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ADB
Aspiring Contributor
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Message 1 of 26

DSCP AF33 marked traffic?

I have noticed that recently the majority of inbound traffic is now marked as DSCP AF33 (30, 011110) - the majority of it being HTTP traffic or my work VPN traffic (UDP/4500).  DNS replies for ages have been marked as DSCP 6 (000110) so I already assumed BT remark traffic once it gets into their network, however up until a few days ago (maybe a couple of weeks?) most inbound traffic was not marked with DSCP (so BE, 0, 000000), now it looks like most is marked with AF33?

Outbound the majority of my traffic is not marked (0) or set to CS1 (8, 001000 - my markdown value for guest WiFi).

 

Any idea what BT have recently implemented?  According to the RFC DSCP AF33 has a high drop precedence so I am not sure if I am getting a potentially degraded service?  I am on BT Infinity Option 3 and my line is trained at 46.8/5.3.

 

Cheers

Andy

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Bamber1972
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Message 2 of 26

Re: DSCP AF33 marked traffic?

ABD,

 

I too have noticed the DSCP value being AF33 on packets through BT's network from my Infinity connection.  As this is 'high drop', I believe it to be responsible for online games such as FIFA (which rely on UDP packets) becoming almost unplayable.

 

My Infinity connection is on-the-whole excellent.  Great up/down speeds (20/80) and (so far!) perfectly stable.

 

The only problem is gaming, which is truly awful and extremely irritating!  I'm an I.T. professional, so I know enough to be able to set up my internet conenction to its peak performance.  Unfortunately, the packets are being tagged outside my network, so I have no control over their delivery (or reception).

 

I haven't seen this problem discussed in any other threads.  I thought someone else would have picked up on it in the multitude of FIFA lag/unresponsiveness threads both on here and on other sites.  Am I barking up the wrong tree?

 

Any other BT Infinity users wanting to see this for themselves can go to 'http://www.speedguide.net/' and click on the TCP/IP Analyser in the left-hand menu.  You'll get a fair bit of info which may help you optimise other settings on your internet connection, but at the bottom you will (probably?) see the line "DSCP (DiffServ): AF33 011110 (30) - Assured Forwarding class 3, high drop precedence (RFC 2597)."  This implies that packets may be dropped during periods of peak traffic - useless for UDP gaming packets!

 

Any response from BT would be helpful, or is this too technical for this forum?  If so, where should we discuss it, as I have been unable to get any help so far (and paying for a 'Tech Experts' subscription to find that they can't help either is NOT an option!)?

 

Thanks,

 

Gary.

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Message 3 of 26

Re: DSCP AF33 marked traffic?

From what I remember during my time working on the BT Wholesale ATM network, the only traffic which is given precedence, is realtime traffic, like VOIP and video streams.

 

General Internet traffic, which is not time critical, can be dropped during high level of traffic on the ATM network.

 

BT used to have their own gaming service, which did have better performance, but this was dropped a while back.

 

This is unlikely to change.

 

 

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Bamber1972
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Message 4 of 26

Re: DSCP AF33 marked traffic?

Keith,

 

Thanks for the response.  It's a shame BT themselves can't admit the problem that must affect almost all users of Infinity who game online (although many might not notice the problem or attribute it to another fault/reason).

 

I have BT Infinity for approximately 6 more months as it was an eighteen month contract.  I absolutely love the fast downloads and reliability, but I will be forced to move to a different provider after my contract is up.

 

I'm just off the phone to BT Broadband Support as they called regarding this issue and tried to get me to contact the 'Tech Experts' through the web address.  As I would have to sign up to a minmum three month contract with them without having any idea if they can help with this issue, I feel stymied in fixing the problem in any way OTHER than leaving BT (which I don't want to do).

 

I would suggest that this inability to play games which rely on UDP packets over BT Infinity is made known to all customers, current and future, and the option to cancel existing contracts is allowed due to the service being unfit for a purpose that many would have expected it to excel at given the download speeds and excellent ping response available.

 

Any suggestions for a fibre capable ISP who DON'T ruin their service with what is effectively packet throttling (which this is, even although BT state that they DON'T throttle any packets)?

 

Thanks,

 

Gary.

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Message 5 of 26

Re: DSCP AF33 marked traffic?

I doubt that there are any ISPs that offer such a service, as many use the BT Wholesale network, and would have to pay a high premium to have their traffic guaranteed 100%, as they would need extra capacity beyond their estimated peak usage.

 

UDP traffic is not considered high priority anyway, and would be given a UBR classification and its CLP value would allow it to be dropped if the traffic level exceeded its traffic contracted rate.

 

I would guess that BT Retail pay BT Wholesale for a certain VC capacity, which can be increased if needed, at a cost. Looking at some of the threads posted on this board, its only done if there is a noticable drop in speed.

 

If an ISP hade their own dedicated network, then they could arrange sufficient capacity to prevent ATM cells being dropped.

 

It must be at least 20 years since I worked on this stuff, and most of the theory and commissioning I was taught, was never really needed in practice, as it was all managed centrally.

 

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Bamber1972
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Message 6 of 26

Re: DSCP AF33 marked traffic?

Keith,

 

The fact of the matter is that many other ISPs offer a service that is good enough for gamers most of the time.  I had ADSL with Sky previously and the problem didn't exist.  Their service obviously couldn't match BTs for speed (or stability), but those are due to ADSL, not any throttling/discarding of packets.

 

The problem manifests itself most obviously when playing FIFA as the opponents players are all running around as usual making crisp passes and not falling over randomly whereas the opposite is true for the person experiencing the problem (me!)  This happens in 95% of games I play online to a greater or lesser extent.  Other FIFA users obviously don't have this problem caused by the ISP, so are their packets being treated differently while passing through the network?  And if so, why?  Surely BT should be capable of giving the packets (no matter which type) the same precedence as other ISPs, especially on their own network?

 

I don't know all the ins and outs of this as you might (although I'd agree with you that it may have changed a bit in twenty years as a 56K modem was a luxury back then!), but common sense would suggest that the problem can't totally be due to capacity as you rightly state that other ISPs will probably use BTs Wholesale network but can still offer a better gaming experience.  

 

So far, in all the tests I have done, the only differentiator is the DSCP value being applied to packets in/out of my connection, so I'd really like them to remove the feature and just treat all of my packets the same as these other ISPs do!

 

I'm truly thinking of downgrading to an ADSL connection again as although I love the speed, the lag caused in FIFA is so frustrating it's not worth the trade-off.  I wonder if BT's ADSL offerings suffer from the same problem as the Infinity ones do?

 

Gary.

 

 

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Message 7 of 26

Re: DSCP AF33 marked traffic?

I am not sure whether ADSL is any better, however when I read about the problems people are having with Infinity, such as poor speeds and ping response, I would guess that Infinity is more suitable for stuff like multicast video, and for faster streaming/downloads, and not gaming as such.

 

I am on ADSL2+, and I get a consistent download rate of 10MBs, all of the time. I do not do any gaming.

 

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Message 8 of 26

Re: DSCP AF33 marked traffic?


@Bamber1972 wrote:

I'm truly thinking of downgrading to an ADSL connection again as although I love the speed, the lag caused in FIFA is so frustrating it's not worth the trade-off.  I wonder if BT's ADSL offerings suffer from the same problem as the Infinity ones do?

 

Gary.

 

 


I don't know what is causing the problem but in relation to you downgrading to ADSL. There was one poster, I forget his username, felt the same as you and reluctantly he downgraded to ADSL. He reported back after that his gaming on Fifa improved dramatically and had no regrets about the downgrade. 

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Bamber1972
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Message 9 of 26

Re: DSCP AF33 marked traffic?

Thanks gg30340 (if that IS your real name...),

 

Do you know if he downgraded to a BT ADSL account, and if that was possible to do without penalty while still under contract?

 

I suppose the best option would be to get an additional line put in with an ADSL service on it and route my gaming traffic through it.  Costly solution to a problem that BT could obviously solve (assuming it WAS a BT ADSL connection he switched back to).  At least that way I'd get to keep the stability and speed I've grown used to for everything bar gaming!

 

Gary.

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Message 10 of 26

Re: DSCP AF33 marked traffic?

It was to a BT ADSL account. I don't know if it was without penalty as he never said but I suspect if it was he would have mentioned it. You could contact the Options Team 0800.800.030 and they would be able to advise you re costs etc.

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