Designing scalable wireless networks in the
campus LAN
Sebastian Bttrich, wire.less.dk/NSRC
edit: March 2010, KENET
http://creativecommons.org/licenses/by-nc-sa/3.0/
Agenda Introduction to wireless networking
Standards, Modes, Topologies
Wireless Hardware Routers & Access Points Antennas
Integration with a Campus LAN
Wireless security
Captive portals
Wireless roaming
LAB: hands-on wireless
Goals Understanding the basics
Understanding that in wireless
cost and quality are not always correlated
See how skills and brains matter
See that we need the same brains, whether we go
low budget or BIG BUDGET
Develop a good feeling for layer thinking
Work towards a set of best practices for campus
wireless
And ...
Goals Hopefully, see that low cost wireless is fun
and can bring you wonderful places :)
Learning more http://wirelessu.org
http://nsrc.org
http://wireless.ictp.it/
Wireless Training Kit (ICTP/ITU) out soon!
The green book: http://wndw.net
The basics Introduction to wireless networking
Standards, Modes, Topologies
Wireless Hardware Routers & Access Points Antennas
Integration with a campus LAN
All the rules and best practices for general
network architecture apply
They matter even more in wireless, as your logical
network architecture no longer is reflected in your
physical architecture
A user on the library network might in fact be 10
miles away!
Rules and best practices
Build a structured network, not a flat one! Build stars
and trees, not chains or clouds
(except where you like a cloud :)
Subnet! Subnet! Subnet!
Reflect organisation and policies in your IP design
Separate core and edge networks
Planning of maximum size of subnets becomes
even more important as the capacity of wireless cells
is limited!
Specifically wireless
In contrast to a wired network, you now have to
consider additional planning as your medium is now
boundless.
Network separation on Layer 1 / 2 by means of Frequency (Standards, Channels)
and Polarization planning
Reach and Power planning, Antennas
Naming (SSIDs)
Frequency planning
If two people give you torch signals with a red torch,
you cant tell one from the other
If one uses red, the other green you can 'read' both
Frequency planning
Important wireless planning activities
A Link Budget is the calculation of power starting
with output power and including all gains and losses
(mostly for P2P, long distance links)
no (long) link without a Link Budget!
Important wireless planning activities
A Site Survey is the on-site recording of all relevant
conditions from technical (e.g. finding existing
wireless networks) to human (social factors) to
environmental no wireless deployment without
Site Survey!
Wireless on Layer 2
The physical layer - Modes:
Master / Station (managed mode) typically used
for Point-to-Multipoint (P2MP):
hotspots, access points
Ad-hoc:
typically used for P2P or MP2MP
Modes do not have to match topologies!
You might find a P2P link consisting of Master and
Client
Wireless on Layer 3
The behaviour of wireless units with regards to TCP/IP
may be:
Pure bridging
Routing DHCP, NAT, Masquerade, etc
DHCP may be integrated with network-wide DHCP (bridge through), but separate DHCP for wireless subnets is sometimes advisable
Again, typical behaviour on Layer 2 is not necessarily
reflected on Layer 3! Dont get confused!
Putting it all together -wired
Putting it all together -adding wireless elements
Typical roles for wireless:
Wireless links may replace fiber/wired links in the core
network where distance or budget or security aspects
suggest this
Wireless hotspot access on the edges: offices, cafes,
libraries, workspaces, ...
Wireless mesh clouds on the edges, e.g. for
compounds, housing, villages
Putting it all together -adding wireless elements
Design 1+ wireless here
Putting it all together -IP design
IP design must reflect organisation and logic in order to
be manageable especially for wireless networks
E.g. IP subnets like this: 10.1.0.0 Infrastructure 10.10.0.0 University internal networks, Admin 10.20.0.0 Students 10.30.0.0 Open networks for guests etc
Other IP design principles: by location by department by physical carrier, e.g. wired/wireless
Putting it all together -IP design
The important thing is that
you are able to treat network segments in
meaningful ways (e.g. bandwidth management,
security, access time, usage rules, incident
response)
When things go wrong, you are able to isolate and
address network segments
This is even more important for wireless than for wired
networks! Why?
IP design for edge access
Let us focus on edge access
There isn't one golden rule how to do it right -
but there are several best practices to discuss
IP design for edge access
Example 1:
aligning IP design with organisational logic
For example, wireless access for administrative
employees
Recommendation: place the wireless access on the
same subnet as the wired workplaces - with strict
access control, DHCP bridged through
IP design for edge access
Example 2:
open access in cafeteria, library, etc
Usergroup is uncontrollable
Recommendation: place the wireless access on separate subnet VLAN with access control, back end integration (e.g.
through RADIUS) DHCP bridged through, in order to secure roaming
IP design for edge access
IP design for edge access
Example 3 an alternative:
open access in cafeteria, library, etc
Usergroup is uncontrollable
Recommendation: Keep wireless access completely open! Consider it
open internet Make sure the wireless subnet is properly isolated Ensure access control and security on level of
Service / server Application
Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25