Chapter08

Slide1: 

Chapter 8: Local Area Networks: Internetworking Data Communications and Computer Networks: A Business User’s Approach Third Edition

Topics: 

Topics Interconnecting different LAN segments Interconnecting LANs to WANs How Hubs, Bridges, Switches, Routers are used to connect networks

Introduction: 

Introduction Bridges are used to connect different LAN segments or to partition LANs Routers are used to interconnect LANs to WANs or WANs to WANs Switches are replacing hubs for connecting workstations to form a LAN Switches are also being used to replace certain routers

Hubs: 

Hubs Connect workstations to form a LAN Hub sends transmitted data frames out to all connecting links Managed hubs have extra circuitry provide network management information can be accessed from a remote location

General Bridge Features: 

General Bridge Features Segment LAN to relieve traffic congestion Connect existing LANs for resource sharing Connect two LANs using different protocols To isolate different types of users for security reasons

Bridge Functionality: 

Bridge Functionality Can connect LANs using the same or dissimilar protocols Filters frames that are addressed to stations on same segment Forwards frames addressed to stations not on same segment to appropriate LAN segment

Slide7: 

Bridges Illustrated

Transparent Bridge: 

Transparent Bridge Associate port addresses with destinations Observes each frame that arrives at port Extracts the source address from the frame Places source address in the port’s routing table Self-learning Transparent Bridges used on CSMA/CD LANs

Slide9: 

Bridge and Port Tables

Slide10: 

Internal Port Tables

Translating Bridge: 

Translating Bridge Convert frame formats across segments Sometimes referred to as a gateway Source headers and trailers removed Destination header and trailers in new format are then added CSMA/CD to Token Ring and vice versa

Remote Bridge: 

Remote Bridge Forwards data frames between LANs connected by a wide area network Source remote bridge adds WAN headers and trailers to a frame Destination remote bridge removes the WAN headers and trailers Filtered frames remain on source LAN

Slide13: 

Remote Bridge Illustrated

Switches: 

Switches Bridge-like device with multiple ports Connect work stations like a hub does Observes traffic flow and builds routing tables like a bridge does Creates a temporary circuit and forwards frame to destination workstation using routing table information Hubs share available bandwidth Switches provide dedicated bandwidth

Slide15: 

Switches Illustrated

Switch Architecture: 

Switch Architecture Switches are designed to support multiple data transfers concurrently Purchase switches based upon full capacity needed for your LAN Cut-through switches forward frames on as they arrive at the switch Store-and-forward switches use memory to store frames and check them for errors before forwarding

Simultaneous Access: 

Simultaneous Access Dedicated segments provide an efficient means for isolating traffic on the network A switch can allow simultaneous access to multiple servers, or multiple simultaneous connections to a single server

Slide18: 

Workstations Connected to Dedicated Segments

Slide19: 

Simultaneous Access for Two Servers

Slide20: 

Single Server with Two Separate Lines

Slide21: 

Isolating Traffic using Remote Bridges and a Switch

Slide22: 

Using Hubs and a Switch to Provide Multiple Access to E-mail Traffic

Full-Duplex Switches: 

Full-Duplex Switches Provide simultaneous data transmission and reception Full duplex connections require two pairs of wires One pair to transmit One pair to receive Using separate wire pairs essentially eliminates collisions Currently most organizations install four pairs of wire to accommodate full-duplex transmissions

Slide24: 

Full-Duplex Switches Illustrated

Network servers: 

Network servers Provide necessary storage for LAN data and software Primary network operating system controller Increasingly, network servers are functioning as bridges, switches, and routers Circuit boards may be added so servers can assume multiple functions

Routers: 

Routers Layer 3 devices that interconnect LANs to WANs or WANs to WANs Use route tables and network layer addresses to route packets Routers remove existing layer 2 headers and trailers Examine layer 3 destination address Add WAN headers and trailers for trip to next node May act as “firewalls” for security purposes

Slide27: 

Encapsulation and Routing

LAN Internetworking in Action: A Small Office Revisited: 

LAN Internetworking in Action: A Small Office Revisited Recall example from Chapter Seven A small office with 20 workstations in one room and 15 workstations in another room were connected to a server via 100BaseTX One hub was kept in a closet near the 20 workstations while a second hub was near the server

Slide29: 

Fiber-Optic Cable Replacement

LAN Internetworking in Action: A Small Office Revisited: 

LAN Internetworking in Action: A Small Office Revisited Hannah wants to connect the LAN to the Internet She adds a router next to the server and connects it to the hub She connects the router to a high-speed telephone line such as a T-1 service She will also have to program the router to perform IP addressing and firewall functions

Slide31: 

LAN Internetworking in Action: Router to the Internet

LAN Internetworking in Action: A Small Office Revisited: 

LAN Internetworking in Action: A Small Office Revisited High network usage requires segmenting the network Hannah decides to install a database server near the original server and replace both hubs with switches

Slide33: 

LAN Internetworking in Action: Switches Replace Hubs

Summary: 

Summary Interconnecting multiple LAN segments as well as LANs and WANs Interconnection devices Hubs Transparent bridges Switches Routers