LOCAL AREA NETWORK A local area network (lan) is a communication network that interconnects a variety of data communicating devices within a small geographic area. A local area network (lan) is a communication network that interconnects a variety of data communicating devices within a small geographic area. A lan broadcasts data at high data transfer rates with very low error rates. A lan broadcasts data at high data transfer rates with very low error rates. lan enables the sharing of resources such as files or hardware devices that may be needed by multiple users. lan enables the sharing of resources such as files or hardware devices that may be needed by multiple users.

It is limited in size, typically spanning a few hundred meters, and no more than a mile. It is limited in size, typically spanning a few hundred meters, and no more than a mile. Is fast, with speeds from 10 Mbps to 10 Gbps. Requires little wiring, typically a single cable connecting to each device. Has lower cost compared to MAN’s or WAN’s

PRIMARY FUNCTION OF LAN File serving File serving large storage disk drive acts as a central storage repository large storage disk drive acts as a central storage repository Print serving Print serving Providing authorization to access a printer, accept and queue print jobs, and administer printing duties Providing authorization to access a printer, accept and queue print jobs, and administer printing duties serving serving Interconnecting multiple systems Interconnecting multiple systems Video transfer Video transfer High speed LANs support image and video streaming High speed LANs support image and video streaming Distributed computation (e.g., grid computing) Distributed computation (e.g., grid computing) Applied fields: Applied fields: E.g., Manufacturing, office, academics E.g., Manufacturing, office, academics

Basic LAN Topologies Bus/tree Bus/tree Star-wired bus Star-wired bus Star-wired ring Star-wired ring Wireless Wireless

Bus/Tree Topology Original topology in 70s, almost extinct for LAN, but still used in cable television signaling Original topology in 70s, almost extinct for LAN, but still used in cable television signaling Workstation’s Network Interface Card (NIC) attaches to bus (e.g., a coaxial cable) via a tap. Workstation’s Network Interface Card (NIC) attaches to bus (e.g., a coaxial cable) via a tap. Two signaling technologies: Two signaling technologies: Baseband digital signaling: bidirectional (broadcast) Baseband digital signaling: bidirectional (broadcast) Broadband analog signaling: FDM, unidirectional (require special wiring) Broadband analog signaling: FDM, unidirectional (require special wiring) Forming Trees: buses can be split and joined Forming Trees: buses can be split and joined Disadvantage: difficult to add if there is no tap, but anticipate tap need in advance is difficult Disadvantage: difficult to add if there is no tap, but anticipate tap need in advance is difficult

Star-wired Bus Topology Differs from Star LAN, an old star topology Differs from Star LAN, an old star topology Logically operates as a bus, but physically looks like a star Logically operates as a bus, but physically looks like a star Components: Components: Hub Hub non-intelligent, takes incoming signal and immediately retransmit it to all connected links non-intelligent, takes incoming signal and immediately retransmit it to all connected links Workstations linked to Hub via Unshielded TWP Workstations linked to Hub via Unshielded TWP Hubs can be interconnected to extend network size Hubs can be interconnected to extend network size e.g., 24-port hub e.g., 24-port hub Inter hub connections can use TWP, coaxial, or fiber optic cable Inter hub connections can use TWP, coaxial, or fiber optic cable Adv: simple installation & maintenance, low-cost, biggest market share Adv: simple installation & maintenance, low-cost, biggest market share Biggest disadv: – Shared Network Biggest disadv: – Shared Network one talks, everyone hears it one talks, everyone hears it

Star-wired Ring Topology Logically operates as a ring, but physically looks like a star Logically operates as a ring, but physically looks like a star Use baseband signals which has only one channel, signals are unidirectional Use baseband signals which has only one channel, signals are unidirectional Components: Components: MAU (Multistation Access Unit) MAU (Multistation Access Unit) similar to Hub, but only retransmit in unidirection similar to Hub, but only retransmit in unidirection TWP wiring TWP wiring MAUs can be interconnected to increase network size MAUs can be interconnected to increase network size Adv: simple installation & maintenance Adv: simple installation & maintenance Disadv: slower transmission, higher cost, more complex software – close to extinction Disadv: slower transmission, higher cost, more complex software – close to extinction

Wireless LANs No cabling, No any set physical pattern No cabling, No any set physical pattern Workstation within acceptable transmission range to AP; a few feet up to 800 feet Workstation within acceptable transmission range to AP; a few feet up to 800 feet 3 Components: 3 Components: User device/wireless station: e.g., NIC w/ antenna User device/wireless station: e.g., NIC w/ antenna Access Point (AP) – e.g., Ethernet port plus transceiver Access Point (AP) – e.g., Ethernet port plus transceiver AP acts as a bridge betw. wireless and wired networks AP acts as a bridge betw. wireless and wired networks Can perform basic routing functions Can perform basic routing functions Wired LAN which links to services Wired LAN which links to services 3 Configurations: 3 Configurations: BSS: single-cell w/ one AP BSS: single-cell w/ one AP ESS: multiple-cell w/ multiple APs ESS: multiple-cell w/ multiple APs Peer-to-peer or Ad-hoc: no AP Peer-to-peer or Ad-hoc: no AP

ADVANTAGES OF LAN Share resources efficiently. Share resources efficiently. hardware, software hardware, software Individual workstation might survive network failure if it doesn’t rely upon others Individual workstation might survive network failure if it doesn’t rely upon others Component evolution independent of system evolution Component evolution independent of system evolution Support heterogeneous hardware/software Support heterogeneous hardware/software Access to other LANs and WANs Access to other LANs and WANs High transfer rates with low error rates High transfer rates with low error rates Private ownership vs. lease vs. outsourcing Private ownership vs. lease vs. outsourcing

DISADVANTAGES OF LAN Equipment and support can be costly Equipment and support can be costly Network server, NOS, cabling, security, maintenance, etc. Network server, NOS, cabling, security, maintenance, etc. Management and control can be costly Management and control can be costly Licensing issues for network applications Licensing issues for network applications Some types of hardware/software may not interoperate Some types of hardware/software may not interoperate Upgrades may have ripple effects Upgrades may have ripple effects A LAN is only as strong as it weakest link, and there are many links A LAN is only as strong as it weakest link, and there are many links