Matakuliah
Tahun
Versi
: H0174/Jaringan Komputer
: 2006
: 1/0
Pertemuan 17
Jaringan LAN (Local Area Network)
1

Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu :
• Menyediakan LAN
2

Outline Materi
• Standard IEEE 802
• MAC/LLC
• Hub
• LAN switch
3

LAN Architecture
• Topologies
• Transmission medium
• Layout
• Medium access control
4

LAN Topologies
5

Bus and Tree
• Multipoint medium
• Transmission propagates throughout medium
• Heard by all stations
– Need to identify target station
• Each station has unique address
• Need to regulate transmission
– To avoid collisions
– To avoid hogging
• Data in small blocks - frames
6

Star Topology
• Each station connected directly to central node
– Usually via two point to point links
• Central node can broadcast
– Physical star, logical bus
– Only one station can transmit at a time
• Central node can act as frame switch
7

Protocol Architecture
• Lower layers of OSI model
• IEEE 802 reference model
• Physical
• Logical link control (LLC)
• Media access control (MAC)
8

Shared Medium Bus and Hub
9

Bus and Hub
• Bus configuration
– All stations share capacity of bus (e.g.
10Mbps)
– Only one station transmitting at a time
• Hub uses star wiring to attach stations to hub
– Transmission from any station received by hub and retransmitted on all outgoing lines
– Only one station can transmit at a time
– Total capacity of LAN is 10 Mbps
10

Two Level Star Topology
11

Hub and Layer 2 Switch
12

Layer 2 Switch Benefits
• No change to attached devices to convert bus
LAN or hub LAN to switched LAN
• For Ethernet LAN, each device uses Ethernet
MAC protocol
• Device has dedicated capacity equal to original
LAN
• Layer 2 switch scales easily
– Additional devices attached to switch by increasing capacity of layer 2
13

Media
• High performance UTP
– Cat 5 and above
– High data rate for small number of devices
– Switched star topology for large installations
• Optical fiber
– Electromagnetic isolation
– High capacity
– Small size
– High cost of components
– High skill needed to install and maintain
• Prices are coming down as demand and product range increases
14

802 Layers - Logical Link Control
• Interface to higher levels
• Flow and error control
15

Logical Link Control
• Transmission of link level PDUs between two stations
• Must support multiaccess, shared medium
• Relieved of some link access details by MAC layer
• Addressing involves specifying source and destination LLC users
– Referred to as service access points (SAP)
– Typically higher level protocol
16

Media Access Control
• Assembly of data into frame with address and error detection fields
• Disassembly of frame
– Address recognition
– Error detection
• Govern access to transmission medium
– Not found in traditional layer 2 data link control
• For the same LLC, several MAC options may be available
17

LAN Protocols in Context
18

Generic MAC Frame Format
19

MAC Frame Format
• MAC control
• Destination MAC address
• Source MAC address
• LLC
– MAC layer receives data from LLC layer
• CRC
– MAC layer detects errors and discards frames
LLC optionally retransmits unsuccessful frames
20

Matakuliah
Tahun
Versi
: H0174/Jaringan Komputer
: 2006
: 1/0
21

Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu :
• Menyediakan LAN -Nirkabel
22

Outline Materi
• Ad-Hoc
• Infra strucutre
• Standards
23

802.11b Wireless LAN
• Use multiple frequencies in the 2.4GHz range
• Utilise Direct Sequence Spread Spectrum (DSSS) technology
• Carrier Sense Multiple Access with Collision
Avoidance (CSMA/CA)
• Wired Equivalent Privacy (WEP)
24

Channel Frequency
• Frequency range of DSSS is between 2.4 to 2.4835
GHz
• No. of channels at different part of the world varies
(S.E.A. : 13 channels)
• Each channel bandwidth is approximately 20MHz
25

Channel Frequency
20MHz 20MHz 20MHz
2400
Ch1 Ch6 Ch11
2483.5
26

Wireless LAN Specifications
802.11b+ 802.11b
802.11g
802.11a
Data Transfer Rate Up to 22Mbps Up to 11Mbps Up to 54Mbps Up to 54Mbps
Frequency 2.4GHz
2.4GHz
2.4GHz
5GHz
Compatibiliy 802.11b
802.11g
802.11b
802.11a only
27

KOMPONEN AKSES
• Client (PCMCIA card)
• External Antena
• Access Points
• Enterprise Access Point
• Residential Gateways
• Access Servers (Public Access)
• Outdoor Routers (Outdoor)
28

Two Modes in 802.11b
AdHoc Mode (also known as “peer-to-peer” mode)
Screen Monitor II
PC equipped with wireless LAN adapter
Notebooks equipped with wireless LAN adapters
29

Infrastructure Mode
Screen Monitor II
Wired
Computer with printer sharing
Hardware
Access Point
Wired File
Server
Gateway to
Internet
Wired Ethernet Network
Internet
Wireless Network
Screen Monitor II
PC equipped with wireless
LAN adapter
Notebooks equipped with wireless LAN adapters 30

APLIKASI OUTDOOR
• Biasanya mempunyai Central Outdoor Unit
(Router) dan Remote Oudoor Unit (Router)
• Tiap segment dapat melayani sampai misalnya 32 remote sites
• Cakupan sampai to 15 km
• Kecepatan 11Mbps, 3 channels
• Mendukung indoor/outdoor connectivity
31

OUTDOOR POINT TO POINT

REPEATER POINT TO POINT

POINT TO MULTI POINT

POINT TO MOBILE POINT