Fruct4 n8xx olpc-connectivity
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This document discusses connecting Nokia and OLPC devices in a mesh network. It describes patching the drivers for the Nokia N810 and OLPC XO laptop to enable mesh networking between their different wireless adapters. A proof of concept was able to connect two systems via mesh using different wireless adapters. However, fully enabling mesh between the Nokia and OLPC devices requires further work, as their existing drivers do not currently support mesh networking.
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Fruct4 n8xx olpc-connectivity
- 1. Approach to a problem of mesh‐connectivity between XO laptops and Nokia MAEMO devices Arina Rudakova (Saint-Petersburg Elelectrotechnical University «LETI», Open Source Linux Lab) 4rd FRUCT seminar Tampere 29 November 2008
- 2. Introduction Problem definition Nokia N8x0 and OLPC XO interaction (heterogeneous mesh network) Steps Mesh driver and kernel driver upgrade in Nokia Internet Tablet in OLPC XO Other drivers patching for mesh- interconnection enabling 2
- 3. OLPC XO configuration Dimensions: 242mm × 228mm × 32mm CPU x86-compatible processor AMD Geode LX- 700 433 Mhz, 64KB each L1 I and D cache; at least 128KB L2 cache DRAM memory: 256 MiB dynamic RAM BIOS: 1024KiB SPI-interface flash ROM Mass storage: 1024 MiB SLC NAND flash, high- speed flash controller Wireless Networking: integrated 802.11b/g (2.4GHz) interface; Mesh networking is supported by Marvell Libertas wireless chipset, 88W8388 controller and 88W8015 radio. 3
- 4. Mesh network Mesh – wireless network technology with self-organizing architecture enabling fully connected network creation. Features Self-organizing Self-healing Optimal routing Large scaling Types Infrastructure networks Client networks Hybrid networks 4
- 5. 802.11s and OLPC-mesh Wireless chipset: Libertas - FullMAC driver - enables Wi-Fi and mesh support. Libertas is the Marvel 88w838X series of wireless chipsets. FullMAC drivers can't be used by the mac80211 module. The IEEE802.11s draft is mostly followed in Libertas, but it's an old version of draft. Differences OLPC-mesh from 802.11s standard: Main differences: Non implemented features: - Path asymmetry - Link establishment - Metrics - Security - Medium a protocol - Congestion Control - Power Savings mode 5
- 6. Libertas Kernel Modules Layers /net/mac80211/ mac80211.ko MAC libertas.ko drivers/net/wireless/libertas{_tf} PHY libertas_tf.ko RF 6
- 7. Kernels' features Nokia announced mac80211-based driver – stlc45xx. Nokia and XO use different kernel's modules for their wireless adapters. old kernels: − missing Mesh support in Nokia N8xx kernel − support IEEE802.11s v0.1(current version is 2.0) in XO new Linux kernel of 2.6.26 version supports mesh 7
- 8. Plan Proof of concept Patch stcl45xx driver for Nokia N810 Setup libertas_tf on XO Connect N810 and XO via mesh 8
- 9. Proof of concept Trying to connect two different adapters via wireless mesh network using 2.6.27 kernel Result Two system based on kernel 2.6.27 with wireless adapters rt73usb-based and b43-based send and receive pings from each other 9
- 10. Patch stlc45xx-driver for N810 Trying to include stlc45xx-driver, which was published by Maemo, in 2.6.27 kernel Result Following the driver set-up instructions lead to permanent device reboot Installing driver in clear kernel with busybox doesn't give a working driver 10
- 11. Setup libertas_tf on XO Trying to include libertas_tf driver from wireless- testing kernel branch, in 2.6.27 kernel Result libertas_tf is initialized mac80211 doesn't call libertas_tf 11
- 12. Connect N810 and XO via mesh Trying to connect N810 and XO, using 2.6.27 kernel and required drivers Result Network didn't start as drivers didn't work Potentially the connection should work once drivers are tuned because of proof of concept step 12
- 13. Problems Existing mesh-drivers organization is unknown Network packet format is unknown 13
- 14. Future Traffic control in Mesh Networks Mesh network infrastructure model development QoS control Dynamic topology reconfiguration Management traffic volume control Load balancing Routing algorithm development Open source implementation 14
- 15. Thank you! Your questions, please. 15
Editor's Notes
- The next presentation is about the approach to a problem of mesh-connectivity between XO laptops and Nokia MAEMO devices.
- Mesh networks are becoming more and more popular. Many companies produce new devices supporting mesh interconnections. It is very convenient to use different devices in one heterogeneous mesh network. Here the problem of their interoperability comes. We considered this problem on the example of Nokia Internet Tablet and OLPC XO interaction. The OSLL team updated mesh-drivers and kernels in Nokia Tablet and XO in order to make them interact with each other. Also some other drivers of simple devices were patched and checked for the ability to interact.
- There are some technical characteristics of OLPC XO. This laptop has low-power processor and is rather short of dynamic memory. Wireless networking in XO is supported by Marvell Libertas wireless chipset.
- Lets refresh our memory about what mesh is. Mesh network is a self-organizing fully connected network. It is also self-healing, self-managed and large scaling. The network uses optimal traffic routing. An optimal route can be, for example, the shortest one, or the route with low load ratio. There are 3 main types of mesh networks. They are infrastructure, client and hybrid networks. In infrastructure network mesh routers are not mobile and form an infrastructure for mobile clients. In client network there are only client nodes able to act both as a router and as an access point to the network. Hybrid networks have infrastructure and mobile nodes where part of mobile nodes are also able to act as a router. We are concerned with client networks.
- This slide shows what kind of mesh is there in OLPC XO. The laptop has the Marvell Libertas wireless chipset. It is a FullMAC wireless card so it has its own implementation of MAC Management Entity (MLME) and it cannot work with mesh mac-layer interface of the IEEE 802.11s draft. Libertas follows an older variant of the draft so there are some differences from the current version. Main differences lay in path asymmetry and metrics. In OLPC XO paths are considered to be asymmetric so a path between S and D is not assumed to be also a good path between D and S. And it can be quite true for radio transmissions. But in new variant of draft these paths are considered to be of equal quality. The calculation of link cost is also very different. In new draft it is counted from the time needed to successfully transmit a frame. So such metric includes the probability of error. While in XO a link cost is derived only from the data rate of each received route request. This metric doesn't account for the probability of error. Some features from mesh draft are not implemented in XO. First of all, there is no link establishment. XO doesn't check whether a link is still active. An active neighbour will be a one hop distant neighbour from the forwarding table, and nothing else. The next point is security. Currently no security mechanism is implemented at the link layer. Another lacking feature is medium access protocol. XO uses the Distributed Coordination Function while the draft uses new coordination function called Mesh Deterministic Access. XO also lacks any congestion control mechanism and power saving mode.
- Here you can see how two Libertas editions developed for different Linux kernels. XO laptop uses old kernel with Libertas driver. It enables mesh interconnections on physical, MAC and radio frequency layers. The new 2.6.27 kernel uses an alternative thin driver - called Libertas_tf - based on mac-layer mesh stack.
- Lets have a look at current Nokia Internet Tablet and OLPC XO kernels and at the newest Linux kernel as well. Nokia announced an opensource mac80211-based driver but OLPC XO uses another wireless driver so these devices cannot interoperate. Also new Nokia driver is not supported in its current kernel which lacks mac80211 stack. New Linux kernel solves both the problem of mesh functioning in these devices and the problem of their interoperability by providing the same mesh interface.
- The plan of problem solving consists of 4 steps. First of all it is needed to prove the concept of using new kernel on the example of other drivers. The next steps are patching new Nokia mesh-driver and installing Libertas_tf on XO. The last step is checking the connection between Nokia810 and XO.
- The first step is the proof of concept based on two different adapters. It succeeded as the systems can send and receive pings from each other.
- At first we tried to include driver in new kernel following the instructions but driver starting leads to rebooting. Then we tried to install driver in clear kernel with the help of only busybox. After that the device was trying to join an infrastructure network and not to organise mesh. Some problem with the firmware was detected.
- Libertas_tf was installed and initialized but it doesn't work properly on XO. Its function of network interface creation isn't called by the mac80211 stack.
- We experience some problems while organizing the Nokia-XO connection what slows down the work. Still the finish of drivers tuning is close.
- After having created an acting heterogeneous network it will be possible to work on its efficient usage. So the next goal is to control traffic in Mesh Networks. For doing this the stages are already planned and partly done. These steps are an infrastructure model development, routing algorithm development and open source realization. The network model should be able to control QoS, to reconfigure network's topology dynamically, to control management traffic volume and to balance network's load.
- Thank you! Ask your questions, please.