Network Transmission Equipment Chapter 4

Learning Objectives Describe the purpose of LAN network transmission equipment: NICs, repeaters, MAUs, hubs, bridges, routers, brouters, switches, and gateways Explain how LAN network equipment works continued…

Learning Objectives Describe the purpose of WAN network equipment: Multiplexers, channel banks, private telephone networks, types of modems, ISDN adapters, access servers, and routers Explain how WAN network equipment works

LAN Transmission Equipment NICs Repeaters MAUs Hubs Bridges Routers Brouters Switches Gateways

NIC Enables network device to connect to network Network connection requirements Appropriate connector for network medium Transceiver Controller to support MAC sublayer of Data Link layer Protocol control firmware

A Combination NIC

Role of MAC Controller Unit Works with firmware to correctly encapsulate: Source and destination address information Data to be transported CRC error control information

Transport and Transmission Options Transport options Combined transport options make it easy to upgrade a network for high-speed communication Transmissions options Half-duplex transmissions Full-duplex transmissions

FDDI NICs Connect host systems/file servers to FDDI network equipment using single attachment Attach network equipment to FDDI cabling via dual attachment

ATM NICs Connect ATM switches or servers to an ATM network Available to desktop Relatively expensive

Wireless NIC Modes Provide flexibility and convenience Ad hoc peer-to-peer communication with another wireless NIC Communication with an access point Provide flexibility and convenience

Buses and NICs Industry Standard Architecture (ISA) Extended Industry Standard Architecture (EISA) Microchannel Architecture (MCA) Peripheral Computer Interface (PCI) SPARC Bus (SBUS) NuBus Universal Serial Bus (USB) VESA local bus (VL-bus)

Choosing a NIC For host computer, server, or workstation? Network media and network transport methods in use? Manufacturer? Computer or network equipment bus type? Operating system used by the computer? Use of half- or full-duplex communications? How does it attach to network (for special application)?

Repeater Amplifies and retimes a packet or cell-carrying signal so that it can be sent along all outgoing cable segments attached to that repeater Filters out signal disturbance or noise

Repeaters Are Used to… Extend cable segment Increase number of nodes beyond limit of one segment Sense network problem and shut down cable segment (partitioning) Connect to components in other network devices continued…

Repeaters Are Used to… Connect segments that use different media Extend backbone cable segments in LANs and WANs Extend long, fiber-optic cable segments Increase communications distance of T-carrier lines

A Multiport Repeater

Repeaters Advantage Disadvantage Inexpensive way to extend a network Can create excessive amount of network traffic

Multistation Access Unit (MAU) Central hub that links token ring nodes into a topology that physically resembles a star but in which data signals are transferred in a logical ring pattern

MAUs Are Used to… Connect workstations into a logical ring through physical star topology Move token and frames around the ring Amplify data signals Connect in a daisy-chained manner to expand token ring network Provide for orderly movement of data Shut down ports to malfunctioning nodes

MAUs Passive hub Active hub Patch cables and lobe cables

Ring In and Ring Out Ports

Token Ring MAU Specifications

Hub Central network device used in star topology to join networks

Hubs Are Used to… Provide a central unit from which to connect multiple nodes into one network Permit many computers to be connected on single or multiple LANs Provide multiprotocol services Consolidate network backbone Provide connections for different media types Enable centralized network management and design

Types of Network Hubs Unmanaged hubs Dual-speed hubs Workgroup hubs Stackable hubs Chassis hubs

Bridge Connects different LANs or LAN segments using the same access method Operates in promiscuous mode; can look at frame addresses (unlike repeaters) Operates at MAC sublayer of OSI Data Link layer Protocol independent; only look at MAC address

Bridges Are Used to… Extend a LAN when maximum connection limit has been reached Extend a LAN beyond the length limit Segment LANs to reduce data traffic bottlenecks Prevent unauthorized access to a LAN

Bridged Network

Bridge Functions Learning Filtering Forwarding

Cascade Bridging

Advantages of Bridges Limit traffic to certain network segments; enhance performance Can use as a firewall to keep intruders out of a network

Types of Bridges Local bridge Remote bridge Connects networks in close proximity Can be used to segment a portion of a network to reduce heavy traffic problems Remote bridge Joins networks across the same city, between cities, and between states to create one network

Bridge Token ring source-route bridge Spanning tree algorithm Incorporated into 802.5 token ring LAN specification Performs routing at OSI Network layer Spanning tree algorithm Ensures that frames are not transmitted in an endless loop Enables frames to be sent along most cost-effective network path

Bridge Protocol Data Units (BPDUs) Frame Format

Router Connects networks having the same or different access methods and media Forwards packets to networks by using decision-making process based on: Routing table data Discovery of most efficient routes Preprogrammed information from network administrator Connects LAN at Network layer of OSI model

Routers Are Used to… Efficiently direct packets from one network to another, reducing excessive traffic Join neighboring or distant networks Connect dissimilar networks Prevent network bottlenecks by isolating portions of a network Secure portions of a network from intruders

Static and Dynamic Routing Static routing Controls routing decisions by network administrator through preset routing instructions Dynamic routing Constantly checks network configuration Automatically updates routing tables Makes decisions about how to route packets

Routing Tables and Protocols Contain addresses of other routers Routing protocols Routing Information Protocol (RIP) Communicates entire contents of routing tables to other routers Open Shortest Path First (OSPF) protocol Communicates information about immediate links to other nodes

Advantages of OSPF Protocol Sends only the portion of routing table that pertains to its most immediate router links Packages routing information in more compact format that RIP Only updated routing table information is shared among routers, rather than the entire routing table

Brouter Acts as a bridge or a router, depending on how it is set up to forward a given protocol

Brouters Are Used to… Handle packets efficiently on a multiprotocol network that includes some protocols that can be routed and some that cannot Isolate and direct network traffic to reduce congestion Join networks Secure a certain portion of a network by controlling who can access it

Switch Links network segments Forwards and filters frames between segments Provides bridging capacity and the ability to increase bandwidth on existing networks

Switching Techniques Cut-through switching Store-and-forward switching (buffered switching)

Gateway Enables communications between two different types of networked systems

Gateways Are Used to… Convert commonly used protocols to a specialized protocol Convert message formats Translate different addressing schemes Link a host computer to a LAN Provide terminal emulation Direct electronic mail to the right network destination Connect networks with different architectures

Gateway

WAN Transmission Equipment Designed to work over POTS and leased telephone lines (T-carrier and ISDN) May be analog or digital Either converts a signal for long-distance communications or creates multiple channels

Examples of Basic WAN Transmission Equipment Multiplexers Channel banks Private telephone networks Telephone modems ISDN adapters Cable TV modems DSL modems and routers Access servers Routers

Multiplexer (MUX) Can receive multiple inputs and transmit them to a shared network medium Works at OSI Physical layer, switching from channel to channel using: A single method for optical transmissions (wavelength division multiplexing or WDM), or One of three electrical switching methods Time division multiple access (TDMA) Frequency division multiple access (FDMA) Statistical multiple access

Using Multiplexers

Channel Bank Large-scale multiplexer that combines telecommunications channels in a centralized location First used in voice applications, now handle voice, data, and video

Private Telephone Networks Private branch exchanges (PBXs) Private automatic exchanges (PAXs) Private automatic branch exchanges (PABXs)

Telephone Modems Convert computer’s outgoing digital signal to analog signal that can be transmitted over a telephone line Also convert incoming analog signal to a digital signal the computer can understand Attached internally or externally

Telephone Modems Types of connectors (DB-25, DB-9, PS/2, universal serial bus or USB) Modem data transfer rate measured by baud rate or bits per second (bps) Synchronous or asynchronous communication format

ISDN Adapters Connect a computer or fax to an ISDN line Terminal adapter (TA) converts digital signal to a protocol that can be sent over a digital telephone line

Cable TV Modems Digital modem devices designed for use with cable TV system, providing high-speed data transfer Share bandwidth with others, but dynamically allocate unused cable bandwidth Either internal or external

DSL Modems and Routers Digital Subscriber Line (DSL) Uses advanced modulation technologies on existing telecommunications networks for high-speed networking between subscriber and telco Communication speeds up to 60 Mbps Dedicated to single user; employs full bandwidth of the line

Connecting to DSL

Access Servers Connect synchronous and asynchronous devices to a network, providing routing for both types of communications

Using an Access Server

Remote Routers Join networks in WANs over long distances Connect ATM, ISDN, frame relay, high-speed serial, and X.25 networks Can support multiple protocols Can be set up as firewalls

Chapter Summary Network transmission equipment used on LANs, WANs, or both Modems Bridges Gateways Channel banks Access servers