Hands-on Networking Fundamentals

Hands-on Networking Fundamentals Chapter 4 Connecting Through a Cabled Network

Communications Media Types • OSI Layer 1: communication media and interfaces • Five basic communication media types • Coaxial cable: based on copper wire • Twisted-pair cable: based on copper wire • Fiber-optic cable: glass or plastic cable • Hybrid fiber/coax: combines copper and fiber • Wireless technologies: radio or microwaves • Suitability of media varies with different networks • Example: uses of coaxial cable • Older LANs • LANs in areas with signal interference strong • Connecting wireless antenna to network device Hands-on Networking Fundamentals

Communications Media Types (continued) • Consider capabilities and limitations of media • Factors affecting choice of LAN or WAN medium • Data transfer speed • Use in specific network topologies • Distance requirements • Cable and cable component costs • Additional network equipment that might be required • Flexibility and ease of installation • Immunity to interference from outside sources • Upgrade options • Security Hands-on Networking Fundamentals

Coaxial Cable • Two types of coaxial cable (coax) • Thick: used in early networks, typically as backbone • Backbone: cabling between network equipment rooms, floors, and buildings • Thin: used to connect desktops to LANs • Has much smaller diameter than thick coax • Use of both thick and thin coaxial cables declining Hands-on Networking Fundamentals

Hands-on Networking Fundamentals

Twisted Pair Cable • Twisted-pair cable • Contains pairs of insulated copper wires • Outer insulating jacket covers wires • Communication specific properties • Copper wires twisted to reduce EMI and RFI • Length: up to 100 meters • Transmission speed: up to 10 Gbps • RJ-45 plug-in connector attaches cable to device • Less expensive and more flexible than T-connectors • Two kinds of twisted pair cable: shielded and unshielded (preferred) Hands-on Networking Fundamentals

Activity 4-4: Building a UTP Cable • Time Required: Approximately 20–30 minutes • Objective: Experience building a UTP cable. • Description: In this activity, you attach 4-pair UTP cable to an RJ-45 connector. You need the cable, a crimper, a connector, and a wire stripper. These instructions and Figure 4-6 follow the EIA/TIA-568-B standard. Hands-on Networking Fundamentals

Fiber-Optic Cable • Fiber-optic cable • One or more glass or plastic fiber cores encased in glass tube (cladding) • Fiber cores and cladding are surrounded by PVC cover • Signal transmissions consist light (usually infrared) • Three commonly used fiber-optic cable sizes • 50/125 micron • Micron (μm): millionth of a meter • 50 represents core diameter • 125 represents cladding diameter • 62.5/125 micron • 100/140 micron Hands-on Networking Fundamentals

Gigabit Ethernet • Gigabit Ethernet (1000BaseX) • Provides data transfer of up to 1 Gbps • Uses CSMA/CD access methods • Upgrade path for 100BaseX Ethernet networks • Uses of Gigabit Ethernet • Alternative for backbone LAN congestion • Attract token ring users with star-based topologies • Gigabit Ethernet target • Installations using Layer 3 routed communications • Separate standards for fiber-optic and twisted-pair cables Hands-on Networking Fundamentals

The Role of Firmware and NIC Drivers • Firmware and NIC driver support communications • Firmware: software stored on a chip, such as ROM • NIC Driver: manages how packets or frames sent • Firmware or driver may automatically detect media • Some NIC drivers can be signed • Driver signing: placing digital signature in driver • Functions of digital signature • Ensures driver compatible with operating system • Certifies that driver tested for defects or viruses • Ensures that driver cannot overwrite new driver Hands-on Networking Fundamentals

Half- and Full-Duplex NIC Communications • Two transmission modes for NIC and network equipment • Half-duplex: send and receive, not at the same time • Full-duplex: parallel sending and receiving • Made possible by buffering at NIC • Buffering: temporarily storing information • Full-duplex is a good choice • Usually faster than half-duplex Hands-on Networking Fundamentals

Hands-on Networking Fundamentals Chapter 5 Devices for Connecting Networks

LAN Transmission Devices • Uses of LAN transmission equipment • Connecting devices on a single network • Creating and linking multiple networks or subnetworks • Setting up some enterprise networks • Connecting devices that will be discussed • Repeaters, MAUs, hubs, bridges, routers, brouters, switches, gateways Hands-on Networking Fundamentals

Repeater • Connects two or more cable segments • Retransmits incoming signal to all other segments • Cable segment is run within IEEE specifications • Example: Ethernet segment in star-bus network • Performs four Physical layer functions • Filter out signal disturbance caused by EMI and RFI • Amplify and reshape incoming signal • Retime the signal (in Ethernet applications) • Reproduce the signal on all cable runs Hands-on Networking Fundamentals

Multistation Access Unit • Multistation access unit (MAU or MSAU) • Central hub on a token ring network • May have intelligence built-in to detect problems • Smart multistation access unit (SMAU) • Tasks performed by MAU • Connect nodes in a logical ring upon a physical star • Move the token and frames around the ring • Amplify data signals • Expand token ring network by daisy-chain connections • Provide for orderly movement of data • Shut down ports to malfunctioning nodes Hands-on Networking Fundamentals

Hub • Central network device connecting nodes in star • Functions of a hub • Centrally connect multiple nodes into one network • Permit connections on single or multiple LANs • Provide multi-protocol services • Consolidate the network backbone • Provide connections for several different media types • Enable centralized network management and design • Unmanaged hub (simplest) • Logical bus or token ring physically connected as star • May be active or passive Hands-on Networking Fundamentals

Bridge • Network device connecting LAN segments • Functions of a bridge • Extend LAN when maximum connection limit reached • Example: the 30-node limit on an Ethernet bus • Extend a LAN beyond the length limit • Example: beyond 185 meters for thinnet segment • Segment LANs to reduce data traffic bottlenecks • Prevent unauthorized access to a LAN • Operates in promiscuous mode • Examine frame's physical destination address • Occurs at MAC sublayer of OSI Data Link layer Hands-on Networking Fundamentals

Bridge (continued) • Translational bridge • Converts frame to new access method and media type • Example: from token ring to Ethernet • Discards addressing information not used in Ethernet • Three primary bridge functions • Learning: learn network topology and device addresses • Information stored in a bridging table • Filtering: do not flood certain frames, discard others • Enables bridge to used for security purposes • Forwarding: transmit frames to destination • Based on data built-in to bridging table • Some bridges are used to cascade network segments Hands-on Networking Fundamentals

Spanning Tree Algorithm • Defined by the IEEE 802.1d standard • Bridges frames in networks with more than two bridges • Sets up a system of checks performed by bridges • Two motivations for using spanning tree algorithm • Ensure a frame does not enter infinite loop • Causes congestion that may intensify to broadcast storm • Forward frames along the most efficient route • Efficiency based on distance and utilization of resources • Services for frames performed by algorithm • Create one-way path around network (use bridge data) • Establish maximum number of hops for maximum route • Enable bridges to send frames along best route Hands-on Networking Fundamentals

Router • Learns, filters, and forwards like a bridge • Differs from a bridge in significant ways • Connect LANs at the Network layer of the OSI model • Add intelligence to bridge capabilities • Receive regular communications from nodes • General functions of a router • Reduce traffic by efficiently directing packets • Join neighboring or distant networks • Connect dissimilar networks • Prevent bottlenecks by isolating portions of a network • Secure portions of a network by acting as a firewall Hands-on Networking Fundamentals

Router (continued) • Uses a metric to determine optimal routes • Components which may inform metric calculation • Number of incoming packets waiting at a particular router port • Number of hops between sending and receiving segments • Number of packets that can be handled in time frame • Size of the packet (large packet may be subdivided) • Bandwidth (speed) between two communicating nodes • Whether a particular network segment is available • May isolate segments to avert congestion Hands-on Networking Fundamentals

Static and Dynamic Routing • Static routing requires routing tables • Routing tables specify paths between routers • Tables set up and maintained by network administrator • Dynamic routing independent of network administrator • Functions automatically performed in dynamic routing • Determine which other routers can be reached • Determine shortest paths to other networks with metrics • Determine when path to a router is down or unusable • Use metrics to reconfigure alternative routes • Rediscover router and network path after restoration Hands-on Networking Fundamentals

Routing Tables and Protocols • Routers maintain two important databases • Routing table: contains addresses of other routers • Network status: contains information about traffic, topology, and status of links • Databases updated by regular exchange of data • Router forwards packet on basis of metrics • Routers use one or more protocols • Multiprotocol type: each protocol has address database • Two common communication protocols: RIP and OSPF Hands-on Networking Fundamentals

Routing Tables and Protocols (continued) • Routing Information Protocol (RIP) • Determines shortest number of hops to other routers • Information added to each router's table • Disadvantages • Updates containing entire routing table create traffic • Only uses hop count as a metric • Open Shortest Path First (OSPF) protocol • Sends only portion of table related to immediate links • Packages routing information in compact form • Local routers: LAN-based • Join LANs; segment traffic; act as firewalls Hands-on Networking Fundamentals

Switch • Dual purpose • To provide bridging capacity • To increase bandwidth • Bridge-like characteristics of switch • Operates at Data Link MAC sublayer • Uses table information to filter and forward traffic • LAN uses two switching techniques (fabric) • Cut-through: forward portions of frame • Store-and-forward: frame buffered until link available Hands-on Networking Fundamentals

Gateway • Software or hardware interface • Enables two networked or software systems to link • Functions of a gateway • Convert common protocols to specialized type • Convert message formats from one format to another • Translate different addressing schemes • Link a host computer to a LAN • Provide terminal emulation for connections to host • Direct electronic mail to the right network destination • Connect networks with different architectures • Can function at any OSI layer Hands-on Networking Fundamentals

WAN Transmission Devices • WAN transmission over two network types • PSTN (public switched telephone networks) • Leased telephone lines such as T-carrier or ISDN • Characteristics of WAN transmission equipment • May have analog component or be completely digital • Converts signal for long distance communications • Creates multiple channels in medium (grow bandwidth) • Frequently used WAN transmission devices • Telephone modems, ISDN adapters, cable TV modems, DSL modems/routers, access servers, routers Hands-on Networking Fundamentals

Telephone Modems • Modem (modulator/demodulator) • Converts outgoing binary (computer) signal to analog • Converts incoming analog signal to a binary signal • Two ways to attach a modem to a computer • Internal: installed in computer using expansion slot • External: attached to serial port connector via cable • Three common types of connectors • DB-25 connector, DB-9 connector, USB • Modem data transfer rate measured in two ways • Baud rate: number of signal events per second • Bits per second (bps): bits per second Hands-on Networking Fundamentals

Telephone Modems (continued) • Data terminal equipment (DTE) • Device that prepares data for transmission • Data transfer speed of PC is DTE communications rate • Data communications equipment (DCE) • Device (modem) that converts data from DTE • Speed of modem is DCE communications rate • Modems use two communication formats • Synchronous: continuous data bursts controlled by clock • Asynchronous: discrete signals delimited by start and stop bits Hands-on Networking Fundamentals

Cable TV Modems • Uses two channels to communicate • Upstream: transmit outgoing data, sound, TV signals • Downstream: receive and blend incoming signals • Factors affecting transmission speed • Modem speeds may differ upstream and downstream • Example: 30 Mbps upstream, 15 Mbps downstream • Maximum bandwidth reduced by other subscribers • Cable hub handles maximum of 30 Mbps • Cable service may impose policy limits • Data Over Cable Service Interface Spec (DOCSIS) • Also called Certified Cable Modem Project • Provides standards and certifications Hands-on Networking Fundamentals

DSL Modems and Routers • Digital Subscriber Line (DSL) • Works over copper wire likes ISDN • Requires intelligent adapter in connecting computer • Intelligent adapter: sends digital signal over copper wire • Simplex communication over copper wire • Dedicated lines for incoming and outgoing signals • Transfer 2.3 Mbps upstream, 52 Mbps downstream • Advantages of DSL over cable • Dedicated DSL line more secure • Dedicated DSL provides full bandwidth • DSL networks utilize combined DSL adapter/router Hands-on Networking Fundamentals

Remote Routers • Operate over long distances • Connect ATM, ISDN, frame relay, high-speed serial, and X.25 networks • Example: connect networks from NY to LA into WAN • Similarities with local routers • Can support multiple protocols • Can be set up as a firewall • Most routers connect to WAN through serial interface • CSU/DSU for T-carrier communications • Channel service unit (CSU): interface to T-carrier line • Data service unit (DSU): digital interface to CSU • Modular adapter for other high-speed connections Hands-on Networking Fundamentals

Hands-on Networking Fundamentals