ccna1 m11 tcpip transport application

8/14/2019 CCNA1 M11 TCPIP Transport Application

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CCNA Semester1

Module 11

TCP/IP Appl ic at ion and Tr ansport

Objectives

Functions of the TCP/IP transport layer

TCP concepts and processes

TCP/IP application layer


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TCP/IP Transport Layer

Why we need a transport layer?

Layer 1 allows bit streams to be createdand to travel.

Layer 2 packages those data packets into

frames to be converted to bit streams andmakes data-link delivery possible.

Layer 3 packages data from upper layers inpackets and makes routing and networkdelivery possible.

But they made no provision for assuringour data reliably travels end-to-end acrossthe vast network path.

But they made no provision for assuringour data reliably travels end-to-end across

the vast network path.


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Introduction to transport layer

The transport layer data stream is a logicalconnection between the endpoints of a network.

Its primary duties are to transport and regulate theflow of information from source to destination

reliably and accurately. Transport services include the following basic

services: Segmentation of upper-layer application data

Establishment of end-to-end operations

Transport of segments from one end host to another end host

Flow control provided by sliding windows

Reliability provided by sequence numbers and

acknowledgments

Flow Control

Avoids the problem of a host at one side ofthe connection overflowing the buffers in thehost at the other side.

The two hosts then establish a data-transferrate that is agreeable to both.

Ensures the integrity of the data


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Session Establishment

Multiple applications can share the same transportconnection in the OSI reference model.

Different applications can send data segments on a first-come, first-served basis. This is referred to as the

multiplexing of upper-layer conversations.

TCP and UDP

The emphasis of this curriculum is onTCP/IP Ethernet networks.

The TCP/IP protocol of the OSI model Layer

4 (transport layer) has two protocols - TCPand UDP.


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TCP/IP Protocol Stack

Port

Both TCP and UDP use port (or socket)numbers to pass information to the upperlayers.

RFCRFC--17

0017

00


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Range of ports

2 bytes: 0 65535. Numbers below 255 : for public applications.

Numbers from 255 - 1023 : assigned to companiesfor marketable applications.

Numbers above 1023 : are unregulated.

End systems use port numbers to selectproper applications.

Originating source port numbers aredynamically assigned by the source host;usually, it is a number larger than 1023.

TCP

TCP supplies a virtual circuit between end-userapplications. These are its characteristics:

connection-oriented.

reliable.

divides outgoing messages into segments.

reassembles messages at the destination station.

re-sends anything not received.

Protocols that use TCP include FTP, SMTP, HTTP,Telnet


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TCP Header format

Protocol that provides reliable full-duplexdata transmission.

RFCRFC--7

61

761

TCP Header format: Port number

Source Port 16 bits.

Destination Port 16 bits.

Source Port 16 bits.

Destination Port 16 bits.


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TCP Header format: Sequence

Sequence Number: 32 bits

The sequence number of thefirst data octet in this segment

(except when SYN is present).

Sequence Number: 32 bits

The sequence number of thefirst data octet in this segment

(except when SYN is present).

TCP Header format: Acknowledgment

Acknowledgment Number: 32 bits

This field contains the value of thenext sequence number the sender ofthe segment is expecting to receive.

Acknowledgment Number: 32 bits

This field contains the value of thenext sequence number the sender ofthe segment is expecting to receive.


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TCP Header format: Code bits

Control Bits: 8 bits

ACK: Acknowledgment field significant

RST: Reset the connection

SYN: Synchronize sequence numbers

FIN: No more data from sender

Control Bits: 8 bits

ACK: Acknowledgment field significant

RST: Reset the connection

SYN: Synchronize sequence numbers

FIN: No more data from sender

TCP Header format: Window

Window: 16 bits

The number of data octets beginning

with the one indicated in theacknowledgment field which the senderof this segment is willing to accept.

Window: 16 bits

The number of data octets beginningwith the one indicated in theacknowledgment field which the senderof this segment is willing to accept.


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Three-way handshake

TCP: Simple acknowledgment


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TCP: Sliding window acknowledgment

TCP: Sequence and acknowledgment


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UDP

UDP transports data unreliably between hosts.Following are the characteristics:

Connectionless.

Unreliable. Transmit messages (called user datagrams).

Provides no software checking for message delivery(unreliable).

Does not reassemble incoming messages.

Uses no acknowledgements.

Protocols that use include TFTP, SNMP, DHCP, DNS

UDP Header format

UDP is a simple protocol that exchangesdatagrams, without acknowledgments or

guaranteed delivery.

RFCRFC--76

876

8


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TCP/IP Application Layer

Application Layer: TCP/IP vs. OSI

The session and presentation layers from theOSI model were bundled into the applicationlayer of the TCP model.

This means that issues of representation,encoding, and dialog control are handled in theapplication layer rather than in separate lowerlayers as in the OSI model.


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Session: Functions

Presentation: Functions


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TCP/IP Application Layer

Handles high-levelprotocols, issues ofrepresentation, encoding,and dialog control.

The TCP/IP combines allapplication-related issuesinto one layer, and assuresthis data is properlypackaged for the next layer.

FTP, HTTP, SMTP, DNS,SNMP ...

Format of data, datastructure, encode

Dialog control, sessionmanagement

Interfaces

Direct network application:

The application layer provides a direct interface for the rest ofthe OSI model by using network applications.

Client server: WEB, FTP, Mail

Indirect network application: The application layer provides an indirect interface for the restof the OSI model by using standalone applications.

The redirector directs requests from local computer to theproper network resources. Applications on client never have torecognize the network.

Redirector: network driver, network printer


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Client-Server application

The client side is located on the localcomputer and is the requestor of theservices.

The server side is located on a remotecomputer and provides services inresponse to the clients requests.

The client side is located on the localcomputer and is the requestor of theservices.

The server side is located on a remotecomputer and provides services inresponse to the clients requests.

Network driver

The applications on the client never haveto recognize the network.

Redirectors expand the capabilities ofnon-network software.

The applications on the client never haveto recognize the network.

Redirectors expand the capabilities ofnon-network software.


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Make and Break a connection

The connection to the server wasmaintained only long enough to processthe transaction.

Example : WWW, E-mail

The connection to the server wasmaintained until the user determines thathe/she has finished.

Example : FTP, Telnet

DNS

The Domain Name System (DNS) is a systemused on the Internet for translating names ofdomains and their publicly advertised network

nodes into IP addresses. A domain is a group of computers that are

associated by their geographical location ortheir business type.

The DNS system is set up in a hierarchy thatcreates different levels of DNS servers.

Eg: http://www.cdit.com.vn/itc/


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DNS: System

vnnvnn comcom eduedu govgov

comcom eduedu govgov ukukfrfrvnvn

.

DNS: Resolve www.yahoo.com

vnnvnn yahooyahoo

comcomvnvn

.

Address

of com

server

Address

ofcom

serverAddress of

yahoo.com

server

Address of

yahoo.com

server

Address of

www.yahoo.com

Address of

www.yahoo.com

Address ofwww.yahoo.com

Address ofwww.yahoo.com

RequestRequestRequest

ReplyReplyReply


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FTP

File Transfer Protocol (FTP) is a reliable,connection-oriented service that uses TCP totransfer files between systems that support FTP.

When files are copied from a server, FTP firstestablishes a control connection between theclient and the server. Then a second connectionis established, which is a link between thecomputers through which the data istransferred.

TFTP

Trivial File Transfer Protocol (TFTP) is aconnectionless service that uses UDP.

TFTP is designed to be small and easy toimplement.

TFTP is used on the router to transferconfiguration files and Cisco IOS imagesand to transfer files between systems thatsupport TFTP.

TFTP can read, write, or mail files to or froma remote server but it cannot list directories

and currently has no provisions for userauthentication.


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HTTP

Hypertext Transfer Protocol (HTTP) works with theWorld Wide Web, which is the fastest growing and mostused part of the Internet.

A Web browser is a client-server application, which

means that it requires both a client and a servercomponent in order to function.

A Web browser presents data in multimedia formats. Ahyperlink is an object, word, phrase, or picture, on aWeb page. When that hyperlink is clicked, it directs thebrowser to a new Web page.

The Web page contains, often hidden within its HTMLdescription, an address location known as a Uniform

Resource Locator (URL).

Telnet

Telnet client software provides the ability tologin to a remote Internet host that is running aTelnet server application and then to executecommands from the command line.

Telnet works at the application layer of theTCP/IP model. Therefore, Telnet works at the topthree layers of the OSI model. The applicationlayer deals with commands. The presentationlayer handles formatting, usually ASCII. Thesession layer transmits.


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SMTP

Email servers communicatewith each other using theSimple Mail TransferProtocol (SMTP) to sendand receive mail. The SMTPprotocol transports emailmessages in ASCII formatusing TCP.

The most popular mailclient protocols are POP3and IMAP4, which both useTCP to transport data.

A good way to test if a mail

server is reachable is toTelnet to the SMTP port (25)or to the POP3 port (110).

SNMP

The Simple NetworkManagement Protocol (SNMP)is an application layer protocolthat facilitates the exchange ofmanagement information

between network devices.

An SNMP managed networkconsists of the following:

Network managementsystem (NMS)

Managed device

Agents


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Lab Companion

11.2.4 Protocol Inspector, TCP and HTTP

Summary

TCP/IP transport layer functions

TCP concepts and processes

TCP and UDP header format

TCP and UDP port TCP/IP application layer functions

TCP/IP application layer protocols


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ccna1 m11 tcpip transport application

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