1 / 50

Chapter Five

Chapter Five. Physical and Logical Topologies. Simple Physical Topologies. What does physical topology mean? The physical layout of the network nodes Bus, Ring, & Star What does logical topology mean? Network transmission methods Ethernet, Token Ring, LocalTalk, FDDI, ATM.

barb
Download Presentation

Chapter Five

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter Five Physical and Logical Topologies

  2. Simple Physical Topologies • What does physical topology mean? • The physical layout of the network nodes • Bus, Ring, & Star • What does logical topology mean? • Network transmission methods • Ethernet, Token Ring, LocalTalk, FDDI, ATM

  3. Simple Physical Topologies • Physical topology • Physical layout of a network • A Bus topology consists of a single cable—called a bus— connecting all nodes on a network without intervening connectivity devices Figure 5-1: Bus topology network

  4. Simple Physical Topologies Figure 5-2: A terminated bus network

  5. Simple Physical Topologies • Ring topology • Each node is connected to the two nearest nodes so the entire network forms a circle • One method for passing data on ring networks is token passing • Three byte token used to pass data • Active topology • Each workstation transmits data Figure 5-3: A typical ring network

  6. Simple Physical Topologies • Token passing process: • Computer ready to transmit • Computer picks up the token packet • Adds control and data information plus the destination node’s address (the token is now a data frame) • The token is then passed to the next node • Once received by the destination, an acknowledgment is sent to the originating node • After the originating node receives the acknowledgement, it releases a new free token which is sent down the ring

  7. Simple Physical Topologies • Star topology • Every node on the network is connected through a central device Figure 5-4: A typical star topology network

  8. Hybrid Physical 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 • Fault tolerance of star – reliability of token passing Figure 5-5: A star-wired ring topology network

  9. Hybrid Physical 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 • More expensive that star or bus • Basis for modern Ethernet networks Figure 5-6: A star-wired bus network topology

  10. Hybrid Physical Topologies • Daisy-Chained • A Daisy chain is linked series of devices • Drawback – Large # of hubs may affect transmission integrity Figure 5-7: A daisy-chained star-wired bus topology

  11. Hybrid Physical Topologies • Hierarchical hybrid topology • Uses layers to separate devices by priority or function Figure 5-8: A hierarchical ring topology

  12. Enterprise-Wide Topologies • Enterprise • An entire organization • Backbone networks (commonly fiber, but may be CAT5 wiring) • Serial backbone • Distributed backbone • Collapsed backbone • Parallel backbone

  13. Enterprise-Wide Topologies • Serial backbone (identical to daisy-chained networks) • Two or more hubs connected to each other by a single cable • Not suitable for large networks • Distributed backbone • Hubs connected to a series of central hubs or routers in a hierarchy Figure 5-9: A simple distributed backbone network

  14. Enterprise-Wide Topologies Figure 5-10: A distributed backbone connecting multiple LANs

  15. Enterprise-Wide Topologies • Collapsed backbone • Uses a router or switch as the single central connection point for multiple subnetworks (subnetworks may be different types) Figure 5-11: A collapsed backbone network

  16. Enterprise-Wide Topologies • Parallel Backbone • Collapsed backbone arrangement that consists of more than one connection from central router or switch to each network segment Figure 5-12: A parallel backbone network

  17. Enterprise-Wide Topologies • Mesh networks • Routers are interconnected with other routers, with at least two pathways connecting each router • Internet Figure 5-13: An example of a mesh network

  18. Wide Area Network (WAN) Topologies • Peer-to-peer topology • WAN with single interconnection points for each location • Dedicated circuits • Continuous physical or logical connections between two access points that are leased from a telecommunication provider Figure 5-14: A peer-to-peer WAN

  19. Wide Area Network (WAN) Topologies • Ring WAN topology • Each site is connected to two other sites so that entire WAN forms a ring pattern Figure 5-15: A ring-configured WAN

  20. Wide Area Network (WAN) Topologies • Star WAN topology • Single site acts as the central connection point for several other points Figure 5-16: A star-configured WAN

  21. Wide Area Network (WAN) Topologies • Mesh WAN topology • Many directly interconnected locations forming a complex mesh Figure 5-17: Full-mesh and partial-mesh WANs

  22. Wide Area Network (WAN) Topologies • Tiered WAN topology • Sites connected in star or ring formations are interconnected at different levels, with interconnection points organized into layers Figure 5-18: A tiered WAN topology

  23. Logical Topologies • Refers to the way in which data are transmitted between nodes • Describes the way: • Data are packaged in frames • Electrical pulses are sent over network’s physical media • Logical topology may also be called network transport system • Examples include: Ethernet, Token Ring, LocalTalk, FDDI, and ATM

  24. Switching • Component of network’s logical topology that determines how connections are created between nodes • Circuit switching • Connection is established between two network nodes before they begin transmitting data • Monopolized bandwidth between two nodes (not efficient) • PC - ISP • Message switching • Establishes connection between two devices, transfers information to second device, and then breaks connection • E-mail systems • Packet switching • Breaks data into packets before they are transmitted • Ethernet and FDDI (including the Internet)

  25. Ethernet • Carrier Sense Multiple Access with Collision Detection (CSMA/CD) • The access method used in Ethernet • Collision • In Ethernet networks, the interference of one network node’s data transmission with another network node’s data transmission • Collision rate > 5% is unusual • Jamming • Part of CSMA/CD in which, upon detection of collision, station issues special 32-bit sequence to indicate to all nodes on Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty

  26. Ethernet Figure 5-19: CSMA/CD process

  27. Ethernet • On an Ethernet network, an individual network segment is known as a collision domain • Portion of network in which collisions will occur if two nodes transmit data at same time • Data propagation delay • Length of time data take to travel from one point on the segment to another point • If to long, cannot identify collisions accurately

  28. Ethernet • Demand priority • Method for data transmission used by 100BaseVG Ethernet networks • Demand priority requires an intelligent hub Figure 5-20: CSMA/CD versus demand priority

  29. Ethernet • Traditional Ethernet LANs, called shared Ethernet, supply fixed amount of bandwidth that must be shared by all devices on a segment • Switch • Device that can separate network segments into smaller segments, with each segment being independent of the others and supporting its own traffic • Switched Ethernet • Newer Ethernet model that enables multiple nodes to simultaneously transmit and receive data over logical network segments

  30. Ethernet Figure 5-21: A switched Ethernet network * Increase the effective bandwidth of a network segment

  31. Ethernet • Gigabit Ethernet • 1 Gigabit Ethernet • Ethernet standard for networks that achieve 1-Gbps maximum throughput • 10 Gigabit Ethernet • Standard currently being defined by IEEE 802.3ae committee • Will allow 10-Gbps throughput • Will include full-duplexing and multimode fiber requirements

  32. Ethernet • Ethernet frame types: • IEEE 802.3 (“Ethernet 802.2” or “LLC”) • Novell proprietary 802.3 frame (or “Ethernet 802.3”) • Ethernet II frame • IEEE 802.3 SNAP frame • Padding • Bytes added to data portion of an Ethernet frame to make sure this field is at least 46 bytes in size

  33. IEEE 802.3 (“Ethernet 802.2” or “LLC”) • Default frame type for versions 4.x and higher of Novell NetWare network operating system • Sometimes called LLC (Logical Link Control) frame • In Novell’s lingo, this frame is called Ethernet 802.2 frame Figure 5-22: An IEEE 802.3 frame

  34. IEEE 802.3 (“Ethernet 802.2” or “LLC”) • Service Access Point (SAP) • Identifies node or internal process that uses LLC protocol • Frame Check Sequence (FCS) • This field ensures that data are received just as they were sent • Cyclical Redundancy Check (CRC) • Algorithm used by FCS field in Ethernet frames

  35. Novell Proprietary 802.3 (or “Ethernet 802.3”) • Original NetWare frame type (NetWare 3.12-) • Also called: • 802.3 Raw • Ethernet 802.3 frame • Rarely used anymore Figure 5-23: A Novell proprietary 802.3 frame

  36. Ethernet II • Original Ethernet frame type developed by DEC, Intel and Xerox, before IEEE began to standardize Ethernet Figure 5-24: An Ethernet II frame

  37. IEEE 802.3 SNAP • Adaptation of IEEE 802.3 and Ethernet II • SNAP stands for Sub-Network Access Protocol • Organization ID (OUI) – identifies network type • Rarely used on current networks Figure 5-25: An IEEE 802.3 SNAP frame

  38. Understanding Frame Types • Learning about networks is analogous to learning a foreign language, with the frame type being the language’s syntax • Just as you may know the Japanese word for go but how to use it in a sentence, you may know all about the IPX/SPX protocol but not how devices handle it • Autosense • Feature of modern NICs that enables a NIC to automatically sense what types of frames are running on a network and set itself to that specification

  39. Design Considerations for Ethernet Networks • Cabling – coax or twisted-pair • Connectivity devices – less expensive than comparable Token Ring or LocalTalk • Number of stations – 10BaseT/100BaseTX limited to 1024 • Speed – 10/100 Mbps, 1 and 10 Gbps (soon) • Scalability – easily expandable • Topology – 10BaseT/100BaseTX use star-wired bus hybrid topology (highly fault tolerant)

  40. LocalTalk • Logical topology designed by Apple Computer, Inc. • Uses a transmission method called Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) • Similar to CSMA/CD, except node signals intent before it actually does • A teleconnector is a transceiver used on a LocalTalk network • Macintosh version of TCP/IP is called MacTCP

  41. Token Ring • Token Ring networks use the token passing routine and a star-ring hybrid physical topology • The 100-Mbps Token Ring standard is known as High-Speed Token Ring (HSTR) • On a Token Ring network, one workstation, called the active monitor, acts as the controller for token passing

  42. Token Ring • Multistation Access Unit (MAU) • Regenerates signals Figure 5-26: Interconnected Token Ring MAUs

  43. Token Ring • Control Access Unit (CAU) • Connectivity device used on a Token Ring network, similar to MAU but more flexible and allows easier management of nodes • Lobe Attachment Module (LAM) • Device that attaches to a CAU to expand the capacity of that device

  44. Token Ring • Token Ring networks with STP cabling may use a type 1 IBM connector • A DB-9 connector is another type of connector found on STP Token Ring networks Figure 5-27: Type 1 IBM and DB-9 Token Ring connectors

  45. Token Ring • Media filter • Device that enables two types of cables or connectors to be linked • Token Ring media filter • Enables DB-9 cable and type 1 IBM cable to be connected Figure 5-28: A Token Ring media filter

  46. Token Ring • Token Ring switching • Like Ethernet networks, Token Ring networks can take advantage of switching to better utilize limited bandwidth • Token Ring frames • IEEE 802.5 Token Ring frame • IBM Token Ring frame Figure 5-29: An IBM Token Ring frame

  47. Design Considerations for Token Ring Networks • Cabling – shielded/unshielded twisted pair • Connectivity devices – more expensive than Ethernet • Number of stations – 255 STP – 72 UTP • Speed – 4/16/100 Mbps • Scalability – Easily daisy-chain MAUs • Topology – Star-wired ring topology (highly fault-tolerant)

  48. Fiber Distributed Data Interface (FDDI) • Logical topology whose standard was originally specified by ANSI in mid-1980s and later refined by ISO • Double ring of multimode or single mode fiber to transmit data Figure 5-30: A FDDI network

  49. Asynchronous Transfer Mode (ATM) • Describes both a network access method & a multiplexing technique • Logical topology that relies on a fixed packet size to achieve data transfer rates up to 9,953 Mbps • Typically used on WANs • The fixed packet in ATM is called a cell • A unique aspect of ATM technology is that it relies on virtual circuits • Connections between network nodes logically appear to be direct, dedicated links between the two nodes

  50. Asynchronous Transfer Mode (ATM) • ATM uses circuit switching, which allows ATM to guarantee a specific quality of service (QoS) • QoS – standard that specifies that data will be delivered within a certain period of time after the transmission • ATM technology can be integrated with Ethernet or Token Ring networks through the use of LAN Emulation (LANE) • ATM is very expensive • Gigabit Ethernet is a better choice

More Related