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