Remote Access for Mobile Computing

Andrew Jessett

NT Support and Development Group (a.k.a. PC Support)

www.pcsupport.rl.ac.uk

Business and Information Technology Department

The Dial-up Servers

Server Name DIALUP01 DIALUP05 DIALUP??

Modems 5 x V.34 8 x V.90 30 x V.90

Telecoconnection

Standard BTPOTS

ISDN BRI viaMD110

ISDN PRI viaMD110

Maximumdownlinkspeed

33.6 kbps 56 kbps 56 kbps

Maximumuplinkspeed

33.6 kbps 33.6 kbps 33.6 kbps

RAL RAS Service - VPN

•Virtual Private Network

•PPTP - Point to Point Tunnelling Protocol

•Allows secure connection from any* Internet connection

Point to Point Tunneling Protocol

Provides a secure tunnel between client and corporate

LAN creating what is termed a Virtual Private

Network

RAL RAS Service

•Authentication is by CLRC NT domain not RAS

•User account must have dial-up permission set

•Each server issues IP addressess from pool

•Though user can have fixed address if required

RAL RAS ServiceConnection problems

•Usually bad line

•Local loop fault

•House wiring - REN

•DACS -line sharing device limits speed

•Modem incompatibility

•WinModems and low cost modems

•Modem configuration files (drivers)

•Rarely server problem :-)

Global Roaming (GRIC)

•Allows connection to local ISP wherever user is visiting

•Local call charge to user + per minute charge to account

•Allows access to mail at RAL

•Used with PPTP allows access to the RAL Intranet

Other connection methods

•Integrated Services Digital Network

(BT Home Highway)

•Asymmetric Digital Subscriber Line

•Cable modems

•Wireless networking

Wireless Networking

•Wireless Ethernet

•Bluetooth

•Mobile phone - GSM, GPRS, UMTS

Wireless Ethernet

Two or more wireless-enabled devices create own wireless network without an AP

Using an Access Point Wireless clients connect to the LAN

Wireless Ethernet

IEEE 802.11b 11Mbps 2.45 Ghz (ISM)

IEEE 802.11g 54 Mbps 2.45 Ghz (ISM)

IEEE 802.11a 54 Mbps 5 Ghz

(IEEE 802.11h 54 Mbps 5 Ghz)

HiperLan2 54 Mbps 5 Ghz

Wireless Ethernet Security•Service Set Identifier (SSID)

Associated with AP or AP group. Can be used to

segment wireless network

•Media Access Control (MAC) address filtering

Access allowed/denied by physical address

•Wired Equivalent Privacy (WEP)

Encryption and authentication via common key

•Very weak - even WEP can be cracked

•Latest hacker sport - “War Driving”

Bluetooth•Alternative to IR port

•Wireless connection of all peripherals

•Connection to LAN

•Uses 2.45 Ghz ISM band

•721 kbps

•Up to 8 active devices in Piconet

•Interconnect Piconets to form Scatter Nets

Mobile phone

•With external GSM modem allows connections typically 9.6 kbps, possible 14.4 kbps depending on service provider

•More recent WAP enabled phones have internal modem

•WAP - Wireless Access Protocol

•Circuit-switched therefore cost depends on duration of call

GSM - Global System for Mobile

Mobile phone

•Works on top of GSM but is connectionless. Therefore costs are base on the amount of data passed

•Data rates of 56 - 114 kbps plus

•Generation 2.5 therefore stopgap until 3G

GPRS - General Packet Radio Service

Mobile phone

•Third generation - 3G

•Completely separate system requiring new infrastructure

•Data rates of 2 Mbps plus

•Connectionless

UMTS - Universal Telecommunications System