[asterisk-users] WAS: 64 analog phones NOW: Selection criteri a and recipie for a good Asterisk install [long]

Colin Anderson ColinA at landmarkmasterbuilder.com
Thu Sep 28 07:44:55 MST 2006

>I concur with your approach, but "Tier 1" means as little here as it
>does when evaluating Internet backbone carriers.  could you expand on
>what evaluation criteria you use?  I'm going to be pre-speccing some
>stuff myself this month...

Sorry I should have been more clear. A good Asterisk install needs a
holistic approach to use a hippy dippy phrase. A Tier 1 server, which is a
midrange to high end name brand server from the Big 3 (Dell, HP/Compaq, IBM,
am I missing someone?) is usually highly optimized for bus bandwidth
although that design was intended for a different use - usually massive disk
I/O. As well, a Tier 1 server will have two seperate, independent PCI buses
and this to me is a critical feature - it allows you to completely separate
your TDM traffic from network, disk I/O etc. On my big production Netfinity,
I took great care to ensure the Digium cards were all on their lonesome on a
single bus, and everything else on the other bus. This is how I can run two
TE110's in a single box with no problems. zttest does not give me 100% all
the time, but on the other hand it *never* drops below 99.9987%, even under
load. I selected this Netfinity because of the obvious care put into it's
design, but the specs are unimpressive: quad Xeon 700's. CPU is over rated
for Asterisk, IMO unless you are doing tons of transcoding and if you are
doing that, then your design is flawed. 

Anyway, the holistic approach (to go on a small rant for the newbie lurkers)
be summed up as follows:

1. Good box, see above
2. Good LAN - this is so critical and so often overlooked in the day and age
of guys crimping their own cables and running $150 switches. You can't do
that, and if you do, you do so at your own peril. Managed swiches,
professional cable installation. This is not a problem for me since I *am* a
professional cable installer but I have actually witnessed people making
patch cables with a flat blade screwdriver and a hammer!
3. Tuning of the LAN - VLAN's are good. QoS packets are good. Switches that
honor the QoS packets are good. 
4. Handset selection - this is another biggie. I've selected Snom 360's, and
yes they have warts, but they are feature rich for the price and Snom is
really good about revising firmware. When you select handsets, GET YOUR
5. Tuning of Asterisk box itself - this cannot be under emphasized. This is
a very important step and tuning methodologies vary according to distro,
skill of the admin, and particular circumstances. I've learned *way* more
than I ever wanted to about processor affinity sinc I started using
6. Termination of PSTN. Basically I would never do an Asterisk install where
I was forced to do something stupid like aggregate a dozen Centrex lines or
some mickey mouse deal with FXO ATA's or whatever except for a hobby or
prototype install. PRI, BRI, IAX or SIP, don't mess around with anything
7. Relationship with provider. What is their SLA? Is it the incumbent or the
clec? An incumbent will be more expensive and more difficult to deal with
but they will tend to be more reliable. A clec will be cheaper and they will
be way more accomodating but you will most likely not get five 9's from
them. A VoIP provider should never be trusted, period. You will not get five
nines from them, ever. Plan failover situations accordingly. 
8. Plan plan plan plan. A good install of ANYTHING is 80% planning 20% doing
it. What is your plan when your primary PSTN provider fails? What is your
plan if your Asterisk box goes pear shaped? My dialplan can survive either
PSTN, WAN or LAN failure (albeit with reduced functionality). I also keep a
cold spare, an identically configured box that I can literally throw into
the rack, turn it on, plug in the PRI's and no problem. 
9. Internet bandwidth and latency. I am fortunate enough to have a great IP
provider. Ask for demos - most guys will install a 90 day trial or something
like that. Do not believe the brochure, get the product installed and put it
under load. 
10. Traffic prioritization at the IP demarc - total no brainer. 
11. Constant, constant user feedback and remediation. If you are not talking
to your users, your install will ultimately fail even if you have the best
of everything. Underpromise and overdeliver. Never loose sight of the basics
- they have to pick up the phone, and it has to work. Always. 

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