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. Simple LAN Topologies  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  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 chain is 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