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Guide To TCP/IP, Second Edition 1

Guide To TCP/IP, Second Edition

Chapter 1

Introducing TCP/IP

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Objectives

Understand TCP/IPs origins and history

Explain the process by which TCP/IP standards and otherdocuments, called Requests for Comments (RFCs), are

created, debated, and formalized (where appropriate) Understand the Open Systems Interconnection network

reference model, often used to characterize networkprotocols and services, and how it relates to TCP/IPs owninternal networking model

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Objectives (cont.)

Define the terms involved and explain how TCP/IP

protocols, sockets, and ports are identified

Understand data encapsulation and how it relates to the

four layers of the TCP/IP protocol stack

Understand and apply the basic practices and principles

that underlie network protocol analysis

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What is TCP/IP?

Large collection of networking protocols

and services

Two key protocols

Transmission Control Protocol (TCP)

Reliable delivery for messages

Internet Protocol (IP) Manages the routing of network transmissions

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Origins and History

1969, Department of Defense (DoD) andAdvanced Research Projects Agency (ARPA)funded research for packet-switched networking

The sender and receiver are identified by uniquenetwork addresses

Do not require all packets to follow the same path

in transit The network built as a result of this project is

known as the ARPANET

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TCP/IPs Design Goals

Withstand a potential nuclear strike

Need for packet switching

Permit different kinds of computer systems

to easily communicate

Need to interconnect systems across long

distances

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A TCP/IP Chronology

1978: Internet Protocol version 4 (IPv4) came intoexistence

1983: Defense Communications Agency tookover operation of the ARPANET

1986: National Science Foundation (NSF)launches a long-haul, high-speed network, known

as NSFNET 1987: Number of hosts on the Internet breaks

10,000

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A TCP/IP Chronology (cont.)

1989:

Number of hosts on the Internet breaks 100,000

NSFNET backbone upgraded to 1.544 megabits persecond (Mbps)

1990:

McGill University releases the Archie protocol andservice

Work begins on the Hypertext Transfer ProtocolWorldwide Web is born at Centre European Researche

Nucleaire (CERN)

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1991:

Commercial Internet Exchange (CIX) is formed

Wide Area Information Service (WAIS) protocol andservice allowing Internet searches of multimegabyte

databases

Gopher allows searching of text-based archives

1992: Internet Society (ISOC) is chartered

Number of hosts on the Internet breaks one million

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1992:

NSFNET backbone upgraded to 44.736 Mbps

CERN releases HTTP and Web server technology tothe public

1993:

Internet Network Information Center (InterNIC) is

chartered Mosaic, the first high-powered graphical browser

The U.S.White House goes online at whitehouse.gov

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1994:

U.S. Senate and House of Representatives establishinformation servers on the Internet

Online junk mail and shopping malls begin toproliferate

1995:

Netscape launches Netscape Navigator

Number of hosts on the Internet breaks five million

1996: Microsoft launches Internet Explorer Webbrowser

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1997: Number of registered domain names reaches

31 million

2000: Love Letter worm infects over one millionpersonal computers

2001:

Number of hosts on the Internet breaks 150 million

Sircam virus and Code Red worm infect thousands of

Web servers and e-mail accounts

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2002:

Number of hosts on the Internet breaks 204

millionThe Internet2 backbone utilizes native IP

version 6

2003: Public Interest Registry (PIR)assumes responsibility as .org registry

operator

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Who Owns TCP/IP?

TCP/IP falls squarely into the public

domain

Funded with public monies since its

inception

Both everybody and nobody own TCP/IP

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Meet the Standards Groups that Manage

TCP/IP Internet Society (ISOC)

Internet Architecture Board (IAB)

Internet Engineering Task Force (IETF)

Internet Research Task Force (IRTF)

Internet Societal Discussion Forum (ISDF) Internet Corporation for Assigned Names

and Numbers (ICANN)

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TCP/IP Standards and RFCs

Request For Comments (RFC)

www.faqs.org/rfcs

RFC 2026 describes how a RFC is created RFC status designations

Proposed Standard, Draft Standard, Internet

Standard, Retired Standard, and HistoricStandard

Best Current Practice (BCP)

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OSI Reference Model Overview

Network reference model

Formally (ISO/OSI )

Designed to replace TCP/IP

OSI model is the standard way to explain

how networks operate

TCP/IP remains the open standard protocol

suite of choice

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OSI Network Reference Model

Models break networking into layers

The OSI network reference model

How protocol layers behave Physical Layer Data Link Layer

Network Layer

Transport Layer Session Layer

Presentation Layer

Application Layer

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OSI Network Reference Model (cont.)

The reference model described in ISO

Standard 7498 breaks network

communication into seven layers

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Models Break Networking into Layers

Divide and conquer approach

Separate networking hardware concerns from

those related to networking software

Key points about networking Easier to solve problems when broken into layers

Layers operate independently of one another Changes to one layer need not affect other layers

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Models Break Networking into Layers

(cont.) Key points about networking (cont.)

Individual layers work together on pairs of computers

Different expertise is needed at each layer Layers working together is known as networking

Network protocols usually map into one or more layers

TCP/IP is designed around a layered model

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Seven Layers Of The OSI Model

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How Protocol Layers Behave

Layers exist to encapsulate or isolatespecific types of functionality

Layers provide services to the layer above Layers deliver data to or accept data from

the layer below

Protocol Data Units (PDUs) PDUs include envelope information in the

form of specific headers and trailers

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Physical and Data Link Layers

Physical Layer

Includes the physical transmission medium

Physical and electrical characteristics of the interfaces

PDUs consist of specific serial patterns of signals

Data Link Layer

Manages point-to-point transmission

Handles sequencing of data from sender to receiver Data transmission control: called media flow control

PDUs are specific bit patterns and are called frames ordata frames

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Network and Transport Layers

Network Layer

Logical addresses associated with individual machines

Uses logical addressing to determine how to send PDUtraffic to other physical segments

PDUs are structured data called a packet

Transport Layer

Ensure reliable end-to-end transmission of PDUs

Includes end-to-end error-detection and error-recovery

PDUs are structured numbered sequence data calledsegments or data segments

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Sessions and Presentation Layers

Sessions

Conversations are set up, maintained, and thenterminated

Includes mechanisms to maintain reliable ongoingconversations called checkpoints

PDUs at this level are Session PDUs, or SPDUs

Presentation

Manages how data is presented to the network and to aspecific machine/application

PDUs are generically called Presentation PDUs

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Application Layer

Defines an interface that applications can

use to request network services

Defines a set of access controls over thenetwork

PDUs are generically called Application

PDUs

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OSI and TCP/IP Models

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TCP/IP Network Access Layer

Includes Ethernet, token ring, and wireless media

Includes WAN and connection-management

protocols Include the IEEE 802 family of standards

802.1 Internetworking

802.2 Media Access Control

802.3 CSMA/CD

802.5 Token Ring

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TCP/IP Network Access Layer Protocols

High-level Data Link Control (HDLC)

Frame Relay

Asynchronous Transfer Mode (ATM)

PPP and SLIP

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TCP/IP Internet Layer Functions

Handle routing between machines across

multiple networks

MTU fragmentation

Addressing

Routing

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TCP/IP Internet Layer Protocols

Internet Protocol (IP)

Internet Control Message Protocol (ICMP)

Packet Internetwork Groper (PING)

Address Resolution Protocol (ARP)

Routing Information Protocol (RIP)

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TCP/IP Transport Layer Functions

Functions

Reliable delivery of data from sender to receiver

Fragmentation of outgoing messages and theirreassembly prior to delivery to the Application layer

Protocols

Transmission Control Protocol (TCP)

Connection oriented

User Datagram Protocol (UDP)

Connectionless

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TCP/IP Application Layer

Function

Interfaces with applications or processes on a

host machine

Protocol and Services

File Transfer Protocol (FTP)

Telnet

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TCP/IP Protocols, Services, Sockets, And Ports

TCP/IP protocol numbers

Protocol numbers are used to identify distinct protocols,

and those protocols use port numbers

TCP/IP port numbers

TCP/IP application are identified by port numbers

The source or destination port number identifies the

process that sent or receives, respectively, the data

TCP/IP sockets

Dynamically assigned port address is called a socket

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TCP/IP Protocol Numbers

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Data Encapsulation In TCP/IP

Outgoing data is packaged and identified for

delivery to the layer underneath

Incoming data has its encapsulating informationfrom the underlying layer stripped off before its

delivered to its upper-layer

Each PDU has an opening component, called a

header, and closing component called a trailer

Data portion of the PDU is known as the payload

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About Protocol Analysis

Protocol analysis is the process of

Tapping into the network communications

systemCapturing packets

Gathering network statistics

Decoding packets

Protocol analyzers can also transmit packets

A task for testing a network or device

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Roles for Protocol Analysis

Used to troubleshoot network

communications

Used to test networksPassive

Active

Gather trends on network performance

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Protocol Analyzer Elements

Promiscuous mode card and driver

Packet filters

Trace buffer

Decodes

Alarms

Statistics

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Network Analyzer Process

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Decodes

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Statistics

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Placing a Protocol Analyzer on a Network

Hubbing out

Placing a hub between a device of interest and the

switch, and connecting the analyzer to the hub

Port redirection

Switches can be configured to redirect (to copy) the

packets traveling through one port to another port

Remote monitoring (RMON) Collect traffic data at a remote switch and send the data

to a management device

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Analyzer Placement Example

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Chapter Summary

TCP/IP was designed with the following goals inmind

(1) To support multiple, packet-switched pathways

through the network so that transmissions can surviveall conceivable failures

(2) To permit dissimilar computer systems to easilyexchange data

(3) To offer robust, reliable delivery services for bothshort- and long-haul communications

(4) To provide comprehensive network access withglobal scope

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Chapter Summary (cont.)

Initial implementations of TCP/IP were funded under the

auspices of the ARPA and Department of Defense

Until the late 1980s, the ARPANET remained largely in

government hands and supported by government funding

TCP/IP remains in the public domain as an open and

collaborative set of standards and best practices

The documents that govern TCP/IP standards and practices

are called RFCs, and the process of their creation,development, and approval involves representatives from

government, industry, research, and academia

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The standards creation and management processes

fall within the IETF, and final approval of Internet

standards rests in its parent organization, the IAB

Although the process of creating such standards is

rightfully called rough consensus , this process

works well enough to define literally hundreds of

protocols and services used every day on theInternet

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As Standard RFCs go through the approval process, they

begin life as Proposed Standard documents

After discussion and debate, and demonstration that two or

more separate reference implementations can successfullyinteroperate, RFCs can become Draft Standards

After further discussion and revisions, and approval from

the parent working group within the IETF, the Draft is

turned over to the IAB for final approval When the Draft is approved, it becomes a Standard RFC

(sometimes called an Internet Standard)

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Another popular type of RFC is an informational (non-

standard) RFC called a Best Current Practice, or BCP

Although these documents do not have the force of a

Standard RFC, they do provide useful information thatrepresents best approaches to designing, configuring,

implementing, or maintaining TCP/IP-based networks and

related services

For those reasons, BCPs are highly regarded and can beuseful tools for network administrators seeking to make the

most out of their TCP/IP networks

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In general, networking is a big, complex problem that is

most easily solved if broken up into a series of smaller,

less-complex, and interrelated problems

The ISO/OSI network reference model breaks networkinginto seven distinct layers that allow issues related to

hardware, media, and signaling to be separated from issues

related to software and services

Likewise, this model permits activities in software to bedistinguished on the basis of machine-to-machine

communications

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This communication involves handling informationdelivery from any sender to any receiver, moving largeamounts of data across the network, and handling various

issues related to ongoing communications, data formats,and application interfaces for network access

TCP/IP uses an older, simpler, four-layer model that lumpsthe latter three issues into a single application/serviceslayer, but is otherwise very much like the ISO/OSI

reference model TCP/IP uses a variety of encapsulation techniques at its

various layers to label the type of data contained in thecontents, or payloads, of its PDUs

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TCP/IP also uses numbering techniques to identify well-known protocols at the lower layers (protocol numbers)and to support ready access to well-known applications

and services at upper layers (well-known ports) When a client makes a request to a server that requires an

ongoing exchange of information, a listening process onthe server creates a temporary connection that combines acomputers numeric IP address with a specific port address

for the process involved (called a socket address) This ensures that the right process on the right computer

may be accessed on both sending and receiving machines

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Protocol analysis is a process whereby a network interfaceis used to inspect all traffic moving across a segment ofnetwork medium

Protocol analyzers are software programs that can managethis task and can capture not only healthy (properlyformed) traffic, but also erroneous or ill-formed traffic

This lets protocol analyzers characterize network traffic ona descriptive basis (the protocols used, the active station

addresses, the conversations, and the parties involved), andon a statistical basis (percentage of errors, percentage oftraffic per protocol, peak loads, low loads, average loads,and so forth)

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G ide To TCP/IP Second Edition 55


Much of the remaining text depends on putting the

topical and theoretical discussions about TCP/IP

protocols together with the traces and decodes

(formatted contents of packets) to see how theory

and practice fit together

TCP/IP Chap 01

Documents

Transcript of TCP/IP Chap 01