Wireless IP
Marko Ovaska
1998
Introduction to the Wireless IP
Basic concepts
MOWGLI
WAP
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 1
Levels of analysis in this presentation
Products
Markets
•Wireless local network
•wireless LANs
Specifications, RFCs, draft specs
•Wireless LAN: IEEE 802.11, (MobileIP), WAP, Mowgli
Protocols
•MOWGLI, WAP protocols
Principles, Requirements
•wireless environment
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 2
Wireless IP
•
Wireless environment
•
•
•
•
mobility
Internet protocol in wireless environment
Non-tcp/ip solutions
•
•
© NOKIA
networks
Mowgli
WAP
wireless_ip98.ppt / 07.11.1998 / MOv
page: 3
Wireless Networking
•
Wireless networking is the basic obstacle to be solved for the mobile
computing
•
Wireless media has different characteristics than the current wired
networks
•
Data networking protocols are optimized for the current wired networks
•
•
The protocols are not efficient in the wireless environments
Wireless network can be categorized to:
•
Wireless LAN’s
•
•
Wireless WAN’s
•
•
GSM, GPRS, CDPD, CDMA, PHS, DoCoMo, Ricochet
Microcell
•
© NOKIA
IEEE 802.11
Bluetooth
wireless_ip98.ppt / 07.11.1998 / MOv
page: 4
Wireless Network
•
The wireless network properties differ from the wireline one
•
•
•
•
•
latency
•
802.11: round-trip 2 ms
normal tcp buffer size: 8KB, some W-WAN’s latency*bandwidth exceeds
this
•
GSM: 0.7 s with one byte packet
extra kilo adds round trip time 0.6 seconds per kilo
•
tcp throughput is related to latency: high latency, low throughput
•
interactive applications suffer from long latency times
jitter
error rate
•
non-transparency data connection in GSM offers less than 10-8 bit error rate
however this results in highly variable transmission delays
•
example: 10Mbs LAN has an average of below 10-9 bit error rate
throughput: wireless networks could be characterized "thin”
unexpected disconnections
•
© NOKIA
will the underlying protocol support recovery?
wireless_ip98.ppt / 07.11.1998 / MOv
page: 5
Mobility
•
The mobile wireless networking architecture
•
•
•
•
•
a wireless link
a base station (access point)
a wireline link and landline internet
Wireless mobile device
•
•
•
•
•
•
a wireless mobile device (mobile node)
a laptop, cellular phone, personal communicator
different communication needs: office workstation vs cellular phone vs pager
transmission: packet data vs circuit switched
level of mobility
•
travels from home network to foreign network
•
full mobility, roaming from network to network
Wireless link can consist of several hops
Base station is an intermediating agent
•
© NOKIA
connects the mobile device to wirelined world, acts as a proxy
wireless_ip98.ppt / 07.11.1998 / MOv
page: 6
Wireless components
Internet
(HER, MGBR)
Mobile node
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 7
Typical IP network architecture
ADSL
PSTN/ISDN, (PR)
PC
File Edit LocateView
Topology
Network
Traffic
Help
Help
Mount
431
7437
1950
79%
/
GSM
PC
File Edit LocateView
Topology
Network
Traffic
HUB/SWITCH
Help
Help
ACCESS ROUTER
Mount
431
7437
1950
79%
/
SWITCH/ROUTER
PC
File Edit LocateView
Topology
Network
Traffic
Help
Help
Mount
431
7437
1950
79%
/
(BOR,MRR)
PC
File Edit LocateView
Topology
Network
Traffic
EDGE ROUTER
Help
Help
Mount
431
7437
1950
79%
/
(MRR, HER, MGBR)
ACCESS SERVER
PC
File Edit LocateView
Topology
Network
Traffic
HUB/SWITCH
Help
Help
Mount
431
7437
1950
79%
/
Internet
(HER, MGBR)
PC
File Edit LocateView
Topology
Network
Traffic
© NOKIA
Help
Help
Mount
431
7437
1950
79%
/
wireless_ip98.ppt / 07.11.1998 / MOv
page: 8
Mobile node
Internet Protocol
•
•
Internet protocols are optimized for megabit per second wireline connections
Wireless networking solutions
•
unrelated to IP
•
•
solutions on the top of the IP
•
•
LEO and GEO satellite links
IP packets checksum might not be strong enough
•
•
MobileIP, optimized IP and TCP, modified TCP
researched:
•
•
WAP, Mowgli, SNOOP
PPP has 16-bit CRC
IP is end-to-end protocol
•
© NOKIA
designed to operate in a rather homogenous network
wireless_ip98.ppt / 07.11.1998 / MOv
page: 9
IP cont.
•
•
Purely IP based wireless internet
Link layer enchangements:
•
•
•
forward error correction
retransmissions
improved error detection
•
•
MobileIP solves the addressing and routing problem
•
TCP might be heavy solution to tackle the wireless problem
Path MTU discovery helps to set more optimized end-to-end
•
•
lightweight mobile devices: communication needs versus protocol overhead
Compatibility is a strong need
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 10
TCP/IP cont.
•
TCP optimization
•
•
•
•
slow start termination/modification
•
how will the networks congestion propagate, if slow start is abandoned?
•
Increased initial sending window
TCP header compression
IP payload compression
•
some or most of the data is already compressed
•
files transferred over ftp, published pictures in web
fast retransmit and fast recovery
•
•
© NOKIA
multiple ACKs notify the sender to adjust the send window and initiate fast
retransmissions of the lost packet
scheduling in TCP
•
fairness: fair queuing, class-based queues
•
throughput
wireless_ip98.ppt / 07.11.1998 / MOv
page: 11
Wireless LAN
•
•
•
Wireless LAN specified in IEEE 802.11 spec
Guarantees multi hardware vendor interoperability
Main features:
•
Robust
•
•
•
•
•
© NOKIA
Data acknowledgement, RTS/CTS, data fragmentation
Multi channel roaming. Allows multiple cells resulting in higher capasitity
Power management
Automatic rate selection from 1Mbps to 2Mbps
Security WEP (wired equivalent privacy)
wireless_ip98.ppt / 07.11.1998 / MOv
page: 12
Wireless LAN architecture
•
•
•
Cell consists of work stations and an access point
Access points are interconnected via distribution system (ethernet)
The interconnected network forms an extended service set
•
© NOKIA
Portal connects different 802 based LAN’s
wireless_ip98.ppt / 07.11.1998 / MOv
page: 13
Wireless LAN architecture
•
•
MAC similar to IEEE 802.3 (Ethernet)
Offers common access to three physical layer interfaces
•
•
•
Direct Sequence Spread Spectrum
Frequency Hopping Spread Spectrum
Infrared
Medium access control layer
DSSS
PHY
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
FHSS
PHY
page: 14
IR
PHY
Wireless LAN architecture
•
MAC features
•
•
message fragmentation
CSMA/CD with acknowledgement
•
•
exponential random backoff after successful
sending, in collision and retransmission
RTS/CTS protocol
•
•
data
handles interference
•
•
less impact for lost messages
permission to send
DSSS physical layer features
•
•
© NOKIA
2 Mbps raw data rate with a fallback to 1 Mbps
2.4 GHz band
•
US - 11 overlapping channels
•
ETS - 13 overlapping channels
•
Japan - 1 channel
wireless_ip98.ppt / 07.11.1998 / MOv
page: 15
ack
Wireless LAN architecture
•
•
Station joins a cell
•
find a cell: beacon frame or
active probe request
•
•
authentication
association
Wireless distribution system
•
wireless bridges
•
Automatic rate selection
1Mbps / 2Mbps
•
•
Multi channel roaming
Roaming from cell to cell:
•
•
not in the specification!
Synchronization
•
•
•
© NOKIA
beacon frames
frequency hopping
power saving
wireless_ip98.ppt / 07.11.1998 / MOv
page: 16
Wireless LAN architecture
•
Frame formats
•
MAC frame
Frame
control
•
•
header 30 octets
•
data 0 to 2321 octets
•
crc 4 octets
Duration
/ ID
Address
1
Address
2
Address
3
Address
4
Frame
body
ACK frame
•
header 10 octets
•
crc 4 octets
Frame
control
© NOKIA
Sequence
control
wireless_ip98.ppt / 07.11.1998 / MOv
page: 17
Duration
RA
CRC
CRC
Wireless LAN, prices
Card
Aironet Arlan655, ISA, 2Mbps
Aironet Arlan690, PCMCIA, 2Mbps
BreezeCom PCMCIA, 2Mbps
Lucent Wavelan ISA, 2Mbps
Lucent Wavelan PCMCIA, 2Mbps
Price $
813
654
814
545
495
Access Point
Aironet Arlan630, 2Mbps
BreezeCOM, 3Mbps
Lucent WavePOINT II, 2Mbps
Price $
1800
2100
900
Bridges
Aironet wireless bridge, 4Mbps
Aironet wireless bridge, 2Mbps
BreezeCOM wireless bridge
Lucent WavePOINT II (ethernet to
wireless)
Wireless links
BreezeLink 2Mbps, up to 50 km
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 18
3600
2100
2800 to 3300
1300
5400
MOWGLI
•
Mowgli is a research project to connect a mobile office workstation to the
internet
•
•
•
funding by Nokia, Digital, Sonera and Ministry of Education
The mobile node is connected via a wireless link to the internet/office network
•
•
University of Helsinki’s CS department
the link is GSM non-transparent data connection
Architecture:
•
•
•
•
© NOKIA
Mobile node
Wireless link
Mobile-Connection host (MCH)
Fixed host
wireless_ip98.ppt / 07.11.1998 / MOv
page: 19
Mowgli architecture
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 20
Mowgli
•
Mowgli preserves the socket interface
•
•
•
tcp/ip is replaced
socket interface is modified: wireless environment related extensions
Mowgli data channel service (MDCS)
•
•
•
•
•
•
bidirectional data channel
streamed and message channels (similar to tcp and udp)
256 simultaneous channels
independent per channel flow control
priorities
handles disconnections
•
•
closing if idle, reconnections
The MDCS properties are Mowgli socket API’s QoS services
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 21
Mowgli performance
•
Measurements:
•
One 100 Kb file transferred, times in seconds
Network
LAN
WAN
•
From fixed host to mobile
node
From mobile node to fixed
host
MDCP
TCP
MDCP
TCP
Mean
108,8
139,2
109,2
171,9
Mean
108,4
126,3
109,2
231,2
Min
107,8
116,6
107,5
117,6
Med
108,5
143,1
108,5
154,6
Max
110,2
168,2
116,9
252,7
Min
108,3
114,4
107,1
121,4
Med
108,4
114,7
108,5
152,6
Max
108,6
160,5
115,7
497,1
Three 100 Kb file transferred concurrently, times in seconds
Network
LAN
WAN
© NOKIA
Protocol
Protocol
From fixed host to mobile
node
From mobile node to fixed
host
MDCP
TCP
MDCP
TCP
Mean
326,4
513,8
328,5
362,9
Mean
331,5
344,8
339,7
388,9
wireless_ip98.ppt / 07.11.1998 / MOv
Min
320,8
413,3
254,6
251,0
page: 22
Med
326,2
495,4
325,6
364,1
Max
330,4
591,4
385,2
480,0
Min
315,8
299,7
307,4
253,0
Med
324,2
325,9
324,1
358,9
Max
494,3
490,9
584,8
759,9
Wireless Application Protocol
•
•
Wireless Application Protocol (WAP) is developed by WAP Forum
WAP Forum is multivendor
•
•
First WAP specification 1.0 was released April 1998
•
•
the work groups carry on to include a broader representation
WAP is aimed to
•
•
•
grounded by Ericsson, Motorola, Nokia and Unwired Planet
bring Internet content to wireless mobile device
create a global wireless protocol specification to work across different networks
The WAP model resembles WWW-model
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 23
WAP Model
•
•
The WAP model resembles WWW-model
The WAP Gateway contains the protocol conversion services
•
© NOKIA
gateway has internet protocol specific WAP proxies
wireless_ip98.ppt / 07.11.1998 / MOv
page: 24
WAP defines
•
WAP defines
•
•
•
•
micro-browser, similar to web browser
scripting (WMLScript), similar to JavaScript
telephony support
formalized interfaces for different content types
•
•
© NOKIA
business cards, calendar events etc.
telecommunication stack
•
transport
•
security
•
session
wireless_ip98.ppt / 07.11.1998 / MOv
page: 25
WAP network
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 26
WAP architecture
•
•
The WAP protocol stack replaces tcp/ip in mobile devices
•
WDP and the bearer
networks handle roaming
•
WDP has bearer specific
profiles
•
WTLS is similar to SSL
The WDP unifies the different bearer properties
•
•
denial-of-service
protection
WSP offers two interfaces
•
•
© NOKIA
stream data (TCP)
datagram (UDP)
wireless_ip98.ppt / 07.11.1998 / MOv
page: 27
WAP: WDP
•
Two different WDP bearer specifications:
•
© NOKIA
WDP over GSM circuit switched data connection
wireless_ip98.ppt / 07.11.1998 / MOv
page: 28
WAP: WDP cont.
•
© NOKIA
WDP over GPRS
wireless_ip98.ppt / 07.11.1998 / MOv
page: 29
WAP: WTA
•
The WTA (wireless telephony application) allows telephony functionality in the
mobile device
•
•
WTA interface contains subspecifications for different networks
•
•
calling, incoming call, voice mail
for example: GSM, PDC, IS-136
Examples of the WTA interface:
<WML>
<FORM>
<DO TYPE=“ACCEPT” TASK=”GO”
URL=”wtai:cc/mc;$(N)”/>
Enter phone number:
<INPUT TYPE=”TEXT” KEY=”N”/>
</FORM>
</WML>
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 30
WAP: WTA
<WML>
<COMMON>
<SCRIPT>
function checkNumber(N) {
if (Lang.isInt(N))
WTAI.makeCall(N);
else
Dialog.alert(“Bad phone
number”);
}
</SCRIPT>
</COMMON>
<FORM>
<DO TYPE=”ACCEPT” TASK=”GO”
URL=”wtai:cc/mc;$(N)”/>
Enter phone number:
<INPUT TYPE=”TEXT” KEY=”N”/>
</FORM>
</WML>
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 31
Markets
•
The broadband future of online services and Internet access in Europe
(Datamonitor, 1997)
Households (000)
33,6 kb/s and below
56 kb/s + (analogue)
ISDN
Cable modems
XDSL
Digital sat./ wireless
Other broadband
Total
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
1996
2 625
375
3 000
page: 32
1997
1998
4 715 7 239
872 3 363
872 1 749
116
485
87
396
29
135
18
84
6 709 13 451
1999
8 050
8 175
2 725
1 262
1 001
348
238
21 799
2000
7 100
13 950
3 450
2 408
1 889
733
469
29 999
2001
5 200
20 000
3 800
4 000
3 000
1 200
800
38 000
Markets
•
Worldwide LAN switch market split by technology, 1995-2001 (Datamonitor,
07/97)
© NOKIA
USD millions
ATM
10Mbps
Ethernet
100Mbps
Ethernet
Gigabit
Ethernet
Token ring
IP / L3
switching
Other
1995
140
1 080
1996
340
2 480
1997
650
3 430
1998
1 020
4 150
1999
1 340
4 370
2000
1 700
4 400
2001
2 000
4 450
80
240
610
1 350
2 700
3 900
5 100
0
0
50
200
450
950
1 700
100
0
260
0
450
60
600
200
600
420
550
800
450
1 150
100
200
330
400
450
400
350
Total
1 500
3 520
5 580
wireless_ip98.ppt / 07.11.1998 / MOv
page: 33
7 920 10 330 12 700 15 200
Markets
1200
Millions of Users
1000
800
Internet Users
600
Cellular Subscribers
400
Exchange Lines
200
0
1996
© NOKIA
wireless_ip98.ppt / 07.11.1998 / MOv
page: 34
2000