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
Pertemuan 18
Jaringan LAN - Nirkabel
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
Ch1
Ch6
2480
2475
2470
2465
2460
20MHz
2455
2450
2445
2440
2435
20MHz
2430
2425
2420
2415
2410
2405
2400
Channel Frequency
20MHz
2400
2483.5
Ch11
26
Wireless LAN Specifications
802.11b+
Data Transfer Rate
802.11b
802.11g
802.11a
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
Ad-Hoc Mode (also known as “peer-to-peer” mode)
Screen Monitor II
PC equipped with
wireless LAN
adapter
Notebooks equipped
with wireless LAN
adapters
29
Two Modes in 802.11b
Infrastructure Mode
Internet
Wired
Computer
with printer
sharing
Screen Monitor II
Wired File
Server
Gateway to
Internet
Wired Ethernet Network
Hardware
Access Point
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