Overview of TCP-IP suite

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N. Ganesan, All rights reserved.

Chapter

Overview of TCP/IP


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Reference

Highly Recommended:

TCP/IP White Paper by Microsoft
http://www.microsoft.com/NTServer/nts/techdetails/compares/TCPIntrowp.asp?RLD=264http://www.microsoft.com/NTServer/nts/techdetails/compares/TCPIntrowp.asp?RLD=264


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Questions

How many layers are there in the TCP/IP model?How do they relate to the ISO-OSI model?

What are some of the TCP/IP related protocols? Explain the purpose and function of the above

protocols?

What are ports? Explain the implication of keeping

the ports open. How can the ports be protected fromhacker attacks?

Where would one use the UDP protocol in place ofthe TCP protocol?


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Chapter Modules

TCP/IP Overview and Layers

TCP/IP Related Protocols

TCP/IP Ports and Windows API


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Module

Overview of TCP/IP


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TCP/IP

A highly standardized protocol usedwidely on the Internet

Standards area available in the form ofRFC documents

Request For Comments (RFC)

Standards are overseen by the InternetEngineering Task Force (IETF)
http://www.ietf.org/rfc/http://www.ietf.org/http://www.ietf.org/http://www.ietf.org/http://www.ietf.org/http://www.ietf.org/rfc/


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Layers of TCP/IP ReferenceModel

There are four layers of the TCP/IP referencemodel (DARPA model as named by the US

Government Agency) The ISO-OSI reference model is composed of

seven layers

The next slide shows the mapping of the

ISO/OSI model to the TCP/IP model Note that the ISO/OSI model is more widely

used and accepted but the TCP/IP model iseasy to comprehend


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ISO-OSI Seven Layer ModelRecalled

Layer 7 ApplicationLayer 6 PresentationLayer 5

Session

Layer 4 TransportLayer 3 NetworkLayer 2 Data LinkLayer 1 Physical

Source: http://starter.sdsu.edu/remote/demo/osi-tcp.html
http://starter.sdsu.edu/remote/demo/osi-tcp.htmlhttp://starter.sdsu.edu/remote/demo/osi-tcp.htmlhttp://starter.sdsu.edu/remote/demo/osi-tcp.htmlhttp://starter.sdsu.edu/remote/demo/osi-tcp.html


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Comparison of ISO-OSI Modeland the DOD (TCP/IP) Model

ApplicationApplicationPresentation

SessionTransport

Host-to-Host

Network InternetData Link

Network AccessPhysical



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Layer Reference to ProtocolRecalled

ApplicationApplication FTP, Telnet, SMTP, HTTP..

PresentationSessionTransport Host-to-Host TCP, UDPNetwork Internet IP, ICMP, IGMPData Link Network

Access Ethernet, Token-Ring ...Physical



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Source: TCP/IP White Paper by Microsoft


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TCP/IP Layers

Network interface layer

Internet layer

Host-to-host transport layer

Application layer


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Layer Properties

In the following slides, the following isdescribed for each layer

Layer function

Core protocols

Relationship to ISO/OSI model


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Network Interface Layer

Responsible for sending and receivingTCP/IP packets on the network medium

(physical/Data Link) Applicable LAN technologies

Ethernet, Token Ring, FDDI etc.

Applicable WAN technologies

X.25 (old), Frame Relay, ATM etc. Note that some technologies such as ATM

and FDDI may be used at both the WAN andthe LAN levels


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Some Core Protocols

IEEE 802.3, IEEE 802.5 and IEEE 802.11series of protocols


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Relationship to OSI Model

Data Link Layer

Physical Layer

Network InterfaceLayer


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Core Internet Layer Protocols

IP A connectionless unreliable protocol that is part of

the TCP/IP protocol suite

ARP (Address Resolution Protocol) Resolves IP addresses to MAC addresses

ICMP (Internet Control Message Protocol)

Diagnostics and error reporting (IGMP) Internet Group Management Protocol

Management of group multicast


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More on Address ResolutionProtocol (ARP)

NIC ID

AA.BB.CC.DD

NIC ID

AB.BD.CD.DE

130.182.190.90 130.182.190.50

Resolves, for example, IP addresses to the corresponding

MAC level hardware address by for instance broadcasting.

IP

HAW


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Relationship to ISO Model

Network Layer Internet Layer


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Transport Layer

Sequencing and transmission of packets

Acknowledgment of receipts

Recovery of packets

Flow control

In essence, it engages in host-to-hosttransportation of data packets and thedelivery of them to the application layer


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Core Protocols of the TransportLayer

TCP(Transmission

Control Protocol)

UDP (UserDatagram Protocol)

Transport Layer


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TCP

Transmission Control Protocol (TCP)

One-to-one and connection-oriented

reliable protocol Used in the accurate transmission of

large amount of data

Slower compared to UDP because ofadditional error checking beingperformed


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UDP

User Datagram Protocol (UDP) One-to-one or one-to-many,connectionless and

unreliable protocol

Used for the transmission of small amount of data Accuracy is not of prime concern The overhead of establishing a TCP connection is not

warranted

Used in video and audio casting

Multicasting Broadcasting

Also used for multimedia transmission Faster compared to TCP


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Transport Layerand somefunctions of theSession Layer

Transport Layer


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Application Layer

Provides applications with the ability toaccess the services of the other layers

New protocols and services are alwaysbeing developed in this category


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Some Core Protocols

HTTP

FTP

Telnet

SMTP

POP3 IMAP

SNMP etc.


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End of Module


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Some Application RelatedApplication Layer Protocols

HTTP

FTP

SMTP

Telnet


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Some LAN

Management/Operation RelatedApplication Layer Protocols

DNS

RIP

SNMP

f l


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Hyper Text Transfer Protocol(HTTP)

Protocol relating to web applications

Current version of HTTP 1.1 hasadditional features Upload information to the server

Etc.

Default port number is 80


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File Transfer Protocol (FTP)

File Transfer Protocol Used for downloading from most MP3 sites, for

example

Designed for faster file transfer over theInternet compared to using the HTTPprotocol

FTP sites can be configured alongside a website to support FTP file transfer

FTP default ports are 20 and 21


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Si l M il T f P l


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Simple Mail Transfer Protocol(SMTP)

Governs the transmission of mailmessages and attachments

SMTP is used in the case of outgoingmessages

More powerful protocols such as POP3

and IMAP4 are needed and available tomanage incoming messages


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POP3/IMAP4

Used for incoming mail

POP3 is the older protocol

IMAP4 is the more advanced protocol


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Telnet

Supports terminal emulation or hostsessions

For example, Telnet can be used foraccessing a Unix machine andemulating a terminal attached to the

Unix computer


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R ti I f ti P t l


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Routing Information Protocol(RIP)

Router

Network 1

Network 2

Used by Routers to routedata packets on an IP Internet.

Network 1

Si l N t k M t


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Simple Network ManagementProtocol (SNMP)

Router

Router

RemoteManagement

Console

Switch

Bridge

Facilitates the management of SNMP compliantrouters, bridges, switches etc. by enablingthe collection and exchange of

network management information.


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SNMP

Used by network management utilitiesto manage network devices

For example, a manageable hub thatsupport SNMP can be managed from aremote location using a SNMP based

LAN management software


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PresentationLayer

Application Layer


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End of Module


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Module

TCP/IP Ports and Windows API


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Ports

TCP requires port numbers on the hostand destination for communication

Different port numbers are assigned todifferent protocols by defaultHTTP 80, Telnet 23, FTP 20/21, RPC 135,

NetBIOS 139 etc.

Standard port numbers have beenassigned by the Internet AssignedNumber Authority (IANA)


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Sample TCP Port Numbers

20 FTP Data Channel

21 FTP Control Channel

23 Telnet

80 HTTP on WWW

135 RPC

139 NetBIOS SessionServices

Note: There are port numbers applicable to UDP as well.


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Port Scanning

To test the security of a computer, its portscan be scanned and the port status can bedisplayed

Access Shieldup in www.grc.comto scanyour computers port

Ports

Open is insecure Closedis somewhat secure

Stealthis most secure
http://www.grc.com/http://www.grc.com/


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TCP/IP Application Interface

Applications require an ApplicationProgramming Interface (API) to use the

services of TCP/IP

API is a standardized interface between theapplications and the TCP/IP services

Windows Sockets interface and NetBIOSinterface are two of the prominent examplesof Windows API


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WindowsAPI with

TCP/IP


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Windows APIs

Windows socket

Protocol, IP Address and Port number

NetBIOS interface NetBIOS over TCP/IP (NetBT)

Supports NetBIOS Name Management, NetBIOSDatagram and NetBIOS sessions

If support is required for older NetBIOSapplications, then NetBIOS over TCP/IP must beinvoked in the TCP/IP properties tab


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Other References

TCP/IP, MCSE Examcram, Tittel Ed.,Hudson Kurt and Stewart Michael J.,

The Coriolis Group, 1998.


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End of Module


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End of Module

END OF CHAPTER

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Overview of TCP-IP suite