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Chapter 1
Introduction
TCP/IP Assignment
-by Harshwardhan Pusadkar
Bhavesh Bhandarkar

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OBJECTIVES:
 To give a brief history of the Internet.
 To give the definition of the two often-used terms in the
discussion of the Internet: protocol and standard.
 To categorize standard organizations involved in the Internet
and give a brief discussion of each.
 To define Internet Standards and explain the mechanism
through which these standards are developed.
 To discuss the Internet administration and give a brief
description of each branch.

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Chapter
Outline
1.1 A Brief History
1.2 Protocols and Standards
1.3 Standards Organizations
1.4 Internet Standards
1.5 Internet Administration

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1-1 A BRIEF HISTORY
A network is a group of connected, communicating
devices such as computers and printers. An internet
is two or more networks that can communicate with
each other. The most notable internet is called the
internet, composed of hundreds of thousands of
interconnected networks. Private individuals as well
as various organizations such as government
agencies, schools, research facilities, corporations,
and libraries in more than 100 countries use the
Internet.

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Topics Discussed in the Section
ARPANET
Birth of the Internet
TCP/IP
MILNET
CSNET
NSFNET
ANSNET
The Internet Today
World Wide Web
Growth of the Internet

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Figure 1.1 Internet today

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1-2 PROTOCOLS AND STANDARDS
In this section, we define two widely used terms:
protocols and standards. First, we define protocol,
which is synonymous with “rule.” Then we discuss
standards, which are agreed-upon rules.

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Topics Discussed in the Section
Protocols
Standards

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1-3 STANDARDS ORGANIZATION
Standards are developed through the cooperation
of standards creation committees, forums, and
government regulatory agencies.

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Topics Discussed in the Section
Standards Creation Committees
Forums
Regulatory Agencies

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1-4 INTERNET STANDARDS
An Internet standard is a thoroughly tested
specification that is useful to and adhered to by
those who work with the Internet. It is a formalized
regulation that must be followed. There is a strict
procedure by which a specification attains Internet
standard status. A specification begins as an
Internet draft. An Internet draft is a working
document with no official status and a six-month
lifetime.

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Topics Discussed in the Section
Maturity Levels
Requirement Levels

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Figure 1.2 Maturity levels of an RFC

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Figure 1.3 Requirement levels of an RFC

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1-5 INTERNET ADMINISTRATION
The Internet, with its roots primarily in the research
domain, has evolved and gained a broader user
base with significant commercial activity. Various
groups that coordinate Internet issues have guided
this growth and development. Appendix G gives the
addresses, e-mail addresses, and telephone
numbers for some of these groups. Figure 1.4
shows the general organization of Internet
administration.

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INTERNET ARCHITECTURE
• Sometimes called TCP/IP
• Evolved from an earlier packet-switched network called ARPANET
• Internet and ARPANET were funded by ARPA (Advanced Research Projects Agency)
• Both existed before the OSI architecture
• Both affected the OSI model

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INTERNET ARCHITECTURE
Internet Protocol Graph
Alternative view of the Internet
architecture. The “Network”
layer shown here is sometimes
referred to as the “sub-
network” or “link” layer.

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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 (host-to-host connectivity is separate from all channel types)
• 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

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INTERNET ARCHITECTURE
• NET1, NET2, …
• Could be Ethernet, Wireless, etc.
• Encapsulate both hardware and data link layers from OSI model
• IP (Internet Protocol)
• Supports the interconnection of multiple networking technologies into a single logical
internetwork
• Analogy to the network layer in the OSI
• The routing protocol

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INTERNET ARCHITECTURE
• TCP provides reliable, byte-stream channel (connection oriented protocol)
• UDP provides unreliable, datagram (message) delivery channel.
• TCP and UDP are called (besides Transport) end-to-end protocols

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INTERNET ARCHITECTURE
• Application Protocols
• HTTP, FTP, Telnet (remote login), Simple Mail Transfer Protocol (SMTP), and much
more
• Enables the interoperation of popular applications
• Many different web browsers interoperate with web servers because they all conform/use the HTTP
protocol

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NETWORK ARCHITECTURE
Example of a layered network system

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NETWORK ARCHITECTURE
Layered system with alternative abstractions available at a given layer

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Figure 1.4 Internet administration

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CONNECTIVITY
• Need to understand the following terminologies
• Scale: A system that is designed to support growth to an arbitrarily large size
• Link: Physical medium that connects nodes
• Node: a device (could be a computer, switch, etc) on the network
• Point-to-point: direct link between two nodes
• Multiple access: multiple nodes share the same link
(a) Point-to-point
(b) Multiple access

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CONNECTIVITY
• Switched Network: a network that uses switches for forwarding
• Circuit Switched
• Telephone companies
• Dedicated/reserved when connection is established
• Less utilization of the resources
• Packet Switched
• Overwhelming majority of computer networks
• Messages are divided into pieces (discrete blocks) called packets
• No dedication is required
• More sharing, thus more utilization
• Store-and-forward: a switch stores the incoming traffic (packets) in its own buffers
then forwards them.

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CONNECTIVITY
• Cloud: used to represent any kind of network technology
• Point-to-point, multiple-access, or switched network
• Hosts: nodes outside the cloud (usually computer or end users devices and use the
network)
• Switches: nodes inside the cloud and implement the network (store and forward
packets)
• Internetwork (or internet with small “i”): a set of independent interconnected
networks (clouds)
• Internet (with big “I”): is the globally known network

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CONNECTIVITY
• Router/gateway: connects two or more networks (plays much the same role as a switch—stores and
forwards)
• Host-to-host connectivity: hosts can talk to hosts
• Address: the way to find nodes. It is a byte string that identifies a node.
• Routing: the process of determining systematically how to forward messages toward the destination node
based on its address
• Unicast: send to single destination
• Broadcast: send to all nodes on the network
• Multicast: send to subset of nodes

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CONNECTIVITY
(a) A switched network
(b) Interconnection of networks
(a) (b)

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LAN, MAN, WAN, AND SAN
• Characterize networks according to their size (they usually use diff. technologies):
• LAN: Local Area Network, typically less than 1km
• WAN: Wide Area Network, worldwide
• MAN: Metropolitan Area Network, tens of kilometers
• SAN: Systems/Storage Area Network, single room that has high-performance
components (like leading-edge storage devices) connected together

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ABSTRACTION AND LAYERING
• Abstraction
• The hiding of details behind a well-defined interface
• Define a model
• Capture important aspects of the system
• Abstractions naturally leads to layering
• The general idea
• Start from services offered by the underlying hardware
• Add a sequence of layers, each providing a higher (i.e., more abstract) level of service.
• Manageability and Mudularity

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PROTOCOALS
• The abstract objects the make up the layers of a network system
are called protocols
• Building blocks of a network architecture
• Each protocol object has two differentinterfaces
• service interface: operations on this protocol
• peer-to-peer interface: messages exchanged with peer (indirect
communication, except for the hardware)

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INTERFACES
Service and Peer Interfaces

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PROTOCOLS
• Protocol Specification:
• Written description (prose)
• pseudo-code
• state transition diagram
• Packet format
• RFCs: Request For Comments
• IETF: Internet Engineering Task Force
• Standardization body
• Ex. RFC 2616 for HTTP protocol
• Interoperable: when two or more protocols that implement the specification accurately

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PROTOCOL GRAPH
Example of a protocol graph
nodes are the protocols and links the “depends-on” relation

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

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ABSTRACTION AND LAYERING
• Abstraction
• The hiding of details behind a well-defined interface
• Define a model
• Capture important aspects of the system
• Abstractions naturally leads to layering
• The general idea
• Start from services offered by the underlying hardware
• Add a sequence of layers, each providing a higher (i.e., more abstract) level of service.
• Manageability and Mudularity

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APPLICATION PROGRAMMING INTERFACE
• 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, when we refer to the interface
“exported by the network”, we are generally referring to the interface that the
OS provides to its networking subsystem
• The interface is called the network Application Programming Interface (API)

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APPLICATION PROGRAMMING INTERFACE (SOCKETS)
• Socket Interface was originally provided by the Berkeley
distribution of Unix
- Now supported in virtually all operating systems
• Each protocol provides a certain set of services, and the API
provides a syntax by which those services can be invoked in this
particular OS

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SOCKET
• What is a socket?
• The point where a local application process attaches to the network
• An interface between an application and the network
• An application creates the socket
• The interface defines operations for
• Creating a socket
• Attaching a socket to the network
• Sending and receiving messages through the socket
• Closing the socket

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BANDWIDTH
• Frequency band (measured in Hertz): we don’t mean that
• Number of bits per second that can be transmitted over a communication link
• Throughput vs. bandwidth (from the most confusing terms in computer networks.
• Bandwidth: the maximum data rate (bits per second)
• Throughput: number of bits per second that we actually transmit over the link in practice
• 1 Mbps: 1 x 106 bits/second = 1x220 bits/sec
• 1 x 10-6 seconds to transmit each bit or imagine that a timeline, now each bit occupies 1
micro second space.
• On a 2 Mbps link the width is 0.5 micro second.
• Smaller the width more will be transmission per unit time.

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BANDWIDTH
Bits transmitted at a particular bandwidth can be regarded as having
some width:
(a) bits transmitted at 1Mbps (each bit 1 μs wide);
(b) bits transmitted at 2Mbps (each bit 0.5 μs wide).

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LATENCY
• How long it takes a message to travel from one end of a network to the other.
• Measured in time

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LATENCY
• Three components
• Speed-of-light propagation delay
• Different media at different speeds
• 3.0 × 108 m/s in a vacuum
• 2.3 × 108 m/s in copper cable
• 2.0 × 108 m/s in optical fiber
• Amount of time to transmit a unit of data
• Queuing delays (switches store packets)

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THANK YOU!