Designing scalable wireless networks in the campus LAN Sebastian Büttrich, NSRC Last edit: March

Agenda Basic Radio Physics Introduction to wireless networking: Standards, Modes, Topologies Wireless Hardware: What to choose Antennas Integration with a Campus LAN Wireless security Authentication in wireless networks Wireless roaming Structured Wireless Troubleshooting Summary: Essentials of Wireless Networking (A little bit of) Wireless Ipv6 (Mesh networking) LAB: every afternoon – and in the evenings (if you like … I like :) )

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 Wireless Training Kit (ICTP/ITU) The green book:

The basics Basic Radio Physics Introduction to wireless networking – Standards, Modes, Topologies Wireless Hardware – Routers & Access Points Antenna

Go to... Separate Units on... Basic Radio Physics 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, distribution and edge/access networks Planning of maximum size of subnets becomes even more important – as the capacity of wireless cells is limited!

At this point: layers!

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, Link budgets, 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) wireless 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: – Infrastructure – University internal networks, Admin – Students – 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 (bridged) - with strict access control, DHCP

IP design for edge access Example 2: open access in cafeteria, library, etc Usergroup is uncontrollable Recommendation: – place the wireless access on separate subnet – with access control, back end integration (e.g. through RADIUS) – Option: DHCP bridged through, in order to secure roaming

IP design for edge access

Example 3 – an alternative: open access in cafeteria, library, etc Usergroup is uncontrollable Option: – Keep wireless access completely open! Consider it “open internet”. Pros and cons? – Make sure the wireless subnet is properly isolated – Throttle it, if it eats too much bandwidth – Ensure access control and security on level of Service / server Application