2. LECTURE – 1
Objectives
1. Transport Layer - Concept
2. Types of delivery
3. Transport Layer - Functions
4. Why Transport Layer?
5. Design issues of Transport layer
Introduction to Transport Layer
2
3. TRANSPORT LAYER
1. 4th layer of OSI reference model.
2. It’s the layer between application layer and network layer.
3. The conceptual division of methods in the layered architecture of protocols.
• Concept
3
4. CRITICAL ROLE
1. Provide communication services directly to the application processes
running on different hosts.
2. i.e; Process-to-process communication.
• Transport Layer
4
6. FUNCTION OF TRANSPORT LAYER
1. Extend the network layer delivery service - host to host system To process
to process system.
2. Provide reliable communication between end processes.
3. Port Addressing
4. Multiplexing and Demultiplexing.
• Operations -1
7. FUNCTION OF TRANSPORT LAYER
1. Fragmentation and Re-assembly.
2. Data Integrity and Error Control [end-to-end].
3. Control packet loss & corrupt data.
4. Flow Control [end-to-end].
5. Congestion control.
• Operations -2
8. DESIGN ISSUES OF TRANSPORT
LAYER
1. Accepting data from Session layer, split it into segments and send to the
network layer.
2. Ensure correct delivery of data with efficiency.
3. Isolate upper layers from the technological changes.
4. Error control and flow control.
• Implementation issues
9. WHY IS TRANSPORT LAYER
CHOOSEN TO PROVIDE RELIABLE
SERVICE? [OPTIONAL]
1. Users have no control over subnet.
2. Cannot solve problem
by using better routers – which act at Network Layer.
by implementing error handling mechanism – which act at data link
layer.
9
10. SUMMARY
Q.1 What is transport Layer?
Q.2 What are the functionalities of transport layer?
Q.3 What is the critical role of transport layer?
Q.4 What are the types of delivery in computer communication
network?
Q.5 What are the design issues of transport Layer?
• Lecture 1: Introduction to Transport Layer
10
11. ACTIVITY
Reading:
1. What is the relationship between Transport and Application Layer?
2. What are the requirements of Transport Layer?
• Lecture 1: Introduction to Transport
layer
11
12. LECTURE – 2
Recap
1. Transport Layer - Concept
2. Types of delivery
3. Transport Layer - Functions
4. Why Transport Layer?
5. Design issues of Transport layer
Objectives
• Transport services
• Difference between
Network layer and
Transport Layer
• Transport service
primitives
Transport Layer Service -1
12
13. TRANSPORT SERVICE
1. Services provided to the upper layers
2. Transport service primitives
3. Transport layer interface ( Socket)
• Service users
13
14. TRANSPORT LAYER VS NETWORK
LAYER
1. Comparison
Features Network Layer Transport Layer
Delivery Host-to-Host delivery Process- to Process delivery
Addressing Ip addressing Port addressing
Data Unit PacKets delivery btw
source to dest through
multiple networks
Segment delivery or entire message delivery to
process
Services Connectionless Connection and connectionless services
Encapsulation & De-
encapsulation
It translates logical
network address into
physical machine address
It divides each message into the packets at the
source and reassembles then at the destination.
14
18. CONNECTION ORIENTED
1. Service Primitives
CONNECT DESCRIPTION
DATA, DATA-
ACKNOWLEDGE,
EXPEDITED-DATA
Data and information is sent using thus
primitive
CONNECT Primitive for closing the connection
RESET Primitive for resetting the connection
18
19. CONNECTION-LESS ORIENTED
1. Service Primitives
UNIDATA This primitive sends a packet of data
FACILITY, REPORT Primitive for enquiring about the performance of the
network, like delivery statistics.
19
21. SUMMARY
Q.1 What is meant by service provider and service user?
Q.2 What are the differences between network layer and transport
layer?
Q.3 What are the services offered by transport layer?
Q.4 What is transport service primitives?
Q.5 What is interface?
• Lecture 2: Transport Layer Service
21
22. ACTIVITY
1. Video :
Transport layer services
https://www.youtube.com/watch?v=EqzDTO9tdqs
• Lecture 2: Transport Layer Service
22
24. LECTURE- 3
Recap
1. Transport services
2. Difference between Network layer and Transport Layer
3. Transport service primitives
Objectives
• Berkley Socket
• Elements of
Transport Layer
• Port Addressing
Transport Layer Service -2
24
25. SOCKET
1. Transport Layer provides service to application not directly but via Interface
– Socket.
2. SOCKET = IP number + Port Number
3. Ex: 198.168.254.1:80
• Interface
25
27. ELEMENT OF TRANSPORT LAYER
1. Addressing
2. Connection Establishment
3. Connection Release
4. Multiplexing
5. Flow control and buffering
6. Crash recovery
• Requirements
27
28. PROCESS-TO –PROCESS
IMPLEMENTATION
1. One of the common way is – client/server paradigm
2. Process on local host – Client
3. Process on the remote hist – Server
4. For process-to –process communication we define:
5. Local host , Local Process.
6. Remote host ,Remote Process.
• Achieved
28
29. PORT ADDRESSING
1. To delivery message to right process among several process
2. Use transport layer address => port number.
3. Port number => 16-bit integers between 0 and 65,535.
4. Client choose random port number (assigned by transport layer). - This is
the ephemeral port number.
5. Server choose random port number or universal port number for servers –
called well-known port number.
• Transport layer service
29
30. IANA RANGES
1. Internet Assigned Number Authority – divides the port number into 3
ranges.
2. Well –known port- 0 to 1023 (IANA responsible).
3. Registered ports: 1024 to 49,151 ( IANA responsible).
4. Dynamic port: 49,152 to 65,535 (ephemeral ports).
• Authority
30
31. IANA RANGES
1. Internet Assigned Number Authority – divides the port number into 3
ranges.
2. Well –known port- 0 to 1023 (IANA responsible).
3. Registered ports: 1024 to 49,151 ( IANA responsible).
4. Dynamic port: 49,152 to 65,535 (ephemeral ports).
• Authority
31
32. COMMON PORT NUMBERS
1. Authority
COMMON PORT NUMBERS
Number Assignment
20 File Transfer Protocol (FTP) Data Transfer
21 File Transfer Protocol (FTP) Command Control
22 Secure Shell (SSH) Secure Login
23 Telnet remote login service, unencrypted text messages
25 Simple Mail Transfer Protocol (SMTP) E-mail routing
53 Domain Name System (DNS) service
67, 68 Dynamic Host Configuration Protocol (DHCP)
80
Hypertext Transfer Protocol (HTTP) used in the World Wide
Web
110 Post Office Protocol (POP3)
119 Network News Transfer Protocol (NNTP)
123 Network Time Protocol (NTP)
143
Internet Message Access Protocol (IMAP) Management of
digital mail
161 Simple Network Management Protocol (SNMP)
194 Internet Relay Chat (IRC)
443 HTTP Secure (HTTPS) HTTP over TLS/SSL
32
33. SUMMARY
Q.1 What is the importance of transport service primitives in state diagram ?
Q.2 What is socket?
Q.3 What is Berkley socket?
Q.4 What is transport layer addressing ?
Q.5 What is IANA is responsible for?
• Lecture 3: Transport Layer Service
33
36. LECTURE – 4
Recap
1. Transport service primitives
2. Berkley Socket
3. Elements of Transport Layer
4. Port Addressing
Objectives
• Multiplexing &
Demultiplexing
• Connectionless Service
• Connection-oriented
Service
• Connectionless
Multiplexing &
Demultiplexing
• Connection Multiplexing &
Demultiplexing
Multiplexing & DeMultiplexing
36
37. MULTIPLEXING - MUXING
1. Method/Process : by which multiple analog or digital signals are
combined into one signal over a shared medium.
2. Aim : Share a resource.
3. Mathematical Representation : Many-to-One
• In telecommunications and computer
networks
•
37
38. DEMULTIPLEXING -DEMUXING
1. Method/Process : demultiplex is reconverting a signal containing multiple
analog or digital signal streams back into the original separate and
unrelated signals.
2. Mathematical Representation : One- to- Many
• Concept
38
39. CONNECTION-ORIENTED SERVICE
1. Dedicated connection (establishment of connection)
2. Handshaking
3. Data communication
4. Release the connection.
NOTE : Protocol used – TCP
• Concept
39
40. CONNECTIONLESS –ORIENTED
SERVICE
1. No Dedicated connection (establishment of connection)
2. No Handshaking
3. Data communication
4. No Release the connection.
NOTE: Protocol used – UDP
• Concept
40
43. SUMMARY
Q.1What is Multiplexing?
Q.2 What is Demultiplexing?
Q.3 What is the importance of connection-oriented and connectionless
service?
Q.4 What is connection-oriented multiplexing and demultiplexing?
Q.5 What is connectionless multiplexing and demultiplexing?
• Lecture 4: Multiplexing &
DeMultiplexing
43
46. LECTURE – 5
Recap
1. Multiplexing & Demultiplexing
2. Connectionless Service
3. Connection-oriented Service
4. Connectionless Multiplexing & Demultiplexing
5. Connection Multiplexing & Demultiplexing
Objectives
• Reliable service
• Unreliable service
• TCP service
• UDP service
• Error control & Flow
control
Reliable & Unreliable Services
46
47. RELIABLE SERVICE
1. Based on application requirement .
2. Transport layer provides – reliable or unreliable services.
3. Reliable service- by implementing flow and error control @ the transport
layer.
4. Impact/effect => slower and more complex service.
• Concept
47
48. UNRELIABLE SERVICE
1. Application prefer unrelaible services:
2. Reliability (error & flow control) implemented at application level itsef.
3. Nature of application does not demand flow and error control.
4. It needs fast service.
• Concept
48
49. TCP SERVICE
1. TCP connection exist between the sockets of the two processes.
2. Connenction-oriented service.
3. Full-duplex connection.
4. Provides reliable services.
5. Congestion control mechanism.
• Concept
49
50. UDP SERVICE
1. Light weight protocol – ie; provides minimal services.
2. Connectionless oriented service
3. Provides unreliable data transfer service.
4. Don’t include congestion-control mechanism.
5. No packet overheads.
• Concept
50
51. ERROR CONTROL
1. The Link level error control - packet-by-packet basis on each and every
link.
2. EX: For Ethernet, this is a CRC-32 over the entire frame. This is implemented
in hardware.
3. The Transport checksum is within TCP and optionally UDP.
4. Ex: Implement at software level ( program level).
• Mechanism in 2 different layers
51
52. FLOW CONTROL
1. To match the speed between source and destination.
2. Flow control - @ DLL - restricts the number of frames, the sender can send
before it waits for an acknowledgment from the receiver. ( implements –
Feedback –based Flow control).
3. Flow control- @ TL – implements – Rate-based Flow control).
• Mechanism in 2 different layers
52
53. SUMMARY
Q.1 What is reliable service?
Q.2 What is unreliable service?
Q.3 What are the services offerred by TCP & UDP service?
Q.4 What is difference between error control in data link and transport layer?
Q.5 What is the diffreence between error control in data link and transport?
• Lecture 5: Reliable & Unreliable Services
53
54. ACTIVITY
Reading :
TCP Flow control ( difference between Flow control & congestion control)
https://www.brianstorti.com/tcp-flow-control/
• Lecture 5: Reliable & Unreliable
Services
54
56. LECTURE – 6
Recap
1. Reliable service
2. Unreliable service
3. TCP service
4. UDP service
5. Error control & Flow control
Objectives
• Transport control Protocol
• User datagram Protocol
• TCP VS UDP
Transport Layer Protocol
56
58. UDP USES
1. Simple request-response communication
2. Internal flow and error control mechanism
3. Multicasting
4. Managing process
5. Used by route updating protocol => RIP
• Application
58
62. TCP VS UDP
1. Comparison
TCP UDP
• Secure • Unsecure
• Connection-oriented • Connectionless
• Slow • Fast
• Guaranteed transmission • No Guaranteed transmission
• Packet reorder • No Packet reorder
• Flow control • No Flow control
• Error checking • No Error checking
• 3-way handshake • No handshake
• DNS,HTTP,HTTPS,FTP, SMTP, Telnet, SNMP • DNS,DHCP,TFTP,SNMP,RIP,VOIP
62
63. SUMMARY
Q.1 What are the characteristics/Features of TCP ?
Q.2 What are the characteristics of UDP?
Q.3 Which protocols uses UDP ?
Q.4 Which protocols uses TCP?
Q.5 Differences between TCP Vs UDP?
• Lecture 6: Transport layer Protocol
63
75. LECTURE – 7
Recap
1. Transport control Protocol
2. User datagram Protocol
3. TCP Vs UDP
Objectives
• Introduction to Application
layer
• Functionality of Application
layer
• Design issues of
Application layer
• Application layer protocol
75
76. APPLICATION LAYER
An application layer is an abstraction layer that specifies the shared
communications protocols and interface methods used by hosts in a
communications network.
• Definition
76
78. DESIGN ISSUES OF APPLICATION
LAYER
1. Pattern Language for Application-level Communication Protocols
2. Service Design Patterns
3. Patterns of Enterprise Application Architecture
4. Pattern-Oriented Software Architecture
• Challenges
78
79. APPLICATION LAYER PROTOCOLS
1. Hyper Text Transfer Protocol, HTTP − underlying protocol for world wide web.
2. File Transfer Protocol, FTP − client-server based protocol for transfer of files.
3. Domain Name System, DNS − It is a naming system for devices in networks.
4. Simple Mail Transfer Protocol, SMTP − It lays down the rules and semantics for
sending and receiving electronic mails (e-mails).
5. Simple Network Management Protocol, SNMP − It is for managing, monitoring the
network and for organizing information about the networked devices.
• Challenges
79
80. SUMMARY
Q.1 What is Application Layer?
Q.2 What are the functions of Application layer?
Q.3 What are the design issues of Application layer?
Q.4 What are the different types of Application layer Protocols?
• Lecture 7: Introduction to Application Layer
80
83. LECTURE - 8
Recap
1. Introduction to Application layer
2. Functionality of Application layer
3. Design issues of Application layer
4. Application layer protocol
Objectives
• World Wide Web
• WWW Vs Internet
• WWW Features
• WWW Components
• Universal Resource
Locator
World Wide Web
83
84. WORLD WIDE WEB
1. Sir Timothy John Berners-Lee – Inventor
2. Commonly known as web .
3. It is viewed as
1. Information System.
2. One which operates on demand – at any time & at any location.
• Concept
84
86. WWW VS INTERNET
1. Comparison
INTERNET WWW
Global System Online Content
Massive interconnection of
Computer Networks
Application layer built using Internet
service.
TCP /IP Protocol Websites, Email service, File transfer
service
86
87. WWW FEATURES
1. HyperText Information System
2. Cross-Platform
3. Distributed
4. Open standards and Open source
5. Web browser
6. Dynamic , Interactive , Evolving – Web 2.0
• Details
87
90. UNIVERSAL RESOURCE LOCATOR
http://www.vpc.com:80/abc/index.html
1. http – Service or Protocol
2. :// - Delimiter
3. www - Host Name
4. vpc –Subdomain
5. com – Domain Name
6. 80 – Port Number
7. abc – Directory on the server
8. Index.html – File Name or Resource Name
• Example
90
91. SUMMARY
Q.1 What is World wide web?
Q.2 What is the difference between WWW and Internet?
Q.3 What are the features of WWW?
Q.4 What are the components of WWW?
Q.5 What is Universal resource locator?
• Lecture 8: World Wide Web
91
96. LECTURE - 9
Recap
1. World Wide Web
2. WWW Vs Internet
3. WWW Features
4. WWW Components
5. Universal Resource Locator
Objectives
• Hypertext Transfer protocol
• HTTP features
• HTTP request-response
cycle
• HTTP Message Structure
World Wide Web
96
97. HYPER TEXT TRANSFER PROTOCOL
1. Web application-level protocol for distributed, collaborative, hypermedia
information .
2. Used for data exchange between client program and server program.
• HTTP
97
103. SUMMARY
Q.1 What is HTTP?
Q.2 What are the features of HTTP?
Q.3 How HTTP works or What is HTTP request-response cycle?
• Lecture 9: Hypertext Transfer
Protocol
103
106. LECTURE – 10
Recap
1. Hypertext Transfer protocol
2. HTTP features
3. HTTP request-response cycle
4. HTTP Message Structure
Objectives
• Domain Name System
• Components of Domain
Name System
• Name Space
• Domain Name Space
• Domain Name Server
Domain Name Server
106
107. DOMAIN NAME SYSTEM
1. It is standard protocol – application layer .
2. Directory services – that translates hostnames to IP addresses.
• Concept
107
109. DOMAIN NAME SYSTEM
1. A distributed database implemented in a hierarchy of DNS Server.
2. A protocol which allows hosts to query the distributed database.
• More Particular
109
110. DNS COMPONENTS
1. Namespace &
2. Domain Name space
3. Distibution of Namespace – Domain Name Server
4. DNS Message
5. DNS Record Types
• Terminologies
110
111. NAME SPACE
1. Unique mapping between IP address and Names.
2. Namespace types:
1. Flat Namespace :
The name (sequence of characters) in a space without structure.
Cannot be used in Large system.
Centrally controlled to avoid ambiguity and duplication.
2. Hierarchical Namespace
A name in space is made of several parts
Decentralized in nature
• Concept
111
112. DOMAIN NAME SPACE
1. To implement Hierarchical NS – Domain Name Space is designed.
2. Defined – inverted-tree structure with the root at the top.
3. Tree is fixed in Size – in terms of levels .
1. Has only 128 levels : level 0( root ) to level 127
• Concept
112
114. SUMMARY
Q.1 What is Domain Name System?
Q.2 What is NameSpace?
Q.3 What is Domain Name Space?
• Lecture 10 : Domain Name Server
114
115. ACTIVITY
Video : DNS Working
1. https://www.youtube.com/watch?v=mpQZVYPuDGU
2. https://www.youtube.com/watch?v=e2xLV7pCOLI
• Lecture 10 : Domain Name Server
115
117. LECTURE – 11
Recap
1. Domain Name System
2. Components of Domain Name System
3. Name Space
4. Domain Name Space
5. Domain Name Server
Objectives
• Domain Name Servers
• Hierarchy of Name Servers
• Zone & Domains
• Types of DNS server
• Types of Records
• DNS Working
Domain Name Server
117
118. DOMAIN NAME SERVER
1. The Domain Name Space is stored and distribute the information among
many computers – DNS servers.
2. Implemented – by dividing the whole domain name space to domain levels
( smaller domains)
• - Distrubution of Namespace
118
120. ZONE & DOMAINS
1. A portion of the DNS namespace - managed by a specific organization or
administrator.
2. A DNS zone is an administrative space which allows for more granular
control of DNS components.
• Concept
120
121. TYPES OF DNS SERVER
1. Root Server
2. Primary Server
3. Secondary Server
• 2 types of Server
121
123. DNS WORKING
1. A user types ‘reva.edu.in’ into a web browser.
2. The query travels into the Internet and is received by a DNS recursive
resolver.
3. The resolver then queries a DNS server.
4. The IP address for ‘reva.edu.in’ is then returned to the resolver from the
nameserver.
5. The DNS resolver then responds to the web browser with the IP address of
the domain requested initially.
• Step-by-step
123
124. SUMMARY
Q.1 What is Domain Name Server?
Q.2 Diffrence between Domain Name System & Domain Name Server?
Q.3 What is Zone?
Q.4 What are the types of DNS Servers?
Q.5 What are the step carried out to retrieve IP from DNS server?
• Lecture 11 : Domain Name Server
124
125. ACTIVITY
Video :
DNS Zone & Domains
1. https://www.youtube.com/watch?v=ci8jExvzVEY
2. https://www.youtube.com/watch?v=833Qnc-7-ug
DNS Works
1. https://www.youtube.com/watch?v=T-eghY-9WdE
• Lecture 11 : Domain Name Server
125
131. LECTURE – 12
Recap
1. Domain Name Servers
2. Hierarchy of Name Servers
3. Zone & Domains
4. Types of DNS server
5. Types of Records
6. DNS Working
Objectives
• Electronic Mail
• Email System & Subsystem
• Email Structure
• SMTP
• POP3 & IMAP
Email
131
132. ELECTRONIC MAIL
1. Messages distributed by electronic means from one computer user to one
or more recipients via a network.
2. Intially communicated – FTP
1. No internal message structure
2. No group message
3. Poor User interface.
4. Only Textual format.
• Concept
Limitations
132
133. EMAIL SYSTEM
1. Private e-mail system : Outlook , Thunder bird
2. Web-based e-mail system: gmail, yahoo
• 2 types
133
135. EMAIL STRUCTURE
1. Details -1 Header Meaning
• To • Primary recipient
• CC (carbon copy) • Secondary recipient
• BCC(Blind carbon copy) • Third pary receipient
• From • Person who created message
• Sender • Actual sender
• Received • Line added by each transfer agent along
the route.
135
136. EMAIL STRUCTURE
1. Details -2 Header Meaning
• Date • The date and time the message was sent.
• Reply to • Email address to which replies should be sent
• Message ID • Unique number for reffereing this message later
• In-reply To • Message-Id of the message to which this is a reply.
• References • Other relevant Message-Ids
• Keywords • User- choosen keywords
• Subject • Short summary of the message for the on-line display.
136
137. SIMPLE MAIL TRANSFER
PROTOCOL
1. It is part of application layer of the TCP/IP protocol.
2. Works on store and forward principle.
3. A method to transfer mail from one user to another.
4. Uses TCP connection (connects through port no : 25,465,2525)
5. Mail are pushed to SMTP servers.
• Message transfer agent
137
138. POP3 & IMAP
1. POP – Post office protocol
2. IMAP-Internet message access protocol
3. Both used to retrieve e-mail from a server – POP protocols.
4. POP3: protocol assumes that your email is being accessed only from one
application.(port no. 110 & 995)
5. IMAP: allows simultaneous access by multiple clients. ( port No. 143 & 993)
• Internet mail Protocols
138
139. SUMMARY
Q.1 What is E-mail?
Q.2 What are the functions of e-mail?
Q.3 What are the limitation of FTP use in e-mail?
Q.4 What is the message format of e-mail?
Q.5 What are the types of MTA or Internet mail transfer Protocol?
• Lecture 12 : Email
139
