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Serial ways to Internet Ksenija Furman Jug ARNES [email protected] Serial Communications The goal of our session Agenda General overview Theoretical fundaments Practice ? ? ? ? Connecting to Internet Why? How? Costs? Overview Dial-up Provider perspective User perspective

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serial ways to internet

Serial ways to Internet

Ksenija Furman Jug

ARNES

[email protected]

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

serial communications
Serial Communications
  • The goal of our session
  • Agenda
    • General overview
    • Theoretical fundaments
    • Practice

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

connecting to internet

?

?

?

?

Connecting to Internet
  • Why?
  • How?
  • Costs?

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

overview
Overview
  • Dial-up
    • Provider perspective
    • User perspective
      • Dial-out host
      • Dial-out LAN
  • Leased lines

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

serial
Serial

Serial data pipes

Internet user

Internet service provider

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

slide6
How?
  • Dial-Up
  • Leased line
  • Public Data Services (X.25,Frame Relay, ATM,..)

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

serial7
Serial
  • Dial-up
    • Provider perspective
    • User perspective
      • Dial-out host
      • Dial-out LAN
  • Leased lines

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial up
Dial-up
  • Technology type
    • POTS - Plain Old Telephone System
    • ISDN - Integrated Services Digital Network
  • Type of services
    • host
    • LAN

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial up host

Internet

Dial-up host

Provider’s

Access Server

Asynchronous modem

User’s PC

POTS

Asynchronous modem

dial up lan

Internet

Dial-up LAN

Provider’s

Access Sever

Asynchronous

modems

LAN

POTS

Router

Asynchronous modem

serial11
Serial
  • Dial-up
    • Provider perspective
    • User perspective
      • Dial-out host
      • Dial-out LAN
  • Leased lines

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

provider perspective
Provider perspective
  • Choose the equipment
  • Form a user database
  • Create a security mechanism
  • Create an IP addressing scheme
  • Select the routing scheme for LAN

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

choosing equipment pots cont
Choosing equipment - POTS (cont.)
  • Sufficient number of telephone lines
    • geographical distribution helps decrease calling costs
    • number of users per line
  • Asynchronous modems
    • modem management (SNMP)
    • software upgradable

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

choosing equipment pots cont14
Choosing equipment - POTS (cont.)
  • Access server
    • protocols (SLIP/PPP)
    • terminal services
    • users database
    • security tools
    • IP routing
    • management (SNMP)
    • filters

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

user database
User database
  • on the Access Server
  • on a special host

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

security mechanism
Security mechanism
  • DIAL-UP - a big security thread
  • Authentication, Authorization, Accounting
  • Security servers (TACACS+, RADIUS,..)

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

tacacs radius
TACACS+

based on TCP

encrypts all data

separated AAA

more complex

open for future extensions

RADIUS

based on UDP

encrypts only challenge responses

supported by more vendors

TACACS+/RADIUS

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

authentication
Authentication
  • Each user having a “good” password
  • Users forced to change password
  • One time passwords
  • Login procedure
  • PPP authentication (PAP, CHAP)
  • Caller Line Identification (ISDN)

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

authorization
Authorization
  • Who is allowed to do what

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

user accounting
User Accounting
  • In case of dynamic addressing helps to trace intruders
  • For charging

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

ip addressing scheme dial in host
IP addressing scheme - Dial-in host
  • Dynamic address allocation
    • saves address space
    • users can not be always reachable at same IP address
  • IP address dedicated per user
    • “impossible” with large number of users
    • useful for some services

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

ip addressing scheme dial in lan
IP addressing scheme - Dial-in LAN
  • Addresses on LAN side
    • registered IP addresses
    • IP masquerading - using private address space

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

routing scheme for lan
Routing scheme for LAN
  • Static routing
    • dedicated address on PPP side to which a static route is pointing
  • Dynamic routing
    • filter routing information to disable advertisement of invalid routes

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

static routing
Static routing

Network: 193.225.219.0

193.225.220.6

User’s router

Provider’s Access Server

Static route for 193.225.219.0

Default route pointing to the

asynchronous interface

to address 193.225.220.6

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dynamic routing
Dynamic routing

Network: 193.225.219.0

User’s router

Provider’s Access Server

Enable routing protocol on

both interfaces

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

serial26
Serial
  • Dial-up
    • Provider perspective
    • User perspective
      • Dial-out host
      • Dial-out LAN
  • Leased lines

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial out host
Dial-out host
  • Get the account
    • inform yourself about number of users per modem, types of services and charging
  • Choose equipment
  • Take care about the password

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

choosing equipment dial out host pots
Choosing equipment - Dial-out host - POTS
  • Asynchronous modem
    • the compatibility to provider modems
    • latest standard
  • PC

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

choosing equipment dial out lan pots cont
Choosing equipment - Dial-out LAN - POTS (cont.)
  • Asynchronous modem
    • compatibility with providers modems
    • latest standard
  • Dial on Demand Router
    • commercial
      • dedicated box for higher price
      • reliable and easy to manage

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

choosing equipment dial out lan pots cont30
Choosing equipment - Dial-out LAN - POTS (cont.)
  • PC with DOS, Linux, WIN NT,..
    • non-dedicated box for lower price
    • also usable for Internet server
    • less reliable, more complex to manage
  • Features
    • Dial on Demand

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial out host types of services
Dial-out host - types of services
  • Low cost - accessible to anyone
  • Telnet access
    • less friendly user interface

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial out host types of services32
Dial-out host - types of services
  • PPP/SLIP
    • Complete individual Internet connectivity
    • user friendly client software
    • e-mail:
      • POP server

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial out host types of services33
Dial-out host - types of services
  • Internet servers
    • not convenient
    • you need a fixed IP address and dialing in both directions
    • provider can offer an host for users homepages

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial out lan types of services cont
Dial-out LAN - types of services (cont.)
  • PPP/SLIP
  • Full connectivity for LAN on demand
  • Low cost
  • E-mail:
    • UUCP

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial out lan types of services cont35
Dial-out LAN - types of services (cont.)
    • SMTP demon with spooler
      • at time of activation of line, mail has to be transferred to destination LAN
  • Internet servers
    • not convenient
    • you need a fixed IP address and dialing in both directions

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

dial on demand
Dial on Demand
  • Define interesting packets
  • Define idle-timers

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

serial37
Serial
  • Dial-up
    • Providers perspective
    • Users perspective
      • Dial-out host
      • Dial-out LAN
  • Leased lines

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

leased line characteristics
Leased Line Characteristics
  • Higher cost
  • Full time connectivity
    • convenient for Internet servers

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

leased line

Internet

Leased line

Provider’s router

LAN

Synchronous modem

Leasedline

Synchronous modem

Router

provider perspective40
Provider perspective
  • Establish geographically distributed points of presence
  • Offer ports (synchronous, asynchronous)
  • Establish routing for user’s IP subnets
  • Using different types of modems according to:
    • distance
    • speed

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

user perspective cont
User perspective (cont.)
  • Register IP addresses
  • Select appropriate router
    • number and type of ports according to network topology
    • protocols
    • routing protocols
    • manageable

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

user perspective cont42
User perspective (cont.)
    • security mechanism
  • Establish e-mail, DNS,WWW servers
    • no problem with full time connectivity

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

security
Security
  • DONT’T LET THE WHOLE WORLD TO ENTER YOUR DOOR!
  • Use security mechanisms
    • firewalls of different types

Serial Communications, CEENet Workshop \'97, Zagreb, August \'97

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