Course11:Basic - Compact Flash Card

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This book describes the usage of CF cards with innovaphone gateways.

Contents

Concept

The Compact Flash slot enables the innovaphone gateway to work as a WebDAV server. You can use the CF card to store files/data and access them via HTTP. The CF card can be mounted to your local filesystem, so that all standard functions for manipulating files and folders (copy, delete, paste etc.) can be used. The single limitation of the innovaphone WebDAV implementation is the inability to handle file attributes (e.g. write protected, hidden).

To make it short, by using the CF card you can save the cost for running an additional WebDAV server.
The different usage areas of the CF card are:
  • storage of customized announcements
  • voicemail storage
  • update server
  • logging server
  • Certificate authority(CA) for the creation of certificates
Technical fish-help.png information on recommended manufacturers and card types, can be found in our wiki.

Accessing the WebDAVserver

Accessing the CF-card

To check the content of the CF card a simple web browser (e.g. Internet Explorer, Firefox) can be used. Also it is possible to perform some basic operations like mounting/unmounting or formatting the card. The process of mounting/unmounting the CF card is important when removing the card from the slot. By unmountig it first, you prevent damaging stored data.

If advanced file handling operations are needed, you must use a WebDAV client. The WebDAV client enables you to add/create, copy, delete, rename and move files and directories on the CF card.

You can use a stand-alone client, such as WinSCP which we at innovaphone have tested successfully.
However, it is often more convenient to use Microsoft's WebDAV client, that is built-in to the operating system. This allows you to work with files on the CF card just like with any other file on a local or network drive by letting you access the directories with an UNC path such as \\172.16.0.10\DRIVE\CF0. This will work from within just any program, not only the windows explorer.

When using Windows operating system higher than 2000 (2003, Vista, XP, 7 or 8) you have a built-in client (WebDAV client) offering this mounting function. On server platforms, your administrator may need to enable WebDAV client support. In Windows 2000 an older WebDAV client version (named WebFolders) is implemented, which is only able to display the content of the WebDAV directory. To include the directory to your file system you will have to use an external application, for example Novell NetDrive.

A Linux operating system usually offers davfs or davfs2 to mount a WebDAV server.

Enable HTTP access of the CF-card contents for PBX instances

Access to the CF card from the PBX will only work if HTTP (or HTTPS) services are enabled. This is done via fish-help.png Services/HTTP.

If the card is plugged to the same device where access should be granted to, entering the data path /DRIVE/CF0/ for read and/or write access has to be enabled at Services / HTTP / Server within the section Public compact flash access.

If objects of the PBX shall use any CF-card contents located in remote WebDAV servers, access authorisation has to be given via Services / HTTP / Client including the complete path and access credentials within Authenticated URLs field.

Backup & Syncronisation of the CF card data

Backup

As already mentioned, the CF card is used for storing data. This can contain voicemails, recorded conversations or certificates, which are usually regarded as sensitive data and must therefore be backed up.

As we have seen, these file can be accessed just like any other network resource. This allows users to perform backups using standard tools such as NTBackup on Windows or tar/cpio on unix-ish platforms.

One limitation of a WebDAV server however is that it does not manage file attributes such as the archive attribute. The result for our backup concept is that we cannot use incremental backup methods but must always do a full backup of the CF card content.

The file system used on the compact flash card is FAT32. This enables an administrator to perform disaster recovery by accessing the damaged card on a CF card reader at his local PC. Depending of the used operating system various repair tools can be used to recover the damaged data.

Synchronisation

In redundancy scenarios using a standby PBX, you will want to have the WebDAV server content available in case that the first PBX is defect.
There are two solutions for this problem:

1. Use an external WebDAV server.

Do not use the CF card to store information that must be available in the redundancy case. Install a external WebDAV server and point your master as well as the slave/standby PBX to it. In case that the master is down the WebDAV server is still working and handles request coming from the standby PBX.

2. Synchronize the content of all CF cards

Again an external server is needed, running something like an synchronization service. At a Windows server you could use for example wikipedia.ico Robocopy to check and compare the content of all CF cards periodically. It will then copy new or modified files from the master PBX card to the slave PBX card. Please keep in mind, that this method will generate a higher CPU load for the innovaphone gateway since it continuously must access, read and write files from the compact flash card.

Usage scenarios

Announcements

The simplest way to use a CF card is for deploying custom announcements. These announcements can then be used by the innovaphone PBX for Waiting Queues or as Music on Hold source.
To avoid format conversion or encoding during a call, the announcements have to be present as coder - specific raw sound stream data files (i.e. G.711, G.722. G.723 or G.729 format).

The conversion of source files coded in wav, mp3, flac or ogg formats into the telco-specific formats can easily be done via our link_intern.png audio converter freely accessible at our homepage. 

Uploading a source file will automatically download a zipped file including all conversions.

Voicemail

The next common scenario for the CF card is the usage in combination with the PBX Voicemail object. It stores files and XML - scripts to be executed by the Voicemail - PBX - object and also the recorded messages. This brings up the questions on the disk space requirements needed for one Voicemail message. As a rule of thumb you can assume that a G.711 message of 1 minute uses approximately 500 kBytes, while a lower quality message in G.729 format of the same length uses only 60 kBytes. Depending on the consumer behaviour, you must now estimate the average length of one message in order to calculate the maximum amount of messages that fits on your CF card.

Logging

When using the CF card for logging all information created by the syslog interface of the innovaphone gateway will be saved on the card. A log directory will be created automatically. You can fish-help.png configure the maximum size of the log files as well as the storage time of the log files.

Certificate authority

Since v7 firmware an innovaphone device having a compact flash card can also be used as a Certificate authority to manage device certificates. This certificates are used for special protocols like HTTPS or SIPS which need them for their encryption features. When deploying an innovaphone gateway as CA, you can create certificates for other IP devices in order to use encryption for VoIP and HTTP traffic in the customers network.

Update Server

Another common scenario for using a CF card is as a update server. You can execute update-scripts from the local WebDAV server and also store your configuration and firmware files.

Summary

The CF card is an easy to implement solution for configuring additional functions like voicemail and logging for the innovaphone PBX. It is an alternative to using external WebDAV server.
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