APPLICATION LAYER

Chapter 10

Intro to Routing & Switching

OBJECTIVES Upon completion of this chapter, you

should be able to: Explain how the functions of the application layer, session

layer, and presentation layer work together to provide network services to end user applications.

Describe how common application layer protocols interact with end user applications.

Describe common application layer protocols that provide Internet services to end-users, including WWW services and email.

Describe application layer protocols that provide IP addressing services, including DNS and DHCP.

Describe the features and operation of well-known application layer protocols that allow for file sharing services.

Explain how data is moved across the network, from opening an application to receiving data.

APPLICATION, PRESENTATION, & SESSION

10.1

MODEL REVIEW

APPLICATION LAYER Provides the interface between the

applications we use to communicate & the network

Used to exchange data between source & destination

What are some of the application layer protocols?

PRESENTATION LAYER

Formats data so it can be read Compress/decompress data Encrypt/decrypt data

MPEG, JPG, GIF

APPLICATION LAYER PROTOCOLS- PART 1

DNSNames to IP addresses

TelnetRemote access to

servers/switches/routers/devices DHCP

Automatically assign IP/SM/DG/DNS server addresses

BOOTPOlder version of DHCP

APPLICATION LAYER PROTOCOLS- PART 2

HTTP Transfers web pages

FTP File transfer

SMTP Transfers email

POP Gets email from email server to client Then deleted from server

IMAP Gets email from email server to client Kept on server until you delete it

ACTIVITY 10.1.1.5

REVIEW- 5Q What 3 OSI layers are similar to the

TCP/IP Application Layer? Application, Presentation, Session

What are 3 functions of the Presentation Layer? Data formatting, compression, encryption

Name some application layer protocols. DNS, DHCP, Telnet, POP, IMAP, SMTP, FTP,

HTTP, BOOTP What protocol handles web transfer?

HTTP What protocol handles file transfer?

FTP

HOW THE PROTOCOLS INTERACT WITH

APPLICATIONS

10.1.1

PEER TO PEER NETWORKS

2 or more connected computers with NO SERVERShares files on each other’s HD &

connected printersEvery device acts as client AND serverNo one device in chargeNo central user accounts

PEER TO PEER APPLICATIONS

P2P applications allow users to directly share specified file types across peer-to-peer or client-server networks.

COMMON P2P APPLICATIONS

BitTorrent LimeWire

No central serverUses files found on

client hard drives

CLIENT-SERVER NETWORKS

Client requests a service from a dedicated server

REVIEW- 3Q What type of network has centralized

resources, such as central file storage?Client-server

What type of network shares resources located on local computer hard drives?Peer to peer

You type www.gcit.org into your web browser. A DNS request is created and then a we request is sent. What type of network is this?Client-server

COMMON APPLICATION LAYER PROTOCOLS

10.2.1

COMMON PROTOCOLS

What application layer protocols would you use on a daily basis?

HTTP & HTML http://www.cisco.com/index.html

HTTP is the protocolCisco.com is the server name Index.html is the document you requested

HTTP & HTTPS Layer 4 port:

HTTP: 80HTTPS: 443

Browser messagesGET (requests page from web server)POST & PUT (uploads to web server)

HTTPSSecureUses SSL to encrypt

SMTP, POP, IMAP Layer 4 ports:

SMTP-25POP3- 110 IMAP-143

Send mail to server & server to server; SMTP

Get mail from email server; POP3 & IMAPPOP deletes mail from server when sent to

client IMAP sends copy of email to client and

server keeps mail until deleted

ACTIVITY PT Lab 10.2.1.8 Web & Email

In this activity, you will configure HTTP and email services using the simulated server in Packet Tracer. You will then configure clients to access the HTTP and email services.

REVIEW Why would you use IMAP instead of

POP? IMAP keeps the emails until manually

deleted Which protocol uses GET, PUT, and

POST?HTTP

Which email protocol send you a copy of the email and deletes it from the server?POP

What port # is POP?110

What does HTTPS use to encrypt?SSL

IP ADDRESSING SERVICES

10.2.2

DNS Layer 4 port: 53

Servers that translates names to IP addresses

DNS servers know some, forward rest to other DNS servers

Nslookup Get in the mode and then enter domain

Ipconfig /displaydns Displays cached DNS

DNS DNS servers are in a hierarchy

Top-level, most trusted: .com, .edu, .gov Contains 2nd-level domain server records

Second-level: Contains records for the company only

MX used for mail

DHCP Layer 4 port: 67/68

At home, your router is a DHCP server At work, you may have a dedicated

DHCP server

Used for general purpose/PC devicesStatic addressing for routers, switches,

printers, Internet-accessible devices DHCP addresses are leased

DHCP

ACTIVITY PT Lab 10.2.2.8

DHCP & DNS Services In this activity, you will configure and verify

static IP addressing and DHCP addressing. You will then configure a DNS server to map IP addresses to the website names.

HW: Lab 10.2.2.9 Observing DNS You will observe the DNS Conversion of a

URL to an IP Address, observe DNS Lookup Using the nslookup Command on a Web Site, and observe DNS Lookup Using the nslookup Command on Mail Servers.

REVIEW- 4Q Which broadcast message gets sent out

from a PC to a DHCP server when it turns on?DCHPDiscover

What does the DHCP server send back to the PC?DHCPOffer

What does the DHCP request look like?All 255’s

Who gets & responds to that request?Everyone in local network gets it; only DHCP

server responds

FILE SHARING SERVICES

10.2.3

FTP Layer 4 port:

20/2120- data21- control info

Download/upload data from a serverExample: sending

a designed web page to the web server

FTP SOFTWARE

SMB Server Message Block

Client-server file sharing protocol for file, printer, and directory sharing

Used for long-term connections to keep connection active

Authenticates the session

Example:Use SMB (instead of FTP) when downloading

a TON of files from a server

ACTIVITY PT Lab 10.2.3.2

In this activity, you will configure FTP services. You will then use the FTP services to transfer files between clients and the server.

REVIEW- 3Q What program runs on an FTP server

that listens for requests?FTPdaemon

What runs on a PC that will request services from an FTP server?FTP Client software

If you need to download many files from a server, which could take hours, which protocol would you use?SMB

REVIEW- Q Which command did you use to

manually get the name to IP information?nslookup

What port is HTTPS?443

What type of applications need a specific application interface and background service running between hosts?P2P application, like IM

SUMMARY Applications are computer programs with

which the user interacts and which initiate the data transfer process at the user’s request.

Services are background programs that provide the connection between the application layer and the lower layers of the networking model.

Protocols provide a structure of agreed-upon rules and processes that ensure services running on one particular device can send and receive data from a range of different network devices

SUMMARY HTTP supports the delivery of web pages to end

devices SMTP, POP, and IMAP support sending and

receiving email FTP enable users to share files P2P applications make it easier for consumers to

seamlessly share media DNS resolves the human legible names used to

refer to network resources into numeric addresses usable by the network

All of these elements work together, at the application layer.

The application layer enables users to work and play over the Internet.

REVIEW & STUDY Complete the study guide handout

Take the quiz on netacad.com

Jeopardy review

APPLICATION LAYER

Chapter 10

Intro to Routing & Switching