QoS of Video and VOIP over and encrypted link

[olyclimberpaul]

Hi there,

I have been tasked with improving VOIP/Video over a poor link.  After the traffic leaves the router it hits an encrypter>router>Satellite connection>router>internet.....

My question is can you use QoS on the local router prior to encryption and will this improve Video/Voice?  Kind of new to QoS so any help/guidance would be appreciated.  The encrypter has 100Mb connection, and I would guess the Satellite is likely no greater then 10Mb and more likely a T1.  Thanks!

-Paul

[ngkin2010]

Hi,

If we assume the 'encrypter' would copy the DSCP (IP Header) value from the original packet, and paste into its newly encapsulated packet, then it will work.

For example, your voice packet (that marked DSCP value of EF)  doesn't changed by your 1st router, it will leave the DSCP value unchanged in the packet, and forwarded to the 'encrypter'.

The 'encrypter' see the incoming packet with DSCP value, it may copy the DSCP (or the ToS) value into its new outermost header, and forward to satellite router.

Satellite router could based on different DSCP value, provide different QoS treatment. For example, DSCP value of EF will fall into prioritize queue and always be the first packet forwarded out its satellite interface.

FYI:

Alternatively, if your 1st router is the only router that connected to your encrypter (and to your satellite router), you could simply control the traffic on your 1st router. 

[Joseph W. Doherty]

"If we assume the 'encrypter' would copy the DSCP (IP Header) value from the original packet, and paste into its newly encapsulated packet, then it will work."

BTW, just having a DSCP tag does not, in itself, guarantee different service treatment, especially when part of the path, as noted in OP, appears to be across the Internet.

"Alternatively, if your 1st router is the only router that connected to your encrypter (and to your satellite router), you could simply control the traffic on your 1st router."

Indeed, the 1st router increases the changes of doing some form of QoS that might help, but also that alone, also does not guarantee success.

[Joseph W. Doherty]

"My question is can you use QoS on the local router prior to encryption and will this improve Video/Voice?"

Maybe, maybe not.  This is a "it depends" answer.

To really guarantee, i.e. 100%, a level of service, which VoIP and/or video (especially real-time variants) need, we need to control/manage bandwidth end-to-end.  Very likely you don't have that level of management.  (Also very likely, it's not obtainable if your traffic will also transit the Internet.)

However, if we don't have 100% control, we can often do much, with QoS, if we "know" we will have a fixed amount of bandwidth end-to-end.  If we don't have a fixed amount of bandwidth guarantee, it's still (sometimes) possible to obtain the benefit of QoS if we can constantly dynamically determine amount of bandwidth along the path, and use that.

So, first thing you need to address is find out just what your bandwidth guarantees are end-to-end, if any.  For sections of the transit topology that cannot guarantee a fixed amount of bandwidth, you'll want to find out how it might vary.

If you can assemble such information, come back here, and we can them explore what options you might have, if any.

Also BTW, I've supported VoIP/Video and other traffic, using VPN across the Internet, often with much success.  The trick, though, were those Internet connections were strictly reserved for VPN usage so by controlling one side's bandwidth egress I also control the other side's bandwidth ingress.  Fortunately, many ISPs work hard to insure their interior links do not congest.  So, usually, the bandwidth bottlenecks are your connections to your ISPs.