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Gliffy name AP Bridge Diagram
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OS integration
The software in the AP Bridge package has several additional requirements:
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AP Bridge software assumes that it is running on a Linux system and assumes that a variety of OS facilities are available. The AP Bridge software uses the Boost libraries to provide a common framework for some platform-specific operations, such as threading, serial I/O and timekeeping.
External packages
The AP Bridge software relies on several external packages for essential services. The AP Bridge does not build against these packages, but they must be installed for the AP Bridge to operate properly. These packages are commonly available on Linux distributions and should be installed with the distribution's package manager.
- stunnel and openssl are used to encrypt network communication.
- supervisor provides a central service for starting and stopping processes.
- NTP provides time synchronization.
- Python 2.7 and several and several additional Python packages . Some of are required by the Console interface to the AP Bridge and several configuration scripts are written in Python. The AP Bridge Console is also written in Python. Stunnel
- configobj is used by the configuration scripts for reading and updating the AP Bridge configuration files.
- configobj
- pyzmq
- protobuf
- Supervisor
- and protobuf are used for inter-process communication between the AP Bridge and AP Bridge Console processes.
On the Raspberry Pi, these packages can be installed using:
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$ sudo apt-get install python2.7 python2.7-dev supervisor stunnel4 ntp
$ sudo pip install configobj pyzmq protobuf pyserial |
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The AP Bridge software does not implement the TLS security layer itself. Instead, to implement secure communication with the VManager, the AP Bridge uses stunnel running on the same device. To secure the AP Bridge connection, stunnel is configured to listen to local TCP port 9100 and connect to TCP port 9101 on the VManager host. From the AP Bridge, stunnel establishes a connection to the remote VManager and negotiates the cipher suite with stunnel on the VManager. Stunnel uses the host's openssl library, so both the stunnel and openssl packages should be kept up to date on the VManager and AP Bridge systems. If you do not specify a specific set of security suites to use, stunnel will revert to openssl defaults. Configuring openssl for a particular security suite, or operation in FIPS mode, is left to the system operator.
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- The AP Bridge binaries are installed in APC_HOME/bin.
- The AP Bridge software reads its configuration from APC_HOME/conf.
- The AP Bridge generates log files to APC_HOME/logs. Log files are automatically rotated when they reach a certain size.
- The AP Bridge writes certain runtime information to APC_HOME/var/run.
OS integration
The AP Bridge software assumes that it is running on a Linux system and assumes that a variety of OS facilities are available. The AP Bridge software uses the Boost libraries to provide a common framework for some platform-specific operations, such as threading, serial I/O and timekeeping.
External packages
The AP Bridge software relies on several external packages for essential services. The AP Bridge does not build against these packages, but they must be installed for the AP Bridge to operate properly. These packages are commonly available on Linux distributions and should be installed with the distribution's package manager.
- stunnel and openssl are used to encrypt network communication.
- supervisor provides a central service for starting and stopping processes.
- NTP provides time synchronization.
- Python 2.7 is required by the console interface to the AP Bridge and several configuration scripts.
Network connectivity
If the system is being built with APs physically separated from the VManager system, then the simplest implementation is to connect all the devices to the same Ethernet network. Any method that provides a reliable TCP/IP connection between the APs and VManager can be used including WiFi, or cellular. The network connectivity must be consistent and reliable so that the APs can communicate constantly with the VManager. The VManager will consider an AP to be lost if its connectivity is interrupted for 30 seconds. In the event that an AP is lost, the VManager will immediately reassign all mote paths through the remaining APs and motes that are only connected through the lost AP may be lost as well. If the AP returns later on, then the VManager will slowly re-integrate the AP into the network topology through normal optimization cycles.
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$ ntpdate -q pool.ntp.org ... 25 Mar 14:09:49 ntpdate[12569]: step time server 132.163.4.101 offset -26.481737 sec |
References