Bab I

1
Bab I

• Pengenalan Wireless LAN

2
Pasar Wireless LAN

• Terlihat seperti fashion dalam industri network
• Pertumbuhan sangat pesat
• Wireless LAN sangat fleksibel dalam implementasi

3
Sejarah Wireless LAN

• Spread spektrum wireless network
• Harga teknologi wireless semakin turun dan
  kualitas semakin bagus
• Menawarkan koneksi yang tidak mahal bagi
  perusahaan/kampus untuk menghubungkan antar
  gedung
• Sekarang, banyak bisnis yang mengimplementasikan
  wireless dalam networknya
• Mampu menghemat waktu dan uang perusahaan ketika
  memerlukan fleksibilitas perpindahan

4
Standart Wireless LAN

• IEEE 802.11
• Standart asli wireless LAN
• Transfer data paling lambat
• IEEE 802.11 b
• Transfer data lebih cepat
• Dikenalkan sebagai Wi-FiTM oleh WECA
• IEEE 802.11 a
• Transfer data lebih cepat lagi
• Tidak kompatibel dengan lainnya, frekuensi 5 GHz
• IEEE 802.11 g
• Transfer data sama cepat dengan IEEE 802.11 a
• Kompatibel dengan IEEE 802.11 b

5
Dasar Radio Frequensi (RF) 2

• Gain ?
• digambarkan sebagai sebuah penambahan amplitudo
  signal RF
• Loss ?
• digambarkan sebagai sebuah pengurangan amplitudo
  
• signal RF

6
Voltage Standing Wave Ratio (VSWR)

• Apa kah VSWR ?
• suatu keadaan dimana terjadi ketidaksamaan
  impedansi antar peralatan dalam sistem RF
• Penyebab VSWR ?
• disebabkan oleh sebuah signal RF yang
  ter-refleksi pada titik dari impedansi dalam path
  signal
• Akibat VSWR
• return loss kemorosotan energi yang melalui
  sistem

7
Voltage Standing Wave Ratio (VSWR)

• Ukuran VSWR
• direpresentasikan 2 angka sebagai perbandingan
• AB (1.51), A adalah impedansi dari peralatan, B
  impedansi yang seharusnya
• Solusi VSWR
• Gunakan semua kabel, konektor dan peralatan
  mempunyai impedansi yang sama atau paling tidak
  hampir sama untuk semua peralatan.

8
Fresnel Zone Line of Sight
9

• Antenna Gain ??
• ukuran kekuatan antena dalam memancarkan signal
• Intentional Radiator
• peralatan RF yang secara khusus dirancang untuk
  menghasilkan dan memancarkan signal RF, dalam
  hardaware meliputi peralatan RF, semua
  pengkabelan, konektor dan antena
• Equivalent Isotropically Radiated Power (EIRP)
• power yang dipancarkan oleh elemen antena,dan
  menentukan gain dari antena

10
Satuan Ukuran

• Watts (W)
• Miliwatt (mW)
• Decibels (dB)
• dBm

11
Perbandingan ukuran
12
Spread spectrum

• Teknik komunikasi dimana karakternya ditentukan
  oleh lebar bandwith dan low peak power-nya
• Signalnya hampir sama dengan noise
• Kelebihan
• Susah di deteksi
• Susah di modulasi tanpa alat khusus
• Narrow Band Transmission dan Spread Spectrum
  Technology

13
Spread Spectrum
14
Narrow Band Transmission

• Teknologi komunikasi yang menggunakan cukup
  spektrum frekuensi untuk membawa signal data
• High peak power
• Range frekuensi kecil

15
Spread Spectrum Technology

• Menggunakan range frekuensi yang lebar
• Mengurangi kemungkinan data corrupt atau jammed
• Low peak power

16
Penggunaan Spread Spectrum

• Dapat dikirim dibawah komunikasi klasik
• Wireless Local Area Networks
• Wireless Personal Area Networks
• Wireless Metropolitan Area Networks

17
2 Teknologi Spread Spectrum

• Direct Sequence Spread Spectrum (DSSS)
• Frequency Hopping Spread Spectrum (FHSS)

18
Bab 4

• Wireless LANInfrastructure Devices

19
Access Point
20
Install AP dalam wired network
21
3 Mode Konfigurasi AP

• Root Mode
• Repeater Mode
• Bridge Mode

22
Root Mode
23
Bridge Mode
24
Repeater Mode
25
Wireless Bridge
26
Penggunaan Wireless Bridge
27
4 mode komunikasi wireless bridge

• Root Mode
• Salah satu bridge harus diset sebagai root bridge
• Bisa berkomunikasi dengan non-root bridge lainnya
• Tidak bisa berkomunikasi dengan root bridge
  lainnya
• Non-root Mode
• Komunikasi bisa ke root bridge
• Access Point Mode
• Punya kemampuan memperbolehkan client connect
• Repeater Mode
• Berada diantara 2/lebih bridge
• Memperpanjang segmen wireless bridge

28
Peralatan yang berhubungan dengan wireless bridge

• Fixed or Detachable Antennas
• Advanced Filtering Capabilities
• Removable (modular) Radio cards
• Variable Output Power
• Varied Types of Wired Connectivity

29
Wireless Workgroup Bridges
30
Penggunaan Wireless Workgroup Bridges
31
Wireless LAN client devices

• PCMCIA compact flash cards
• Ethernet serial converters
• USB Adapters
• PCI ISA Adapters

32
PCMCIA Converter
33
Wireless Adapters
34
Wireless LANs Characteristics

• Types
• Infrastructure based
• Adhoc
• Advantages
• Flexible deployment
• Minimal wiring difficulties
• More robust against disasters (earthquake etc)
• Disadvantages
• Low bandwidth compared to wired networks (1-10
  Mbit/s)
• Proprietary solutions
• Need to follow wireless spectrum regulations

35
Infrastructure vs. Adhoc Networks
infrastructure network
AP Access Point
AP
AP
wired network
AP
ad-hoc network
Source Schiller
36
Transmission Infrared vs. Radio

• Infrared
• uses IR diodes, diffuse light, multiple
  reflections (walls, furniture etc.)
• Advantages
• simple, cheap, available in many mobile devices
• no licenses needed
• simple shielding possible
• Disadvantages
• interference by sunlight, heat sources etc.
• many things shield or absorb IR light
• low bandwidth
• Example
• IrDA (Infrared Data Association) interface
  available everywhere

• Radio
• typically using the license free ISM band at 2.4
  GHz
• Advantages
• experience from wireless WAN and mobile phones
  can be used
• coverage of larger areas possible (radio can
  penetrate walls, furniture etc.)
• Disadvantages
• very limited license free frequency bands
• shielding more difficult, interference with other
  electrical devices
• Example
• WaveLAN, HIPERLAN, Bluetooth

Source Schiller
37
Difference Between Wired and Wireless
Ethernet LAN
Wireless LAN
B
A
B
C
C
A

• If both A and C sense the channel to be idle at
  the same time, they send at the same time.
• Collision can be detected at sender in Ethernet.
• Half-duplex radios in wireless cannot detect
  collision at sender.

38
Mobile IP (RFC 2002) Motivation

• Traditional routing
• based on IP destination address
• network prefix determines physical subnet
• change of physical subnet implies
• change of IP address (conform to new subnet), or
• special routing table entries to forward packets
  to new subnet
• Changing of IP address
• DNS updates take to long time
• TCP connections break
• security problems
• Changing entries in routing tables
• does not scale with the number of mobile hosts
  and frequent changes in the location
• security problems
• Solution requirements
• retain same IP address, use same layer 2
  protocols
• authentication of registration messages,

39
Mobile IP Basic Idea
Router 3
MN
S
Home agent
Router 1
Router 2
Source Vaidya
40
Mobile IP Basic Idea
move
Router 3
S
MN
Foreign agent
Home agent
Router 1
Router 2
Packets are tunneled using IP in IP
Source Vaidya
41
Mobile IP Terminology

• Mobile Node (MN)
• node that moves across networks without changing
  its IP address
• Home Agent (HA)
• host in the home network of the MN, typically a
  router
• registers the location of the MN, tunnels IP
  packets to the COA
• Foreign Agent (FA)
• host in the current foreign network of the MN,
  typically a router
• forwards tunneled packets to the MN, typically
  the default router for MN
• Care-of Address (COA)
• address of the current tunnel end-point for the
  MN (at FA or MN)
• actual location of the MN from an IP point of
  view
• Correspondent Node (CN)
• host with which MN is corresponding (TCP
  connection)

42
Data transfer to the mobile system
HA
2
MN
Internet
home network
receiver
3
FA
foreign network
1
1. Sender sends to the IP address of MN, HA
intercepts packet (proxy ARP) 2. HA tunnels
packet to COA, here FA, by encapsulation 3.
FA forwards the packet to the MN
CN
sender
Source Schiller
43
Data transfer from the mobile system
HA
1
MN
Internet
home network
sender
FA
foreignnetwork
1. Sender sends to the IP address of the
receiver as usual, FA works as default router
CN
receiver
Source Schiller
44
Reverse tunneling (RFC 2344)
HA
2
MN
Internet
home network
sender
1
FA
foreignnetwork
1. MN sends to FA 2. FA tunnels packets to HA
by encapsulation 3. HA forwards the packet to
the receiver (standard case)
3
CN
receiver
Source Schiller
45
Mobile IP Other Issues

• Reverse Tunneling
• firewalls permit only topological correct
  addresses
• a packet from the MN encapsulated by the FA is
  now topological correct
• Agent Advertisement
• HA/FA periodically send advertisement messages
  into their physical subnets
• MN listens to these messages and detects, if it
  is in home/foreign network
• MN reads a COA from the FA advertisement messages
• Registration
• MN signals COA to the HA via the FA
• HA acknowledges via FA to MN
• limited lifetime, need to be secured by
  authentication
• Optimizations
• Triangular Routing
• HA informs sender the current location of MN
• Change of FA
• new FA informs old FA to avoid packet loss, old
  FA now forwards remaining packets to new FA

46
Multi-Hop Wireless Networks

• May need to traverse multiple links to reach
  destination
• Mobility causes route changes

Source Vaidya
47
Mobile Ad Hoc Networks (MANET)

• Host movement frequent
• Topology change frequent
• No cellular infrastructure. Multi-hop wireless
  links.
• Data must be routed via intermediate nodes.

Source Vaidya
48
Routing in MANET

• Mobile IP needs infrastructure
• Home Agent/Foreign Agent in the fixed network
• DNS, routing etc. are not designed for mobility
• MANET
• no default router available
• every node also needs to be a router
• Can we use traditional routing algorithms?
• Distance Vector
• periodic exchange of routing tables (destination,
  distance, next hop)
• selection of the shortest path if several paths
  available
• Link State
• periodic notification about current state of
  physical links (flooding)
• router get a complete picture of the network

49
Traditional Routing

• A routing protocol sets up a routing table in
  routers
• A node makes a local choice depending on global
  topology

Source Keshav
50
Distance-vector Link-state Routing

• Both assume router knows
• address of each neighbor
• cost of reaching each neighbor
• Both allow a router to determine global routing
  information by talking to its neighbors
• Distance vector - router knows cost to each
  destination
• Link state - router knows entire network topology
  and computes shortest path

51
Distance Vector Routing Example
2
?
?
?
Source Keshav
52
Link State Routing Example
Source Keshav
53
MANET Routing Protocols

• Reactive protocols
• Determine route if and when needed
• Source initiates route discovery
• Example DSR (dynamic source routing)
• Proactive protocols
• Extension of traditional routing protocols
• Maintain routes between every host pair at all
  times
• Example DSDV (destination sequenced distance
  vector)
• Hybrid protocols
• Adaptive Combination of proactive and reactive
• Example ZRP (zone routing protocol)
• Multicast routing

54
Dynamic Source Routing (DSR) Johnson96

• When source S wants to send a packet to
  destination D, but does not know a route to D, S
  initiates a route discovery
• S floods Route Request (RREQ)
• Each node appends its own identifier when
  forwarding RREQ
• D on receiving the first RREQ, sends a Route
  Reply (RREP)
• RREP sent on route obtained by reversing the
  route appended in RREQ
• RREP includes the route from S to D, on which
  RREQ was received by D
• S on receiving RREP, caches the route included in
  the RREP
• When S sends a data packet to D, entire route is
  included in the header
• Intermediate nodes use the source route in the
  packet header to determine to whom a packet
  should be forwarded

55
Route Discovery in DSR
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Represents a node that has received RREQ for D
from S
Source Vaidya
56
Route Discovery in DSR
Y
Broadcast transmission
Z
S
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Represents transmission of RREQ
X,Y Represents list of identifiers appended
to RREQ
57
Route Discovery in DSR
Y
Z
S
S,E
E
F
B
C
M
L
J
A
G
S,C
H
D
K
I
N

• Node H receives packet RREQ from two neighbors
• potential for collision

58
Route Discovery in DSR
Y
Z
S
E
F
S,E,F
B
C
M
L
J
A
G
H
D
K
S,C,G
I
N

• Node C receives RREQ from G and H, but does not
  forward
• it again, because node C has already forwarded
  RREQ once

59
Route Discovery in DSR
Y
Z
S
E
F
S,E,F,J
B
C
M
L
J
A
G
H
D
K
I
N
S,C,G,K

• Nodes J and K both broadcast RREQ to node D
• Since nodes J and K are hidden from each other,
  their
• transmissions may collide

60
Route Discovery in DSR
Y
Z
S
E
S,E,F,J,M
F
B
C
M
L
J
A
G
H
D
K
I
N

• Node D does not forward RREQ, because node D
• is the intended target of the route discovery

61
Route Reply in DSR
Y
Z
S
RREP S,E,F,J,D
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Represents RREP control message
62
Data Delivery in DSR
Y
Z
DATA S,E,F,J,D
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Packet header size grows with route length
63
DSR Issues

• Optimizations cache routes learnt by any means
• When S finds route S,E,F,J,D to D, S also
  learns route S,E,F to F
• When K receives RREQS,C,G for G, K learns route
  K,G,C,S to S
• When F forwards RREP S,E,F,J,D, F learns route
  F,J,D to D
• When E forwards Data S,E,F,J,D, E learns route
  E,F,J,D to D
• Advantages
• Routes maintained only between nodes who need to
  communicate
• Reduces overhead of route maintenance
• Caching (at intermediate nodes) can further
  reduce route discovery overhead
• Disadvantages
• Packet header size grows with route length due to
  source routing
• Flood of route requests may potentially reach all
  nodes in the network
• Route Reply Storm problem Many intermediate
  nodes reply from local cache
• Stale caches will lead to increased overhead

64
Destination-Sequenced Distance-Vector (DSDV)
Perkins94Sigcomm

• Each node maintains a routing table which stores
• next hop, cost metric towards each destination
• a sequence number that is created by the
  destination itself
• Each node periodically forwards routing table to
  neighbors
• Each node increments and appends its sequence
  number when sending its local routing table
• Each route is tagged with a sequence number
  routes with greater sequence numbers are
  preferred
• Each node advertises a monotonically increasing
  even sequence number for itself
• When a node decides that a route is broken, it
  increments the sequence number of the route and
  advertises it with infinite metric
• Destination advertises new sequence number

65
Destination-Sequenced Distance-Vector (DSDV)

• When X receives information from Y about a route
  to Z
• Let destination sequence number for Z at X be
  S(X), S(Y) is sent from Y
• If S(X) gt S(Y), then X ignores the routing
  information received from Y
• If S(X) S(Y), and cost of going through Y is
  smaller than the route known to X, then X sets Y
  as the next hop to Z
• If S(X) lt S(Y), then X sets Y as the next hop to
  Z, and S(X) is updated to equal S(Y)

Z
X
Y
66
Reactive v/s Proactive Trade-offs

• Reactive protocols
• Lower overhead since routes are determined on
  demand
• Significant delay in route determination
• Employ flooding (global search)
• Control traffic may be bursty
• Proactive protocols
• Always maintain routes
• Little or no delay for route determination
• Consume bandwidth to keep routes up-to-date
• Maintain routes which may never be used
• Which approach achieves a better trade-off
  depends on the traffic and mobility patterns

67
Zone Routing Protocol (ZRP) Haas98

• ZRP combines proactive and reactive approaches
• All nodes within hop distance at most d from a
  node X are said to be in the routing zone of node
  X
• All nodes at hop distance exactly d are said to
  be peripheral nodes of node Xs routing zone
• Intra-zone routing Proactively maintain routes
  to all nodes within the source nodes own zone.
• Inter-zone routing Use an on-demand protocol
  (similar to DSR or AODV) to determine routes to
  outside zone.

68
ZRP Example
Radius of routing zone 2