Tuesday, July 11, 2006

Nerd Vittles Newbie's Guide to TrixBox 1.1 and freePBX

Today we'll show you how to install the latest and greatest TrixBox 1.1 with freePBX 2.1.1 in just over an hour. As with the earlier release of TrixBox, these new Asterisk products are designed to support the casual home or home office user's PBX needs as well as gigantic call centers processing millions of calls a month.

Everything is free except the hardware on which to run your new system. That can be almost any old Pentium PC or a multi-processor RAID box with mainframe horsepower. We also want to get TrixBox properly configured to support our next free application: TrixBox MailCall.
It'll let you retrieve and play back your email messages using any touchtone telephone and your TrixBox 1.1 system. And, yes, you'll need TrixBox 1.1 to make everything work.

To be fully nerded: http://nerdvittles.com/index.php?p=140

Monday, July 03, 2006

Voip Deployment - The Virtual Network

Virtual LANs (VLANs) have nothing to do with quality of service (QOS) in a VoIP / IP Telephony deployment. There, I said it.

So why would you bother use them? For the quality of the deployment (QOD? :-). By logically segmenting the voice and data worlds disruptions in either world will not affect each other (hopefully). You can firewall or use access lists between VLANs to help secure your VoIP deployment. Also, if you want DHCP / DNS to work differently for the phone system it doesn’t affect the data network.

I’m not going to get into the intricacies of VLANs here. Here’s the wikipedia entry (http://en.wikipedia.org/wiki/Vlan) which will help a bit. Get a couple of switches that support VLANs and play with them a bit… learn how to trunk VLANs between switches and how to statically map ports into VLANs. Learn them, live them, love them… you’ll use them all of the time.

On most VoIP deployments I’ll use 3 VLANs at a minimum. Data, Phone and Management. Data is the default VLAN and used for all PC’s, servers & printers. Phone is for all phones, gateways & PBX equipment. Management is for switch / router management IP’s.

Here’s what the VLAN diagram would look like:

Statically map the PBX and gateway ports into the Phone VLAN. Setup all of the ports that will connect to PC’s and phones with the Data VLAN as the default VLAN (untagged) and the Phone VLAN as a tagged VLAN. That means that devices ‘tagging’ their traffic for the Phone VLAN will be placed in that VLAN and devices that don’t know how to tag their traffic will be in the Data VLAN.

Manually set your IP phones to be in the Phone VLAN. This means the phone will tag it’s traffic for that VLAN and pick up DHCP from that VLAN. It is possible for some phones to pick this up off of the initial DHCP reply to the phone and then switch to the Phone VLAN and get another DHCP address from that VLAN. However, now you are depending on the DHCP server on the Data VLAN to be working.

Saturday, July 01, 2006

Voip Deployment - The Physical Network

So, you want to install a VoIP / IP Telephony system. How do you prepare your LAN / WAN for this new application where timing is critical? How well your VoIP system runs will depend largely on how good your network infrastructure is.

Cabling - Make sure your network cabling is up to standards. Properly run Cat 5/5e/6 cabling with patch panels in the closets & wall jacks on the wall. Use manufactured patch cords. And if you really want to be sure it is right, have it certified by a cabling contractor.

Network Switching - This is one of the harder pieces and critical to the success of your deployment. I won't pretend to be able to describe how to properly design a network in a few paragraphs because every organization is different. Here are some basics though.
  • Think about the core of your network. If everything ties back to a single location things are pretty simple. Where are your servers, your wiring closets, your wide area connectivity & your outside world connectivity? Start at the core and work out from there with a simple star topology (don't try to connect closet to closet to closet, instead connect each closet to the core directly).
  • What other critical line of business applications do you run that may need to be considered in the design.
  • What do you have for existing equipment that you might be able to utilize?
  • Figure out which manufacturer's gear you want to utilize and learn the different models and their options. This is important! Know your product!
  • How are you going to power your hard phones? PoE switches, mid-spans (power injectors) or power bricks at each desk?
  • How about power protection? Most UPS manufacturers have calculators on their web sites that allow you to estimate consumption and run times of their gear.

Here's an example of a physical network design with a core server room (the core closet area is sometimes referred to as the MDF and the remote closets as IDFs).

Above we see the two closets linked back to the core at 1 Gbps, one with fiber because of distance from the core, and the second with Cat 5e / 6 copper. The servers all connect in to the core network switch at 1 Gbps and the firewall and router connect in to the core. Simple, clean efficient.

I like the HP switching gear (it's about 60% of the cost of an equivalent Cisco design, lifetime replacement, support and software updates). They have a nice broad range of products, their QOS seems pretty good and they are easy to configure. Don't' get me wrong, I like the Cisco stuff too and design plenty of networks with it. I just think I get more bang for the buck with HP. If I need to cheap things out, Linksys has some inexpensive managed PoE switches and so does Dell, Netgear and DLink.

Try to stick with managed switches so that you can create VLANs. Most modern managed switches will support Quality of Service (QOS). Some of the really cheap PoE switches are unmanaged (Netgear, DLink have some models like that).

Adtran makes some nice little stackable PoE switches (1224 series) and they even have one with an integrated router module (1224 r). This makes for a nice all in one device at remote WAN connected locations.

Don't have the coin for all new fancy gear? First off, prepare yourself for small voice quality issues. If you can live with that (hey we all put up with cell phones right?), take the above network design principles into account. Good cabling, star topology, avoid linking switch to switch to switch. Oh, and forget about trying to use any old hubs you have... switches only.

Remember, cabling and switching are the foundation of your VoIP deployment. The rest of the house is only as good as the foundation. Take the time to get it right and people won't be reaching for your throat. Next article I'll get into VLAN design and maybe QOS... we'll see how long it runs...