Lesson 5—Networking BASICS1 Networking BASICS Protocols and Network Software Unit 2 Lesson 5

Lesson 5—Networking BASICS2 Objectives Explain the OSI reference model. Define protocol. List and describe the functions of TCP/IP. Explain the functions of client and server network software.

Lesson 5—Networking BASICS3 OSI Reference Model It was created by the International Standards Organization (ISO). It breaks network functions into seven layers. It illustrates how each layer provides specific services and shares with the layers above and below.

Lesson 5—Networking BASICS4 OSI Reference Model The “flow” between layers goes down when data is sent and up when data is received. The function that each layer performs is to add or remove network information on a packet.

Lesson 5—Networking BASICS5 OSI Reference Model

Lesson 5—Networking BASICS6 OSI Reference Model Physical Data Link Network Transport Session Presentation Application

Lesson 5—Networking BASICS7 Protocols Protocols are rules for communication. A combination of protocols is called a protocol stack or protocol suite. A connectionless protocol assumes that packets will arrive. A connection-oriented protocol establishes a link between devices.

Lesson 5—Networking BASICS8 TCP/IP Transmission Control Protocol/Internet Protocol (TCP/IP) It is the most common protocol suite used today for LANs as well as the Internet. It is composed of several different protocols.

Lesson 5—Networking BASICS9 TCP/IP

Lesson 5—Networking BASICS10 Internet Protocol (IP) The hosts on a TCP/IP network use a logical address. This logical address, called the IP address, is assigned to each host. IP is responsible for the addressing of packets.

Lesson 5—Networking BASICS11 IP Addressing An IP address is four bytes (octets). Each contains eight bits (total of 32 bits in length). Each octet is a number from 1 to 254. IP addresses are usually given as dotted decimal notation.

Lesson 5—Networking BASICS12 IP Addressing

Lesson 5—Networking BASICS13 Classes There are five classes of IP ad- dresses, Class A through Class E. Each class uses a different com- bination of octets to indicate the number of the network and the number of the host.

Lesson 5—Networking BASICS14 Class A The first octet indicates the number of the network, and the remaining three octets indicate the number of the host. 126 network addresses 16 million hosts per network

Lesson 5—Networking BASICS15 Class A

Lesson 5—Networking BASICS16 Class B The first two octets indicate the network number, and last two octets indicate the host. It is intended for organizations that have more networks, but not as many hosts per network. 16,384 network addresses 65,534 hosts per network

Lesson 5—Networking BASICS17 Class B

Lesson 5—Networking BASICS18 Class C The first three octets are for the network number, and last octet is for the host. It is intended for organizations that have many networks, but few hosts per network. Over 2 million network numbers 254 hosts per network

Lesson 5—Networking BASICS19 Class C

Lesson 5—Networking BASICS20 Other Classes Class D and Class E addresses are for special uses. Special IP addresses are known as private addresses.

Lesson 5—Networking BASICS21 Subnet Mask A subnet mask is used to separate a network number from the host number in an IP address. 1 represents a network and 0 represents a host. Subnet masks are also used to subdivide networks.

Lesson 5—Networking BASICS22 Transmission Control Protocol(TCP) TCP is responsible for the reliable transmission of data from one host to another. It is based on port numbers. The combination of an IP address and a port number is called a socket.

Lesson 5—Networking BASICS23 IPv6 The current version of the IP protocol is IPv4. The next generation of the IP protocol is called IPv trillion, trillion, trillion addresses It uses a fixed packet header size of 24 bytes so that information always appears in the same place.

Lesson 5—Networking BASICS24 Network Software Software that runs on the client Software that runs on the server

Lesson 5—Networking BASICS25 Client Software Network Driver Interfaces - “Middleman” between NIC and client’s operating system software. Redirector - Sends request to network. Designator - Keeps track of which drive letter is associated with which network device.

Lesson 5—Networking BASICS26 Server Software Network operating system - Manages and coordinates users and requests across the network. Directory service - Database stored on the network containing information about users and privileges to resources.

Lesson 5—Networking BASICS27 Summary The International Standards Organization (ISO) released a set of specifications that was intended to describe how dissimilar computers could be connected together on a network. Called the Open Systems Interconnections (OSI) reference model, it illustrates how a network device prepares data for delivery over the network to another device and how data is handled when it is received. The key to the OSI reference model is layers. The model breaks networking steps down into a series of seven dif- ferent layers. Each layer cooperates with the layer immediately above and below it by sending and receiving information.

Lesson 5—Networking BASICS28 Summary (continued) The rules for communication between network devices are known as protocols. These protocols are essential for proper communication to take place between the OSI reference models on the network devices. Instead of having just one single proto- col, computer networks typically employ several different proto- cols that function together. This combination of protocols is known as a protocol stack or a protocol suite. Protocols use one of two different methods for delivering data through a network: connectionless protocols, which place the packets on the net- work and then assume that they will arrive at the destination, and connection-oriented protocols, which establish a connection between the two devices before sending any packets. As each packet is received, an acknowledgment is sent back to the sender.

Lesson 5—Networking BASICS29 Summary (continued) The most common protocol suite used today for LANs as well as the Internet is Transmission Control Protocol/Internet Protocol (TCP/IP). Because it is a suite, TCP/IP is composed of several different protocols that all function together. Although the TCP/IP suite is composed of several different protocols, the two major protocols are those that make up its name, TCP and IP. The IP is responsible for addressing the packets and sending them on the correct route to the destination. Each device on a TCP/IP computer network must have a unique number. Com- puters on a TCP/IP network use a logical address instead. This logical address, called an IP address, is assigned to each host computer.

Lesson 5—Networking BASICS30 Summary (continued) IP addresses are also broken down into groups, called classes: Class A through Class E. In addition, special IP addresses, known as private addresses, are used when the computer is not connected to another network. A subnet mask is used to sepa- rate the network number from the host number in an IP address. Subnet masks are also used to subdivide networks. IP uses Address Resolution Protocol (ARP) to determine a host’s IP address. The Transmission Control Protocol (TCP) portion of the TCP/IP suite is responsible for the reliable transmission of data from one host to another. TCP is based on port numbers. A port num- ber identifies what program or service on the receiving computer is being accessed.

Lesson 5—Networking BASICS31 Summary (continued) Because TCP/IP is a connection-oriented protocol, it establishes a session, or link, between the sending and receiving devices. This session is created through a three-way handshake be- tween the devices. The current version of the IP protocol is ver- sion 4, called IPv4. Developed in 1981, long before the Internet was universally popular, IPv4 has begun to show some weak- nesses. The next generation of the IP protocol is IPv6. IPv6 provides several significant improvements. IP addresses under IPv6 will be 16 bytes long or four times the length of IPv4 ad- resses. IPv6 also uses a fixed packet header size of 24 bytes, so information always appears in the same place. This speeds up finding information in the packet and processing the packet.

Lesson 5—Networking BASICS32 Summary (continued) Software that runs on the client computer performs many differ- ent functions that enable the device to function effectively on the network. The Network Device Interface Specifications (NDIS) and Open Date-link Interface (ODI) specifications outline precise standards regarding NIC network driver interfaces. Drivers that follow these standards allow multiple protocols to function simul- taneously on a single computer. Client software called a redirec- tor works closely with the operating system of a client computer. When the user gives a command to the computer, the computer goes first to the client operating system. If that command doesn’t apply to the client computer, the operating system gives the command to the redirector, which sends it out to the network. A designator is designed to keep track of which drive letter is associated with which network device.

Lesson 5—Networking BASICS33 Summary (continued) Server software plays a critical role on a computer network. A network server uses network operating system (NOS) software. NOS software manages and coordinates all users and their requests across the network. A directory service is a database stored on the network. It contains information about users and network devices. A directory service also keeps track of the resources on the network and a user’s privileges to those resources.