[Asterisk-Users] Boosting Shared Internet Bandwidth for Asterisk

[Jean-Christophe Heger]

Depending on you bandwidth, you might not need QoS. Priority could be
enough.

In you sip.conf (if you use SIP), place a tos value:

[general]
tos = 0x10   ; low delay
or
tos = 0x46   ; DiffServ Premium (EF: Expedited Forward)

Remark: for un unknown reason, tos=lowdelay doesn't work anymore on my
asterisk (v1.0.7), but was working in the past. I replaced it by 0x10
(hex value of lowdelay).

Most of the routers support PFIFO (FIFO with priority), which means that
low delay flagged packet will be sent in priority.
I haven't tested the 0x46 value yet. Routers must be configured for
DiffServ values, while ToS is by default. But the low delay TOS bit is
also set within the 0x46 value. If a router treat the the DiffServ byte
as TOS, it should be sent with priority as well (to be validated).

If you want to check what priority is set inside your packets, you might
use Ethereal. You might see either UDP or RTP packets, depending on the
RTP ports that are used. In the branch "Internet Protocol", you will
find the TOS/DiffServ decode, named "Type of service" or "Differential
services Field". The TOS low delay bit is the 5th, and should be 1.

If you have a low bandwidth connection (e.g. 600/100), you might have a
new problem if you are using TOS as low delay. Voice will be good, but
data will stall. QoS won't resolve it, because big packets take too much
time to travell. The only way to share bandwidth for voice and data, on
low bandwidth lines, is to fragment the data. An MTU of 700 is quite
good, but you have to assume about 15% of bandwidth loss, because of
twice more overheads on big packets. Allthough, a 1200/200 kbps line
usually doesn't require such tricks.

Remark about Grandstream:
If you are using a GS device, you must know that QoS is buggy, and will
have no effect at all. You must upgrade to the beta version of the
firmware, which is OK. Therefore, GS recommands a QoS value of 48
(whithout "0x" on a GS device). This is a DiffServ value, which does not
set the los delay TOS bit. Cisco recommands 46, which does.

Jean-Christophe


chawki hammoud a écrit :

>--- Matt Riddell <matt.riddell at sineapps.com> wrote:
>
>
>  
>
>>Assuming your provider completely ignores QOS, it is
>>still not a 
>>complete waste of time.
>>
>>If for example you have 5 people on the LAN, 4
>>uploading files to a 
>>remote server and 1 trying to make a phone call.
>>    
>>
>
>My ISP has the internet connection set-up where 8
>people share the bandwidth. Would the script still
>help boost my voip calls?
>
>
>
>
>		
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