Lesson 24. Protocols and the OSI Model

Objectives At the end of this Presentation, you will be able to:

Define protocol and explain why different protocols are required. Identify the main protocols that make up the TCP/IP Suite including TCP, IP, UDP, POP3, SMTP, IMAP4, SNMP, FTP, TFTP, NTP, and HTTP. Explain the purpose of each of the above protocols.

Network+ Domains covered:

In Networking, Protocols are: Agreements that describe how things work. Industry-wide frameworks that describe every aspect of communications between computers. Grouped together into Protocol Suites.

In the PC world, the main Protocol Suites are: NetBEUI – Used in small Microsoft-based networks. IPX/SPX – Used primarily in Novell-based networks. TCP/IP – Must be used if the network is to connect to the Internet. But it is also widely used even in those networks that do not connect to the Internet.

OSI Model vs. TCP/IP Stack Application Presentation Session Transport Network Data Link Physical IP TCPUDP SMTPFTPSNM P SMBRFSNFS HTTP

Protocols of the TCP/IP Suite: TCP IP UDP POP3/IMAP4 SMTP SNMP FTP TFTP HTTP NTP

Protocols of the TCP/IP Suite: TCP IP UDP POP3/IMAP4 SMTP SNMP FTP TFTP HTTP NTP Delivery Service

Transmission Control Protocol (TCP) Connection-oriented, reliable delivery service. Demands that a connection be established before communications can begin. Views data as a stream that is broken into segments and assigned sequence numbers.

Connection-Oriented Protocol Setup Request Setup Response Sending Host Receiving Host Network

Connection-Oriented Protocol Data Sequence Acknowledgement Sending Host Receiving Host Network

Connection-Oriented Protocol Connection Clear Clear Response Host Network

Setup Request Setup Response Data Sequence Acknowledgement Connection Clear Clear Response Session

Application Presentation Session Transport Network Data Link Physical Transmission Control Protocol (TCP)

Internet Protocol (IP) Another type of delivery service. Not connection-oriented, not guaranteed reliable. Data viewed as a packet. No acknowledgement that packet was received. Provides routing information from the sender to the receiver.

Application Presentation Session Transport Network Data Link Physical Internet Protocol (IP)

TCP vs. IP Connection-oriented Reliable Delivery Transport Layer Protocol High overhead Connectionless “Best-effort” Delivery Network Layer Protocol Low overhead

The IPX/SPX Suite has protocols that are comparable to TCP and IP. SPX is roughly equivalent to TCP IPX is roughly equivalent to IP

Sequenced Packet Exchange (SPX) Connection-Oriented Reliable delivery Views data as a sequence of packets (Stream) Operates at the Transport Layer of the OSI model.

Internetwork Packet Exchange (IPX) Connectionless Reliable delivery cannot be guaranteed Operates at the Network Layer of the OSI model.

Application Presentation Session Transport Network Data Link Physical IP TCP IPX SPX OSI Model TCP/IP Stack IPX/SPX Stack

User Datagram Protocol (UDP) Another delivery service. Has some of the features of both TCP and IP. Like TCP, it breaks data into a sequence of packets and numbers them. Operates at the Transport layer of the OSI Model. Connectionless service, no guarantee of delivery.

Protocols of the TCP/IP Suite: TCP IP UDP POP3/IMAP4 SMTP SNMP FTP TFTP HTTP NTP

Post Office Protocol (POP) Widely used access protocol. Used to download from an server to an client. Version 3 or POP3 is the current version of the software. Used to receive , but not to send it. Uses TCP as its transport protocol, therefore delivery is reliable.

Post Office Protocol (POP) Works best from a single computer. Messages are downloaded and then deleted from the mail server. Not compatible with access from multiple computers. Messages are scattered across all of the computers used for mail access.

Internet Message Access Protocol Version 4 (IMAP4) Used to access electronic mail or bulletin board messages from a mail server. Ability to access messages from more than one computer.

Simple Mail Transfer Protocol (SMTP) Used to send . Used for PC to server communications. Used for server to server communications. Uses TCP as a transport protocol, so it is reliable.

Protocols of the TCP/IP Suite: TCP IP UDP POP3/IMAP4 SMTP SNMP FTP TFTP HTTP NTP Network Management File Transfer HyperText Transfer Time Synchronization

Simple Network Management Protocol Used to communicate network status information. Used to indicate the health of the network to network management consoles. Originally used to monitor bridges and routers. Extended to include servers, hubs, and mainframe computers.

File Transfer protocol (FTP) Both a protocol and a program. Allows fast, secure, and error-free file transfer between two hosts. Uses TCP as its Transport Protocol. Because it is a TCP/IP protocol, it is NOS- independent.

Trivial File Transfer Protocol (TFTP) Can be thought of as a “lite” version of FTP. Similar to FTP except that … It uses UDP as its transport protocol. It does not have any type of authentication and therefore is considered less secure.

Hypertext Transfer Protocol (HTTP) Used to transfer Web pages from a Web Server to a Web Browser. The Uniform Resource Locator (URL) in the Address line of your Browser is often prefixed by HTTP as in: HTTP//

Network Time Protocol (NTP) Widely used on the Internet to synchronize computer clocks to a standard time. A synchronization protocol that can read a server’s clock, transmit the reading to various clients, and adjust each client’s clock accordingly.

Define protocol and explain why different protocols are required. Identify the main protocols that make up the TCP/IP Suite including TCP, IP, UDP, POP3, SMTP, IMAP4, SNMP, FTP, TFTP, NTP, and HTTP. Explain the purpose of each of the above protocols.