1. Wireless MESH Networks
By: Tapu Ahmed
Marshall Grillos

2. Current Cellular Topology

3. Basic Layout

4. Problems with Current Design
Single point of failure

5. Solution
When you have a single node failure in MESH topology, the other nodes can simply “go around” to get to their neighbors.

6. Advantages to MESH Incredible amount of flexibility in session setup.
All that is needed is a radio
Radio acts as both transmitter and receiver
MESH networks can be extremely advantageous to small business owners.

7. Problems with MESH
Distance is the primary disadvantage of MESH networks
Coverage area becomes a problem as well

8. Problems continued Routing Complexity Battery-Life
You must dynamically locate your neighbors.
Battery-Life
Mobiles must remain “on” for a wireless MESH network to be useful.

9. Why not MESH Now?

10. Shannon’s Law (Spectrum Capacity)
Amount of throughput that can be achieved depends on the level of interference.
If interference goes up, throughput goes down.

12. Mesh Protocols

13. Standard
Most MESH operate on this standard since the standard is by far the most widely deployed in wireless LAN.
Thus it will contain: physical, MAC, and link layer.

14. 802.11 Basic design Questions to consider: Source RTS Data
Destination CTS ACK
Questions to consider:
When to initiate a route request
When and how to buffer packets during route discovery
When to update the lifetime of an active route

15. AODV Ad-hoc On Demand Distance Vector
AODV is a reactive routing protocol.
Routes to other nodes are determined only when needed.

16. X Source Node1 Node2 Destination Hello Route Request Route Reply Data
Route Error X

20. AODV Advantages: Disadvantages
Since the nodes can change in and out of the network quickly, you will not run into dead ends
Uses little memory
Good for small applications
Disadvantages
Inefficient when there is a large number of routes needed and for applications that cannot tolerate the delay of route discovery.

21. TBRPF Topology Broadcast based on Reverse-Path Forwarding
TBRPF is a proactive routing protocol.
Each node is provided with the state of each link in the network.

22. Broadcast trees are updated automatically
Creates a link-state design that has minimal overhead.

23. TBRPF Advantages: Disadvantages Improved efficiency
Alternate paths immediately available. Helps the quality of service.
Disadvantages
Better suited for larger applications

24. Extensions

25. Redundancy
The meaning of “redundancy” in general network architecture is a matter of degree and must be carefully specified.
To reach higher levels of redundancy, you may add an additional line of fiber next to an existing one.
In a mesh network, the degree of redundancy is essentially a function of node density.
A network can be deliberately over-designed for reliability simply by adding extra nodes, so each device has two or more paths for sending data.
It can additionally be achieved by increasing the number of simultaneous connections a node may have.

26. Example, Simple vs. Complex Mesh
A simple mesh network is one that requires relationships between the nodes or devices on the LAN.
Devices need not all directly connected for a simple mesh

27. Complex Mesh (Pure Mesh or Logical Mesh)
In a complex mesh, all nodes must be connected to all other nodes.
The number of relationships in a network can be represented by the formula N(N-1) where N is the number of devices in the network.
A complex mesh is vastly more redundant than a simple mesh.
This is often at the cost of higher network overhead.

28. Mesh Networks Security Issues

29. Another Mesh Example Dynamically configured and modified.
What implications on security?
Each node acts as a router and an end user.

30. Security Implications
Security in data transmission (much more than typical WLAN due to multiple hops over wireless).
Actually sending packets over the air.
Ensuring who’s receiving the packets is the intended target.
Security of Network Access
Ensuring everyone on the network should be on the network (user authentication).

31. User Authentication and Partial Mesh
Mesh exists outside of WLAN
Relies on WLAN RADIUS servers for Authentication (much like WLINE networks today)

32. What about pure Mesh authentication?
Each node must have all authentication data or connectivity to an authentication agent.
Generally multiple authentication agents must exist for redundancy and efficiency (number of hops).
ASIC security can be implemented to have pure hardware authentication of a device.

33. MeshDynamics suggests ASIC Security and “Smart Cards”
ASIC - Application-Specific Integrated Circuit: a very large scale integrated circuit (a VLSI chip) designed for a specific customer and function (often on the basis of a Programmable Gate Array).
Security chip devised for one way authentication.
Used by Satellite TV Providers (DishNetworks, DirecTV).
Used by American Express (American Express Blue).

34. ASIC Continued
Security chip contains application specific modifiable software for key decryption.
Card must be ‘activated’ in authentication server to receive proper decryption keys.
Cards are easily changeable/upgradeable by companies.
Removes the need for ‘login’ procedure.
Cards can be read by wireless units (PDA, Laptop, etc).

35. Secure Data Transmission - WPA
Wi-Fi Protected Access
WPA is the Wi-Fi Alliance’s new security standard that supersedes WEP (wired equivalent privacy). WPA is based on an early version of the IEEE i standard.
WPA upgrades WEP encryption with a stronger cipher, Temporal Key Integrity Protocol (TKIP) – timed keys, that fixes known vulnerabilities in the WEP encryption algorithm.
WPA also introduces stronger authentication using RADIUS as well as port-based access control based on IEEE 802.1x.
WPA contributes to network access control and secure data transmission.

36. Modern Day Applications of Mesh

37. MeshDynamics Offers Three-Radio Mesh Network Solution
From neighborhoods up to citywide coverage
Services Include:
Mobile Data, VoIP, and Public Safety Networks

38. U.S. Military
The Pentagon, about a decade ago, set out to design a wireless communications network that could survive a war.
One design that has emerged, in portable military communications gear that has been used in Afghanistan and could be used in the Iraqi theater, is called "mobile ad-hoc" or mesh networking.
This provides instant up to date troop and unit movements (all units are connected to the wireless mesh network).
Surveillance and tracking opposition

39. Industry Mesh based diagnostic networks
Efficiency and stability monitoring
Real Time Diagnostics

40. Industry Diagnostics
Mesh Networks can provide a low-cost diagnostic channel outside of normal control loops.
This enables significant productivity improvements where manual measurements may have previously been required.
By regularly capturing diagnostic data, plants can use predictive maintenance for cost savings.

41. Questions
Q1: What problems do centralized designs present and how does a MESH network go about addressing those problems?
Q2: Would you use a proactive or reactive protocol in a large MESH environment. Why?
Q3: How do you increase redundancy in a Mesh network?

42. Answers
Answer1: MESH networks avoid a single point of failure which can be detrimental to centralized systems. MESH topology eliminates routers, controllers, etc.
Answer2: You should use a proactive (TBRPF) protocol since large applications cannot tolerate the delay of route discovery.
Answer3: In a mesh network, the degree of redundancy is essentially a function of node density. You can increase the number of nodes (to increase the density). Additionally, it can be achieved by increasing the number of simultaneous connections a node may have.

43. References

44. References Cont. http://www.meshdynamics.com/ http://wi-fi.org/