CIM6400 CTNW Lesson 9 – LAN Architectures & Networking Protocols and the OSI Model

LAN Architectures

Ethernet Architecture refers to the overall structure of a computer or communication system. It determines the capabilities and limitations of the system. The Ethernet architecture is based on the IEEE 802.3 standard. The IEEE 802.3 standard specifies that a network implements the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access control method. Standard transfer rates are 10 Mbps or 100 Mbps, but new standards provide for gigabit Ethernet, which are capable of attaining speeds up to 1 Gbps over fiber-optic cable or other high-speed media.

Ethernet 10BASE-T uses a star topology. The 10 stands for the common transmission speed of 10 Mbps, the "BASE" stands for baseband mode, and the "T" stands for twisted pair cabling. Ethernet cable generally describes the UTP cabling, but STP cable can also be used.

Ethernet 100BASE-X (also called Fast Ethernet) comes in several different varieties. It can be implemented over 4-pair Category 3, 4, or 5 UTP (100BASE-T). It can also be implemented over 4-pair Category 5 UTP or Shielded Twisted Pair (STP) (100BASE-TX), or as Ethernet over 2-strand fiber-optic cable (100BASE-FX).

Ethernet 1000BASE-T is Gigabit Ethernet. This architecture supports data transfer rates of 1 Gbps. Its implementation over fiber-optic cable makes it suitable for metropolitan-area networks (MANs).

Token Ring The Token Ring standards are defined in IEEE 802.5. It is often integrated with IBM mainframe systems such as AS400. Token Ring is so named of its logical topology and its MAC method of token passing. The transfer rate for Token Ring can be either 4Mbps or 16Mbps. A Token Ring network uses a token (that is, a special signal) to control access to the cable. A token is initially generated when the first computer on the network comes online. When a computer wants to transmit, it waits for and then takes control of the token when it comes its way. The token can travel in either direction around the ring, but only in one direction at a time.

Fiber Distributed Data Interface (FDDI) FDDI is a type of Token Ring network. It runs on fiber-optic cable, and thus combines high-speed performance with the advantages of the token-passing ring topology. It runs at 100 Mbps, and its topology is a dual ring. The outer ring is called the primary ring and the inner ring is called the secondary ring. Normally, traffic flow only on the primary ring. If primary ring fails, the data automatically flows onto the secondary ring in the opposite direction (fault tolerance). Advantages High speed fiber-optic transmission Not susceptible to EMI and noise Send data for greater distances between repeaters

Networking Protocols and the OSI Model

OSI Model Overview The Open Systems Interconnection (OSI) reference model is an industry standard framework that is used to divide the functions of networking into seven distinct layers. Each layer provides specific services to the layers above and below it in order for the network to work effectively.

OSI Model Overview A message begins at the top application layer and moves down the OSI layers to the bottom physical layer. As the message descends, each successive OSI model layer adds a header to it.

OSI Model Overview A header is layer-specific information that basically explains what functions the layer carried out. Conversely, at the receiving end, headers are striped from the message as it travels up the corresponding layers. The process of data being encapsulated on the sending end and data being de-encapsulated on the receiving end is the function of the OSI model.

OSI Model Layer and Their Functions The OSI model was intended to be a reference model for developing networking protocols.

What is a Protocol? Protocol is a controlled sequence of messages that is exchanged between two or more systems to accomplish a given task. Protocol specifications define this sequence together with the format or layout of the messages that are exchanged.

Transmission Control Protocol/Internet Protocol The Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols has become the dominant standard for inter-networking. TCP/IP represents a set of public standards that specify how packets of information are exchanged between computers over one or more networks.  Internet

Transmission Control Protocol/Internet Protocol

Transmission Control Protocol/Internet Protocol Application Protocols Hypertext Transfer Protocol (HTTP) Govern how files – such as text, graphics, sounds and video – are exchanged on the Internet. A web server runs an HTTP services or daemon. A daemon is a program that services HTTP requests. Hypertext Markup Language (HTML) A page-description language Web designers use HTML to indicate to web browser software how the page should look. Telnet Enables terminal access to local or remote systems

Transmission Control Protocol/Internet Protocol Application Protocols (Cont.) File Transfer Protocol (FTP) Provides services for file transfer and manipulation. FTP uses the session layer to allow multiple simultaneous connections to remote file system Simple Mail Transport Protocol (SMTP) Provides messaging services over TCP/IP and supports most Internet e-mail programs. Domain Name System (DNS) Provides access to name servers, where network names are translated to the addresses used by Layer 3 network protocols.

Transmission Control Protocol/Internet Protocol Transport Protocols Transmission Control Protocol (TCP) Facilities for end-to-end connection establishment, error detection and recovery, and metering the rate of data flow into the network (i.e. for reliable delivery of data) User Datagram Protocol (UDP) Offers a connectionless service to applications Uses lower overhead than TCP Both TCP & UDP identify applications by port number

Transmission Control Protocol/Internet Protocol Internet Protocols Internet Protocol (IP) address Provides source and destination addressing. In conjunction with routing protocols, the IP address provides packet forwarding from one network to another Internet Control Message Protocol (ICMP) Used for network testing and trouble-shooting, it enables diagnostic and error messages Routing Information Protocol (RIP) Operates between router devices to discover paths between networks Address Resolution Protocol (ARP) Maps an IP address to a physical machine address

Internetwork Packet Exchange/Sequenced Packet Exchange Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) is the protocol suite employed originally by Novell®, NetWare. It delivers functions similar to those included in TCP/IP. The native – or original – NetWare protocols remained proprietary

NetBEUI NetBIOS Extended User Interface (NetBEUI) is a protocol used primarily on small Windows NT networks. It was used earlier as the default networking protocol in Windows 3.11, Windows for Workgroups, and LAN manager. NetBEUI is a simple protocol that lacks many of the features that enable protocol suites such as TCP/IP to be used on networks of almost any size. NetBEUI cannot be used to build large networks or to connect several networks. However, it is suitable for small peer-to-peer networks. It can be used in conjunction with another routable protocol such as TCP/IP.

AppleTalk AppleTalk is a protocol suite that is used to network Macintoch computers. AppleTalk is comprised of a set of protocols that span the seven layers of the OSI reference model. AppleTalk protocols were designed to run over the major LAN types, notably Ethernet and Token Ring, and also Apple's own LAN physical topology, LocalTalk. Like Novell, Apple Computer also developed its own proprietary protocol suite to network Macintosh computers.