Understanding LAN and WAN Topologies: Concepts and Technologies

1. Chapter Five Network Architecture

2. Chapter Objectives • Describe the basic and hybrid LAN technologies • Describe a variety of enterprise-wide and WAN topologies • Explain the benefits and uses of different topologies • Discuss several versions of the Ethernet transport system • Explain the structure and functioning of the Token Ring network transport system

3. Physical topology Physical layout of a network Bus topology consists of a single cable—called a bus— connecting all nodes on a network without intervening connectivity devices Simple LAN Topologies • Terminators stop signals after they have reached their destination • Signal bounce • Phenomenon in which signals travel endlessly between the two ends of a bus network

4. Simple LAN Topologies • Terminated bus network

5. Simple LAN Topologies • Ring topology • Each node is connected to the two nearest nodes so the entire network forms a circle • Active topology • Each workstation transmits data • Each workstation functions as a repeater FIGURE 5-3 Typical ring network

6. Dual Ring Topology

7. Simple LAN Topologies • Star topology • Every node on the network is connected through a central device FIGURE 5-4 Typical star topology network

8. Hybrid LAN Topologies • Hybrid topology • Complex combination of the simple physical topologies • Star-wired ring • Star-wired topologies use physical layout of a star in conjunction with token ring-passing data transmission method FIGURE 5-5 Star-wired ring topology network

9. Hybrid LAN Topologies • Star-wired bus • In a star-wired bus topology, groups of workstations are star-connected to hubs and then networked via a single bus FIGURE 5-6 Star-wired bus network topology

10. Hybrid LAN Topologies • Daisy-Chained • Daisy chainis linked series of devices FIGURE 5-7 Daisy-chained star-wired bus topology

11. Hybrid LAN Topologies • Hierarchical • Uses layers to separate devices by their priority or function FIGURE 5-8 Hierarchical ring topology

12. Enterprise-Wide Topologies • Enterprise • An entire organization • Backbone networks • Serial backbone • Distributed backbone • Collapsed backbone • Parallel backbone

13. WAN Topologies • Wide area network (WAN) topologies • Peer-to-peer • Ring • Star • Mesh • Tiered

14. Network Transport Systems • Network transport system • Sometimes referred to as the network’s logical topology • Describes network’s logical interconnection between nodes, rather than its physical interconnection • Switching • Component of a network’s logical topology that manages how packets are filtered and forwarded between nodes on a network

15. Network Transport Systems • Circuit switching • Connection is established between two network nodes before they begin transmitting data • Message switching • Connection is established between two devices in the connection path; one device transfers data to the other, then breaks the connection • Packet switching • Data are broken into packets before they are transported

16. Network Transport Systems • Shared Ethernet • Carrier Sense Multiple Access with Collision Detection (CSMA/CD) • Communication rules used by shared Ethernet networks FIGURE 5-19 CSMA/CD process

17. Network Transport Systems • 100BaseT • Also known as Fast Ethernet • Enables LANs to run a 100 Mbps data transfer rate • 100BaseTX • Achieves its speed by sending the signal 10 times faster and condensing the time between digital pulses and the time a station is required to wait and listen in CSMA/CD

18. Network Transport Systems • 100BaseT4 • Achieves its speed by breaking up the data stream into 3 33Mbps streams and 1 for collision detection • Cannot support full duplexing, an enhancement allowing simultaneous two-way transmission between nodes while eliminating collisions • 100BaseVG • Can transmit data at 100 Mbps • Uses a demand priority access method instead of CSMA/CD. Intelligent Hubs manage the prioritized signals

19. Network Transport Systems • Ethernet design considerations TABLE 5-1 Characteristics of different Ethernet versions

20. Network Transport Systems • Switched Ethernet • Enables multiple nodes to simultaneously transmit and receive data and individually take advantage of more bandwidth because they are assigned separate logical network segments through switching • Switch manages network switching • 1 Gigabit Ethernet • Runs at 1000 Mbps • Usually relies on fiber-optic cable

21. Network Transport Systems FIGURE 5-24 Switched Ethernet network

22. Network Transport Systems Ethernet frame types: Ethernet 802.2 • Default frame type for Novell’s IntraNetWare network operating system • Defining characteristics of its data portion are the source and destination service access points that belong to the Logical Link Control layer

23. Network Transport Systems • Service Access Point (SAP) identifies a node or internal process using the LLC protocol • Frame Check Sequence (FCS) field ensures the data are received as sent • Cyclical Redundancy Check (CRC) is an algorithm used by FCS field in Ethernet frames FIGURE 5-25 Ethernet 802.2 frame

24. Network Transport Systems • Ethernet 802.3 • Original NetWare Ethernet frame type • Default frame type for networks running NetWare versions lower than 3.12 FIGURE 5-26 Ethernet 802.3 frame

25. Network Transport Systems • Ethernet II • Original Ethernet frame type developed by DEC, Intel, and Xerox, before the IEEE began to standardize the Ethernet FIGURE 5-27 Ethernet II frame

26. Network Transport Systems • Ethernet SNAP • Adaptation of Ethernet 802.2 and Ethernet II • SNAP stands for Sub-Network Access Protocol FIGURE 5-28 Ethernet SNAP frame

27. Network Transport Systems • Understanding frame types • Autosense enables a NIC to automatically sense what types of frames are running on a network and set itself to that specification

28. Network Transport Systems • Token Ring networks use token passing routine and a star-ring hybrid physical topology • Active monitor • Maintains timing for token passing • Monitors token and frame transmission • Detects lost tokens • Corrects problems when a timing error or other disruption occurs

29. Network Transport Systems • Multistation Access Unit (MAU) • Regenerates signals FIGURE 5-29 Interconnected Token Ring MAUs

30. Network Transport Systems • Token Ring switching • Token Ring networks can take advantage of switching to better utilize limited bandwidth • Token Ring frames • IEEE802.5 • IBM Token Ring frame FIGURE 5-30 IBM Token Ring frame

31. Design Considerations for Token Ring Networks • Cabling • Connectivity devices • Number of stations • Speed • Scalability • Topology