A special extended edition of Tech Messages for 2010-03-11 through 2010-03-17:

• Is Managed Services the IP Telephony of 2010?
• Coding Horror: Cultivate Teams, Not Ideas
• Create a jQuery Popup Bubble » Digital Visions Queenstown

SIP (Session Initiation Protocol)

SIP is by far the most popular protocol used in VoIP communication today. SIP was designed as a signaling protocol in charge of setting up and tearing down sessions between two or more devices. Additionally, SIP can be used to modify existing sessions. The protocol was designed to be independent of transport protocols. Thus, SIP can be used over both TCP and UDP. As of this writing, popular open source PBX Asterisk only supports SIP over UDP.

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If you have an interest in information security from a technical or managerial point of view, check out Principles of Information Security. It does an excellent job of presenting material for both audiences.

If you have other vendors you would like to see on this list, send me a message. I’ll keep updating the list until we have everything we need.

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If you’ve ever built a site that has different kinds of users, you’ve probably run across the case where you want a limited number of users to appear in a particular list. For example, you may only want staff members to be assigned ownership of a particular object. If your site has a really huge user list, combing through the users to find staff members can get annoying fast.

The key to limiting the choices to staff members only is the limit_choices_to argument to the model ForeignKey field. For example:

class Computer(models.Model):
  admin = models.ForeignKey(User, limit_choices_to={'is_staff': True})

In the above example, objects in our Computer class have an administrator that must be a staff user. This separates them from other users in the company that may not be staff members.

A special extended edition of Tech Messages for 2010-03-05 through 2010-03-09:

• How P2 Changed Automattic — Matt Mullenweg
• Close .tpl access with .htaccess
  You can do this in your Apache configuration file, too.
• Cisco confirms exit from WiMAX RAN market – Rethink Wireless
• The Right Way to Add Custom List Markers to Unordered Lists | Impressive Webs Toronto