CIS 1140 Network Fundamentals

1. CIS 1140 Network Fundamentals Chapter 5 – Topologies and Ethernet Standards Collected and Compiled By JD Willard MCSE, MCSA, Network+, Microsoft IT Academy Administrator Computer Information Systems Instructor Albany Technical College

2. Attention: Accessing Demos • This course presents many demos. • The Demosrequire that you be logged in to the Virtual Technical College web site when you click on them to run. • To access and log in to the Virtual Technical College web site: • To access the site type www.vtc.com in the url window • Log in using the username: CIS 1140 or ATCStudent1 • *Enter the password: student • If you should click on the demo link and you get an Access Denied it is because you have not logged in to vtc.com or you need to log out and log back in. *Remember that passwords are case sensitive so enter it in all lower case letters.

3. Objectives • Describe the basic and hybrid LAN physical topologies, and their uses, advantages, and disadvantages • Describe the backbone structures that form the foundation for most LANs • Understand the transmission methods underlying Ethernet networks • Compare the different types of switching used in data transmission

4. Network Topologies • There are two types of network topologies: • Physical topology is the physical layout of the network, including cable and device configuration • Logical topology refers to the method used to communicate between the devices • It is important to understand the physical topology before designing networks, because they can affect the logical topology chosen, how the building is cabled, and what kind of media is used • Physical topologies are classified according to three geometric shapes: bus, ring and star Types of Topologies Demo

5. Simple Physical Topologies • Physical topology:physical layout of nodes on a network • May create hybrid topologies • Does not specify: • Device types • Connectivity methods • Addressing schemes • Topology integral to type of network, cabling infrastructure, and transmission media used • Three fundamental shapes: • Bus • Ring • Star Physical Topologies Demo

6. Topologies pt. 1Demo Topologies pt. 2Demo

7. Bus • Bus consists of a single cable that connects all the nodes of a network without intervening connectivity devices, and requires a terminator at each end • The single cable is called the bus and supports one channel, where each node shares total capacity • Bus advantages: easy to install and add devices; requires less cable; less expensive • Bus disadvantages: requires 50 ohm terminators at each end of the cable; entire network shuts down if the cable breaks; difficult to troubleshoot; requires grounding loop • Terminators stop signals after reaching end of wire • Prevent signal bounce • Inexpensive, not very scalable • Difficult to troubleshoot, not fault-tolerant The Bus Topology Demo

8. Basic Ethernet Bus • An Ethernet network where all machines are daisy chained using coaxial cable (Thin Ethernet/Thin-net or Thick Ethernet/Thick-net). • Machine 2 wants to send a message to machine 4. • First it 'listens' to make sure no one else is using the network. • If it is all clear it starts to transmit its data on to the network (represented by the yellow flashing screens). • Each packet of data contains the destination address, the senders address, and of course the data to be transmitted. • The signal moves down the cable and is received by every machine on the network but because it is only addressed to number 4, the other machines ignore it. • Machine 4 then sends a message back to number 2 acknowledging receipt of the data (represented by the purple flashing screens).

9. Bus (continued) A terminated bus topology network

10. Ring • Ring is where each node is connected to the two nearest nodes, effectively forming a circle • Data is transmitted in one direction around the ring, and is typically done so using token passing • The ring is used by Token Ring and FDDI networks • Ring advantages: no network collisions; each node functions as a repeater; less cable required • Ring disadvantages: Single malfunctioning node can disable entire network; not flexible or scalable; modifications requires network shutdown The Ring Topology Demo

11. Ring

12. Star • Star is where each node is connected through a central device, such as a hub • All nodes transmit data to the hub, which then retransmits the data to the destination node • Easily moved, isolated, or interconnected with other networks • Scalable - Supports max of 1024 addressable nodes on logical network A typical star topology network

13. Star • Any single cable connects only two devices; Cabling problems affect two nodes at most • More fault-tolerant • Star advantages: a break in the cable does not shut down the network; higher reliability; easier troubleshooting; no terminators required • Star disadvantages: uses more cable than ring or bus networks; hubs are more expensive than terminators; hub failures take down entire LAN segments The Star Topology Demo

14. Hybrid Physical Topologies • Pure bus, ring, star topologies • Rarely exist • Too restrictive • Hybrid topology • More likely • Complex combination of pure topologies • Several options Hybrid Topologies Demo

15. Star-Wired Ring The star-wired ring topology uses the physical layout of a star in conjunction with the token–passing data transmission method. Data are sent around the star in a circular pattern. This hybrid topology benefits from the fault tolerance of the star topology (data transmission does not depend on each workstation to act as a repeater) and the reliability of token passing. Modern Token Ring networks, as specified in IEEE 802.5, use this hybrid topology.

16. Star-Wired Ring Token Ring MAUs can be connected together using straight-through patch cables to connect the Ring Out port of one MAU and the Ring In port of the next MAU until the network of MAUs forms a circle. Up to 255 stations can be connected to the network when using Shielded Twisted Pair cable and 72 when using Unshielded Twisted Pair cable.

17. MAU Showing Internal Ring A Token Ring hub (MAU) simply changes the topology from a physical ring to a star wired ring. The Token still circulates around the network and is still controlled in the same manner, however, using a hub or a switch greatly improves reliability because the hub can automatically bypass any ports that are disconnected or have a cabling fault. 31

18. Star-Wired Bus A star-wired bus topology network

19. Star-wired Bus In a star-wired bus topology, groups of workstations are star-connected to hubs and then networked via a single bus. With this design, you can cover longer distances and easily interconnect or isolate different network segments. One drawback is that this option is more expensive than using either the star or, especially, the bus topology alone because it requires more cabling and potentially more connectivity devices. The star-wired bus topology commonly forms the basis for modern Ethernet and Fast Ethernet networks.

20. Advantages and Disadvantages of the different network topologies

21. Backbone Networks • A network backbone is the cabling that connects the hubs, switches, and routers on a network. Backbones usually are capable of more throughput than the cabling that connects workstations to hubs. This added capacity is necessary because backbones carry more traffic than any other cabling in the network. For example, an increasing number of businesses are implementing fiber-optic backbone but continue to use CAT5 wiring for the cabling from hubs to workstations. • Although even the simplest LAN (including a star or bus topology LAN) technically has a backbone, enterprise-wide back-bones are more complex and more difficult to plan. • The backbone is the most significant building block of these networks.

22. Serial Backbone • A serial backbone is the simplest kind of backbone network. It consists of two or more hubs connected to each other by a single cable. They are not suitable for large networks or long distances. Although the serial backbone topology could be used for enterprise-wide networks, it is rarely implemented for that purpose. • Daisy chain : linked series of devices • Hubs and switches often connected in daisy chain to extend a network • Hubs, gateways, routers, switches, and bridges can form part of backbone • Benefit • Logical growth solution • Modular additions • Low-cost LAN infrastructure expansion • Easily attach hubs • Serial connection of repeating devices • Essential for distance communication • Standards • Define number of hubs allowed • Exceed standards • Intermittent, unpredictable data transmission errors

23. Distributed Backbone • Consists of a number of hubs connected to a series of central hubs or routers in a hierarchy • Allows for simple expansion and limited capital outlay for growth • Layers of hubs can be added to existing layers • A more complicated distributed backbone connects multiple LANs or LAN segments using routers • Provides network administrators with the ability to segregate workgroups and therefore manage them more easily • Adapts well to an enterprise-wide network confined to a single building, where layers of hubs can be assigned according to the floor or department • You must consider the maximum allowable distance between nodes and the server dictated by the network media • Central point of failure is the hub at the uppermost layer • Implementing can be relatively simple, quick, and inexpensive A distributed backbone connecting multiple LANs

24. Collapsed Backbone • Uses a router or switch as the single central connection point for multiple sub-networks • A single router or switch is the highest layer of the backbone. • The dangers of using this arrangement relate to the fact that a failure in the central router or switch can bring down the entire network • In addition, because routers cannot move traffic as quickly as hubs, using a router may slow data transmission. • A substantial advantages is that this arrangement allows you to interconnect different types of sub-networks. • You can also centrally manage maintenance and troubleshooting chores.

25. Parallel Backbone • The most robust enterprise-wide topology. • This variation of the collapsed backbone arrangement consists of more than one connection from the central router or switch to each network segment. • Each hub is connected to the router or switch by more than one cable. • The advantage of using a parallel backbone is that its redundant (duplicate) links ensure network connectivity to any area of the enterprise. • Parallel backbones are more expensive than other enterprise-wide topologies because they require much more cabling than the others. However, they make up for the additional cost by offering increased performance. • As a network administrator, you might choose to implement parallel links to only some of the most critical devices on your network. By selectively implementing the parallel structure, you can lower connectivity costs and leave available additional ports on the connectivity devices. Most Reliable and Most Expensive to Set UP

26. Logical Topologies • Logical topology: how data is transmitted between nodes • May not match physical topology • Bus logical topology: signals travel from one network device to all other devices on network • Required by bus, star, star-wired physical topologies • Ring logical topology: signals follow circular path between sender and receiver • Required by ring, star-wired ring topologies Logical Topologies Demo

27. Switching: Circuit Switching • Switching: component of network’s logical topology that determines how connections are created between nodes • Circuit switching: connection established between two network nodes before transmission • Bandwidth dedicated to connection • Remains available until communication terminated • While connected, all data follows same path initially selected by switch • Monopolizes bandwidth while connected • Resource wasted • Uses • Live audio, videoconferencing • Home modem connecting to ISP

28. Message Switching • Establishes connection between two devices, transfers information, then breaks connection • Information then stored and forwarded from second device to third device on path • “Store and forward” routine continues until message reaches destination • All information follows same physical path • Requires that each device in data’s path have sufficient memory and processing power to accept and store information

29. Packet Switching • Breaks data into packets before transmission • Packets can travel any network path • Contain destination address and sequencing information • Can attempt to find fastest circuit available • When packets reach destination node, they are reassembled • Based on control information • Not optimal for live audio or video transmission • Advantages • No wasted bandwidth • Devices do not process information • Examples • Ethernet networks • Internet

30. MPLS (Multiprotocol Label Switching) • IETF • Introduced in 1999 • Multiple layer 3 protocols • Travel over any one of several connection-oriented layer 2 protocols • Supports IP • Common use • Layer 2 WAN protocols • Advantages • Use packet-switched technologies over traditionally circuit switched networks • Create end-to-end paths • Act like circuit-switched connections • Addresses traditional packet switching limitations • Better QoS (quality of service)

31. 802.3 Ethernet • Ethernet is a LAN standard that specifies an implementation of the physical layer and the MAC sub-layer of the data link layer. • An Ethernet network is a broadcast system; this means that when a station transmits data, every other station receives the data. The frames contain a destination address in the frame header and only the station with that address will pick up the frame and pass it on to upper-layer protocols to be processed. • The access method –Carrier Sense Multiple Access/Collision Detection (CSMA/CD). Ethernet Demo Ethernet/Fast Ethernet/Gigabit Ethernet Demo

32. CSMA/CD (Carrier Sense Multiple Access with Collision Detection) • Network access method • Controls how nodes access communications channel • Necessary to share finite bandwidth • Carrier sense • Ethernet NICs listen, wait until free channel detected • Multiple access • Ethernet nodes simultaneously monitor traffic, access media CSMA/CD Access Method demo

33. CSMA/CD (cont’d.) • Collision • Two nodes simultaneously: • Check channel, determine it is free, begin transmission • Collision detection • Manner nodes respond to collision • Requires collision detection routine • Enacted if node detects collision • Jamming • NIC issues 32-bit sequence • Indicates previous message faulty

34. CSMA/CD (cont’d.) • Heavily trafficked network segments • Collisions common • Segment growth • Performance suffers • “Critical mass” number dependencies • Data type and volume regularly transmitted • Collisions corrupt data, truncate data frames • Network must compensate for them • Collision domain • Portion of network where collisions occur • Ethernet network design • Repeaters repeat collisions • Result in larger collision domain • Switches and routers • Separate collision domains

35. CSMA/CD (cont’d.) • Collision domains differ from broadcast domains • Ethernet cabling distance limitations • Effected by collision domains • Data propagation delay • Time for data to travel • From one segment point to another point • Too long • Cannot identify collisions accurately • 100 Mbps networks • Three segment maximum connected with two hubs • 10 Mbps buses • Five segment maximum connected with four hubs

36. Collision Domain • On an Ethernet network, an individual segment is known as a collision domain, or a portion of a network in which collisions will occur if two nodes transmit data at the same time. • The more nodes transmitting data on a network, the more collisions will take place and you may see performance suffer as a result of collisions. • Collisions are likely to occur at the Physical Layer (on the channel or wire). • Repeaters and Hubs are Physical Layer devices and therefore share the Ethernet channel. • Portions of the network connected by repeaters or hubs must share the bandwidth of the single Ethernet channel. • Repeaters/Hubs simply regenerate any signal they receive, they repeat collisions just as they repeat data. • Networks can be separated into multiple collisions domains by using switches. CollisionDomains Demo

37. 10BASE-T • The “10” represents its maximum throughput of 10Mbps, the “Base” indicates that it uses baseband transmission, and the “T” stands for twisted pair, the medium it uses. • On a 10BaseT network, one pair of wires in the UTP cable is used for transmission, while a second pair of wires is used for reception. By using two pairs of wires, 10BaseT networks use full-duplex transmission. • A 10BaseT network requires CAT3 or higher UTP. • Fault tolerance: capacity for component or system to continue functioning despite damage or partial malfunction • Physical star configuration • Maximum cable length is 100 meters • Nodes connected via concentrator • Maximum of 1024 Nodes per logical segment • Passive Topology connect to Active Hubs • No external terminators • 10Base-T Advantages: 1) the star wiring topology supports easier maintenance and troubleshooting, 2) twisted pair wiring is inexpensive and widely used, and 3) optionally supports full-duplex operation. BASE Terminology Demo

38. 10BASET 5-4-3 Rule 5-4-3 rule of networking: between two communicating nodes, network cannot contain more than five network segments connected by four repeating devices, and no more than three of the segments may be populated

39. 100BaseT Ethernet • 100Base-T (Fast Ethernet) • IEEE 802.3u standard • Similarities with 10Base-T • Baseband transmission, star topology, RJ-45 connectors • Requires CAT5 or higher UTP • Supports three network segments maximum • Connected with two repeating devices • 100 meter segment length limit between nodes • Maximum of 1024 Nodes per logical segment • 100Base-TX • 100-Mbps throughput over twisted pair • Full-duplex transmission: doubles effective bandwidth

40. 1000BaseT Gigabit Ethernet • 1000BASE-T or 802.3ab is a standard for Gigabit Ethernet over copper wiring. It requires, at a minimum, Cat 5e ("Category 5 enhanced") cable. Category 6 cable may also be used. The 1000BASE-T standard was approved by the IEEE 802.3 in 1999. • In a departure from both 10BASE-T and 100BASE-TX, 1000BASE-T uses all four cable pairs to achieve full duplex transmission. The aggregate data rate of 1000 Mb/s is achieved by transmission at a data rate of 250 Mb/s over each wire pair. • Each network segment can have a maximum distance of 100 meters. This usually consists of 90 m horizontal (inside the building), 9 m at the patch panel, and 1 m from the port to the computer or node. • 1000BaseT buses can practically support a maximum of two network segments connected with one hub and 1024 nodes per logical segment.

41. 10GBaseT Ethernet • 10GBase-T • IEEE 802.3an • 10GBASE-T cable infrastructure can also be used for 1000BASE-T allowing a gradual upgrade from 1000BASE-T • Pushing limits of twisted pair • Requires Cat 6 or Cat 7 cabling • Maximum segment length: 100 meters • Benefit • Very fast data transmission, lower cost than fiber-optic • Use • Connect network devices • Connect servers, workstations to LAN

42. 100Base-FX Ethernet • 100Base-FX supports a 100 Mb/s transmission rate over two multimode fiber optic cables. One cable is used to transmit data, and the other is used to receive data. • It allows maximum segment lengths of 412 meters for half-duplex links, and 2000 meters or more for full-duplex links. • The 100Base-FX standard allows several types of fiber optic connectors to be used. Duplex "SC" connectors are recommended, but "ST" and FDDI "MIC" connectors are also permitted. • In full-duplex mode, 100Base-FL segment lengths can be increased from 412 meters to 2000 meters. Even longer distances can be supported with the more expensive single mode fiber (SMF). • The 100BaseFX standard uses a star topology, with its repeaters connected through a bus with a maximum of two repeaters allowed to connect three segments. 2000 2000 Full duplex 2000 Full duplex 6000

43. 1000Base-LX Ethernet • 1000Base-LX operates with a 1300nm laser over single and multi-mode fiber • The "L" in 1000Base-LX stands for "long" as it uses long wavelength lasers to transmit data over fiber optic cable. • Long wavelength lasers are more expensive than short wavelength, but have the advantage of being able to drive longer distances. • Maximum segment lengths range from 550 meters using multimode fiber to 5000 meters using single mode. • One repeater may be used to connect two segments. • Excellent choice for long backbones 550m using MMF to 5000m using SMF

44. 1000Base-SX Ethernet • 1000BASE-SX is a fiber optic gigabit Ethernet standard. • The "S" in 1000Base-SX stands for "short" as it uses short wavelength lasers to transmit data over fiber optic cable. The short wavelength lasers specified by the standard operate at 850 nanometers. Less expensive than long wavelength lasers. • Only multi-mode optical fiber is supported. • Maximum segment lengths range from 275 meters (62.5 micron fibers) to 550 meters (50 micron fibers) depending on the diameter of the fiber used. • Only one repeater may be used between two segments. • Best suited for shorter network runs 275 to 550 meters

45. 10Gigabit Ethernet (802.3ae) • The IEEE 802.3ae standard specifies 10Gigabit Ethernet, also referred to as 10GbE, over multimode and single-mode fiber optics. • 10GbE increases the maximum fiber optic cable lengths up to 40 kilometers. • All use SC or LC connectors. • Common characteristics • Star topology, allow one repeater, full-duplex mode • Differences • Signal’s light wavelength, maximum allowable segment length

46. 10GBase-SR and 10GBase-SW • 10GBase-SR and 10GBase-SW • 10G: 10 Gbps • Base: baseband transmission • S: short reach • Physical layer encoding • R works with LAN fiber connections • W works with SONET fiber connections • Multimode fiber: 850 nanometer signal transmission • Maximum segment length • 300 meters using 50 micron fiber • 66 meters using 62.5 micron fiber

47. 10GBase-LR and 10GBase-LW • 10GBase-LR and 10GBase-LW • 10G: 10 Gbps • Base: baseband transmission • L: long reach • Single-mode fiber: 1319 nanometer signal transmission • Maximum segment length • 10,000 meters • 10GBase-LR: WAN or MAN • 10GBase-LW: SONET WAN links

48. 10GBase-ER and 10GBase-EW • 10GBase-ER and 10GBase-EW • E: extended reach • Single-mode fiber • Transmit signals with 1550 nanometer wavelengths • Longest fiber-optic segment reach • 40,000 meters (25 miles) • 10GBase-EW • Encoding for SONET • Best suited for WAN use

49. Summary of Common Ethernet Standards

50. Ethernet Frames • Ethernet networks may use one (or a combination) of four kinds of data frames: • Ethernet_802.2 (“Raw”) • Ethernet_802.3 (“Novell proprietary”) • Ethernet_II (“DIX”) • Ethernet_SNAP • Frame types differ in way they code and decode packets of data • Ethernet frame types have no relation to network’s topology or cabling characteristics