Virtual Private Networks
Globalizing LANs
Timothy Hohman
What is A VPN?
► Tell
me about it Microsoft:
 “A virtual private network (VPN) is the extension
of a private network that encompasses links
across shared or public networks like the
Internet.” (Microsoft, 2001)
► It
provides LAN access to end systems not
physically located on the LAN
► An alternative to WAN (Wide Area
Networks) which use leased lines to connect
Image courtesy Cisco Systems, Inc.
A typical VPN might have a main LAN at the corporate headquarters
of a company, other LANs at remote offices or facilities and
individual users connecting from out in the field.
How does it work?
► Data
is encrypted (cannot be deciphered
without the key)
► Virtual Point to Point Connection
 To the user, it acts like a point to point
connection
► Data
is packaged with a header
Benefits of Using VPN
►
►
Expand Globally
Costs reduced
 No dedicated lines necessary
Easier
► Technology is on the end systems, which
makes it more scalable
► No single point of failure
► Easier Network Management
►
Types of VPN
► Two
Types:
 Site to Site VPN
 Remote Access VPN
Remote Access VPN
► Essentially
provides LAN access through
dial-up connection
 Typically done by purchasing a NAS (Network
Access Server) with a toll free number
 Can instead be done through normal ISP
connection using the VPN software to make a
virtual connection to the LAN
Site to Site VPN
► Connects
two LANs over local ISP connections
► Very useful if you need to connect a branch to a
main hub (Big business)
► Much less expensive than purchasing one
dedicated line between the hub and branch
► Intranet  connects remote locations from one
company
Extranet  connects two companies (partners)
into one shared Private Network
Site to Site Connection
Two Ways to “Get it Done”
► Two
Tunneling protocols can be used
 PPTP (Point to Point Tunneling Protocol)
 L2TP (Layer Two Tunneling Protocol)
 Tunneling encapsulates frames in an extra
header to be passed over the internet appearing
as normal frames. The process includes:
►Encapsulation
Decapsulation
(adding extra frame), transmission,
Tunneling Protocols
► Both
of these protocols support these
methods:







User Authentication
Token Card Support (one time passwords)
Dynamic Address Assignment
Data Compression
Data Encryption
Key Management
Multi-protocol Support
Tunneling Protocols cont.
► Each
are built on PPP (Point to Point
Protocol)
 4 Phases
►1)
Link Establishment - a physical link between ends
►2) User Authentication – Password protocols used
 PAP, CHAP, MS-CHAP
►3)
Call Back Control – optional
 Disconnects and server calls back after authentication
►4)
Data Transfer Phase – exactly what it sounds like
Tunneling Protocols cont.
► PPTP
 Uses IP datagrams for encapsulation
 Uses TCP for tunnel maintenance
 Uses encryption and compression
► L2TP
 Encapsulation in IP, ATM, Frame Relay, X.25
►IP
when going over internet
 UDP used for tunnel maintenance
Advantages
► PPTP:
 No certificate infrastructure
 Can be used on more operating systems
 Can operate behind NATs
► L2TP:
 More tools to guarantee packet integrity and data
security
 Require user and computer certificates
 PPP authentication is encrypted (takes place after IP
security check)
Security
► Many
types of Security are offered
including:





Firewalls
Encryption
IPSec
Certificates
AAA servers
Firewalls
► Can
be used with VPN is right technology is
set up on the router
 Cisco 1700 router for example
► Can
restrict:
 The type of data being transferred
 The number of ports open
 Which protocols are allowed through
Encryption
► Symmetric
Key Encryption (private key)
 All communicating computers use the same key
stored on their computer
► Asymmetric
Key Encryption
 Uses a Private key and a Public Key
►Private
key on local computer
►Public key sent out to anyone who you want to
communicate with
►Mathematically related through encryption algorithm
►Both must be used to decrypt anything sent
IPSec
► Made
up of two parts
 Authentication Header
►Verify
data integrity
 Encapsulation Security Payload
►Data
integrity
►Data encryption
IPSec continued
► Authentication
Header
 Authentication Data
 Sequence number
► Encapsulating
Security Payload
 Encrypt data
 Another layer of integrity and authentication checks
Certificates
► Used
alongside public keys
 Contains:
► Certificate
Name
► Owner of the public key
► Public key itself
► Expiration date
► Certificate authority
 Verifies that information is coming from the private key
 Can be distributed on disks, smart cards, or
electronically
AAA Servers
► Authentication,
Authorization, Accounting
 These advanced servers ask each user who they
are, what they are allowed to do, and what the
actually want to do each time they connect
 This allows the LAN to track usage from dial up
connections and closely monitor those remotely
connected as they would those physically
connected.
How can I get this up and running?
► You
need:
 Software on each end system
►Windows:
PPTP
 Dedicated hardware (firewalls, routers, etc.)
 Dedicated VPN server
 May need NAS
A Hardware Example
► http://www.youtube.com/watch?v=lq-
ShHMofEQ
An Example of VPN in Action
► 2001,
CISCO direct-connect company filed
for bankruptcy
► Changing
over the 9000 employees to
different direct-connect companies would be
very costly and take 10 times the available
staff to pull off
The VPN Solution
User managed solution based on VPN
software
► Users provide own internet connection
► Cisco provided IT support for VPN problems
and provide gateway from internet to CISCO
network
►
Benefits of the Change
► Productivity
► Employee Satisfaction
 Able to work from home, making home work balance
easier
► Globalization
► Flexibility
► Easier when letting
employees go
 Ex-employees do not have to have their dedicated line
removed, rather they just lose Authentication to AAA
server
► Cost,
cost, cost
Things to Come
► Expansion
 China and India
► Faster
Upgrades
 Use of Microsoft installer
► Better
encryption
 Advanced encryption standard
► Better
compression
► Voice and Video or VPN
Things to come cont.
► Wireless
vendor support
 Access to employees from anywhere
► PDA
support
 Possible software packages to be used on PDAs
► Hardware
for home client
 As shown in previous clip
References
►
►
►
►
►
Cisco Systems (2004). Cisco VPN Client Brings Flexibility and Cost
Reduction to Cisco Remote Access Solution. Retrieved from:
http://www.cisco.com/web/about/ciscoitatwork/downloads/ciscoitatwor
k/pdf/Cisco_IT_Case_Study_VPN_Client_print.pdf
Jeff Tyson (2007). How Virtual Private Network Work. Retrieved from:
http://computer.howstuffworks.com/vpn.htm
Barrel, Matthew D. (2006). Take your network anywhere. PC Magazine,
25(21), p122-122.
Calin, Doru; McGee, Andrew R.; Chandrashekhar, Uma; Prasad, Ramjee
(2006). MAGNET: An approach for secure personal networking in
beyond 3g wireless networks. Bell Labs Technical Journal, 11(1), pp. 79
– 98.
Tanner, John C. (2006). Ethernet rides the NGN wave. America’s
Network, 110(2), pp. 40-43.