Multistation Access Units (MAUs) Chapter 6  Connect workstations in a logical ring through a physical star topology  Move the token and packets around the ring  Amplify data signals  Connect in a daisy-chained manner to expand a token ring network  Provide orderly movement of data

Multistation Access Units (MAUs) Chapter 6  A passive hub connects nodes in a star topology, performing no signal enhance ment as the packet moves from one node to the next through the hub.  An active hub connects nodes in a star topology, regenerating, retiming, and amplifying the data signal each time it passes through the hub.

MAU with Eight Connections Chapter 6

Ring-in (RI) connection MAU Ring-out (RO) connection

MAUs Connected Using the RI and RO Ports

Type 6 patch cable RI RO

Chapter 6

RI RO Type 6 patch cable RI RO

To Draw the Network Diagram Chapter 6  Drawing the token ring network in Microsoft Paint

Multiplexers  A multiplexer is a switch that divides a communication medium into multiple channels so several nodes can communicate at the same time.

 A signal that is multiplexed must be demultiplexed at the other end. Chapter 6

Multiplexers

Chapter 6

Multiplexers Chapter 6  Work at the OSI physical level, switching from channel to channel using one of three physical methods:  Time division multiple access (TDMA)  Frequency division multiple access (FDMA)  Statistical multiple access

Multiplexers  TDMA enables multiple devices to communi cate over the same communications medium by creating time slots in which each device transmits.

  FDMA creates separate channels on one communication medium by establishing different frequencies for each channel.

Statistical multiple access multiplexing allocates the communication resources according to what is needed for the task.

Chapter 6

Repeaters  A repeater amplifies and retimes a packet-carrying signal so it can be sent along all cable segments.

 As used in this context, a segment of cable is one cable run within the IEEE specifications.

Chapter 6

How Repeaters Are Used  To extend a cable segment  To increase the number of nodes beyond the limit of one segment  To sense a problem and shut down a cable segment  To amplify and retime a signal (as a component in other network devices) Chapter 6

Using a Repeater to Extend a Network Research lab

Repeater

Research lab Chapter 6 Business office President’s office

Repeaters  An attached unit interface (AUI) connects coax or fiber-optic backbone cable to a network node, such as a repeater.

 A partitioned segment is one that has been shut down because a portion of the segment is malfunctioning.

Chapter 6

To Diagram the Interoffice Network Chapter 6  Microsoft Paint diagram of two rooms connected by a repeater

Bridges  A bridge is a network device that connects different LAN segments using the same access method.

Chapter 6

How Bridges Are Used Chapter 6  To extend a LAN when the maximum connection limit has been reached  To extend a LAN beyond the length limit  To segment LANs to reduce data traffic bottlenecks  To prevent unauthorized access to LAN (for security)

Bridged Network Chapter 6

Bridge

Bridges  A network device that operates in promiscuous mode reads frame destination address information before sending a packet onto other connected segments of the network. Chapter 6

Types of Bridges  A local bridge connects networks in close proximity and is used to segment a portion of a network to reduce problems caused by heavy traffic.

 A remote bridge joins networks across the same city, between cities, and between states to create one network.

Chapter 6

Important Functions of a Bridge Chapter 6  Learning  Filtering  Forwarding

Cascaded Network Segments Chapter 6

LAN 1 Bridge A LAN 2 Bridge B LAN 3

Token Ring Bridging  Token ring bridges use source routing to forward packets on the network.

 Hops are the number of times a packet travels point to-point from one network to the next.

Source route bridging Chapter 6

Routers Chapter 6  A router connects networks having the same or different access methods.  It forwards packets to networks by using a decision-making process based on:  Routing table data  Discovery of the most efficient routes  Preprogrammed information from the network administrator

How Routers Are Used Chapter 6  To efficiently direct packets from one network to another, reducing excessive traffic   To join neighboring or distant networks To connect dissimilar networks  To prevent network bottlenecks by isolating portions of a network  To secure portions of a network from intruders

A Router Forwarding a Frame to the Right Network Chapter 6

Static and Dynamic Routing Chapter 6  Static routing involves control of routing decisions by the network administrator through preset routing instructions.

 In dynamic routing , the router constantly:  Checks the network configuration  Automatically updates routing tables  Makes its own decisions about how to route frames

Routing Tables and Protocols Chapter 6  Routers maintain information about node addresses and network status in databases.

 The routing table database contains the addresses of other routers and each end node.

  Routers regularly exchange information about network traffic, the network topology, and the status of network lines.

Routers exchange information by using one or more routing protocols.

Local and Remote Routers    A local router joins networks in the same building or between buildings in close proximity.

A firewall is software and/or hardware employed to restrict who has access to a network, to specific network segments, or to certain network resources (such as servers).

A remote router joins networks across large geographical areas, such as between cities, states, and countries.

Chapter 6

A Local Router Connecting Networks in Adjacent Buildings Chapter 6

Business building Manufacturing building Router

Brouters Chapter 6  A brouter , also called a multiprotocol router, is a network device that acts like a bridge or a router, depending on how it is set up to forward a given protocol.

 It is used on networks that operate with several different protocols.

How Brouters Are Used Chapter 6  For efficient packet handling on a multiprotocol network with some protocols that can be routed and some that cannot  To isolate and direct network traffic to reduce congestion  To join networks  To secure a certain portion of a network by controlling who can access it

Hubs  A hub is a central network device that connects network devices in a star topology.  It is also referred to as a concentrator (or switch), which is a device that can have multiple inputs and outputs all active at one time.

Chapter 6

Services Offered by Hubs Chapter 6  Provide a central unit from which to connect multiple nodes into one network  Permit large numbers of computers to be connected on single or multiple LANs  Reduce network congestion through centralizing network design  Provide multiprotocol services

Types of Hubs  MAUs  10BASE-T hubs  100BASE-X hubs  Intelligent and modular hubs Chapter 6

10BASE-T Hubs  One of the simplest hubs  Popular way to connect workgroups on small and large LANs  Uses physical star topology to connect PCs to the central hub  Additional hubs are added by connecting one hub to the next.

Chapter 6

Switching Hubs Chapter 6  Permit significant increase in the throughput capability of an existing 4 Mbps, 10 Mbps, or 16 Mbps network by taking full advantage of exiting bandwidth capabilities   Allow an existing network to be separated into multiple smaller segments, each independent of the others Can be installed on LANs in a WAN where specific LANs are experiencing increased network traffic

100BASE-X Hubs Chapter 6  Multimedia, video, and GUI client/server applications have fostered the need for high-bandwidth, high-speed technologies.

Intelligent and Modular Hubs Chapter 6  An intelligent hub has network management and performance monitoring capabilities.

  A modular hub , also called a chassis hub, contains a backplane into which different modules can be inserted.

A backplane is the main circuit board in modular equipment, containing slots as plug ins for modular cards. It provides connections between the modular boards, a power source, and grounding.

To Diagram 10BASE-T Star Topology on Two Floors Chapter 6  Network diagram of 10BASE-T network segments connected to an intelligent hub

Gateways  A gateway enables communications between two different types of networked systems, such as between complex protocols or between different e-mail systems.

Chapter 6

How Gateways Are Used  To convert commonly used protocols to a specialized protocol  To convert message formats from one format to another  To translate different addressing schemes  To link a host computer to a LAN Chapter 6 continued

How Gateways Are Used  To provide terminal emulation for connections to a host computer  To direct e-mail to the right network destination  To connect networks with different architectures Chapter 6

Systems Network Architecture (SNA) Chapter 6  SNA is a layered communications protocol used by IBM for communications between IBM mainframe computers and terminals.

 It employs seven-layered communications that are similar to the OSI model, but there are differences in the way the services are grouped within the layers.

IBM/Mainframe Connected through an SNA Gateway Chapter 6

SNA gateway

ATM Switches  An ATM switch determines the network channel used to transmit an ATM cell received from a node, taking into account the type of information in the cell (voice, video, data) and the transmission speed needed.

Chapter 6

Capabilities of ATM Switches Chapter 6  Provide high-speed communications on a network backbone  Provide cell transmissions directly to the desktop  Enable high-speed communication between network hubs  Centralize network design for better management continued

Capabilities of ATM Switches Chapter 6  Connect to very high speed networks, such as SONET  Enable network design around workgroup members at dissimilar locations (virtual LANs)  Reduce network bottlenecks through high-speed communications and efficient traffic management through workgroups

ATM Switch Chapter 6

ATM switch

Virtual LANs (VLANs) Chapter 6  A virtual LAN (VLAN) uses switches, routers, and internetworking software to configure a network into subnetworks of logical workgroups, independent of the physical network topology.

Advantages of VLANs  VLANs enable a network to operate at the most efficient level; it is not limited by physical topology.  Network resources can be managed based on the actual work groupings of users.

 VLANs can be reconfigured to move a user from an old workgroup to new one.

Chapter 6

VLAN Workgroups through ATM Switching Chapter 6

ATM switch ATM switch Central ATM switch

OSI Layer

Application Presentation Session Transport Network Data link Physical Networking Devices and the OSI Model

Network Device

Gateways Gateways Gateways Gateways Gateways, routers, source-route bridges, brouters, ATM switches MAUs, intelligent hubs, bridges, gateways, brouters, ATM switches MAUs, multiplexers, passive and active hubs, repeaters, gateways Chapter 6