Designing scalable wireless networks in the campus LAN

Designing scalable

wireless networks in the

campus LAN

Sebastian Büttrich, wire.less.dk/NSRC edit: March 2010, KENET

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

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

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

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) –

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

Wireless on Layer 2

– 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

• _{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

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

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

• There isn't one golden rule how to do it right -but there are several best practices to discuss

IP design for edge access

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

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)

IP design for edge access

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