ITN instructorPPT Chapter10 final

Chapter 10: Application Layer Introduction to Networks Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Chapter 10: Objectives By the end of this chapter, you will 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, at a high level, 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, including: FTP, File Sharing Services, SMB protocol  Explain how data is moved across the network, from opening an application to receiving data Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Chapter 10 10.0 10.1 10.2 10.3 10.4 Presentation_ID Introduction Application Layer Protocols Well-Known Application Layer Protocols and Service The Message Heard Around the World Summary © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 10.1 Application Layer Protocols Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Application, Session and Presentation OSI and TCP/IP Models Revisited The key parallels are in the transport and network layer Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Application Session and Presentation Application Layer Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Application, Session and Presentation Presentation and Session Layers  Presentation layer  Coding and conversion of application layer data  Data compression  Data encryption for the transmission and decryption of data upon receipt by the destination  Session layer  Functions, creates, and maintains dialogs between source and destination applications  Handles the exchange of information to initiate dialogs, keep them active, and to restart sessions Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Application, Session and Presentation Presentation and Session Layers (cont.) Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Application, Session and Presentation TCP/IP Application Layer Protocols  Domain Name Service Protocol (DNS) – used to resolve Internet names to IP addresses  Telnet – a terminal emulation protocol used to provide remote access to servers and networking devices  Bootstrap Protocol (BOOTP) – a precursor to the DHCP protocol, a network protocol used to obtain IP address information during bootup  Dynamic Host Control Protocol (DHCP) – used to assign an IP address, subnet mask, default gateway and DNS server to a host  Hypertext Transfer Protocol (HTTP) – used to transfer files that make up the Web pages of the World Wide Web Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential Application, Session and Presentation TCP/IP Application Layer Protocols (cont.)  File Transfer Protocol (FTP) - used for interactive file transfer between systems  Trivial File Transfer Protocol (TFTP) - used for connectionless active file transfer  Simple Mail Transfer Protocol (SMTP) - used for the transfer of mail messages and attachments  Post Office Protocol (POP)  - used by email clients to retrieve email from a remote server  Internet Message Access Protocol (IMAP) – another protocol for email retrieval Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 10 Providing File Sharing Services File Transfer Protocol  FTP allow data transfers between a client and a server  FTP client is an application that runs on a computer that is used to push and pull data from a server running an FTP daemon  To successfully transfer data, FTP requires two connections between the client and the server, one for commands and replies, the other for the actual file transfer Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 36 Providing File Sharing Services File Transfer Protocol (cont.) Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 37 Providing File Sharing Services Server Message Block  Clients establish a long term connection to servers  After the connection is established, the user can access the resources on the server as if the resource is local to the client host SMB is a client-server, request-response protocol Servers can make their resources available to clients on the network Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 38 Providing File Sharing Services Server Message Block (cont.) A file may be copied from PC to PC with Windows Explorer using the SMB protocol Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 39 10.3 The Message Heard Around the World Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 40 Move It! The Internet of Things Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 41 Move It! Message Travels Through a Network Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 42 Move It! Message Travels Through a Network (cont.) Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 43 Move It! Message Travels Through a Network (cont.) Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 44 Move It! Getting the Data to the End Device Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 45 Move It! Getting the Data through the Internetwork Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 46 Move It! Getting the Data to the Right Application At the end device, the service port number directs the data to the correct conversation Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 47 Application Layer 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  HTTP supports the delivery of web pages to end devices  SMTP, POP, and IMAP support sending and receiving email Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 48 Application Layer Summary  SMB and 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 Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 49 Presentation_ID © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential 50 ... receives all the inbound mail from the MTA and places it into mailboxes  MDA can also resolve final delivery issues, such as virus scanning, spam filtering, and return-receipt handling Presentation_ID