Designing scalable wireless networks in the campus LAN

Size: px

Start display at page:

Download "Designing scalable wireless networks in the campus LAN"

Elwin Robertson
8 years ago
Views:

1 Designing scalable wireless networks in the campus LAN Sebastian Büttrich, wire.less.dk/nsrc edit: March 2010, KENET

2 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

Points Antennas Integration with a Campus LAN Wireless

3 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...

the same brains, whether we go low budget or BIG BUDGET Develop a good feeling

4 Goals Hopefully, see that low cost wireless is fun and can bring you wonderful places :)

5 Learning more Wireless Training Kit (ICTP/ITU) out soon! The green book:

6 The basics Introduction to wireless networking Standards, Modes, Topologies Wireless Hardware Routers & Access Points Antennas

7 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!

as your logical network architecture no longer is reflected in your

8 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!

9 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)

Network separation on Layer 1 / 2 by means of Frequency (Standards,

10 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

11 Frequency planning

12 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!

and including all gains and losses (mostly for P2P,

13 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!

(e.g. finding existing wireless networks) to human (social

14 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

access points Ad-hoc: typically used for P2P or MP2MP Modes do not have

15 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!

DHCP (bridge through), but separate DHCP for wireless subnets is sometimes advisable

16 Putting it all together - wired

17 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

security aspects suggest this Wireless hotspot access on the edges: offices, cafes,

18 Putting it all together - adding wireless elements Design 1+ wireless here

19 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

10.0.0 University internal networks, Admin 10.20.0.0 Students 10.30.0.0 Open networks for guests

20 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?

21 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

22 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

23 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

24 IP design for edge access

25 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

Basic Wireless Infrastructure and Topologies

Basic Wireless Infrastructure and Topologies Developed by Sebastian Buettrich and Alberto Escudero Pascual 1 Goals To be aware of the most common wireless topologies To be able to identify and plan suitable