used to create internetworks, they’re employed to add functionality to an internetwork LAN Switches only “switches” frames from one port to other within a “switched network” Switches break-up collision domains. Collision domain – Ethernet term ! – used to describe a network scenario in which one particular device sends a packet on a network segment, forcing other devices on the same segment to pay attention to it. At the same time, a different device tries to transmit, leading to collision, then both the devices must re-transmit – a situation found in a Hub Each and every port on a switch represent its own collision domain (Hub represents only one collision domain and only one broadcast domain)

41

COMPUTER NETWORKS AND INTERNET PROTOCOLS Circuit Switching and Packet Switching SOUMYA K GHOSH

SANDIP CHAKRABORTY

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

1

Switched Network • Communication between distant stations/ end-devices is typically done over a network of switching nodes. • Switching nodes do not concern with content of data. The purpose is to provide a switching facility that will communicate/transmit the data from source to destination via intermediate node(s). • A collection of nodes and connections forms a communications network. • In a switched communications network, data entering the network from a source station are routed to the destination by being switched from node to node. Ref: Data & Computer Communications by William Stallings

Typical Switching Network

Ref: Data & Computer Communications by William Stallings

Switching Technologies • Switching nodes may connect to other nodes, or to some stations. • Network is usually partially connected – However, some redundant connections are desirable for reliability • Two different switching technologies

– Circuit switching – Packet switching Ref: Data & Computer Communications by William Stallings

Circuit Switching • Dedicated communication path between two stations • Three phases – Establish – Transfer – Disconnect • Must have switching capacity and channel capacity to establish connection • Must have intelligence to work out routing Ref: Data & Computer Communications by William Stallings

Packet Switching • A station breaks long message into packets • Packets are sent out to the network sequentially, one at a time • The stream of packets are routed through the network and are delivered to the intended destination? – Two approaches • Datagram approach • Virtual circuit approach

Circuit Switching - Approaches • Space-Division Switch • Time-Division Switch • TDM Bus • Combinations

Circuit Switching - Approaches

Ref: Data & Computer Communications by William Stallings

Circuit Switching – Space Division Switch

Circuit Switching – Multi-stage Space Division Switch 3-stage Space Division Switch

Ref: Data & Computer Communications by William Stallings

Circuit Switching – Time Division Multoplexing

Ref: Data & Computer Communications by William Stallings

Circuit Switching – Time Slot Interchange

Ref: Data & Computer Communications by William Stallings

Circuit Switching – Properties/Issues • Once connected, transfer is transparent • Developed for voice traffic (phone) • Inefficient – Channel capacity dedicated for duration of connection – If no data, capacity wasted

• Set up (connection) takes time • Data rate is fixed - Both ends must operate at the same rate

Packet Switching – Basics • Data transmitted in small packets – Typically 1000 octets (8 bit byte) – Longer messages split into series of packets – Each packet contains a portion of user data plus some control info • Control info – Routing (addressing) info • Packets are received, stored briefly (buffered) and passed on to the next node – Store and forward

Packet Switched Network

Ref: Data & Computer Communications by William Stallings

Packet Switching – Advantages • Line efficiency – Single node to node link can be shared by many packets over time – Packets queued and transmitted as fast as possible

• Data rate conversion – Each station connects to the local node at its own speed – Nodes buffer data if required to equalize rates

• Packets are accepted even when network is busy – Delivery may slow down

• Priorities can be used

Packet Switching – Techniques • Station breaks long message into packets • Packets sent one at a time to the network • Packets are handled in two ways – Datagram – Virtual circuit

Packet Switching – Datagram • • • • •

Each packet treated independently Packets can take any practical route Packets may arrive out of order Packets may get lost or delayed Up to receiver to re-order packets and recover from missing packets

Packet Switching – Datagram

Packet Switching – Virtual Circuit • Preplanned route established before any packets sent • Call request and call accept packets establish connection (handshake) • Each packet contains a virtual circuit identifier instead of destination address • No routing decisions required for each packet • Clear request to drop circuit • Not a dedicated path

Packet Switching – Virtual Circuit

Packet Switching – VC Switching Table

Virtual Circuit – Source to Destination

Packet Switching – Virtual Circuits vs Datagram •

Virtual circuits – Network can provide sequencing and error control – Packets are forwarded more quickly • No routing decisions to make

– Less reliable

• Loss of a node loses all circuits through that node

• Datagram – No call setup phase

• Better if few packets

– More flexible

• Routing can be used to avoid congested parts of the network

Circuit vs. Packet Switching Circuit Switched • Bandwidth guaranteed • Circuit capacity not reduced by other network traffic • Circuit costs independent of amount of data transmitted, resulting in wasted bandwidth • Suitable for voice communication

Packet Switched • Bandwidth dynamically allocated on as-needed basis • May have concurrent transmissions over physical channel • May have delays and congestion • More cost-effective, offer better performance • Suitable for data communication

26

COMPUTER NETWORKS AND INTERNET PROTOCOLS Protocol Stack – Layered Services SOUMYA K GHOSH

SANDIP CHAKRABORTY

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

1

Network Protocols • • •

Protocol defines the interfaces between the layers in the same system and with the layers of peer system Building blocks of a network architecture Each protocol object has two different interfaces – service interface: operations on this protocol – peer-to-peer interface: messages exchanged with peer

•

“Protocol” includes – specification of peer-to-peer interface – module that implements this interface

•

Features: – – –

Protocol Specification: prose, pseudo-code, state transition diagram Interoperable: when two or more protocols that implement the specification accurately IETF: Internet Engineering Task Force Ref: Computer Networks: A Systems Approach, by Larry L. Peterson and Bruce S. Davie

Key Elements of a Protocol • Syntax – Data formats – Signal levels • Semantics – Control information – Error handling • Timing – Speed matching – Sequencing

Interfaces

Service and Peer Interfaces Ref: Computer Networks: A Systems Approach, by Larry L. Peterson and Bruce S. Davie

Protocol Hierarchy

Ref: Computer Networks: A Systems Approach, by Larry L. Peterson and Bruce S. Davie

Encapsulation

High-level messages are encapsulated inside of low-level messages

OSI (Open Systems Interconnection) Model

Protocol Layers - Functions •

Physical Layer – Handles the transmission of raw bits over a communication link

•

Data Link Layer – Collects a stream of bits into a larger aggregate called a frame – Network adaptor along with device driver in OS implement the protocol in this layer – Frames are actually delivered to hosts

•

Network Layer – Handles routing among nodes within a packet-switched network – Unit of data exchanged between nodes in this layer is called a packet

Lower three layers are typically implemented on all network nodes

Protocol Layers - Functions •

Transport Layer – Implements a process-to-process channel – Unit of data exchanges in this layer is called a message

•

Session Layer – Provides a name space that is used to tie together the potentially different transport streams that are part of a single application

•

Presentation Layer – Concerned about the format of data exchanged between peers

•

Application Layer – Standardize common type of exchanges Transport layer and the higher layers typically run only on end-hosts and not on the intermediate switches and routers

Internet Architecture

Internet Protocol Graph

Internet Architecture • •

Defined by IETF Three main features – Does not imply strict layering. The application is free to bypass the defined transport layers and to directly use IP or other underlying networks – An hour-glass shape – wide at the top, narrow in the middle and wide at the bottom. IP serves as the focal point for the architecture – In order for a new protocol to be officially included in the architecture, there needs to be both a protocol specification and at least one (and preferably two) representative implementations of the specification

Ref: Computer Networks: A Systems Approach, by Larry L. Peterson and Bruce S. Davie

Network Application Programming Interface (API) • Interface exported by the network • Since most network protocols are implemented (those in the high protocol stack) in software and nearly all computer systems implement their network protocols as part of the operating system • The interface is called the network Application Programming Interface (API)

TCP/IP Protocol Stack

TCP/IP Layers – Group of functions in each layer Ref: IBM Redbooks - TCP/IP Tutorial and Technical Overview

TCP/IP Protocol Stack • Application layer – The application layer is provided by the program that uses TCP/IP for communication. – An application is a user process cooperating with another process usually on a different host (there is also a benefit to application communication within a single host). – Examples of applications include Telnet and the File Transfer Protocol (FTP). – The interface between the application and transport layers is defined by port numbers and “sockets”

TCP/IP Protocol Stack • Transport layer – Transport layer provides the end-to-end data transfer by delivering data from an application to its remote peer. Multiple applications can be supported simultaneously. – Most-used transport layer protocol is the Transmission Control Protocol (TCP), which provides connection-oriented reliable data delivery, duplicate data suppression, congestion control, and flow control. – Another transport layer protocol: User Datagram Protocol (UDP) – It provides connectionless, unreliable, best-effort service. – As a result, applications using UDP as the transport protocol have to provide their own end-toend integrity, flow control, and congestion control, if desired. – Usually, UDP is used by applications that need a fast transport mechanism and can tolerate the loss of some data.

TCP/IP Protocol Stack •

Internetwork layer (IP / Network Layer) – The internetwork layer, also called the internet layer or the network layer, provides the “virtual network” image of an internet (this layer shields the higher levels from the physical network architecture below it). – Internet Protocol (IP) is the most important protocol in this layer. It is a connectionless protocol that does not assume reliability from lower layers. – IP does not provide reliability, flow control, or error recovery. These functions must be provided at a higher level. – IP provides a routing function that attempts to deliver transmitted messages to their destination. – A message unit in an IP network is called an IP datagram. This is the basic unit of information transmitted across TCP/IP networks. – Typical internetwork-layer protocols are IP, ICMP, IGMP, ARP, and RARP.

TCP/IP Protocol Stack •

Network interface layer – The network interface layer, also called the link layer or the data-link layer, is the interface to the actual network hardware. – This interface may or may not provide reliable delivery, and may be packet or stream oriented. – In fact, TCP/IP does not specify any protocol here, but can use almost any network interface available, which illustrates the flexibility of the IP layer. – Examples are IEEE 802.2, X.25 (which is reliable in itself), ATM, FDDI, and even SNA. – There should be some underlying physical networks and interfaces

TCP/IP Protocol Stack TCP/IP specifications do not describe or standardize any network-layer protocols per se; they only standardize ways of accessing those protocols from the internetwork layer.

TCP/IP Architecture

TCP/IP : Protocol Architecture and Communication Network

Ref: Data and Computer Communications, by William Stallings

TCP/IP : Protocol Architecture and Communication Network

Ref: Data and Computer Communications, by William Stallings

21

COMPUTER NETWORKS AND INTERNET PROTOCOLS Application Layer - I SOUMYA K GHOSH

SANDIP CHAKRABORTY

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

COMPUTER SCIENCE AND ENGINEERING IIT KHARAGPUR

1

TCP/IP Protocol Stack TCP/IP specifications do not describe or standardize any network-layer protocols per se; they only standardize ways of accessing those protocols from the internetwork layer.

TCP/IP Architecture

Ref: IBM Redbooks - TCP/IP Tutorial and Technical Overview

TCP/IP Protocol Stack

TCP/IP Layers – Group of functions in each layer Ref: IBM Redbooks - TCP/IP Tutorial and Technical Overview

TCP/IP Protocol Stack – Application Layer • Application layer – Application layer is provided by the program that uses TCP/IP for communication. – An application is a user process cooperating with another process usually on a different host (there is also a benefit to application communication within a single host). – Examples of applications: Telnet, SMTP, FTP etc. – Interface between the application and transport layers is defined by port numbers and “sockets”

TCP/IP - Application Layer

TCP/IP : Protocol Architecture and Communication Network

Ref: Data and Computer Communications, by William Stallings

TCP/IP : Protocol Architecture and Communication Network

Ref: Data and Computer Communications, by William Stallings

TCP/IP : Operation

Ref: Data and Computer Communications, by William Stallings

TCP/IP : Concept

Ref: Data and Computer Communications, by William Stallings

TCP/IP : Sample Protocols

Ref: Data and Computer Communications, by William Stallings

Protocol Stack Implementation in a Host Application Transport Network Data Link Physical

Software, Kernel Firmware, Device Driver Hardware

How Application Data Passes Through Different Layers Application

HTTP Header

HTTP Data

Transport

TCP HTTP Header Header

HTTP Data

Network

IP TCP HTTP Header Header Header

HTTP Data

Data Link

MAC IP TCP HTTP Header Header Header Header

HTTP Data

Physical

PHY MAC IP TCP HTTP Header Header Header Header Header

HTTP Data

PHY Trailer

Application Layer Interfacing Application - 1

End to end packet delivery

UDP

Application - 2

Connection Establishment

Application - 3

Reliable Data Delivery

Transport Network Data Link

Application - 4

Flow and Congestion Control

TCP

Ordered Packet Delivery

Application Layer Interfacing Name Service (DNS) End to end packet delivery

UDP

Web (HTTP) Connection Establishment

Email (SMTP, POP, IMAP) Reliable Data Delivery

Transport Network Data Link

Flow and Congestion Control

TCP

File Transfer (FTP) Ordered Packet Delivery

Responsibilities of Application Layer • Identifying and establishing the availability of intended communication partners • Synchronizing cooperating applications • Establishing agreement on procedures for error recovery • Controlling data integrity

Application Layer Examples • • • • • • •

Domain Name System (DNS) File Transfer Protocol (FTP) Hypertext Transfer Protocol (HTTP) Simple Mail Transport Protocol (SMTP) Simple Network Management Protocol (SNMP) Telnet ….

DNS • Domain Name System (DNS) is a system used for translating names of domains into IP addresses. • There are more than 200 top-level domains on the Internet, examples of which include the following: .in - India .us – United States .uk – United Kingdom .edu – educational sites .com – commercial sites

.gov – government sites .org – non-profit sites .net – network service

FTP and TFTP • •

FTP is a reliable, connection-oriented service that uses TCP to transfer files between systems that support FTP. TFTP is a connectionless service that uses User Datagram Protocol (UDP). – TFTP is used on routers to transfer configuration files and Cisco IOS images. – TFTP is designed to be small and easy to implement.

HTTP

SMTP •

E-mail servers communicate with each other using the Simple Mail Transport Protocol (SMTP) to send and receive mail.

SNMP The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices.

Telnet Telnet client software provides the ability to log in to a remote Internet host that is running a Telnet server application and then to execute commands from the command line.

Network API: “Socket” Server and Client exchange messages over the network through a common Socket API

24