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Chapter 10 - Application Layer10.0 Application Layer10.0.1 Introduction >10.0.1.1 IntroductionUpon the completion of this chapter you will be able to:
10.0.1.2 Activity- Application InvestigationNetwork application:
10.0.1 Introduction >10.0.1.2 Activity - Application InvestigationThe figure on this page shows three different applications: Instant Messaging, Podcasting, and Weblog. Network Applications:
Objectives:Explain the operation of the application layer in providing support to end-user applications.
In this activity, you will envision what it would be like not to have network applications available to use in the workplace. You may also estimate what it would cost to not be able to use networked applications for a short period of time.
See page notes for instructions. 10.1 Application Layer Protocols10.1.1 Application, Session and Presentation >OSI and TCP/IP Models RevisitedThe figure on this page shows the relationship between the TCP/IP model and the OSI model. OSI model layers 5, 6, and 7 map to the TCP/IP Transport layer. OSI model layer 4 maps to the TCP/IP model Transport layer. OSI model layer 3 maps to the TCP/IP model Internet layer. OSI model layers 1 and 2 map to the TCP/IP model Network Access layer.
The description given for this table is "The key parallels are in the transport and network layers" 10.1.1 Application, Session and Presentation >10.1.1.2 Application LayerThe figure on this page shows sample Applications for the OS.I model Application layer. Examples include:
10.1.1 Application, Session and Presentation >10.1.1.3 Presentation and Session LayersThe figure on this page shows examples of the OSI Presentation Model. Examples include:
10.1.1 Application, Session and Presentation >10.1.1.4 TCP/IP Application Layer ProtocolsThe figure on this page shows examples of OSI layer functionality.
10.1.1 Application, Session and Presentation >10.1.1.5 Activity – Application Protocols and StandardsThe figure on this page is an interactive activity that allows the learner to practice matching a protocol with its appropriate OSI model layer (5 Session Layer, 6 Presentation Layer, or 7 Application Layer) and TCP/IP Application Layer. Match the appropriate protocol names and standards to the correct OSI and TCP/IP network locations. Each answer will be used twice, once on the OSI model and once on the TCP/IP model locations. The protocol names to be matched are:
10.1.2 How Application Protocols Interact with End-User Applications >10.1.2.1 Peer-to-Peer NetworksThis figure on this page shows an example of Peer to Peer networking using 2 computers on a LAN. Peer1 is the print client and file server while Peer2 is the file client and print server. The printer is directly connected to Peer2. Peer1 has a callout saying, "I have files on my hard drive that are being shared for Peer2. I also have a page that I need to print through Peer2."" Peer2 has a callout saying, "I need to access a file from the hard drive on Peer1. I also need to print a file that I received from Peer1, with a print request."" The description given for this figure is, "A peer-to-peer exchange, both devices are considered equal in the communication process.". 10.1.2 How Application Protocols Interact with End-User Applications >10.1.2.2 peer-to-Peer ApplicationsThe figure on this page shows communication using Instant Messaging as an example of a peer-to-peer application. This demonstrates a program acting as both client and server. Client/Server1 sends the message "Meeting tonight." over the network which is received by Client/Server2. Client/Server2 sends the message "Ill be there." over the network which is received by Client/Server1. Client/Server1 sends the message "Good." over the network which is received by Client/Server2. Both clients simultaneously:
10.1.2 How Application Protocols Interact with End-User Applications >10.1.2.3 Common P2P ApplicationsThe figure on this page shows how Gnutella supports peer-to-peer communication with many peers simultaneously. The figure shows 6 machines connected over a network. PC1 has a callout saying, "Where is mysong.mp3?". PC3, PC5 and PC6 have callouts saying,"I've got it.". The description given for this figure is, "Gnutella allows P2P applications to search for shared resources on peers.". 10.1.2 How Application Protocols Interact with End-User Applications >10.1.2.4 Lab – Researching Peer-to-Peer file SharingSee Lab Descriptions. 10.1.2 How Application Protocols Interact with End-User Applications >10.1.2.5 Client-Server ModelThe figure on this page shows an example of how downloads and uploads work in a client-server model. There is a server and there are 3 devices connected via a network; a computer, a mobile device, and an IP phone.
The figure also has the following 2 buttons:
10.2 Well-Known Application Layer Protocols and Services10.2.1 Common Application Layer Protocols >10.2.1.1Application Layer Protocols RevistedThe figure on this page shows the relationship between the TCP/IP model and the OSI model. OSI model layers 5, 6, and 7 map to the TCP/IP Application layer. OSI model layer 4 maps to the TCP/IP model Transport layer. OSI model layer 3 maps to the TCP/IP model Internet layer. OSI model layers 1 and 2 map to the TCP/IP model Network Access layer.
The figure also shows three protocols that operate at the application layer:
10.2.1 Common Application Layer Protocols >10.2.1.2 hypertext Transfer protocol and Hypertext Markup languageFigure 1 on this page shows a HTTP server and client connected to a network. The URL http://www.cisco.com/index.html is also shown. Figure 2 on this page shows step one, the client requesting the web page http://www.cisco.com. The description given for this figure is, "The client initiates an HTTP request to a server.". Figure 3 on this page shows step two, the server response with an example of the HTML code for web page. HTTP/1.1 200 OK
The description given for this figure is, "In response to the request, the HTTP server returns code for a web page.". Figure 4 on this page shows the web page rendering in a browser on the client. The description given for this figure is, "The browser interprets the HTML code and displays a web page.". 10.2.1 Common Application Layer Protocols >10.2.1.3 HTTP and HTTPSThe figure shows the following HTTP GET request between a client and server:
The description given for this figure is, "Entering in the address bar of a browser generates the HTTP GET message.". 10.2.1 Common Application Layer Protocols >10.2.1.4 SMTP, POP, and IMAPFigure1 on this page shows a client connected to a server. The client is a Mail User Agent (MUA). The client is sending mail using SMTP and receiving mail using POP. The description given for this figure is, "Clients send emails to a server using SMTP and receive emails using POP3.". Figure 2 on this page shows how mail gets relayed between ISPs before reaching its destination. Mail for recipient@cisco.com is sent to ISP A mail server using SMTP. The message is then relayed to ISP B mail server using SMTP. The recipient receives the message from ISP B mail server using IMAP or POP3. 10.2.1 Common Application Layer Protocols >10.2.1.5 SMTP, POP, and IMAP (cont.)The figure on this page shows a client (MUA) sending mail to recipient@domain.com. The message reaches its Mail Transfer Agent (MTA). The MTA has a callout saying, "Is the recipient in my list of recipients? No. Forward email to another server.". The message is forwarded to another MTA. for delivery. The description given for this figure is, "The Mail Transfer Agent process governs email handling between servers and clients.". 10.2.1 Common Application Layer Protocols >10.2.1.6 SMTP, POP, and IMAP (cont.)The figure on this page shows the interaction between all devices involved with an e mail transmission. The sender (MUA) sends the message to the MTA. The MTA has a callout saying, "I do not have the recipient listed. I have forwarded the email to another server.". The MTA forwards the message to another MTA. The second MTA has a callout saying, "I have recipient@domain.com listed. I will place this email in the recipient's mailbox.". Since this MTA has the address of the recipient, it acts as a Mail Delivery Agent (MDA). The message is then sent to the recipient (MUA) using POP3. The description given for this figure is, "The Mail Delivery Agent process governs delivery of email between servers and clients.". 10.2.1 Common Application Layer Protocols >10.2.1.7 SMTP, POP, and IMAP (cont.)The figure shows the completed cycle of an e. mail delivery.
The description given for this figure is, "SMTP is used to send emails from clients to server, and to forward emails between email servers. POP is used to deliver email.". 10.2.1 Common Application Layer Protocols >10.2.1.8 Packet tracer – Web and EmailObjectives:Part 1: Configure and Verify Web Servers Part 2: Configure and Verify Email Services 10.2.2 Providing IP Addressing Services >10.2.2.1 Domain Name ServiceFigures 1 to 5 on this page display the steps involved in DNS resolution. In the figures a PC that is a client is connected to a DNS server through the network cloud. Figure 1 shows the client with the web address http://www.cisco.com/ in the address bar. The client makes a DNS query to a DNS server. The name is easy for people to use. Figure 2 shows an NS record matching www.cisco.com to the IP address 198.133.219.25. The DNS server matches the domain name with numeric address. The devices use numbers. Figure 3 shows the client sending the DNS request to the server. Figure 4 shows the DNS server responding to the DNS query with the IP address for www.cisco.com. The description given for this figure is, "The number is returned to the client for use in making requests of the server.". Figure 5 shows the client now has the IP address to put in the layer 3 header as the destination IP for the HTTP request. The description given for this figure is, "A domain name is resolved to its numeric network device address by the DNS protocol.". 10.2.2 Providing IP Addressing Services >10.2.2.2 DNS Message FormatThe figure on this page shows the DNS message format.
10.2.2 Providing IP Addressing Services >10.2.2.3 DNS HierarchyThe figure on this page shows the DNS hierarchy. At the bottom level is the DNS Client. At the Secondary level domain servers is the Local cisco.com DNS server. At the Top level domain servers are the .com, .org, .au, and .co servers. on the top level are the Root DNS servers.. The DNS client communicates with the local DNS server which has a callout saying, "I have the records for: www.cisco.com and mail.cisco.com.". The description given for this figure is, "A hierarchy of DNS servers contains the resource records that match names with addresses.". 10.2.2 Providing IP Addressing Services >10.2.2.4 nslookupThe figure on this page shows the output from issuing an Microsoft Windows XP [Version 5.1.2600]
C:\Documents and Settings\bradfjoh>cd..
C:\Documents and Settings>nslookup
> www.cisco.com
Name: www.cisco.com
cisco.netacad.net
Non-authoritative answer:
>
10.2.2 Providing IP Addressing Services >10.2.2.5 Syntax Checker – DNS CLI Commands in Windows and UNIXThe figure on this page is Syntax Checker used to practice entering the ns lookup command at a command prompt. The Syntax Checker is inaccessible: The figure also has the following 3 buttons:
Enter the 'nslookup' command to begin a manual query of the name servers. Microsoft Windows [Version 6.1.7601]
The output lists the name and IP address of the closest name server. in this case, the user is in a home network behind a router firewall. The address is the router. You are now in nslookup mode. Enter the domain name 'www.cisco.com'. www.cisco.com
The output lists all the addresses that the server 'e144' currently has in its database. Notice that IPv6 addresses are also listed. In addition, various aliases are shown that will resolve to 'www.cisco.com'. >exit
You can directly query the DNS servers by simply adding the domain name to the 'nslookup' command. Enter'nslookup www.google.com'. c:\>nslookup www.google.com
Non-authoritative answer:
c:\>
-- -- -- -- -- -- -- -- -- -- -- -- user@cisconetacad$ nslookup
Non-authoritative answer:
Notice the output is similar as what you got from the Windows command line. exit
As in Windows, you can directly query the DNS servers by simply adding the user@cisconetacad$ nslookup www.google.com
@@Non-authoritative answer: Name: www.google.com Address: 74.125.225.209 Name: www.google.com Address: 74.125.225.210 Name: www.google.com Address: 74.125.225.211 Name: www.google.com Address: 74.125.225.12 Name: www.google.com Address: 74.125.225.208 user@cisconetacad$@@
You successfully used the nslookup command to verify the status of domain names. 10.2.2 Providing IP Addressing Services >10.2.2.6 Dynamic Host Configuration ProtocolThe figure on this page shows a cloud, or the Internet, connected to 4 networks. Each network has its own DHCP server. Each network is a different size ranging from a single home to a corporate network. In the figure there are three ISP’s; ISP 1, ISP 2 and ISP 3 as well as ISP DHCP server in the network cloud. ISP 1 router is connected to a single home PC where the router acts as a DHCP server and the PC is the DHCP client. ISP 2 router is connected to the router on a corporate network with 6 PCs connected to two switches and the switches are connected to a router and a server this server is the Local DHCP Server and the PCs are DHCP clients. ISP 3 router is connected to the wireless router of a home and small business network. The router is connected to three PCs through wireless connections, here the wireless router is a DHCP server and the PCs are DHCP clients. 10.2.2 Providing IP Addressing Services >10.2.2.7 DHCP OperationThe figure on this page shows the DHCP conversation between a DHCP Client and a DHCP Server. The following 4 steps are listed as explained in the page notes:
10.2.2 Providing IP Addressing Services >10.2.2.8 Packet Tracer – DHCP and DNS Servers.Objectives:Part 1: Configure Static IPv4 Addressing Part 2: Configure and Verify DNS Records 10.2.2 Providing IP Addressing Services >10.2.2.9 Lab – Observing DNS ResolutionSee Lab Descriptions. 10.2.3 Providing File Sharing Services >10.2.3.1 File Transfer ProtocolThe figure on this page shows an FTP conversation between client and server. There are two connections, the control and the data use two different TCP ports.
The description given for this animation is, "Based on commands sent across control connection, data can be downloaded from server or upload from client." 10.2.3 Providing File Sharing Services >10.2.3.2 Packet Tracer – FTPObjectives:Part 1: Configure FTP Services on Servers Part 2: Upload a File to the FTP Server Part 3: Download a File from the FTP Server 10.2.3 Providing File Sharing Services >10.2.3.3 Lab – Exploring FTPSee Lab Descriptions. 10.2.3.4 Server Message BlockFigure 1 on this page shows a client computer using SMB protocol to access documents on a remote Windows server and a printer connected to the remote Windows server. The client PC is connected to the server to which a printer is connected. The client sends SMB requests and Server replies with SMB responses. Shared resources are:
The description given for this animation is, "SMB is a client-server, request-response protocol. Servers can make their resources available to clients on the network." Figure 2 on this page shows two clients using SMB to share files. The description given for this animation is, "A file may be copied from PC to PC with Windows Explorer using the SMB protocol." 10.3 The Message Heard Around the World.10.3.1 Move It! >10.3.1.1 The Internet of ThingsThe image on this page displays buildings in the background with many network able devices connecting to each other. The figure is titled "THE INTERNET OF EVERYTHING IS HERE. As the Internet evolves, so will we.". The figure also states that "37 billion new things will be connected by the year 2020." 10.3.1 Move It! >10.3.1.2 Message Travels Through a networkThis flash animation on this page shows computer H1 on one LAN connected to the Internet and a server on another LAN connected to the Internet. Computer H1 uses the TCP/IP model and passes the message down through the various layers as follows:
10.3.1 Move It! >10.3.1.3 Getting the data to the End DeviceThe figure on this page shows the same network as the previous page. The Transport layer handing the segments to the Internet layer. The Internet layer creates an IP datagram or packet. The packet includes the source and destination IP addresses. The packet is passed to the Network Access layer.. 10.3.1 Move It! >10.3.1.4 Getting the data through the InternetworkThe figure on this page shows the same network as the previous page. The Network Access layer frames the packet with source and destination MAC addresses, and then converts the frame to electrical signals. 10.3.1 Move It! >10.3.1.5 Getting the data to the Right ApplicationThis flash animation on this page shows a computer and a server connected to the Internet. The server is running the following three services:
The following three packets are received by the server:
Each packet is delivered to the appropriate service based on the destination port number. The description given for this animation is, "At the end device, the service port number directs the data to the correct conversation.". 10.3.1 Move It! >10.3.1.6 Warriors of the NetThe YouTube video on this page , titled " Warriors of the Net " follows the journey of an IP packet. It can be accessed via the following link: 10.4 Summary10.4.1 Summary >10.4.1.1 Modeling Activity – Make it happen!The figure on this page shows people around a table collaborating on blueprints. Network applications use protocols to facilitate data communication...
...and the list goes on! 10.4.1 Summary >10.4.1.2 Packet Tracer Multiuser – TutorialObjectives:Part 1: Establish a Local Multiuser Connection to another instance of Packet Tracer Part 2: Verify Connectivity across a Local Multiuser Connection 10.4.1 Summary >10.4.1.3 Packet Tracer Multiuser – Implement ServicesObjectives:Part 1: Establish a Local Multiuser Connection to another instance of Packet Tracer Part 2: Server Side Player - Implement and Verify Services Part 3: Client Side Player - Configure and Verify Access to Services 10.4.1 Summary >10.4.1.4 SummaryThe figure on this page shows a client and a web server connected to the Internet and the client is viewing a web page. End of Chapter 10: Application Layer. Next - Chapter 11: Its a Network. |