After having a bit of a read through of the forums the question 'What is Interleaving?' has come up a few times from new members to the forum, with some mixed answer, some Semi-Accurate some Completely missing the Barn.

So I have put together a small post that should explain the basics of interleaving. What it is, how it
works, why is it used and what is best for you. With the scope being Broadband applications.

Interleaving in terms of Broadband is used for protection from burst errors.

What is a burst error.
A burst error is a burst or sequential piece of BITS missing from a message.

Code error free message: aaaabbbbccccddddeeeeffffgggg message with burst error: aaaabbbbccccd____eeeffffgggg

Where ____ is erroneous data or bits.

Because there is a significant portion of the message missing it may result in the message being
undecodeable or falsely decoded. ie data corruption or missing data.


What does interleaving do exactly?!?

Take you error free message from before.

error free message: aaaabbbbccccddddeeeeffffgggg


and interleave it and add a burst error(this is not actually interlaeved but a simplified example).

Code interleaved error free message: abcdefgabcdefgabcdefgabcdefg

As you can see interleaving the data spreads it around and as you are about to see once de interleaved at your end reduces the chance that the error will be incorrectly decoded or be undecodeable.

Code interleaved w/ burst error: abcdefgabcd____bcdefgabcdefg So you still get the error in the same place but because the data is non-sequential the error doesn't have the same effect on the message once it has been de-interleaved. de-interleaved w/ burst error: aa_abbbbccccdddde_eef_ffg_gg

as a result of the interleaving the message is still very much decodeable which may or may not have a huge impact on the end result and is completely dependant on what the data's intended use is.

By now you should all understand what Interleaving does and why. But still don't know quite why it has the side effects it has.

The net result of the interleaving process is a lower error rate in a decoded message (as seen above).

Yes, yes but why does having interleaving on put my ping up!!!???

When the data reaches you, the connection knows whether or not it is interleaved.

If the connection is NOT interleaved as soon as the data is received it is passed on to the destination for it's intended use.
IE the connection receive the byte of information aaaa on a non-interleaved connection it can then pass on the information to the application for it's intended use immediately.

However if the connection IS interleaved IT must wait for the the block of data that the information is interleaved accoss to de-interleave the information and pass it on.
IE it must wait for abcdefgabcdefgabcdefgabcdefg to be received to be able to decode the first byte of data aaaa and consquently the 2nd 3rd and 4th bytes as well.

which means you are waiting for (in this case) 4 pieces of information to arrive before you can pass on the first piece. which = and incresed time ie HIGHER PING TIME.

OKOKOK but how does it all affect me?!?!?!

Any application that is Error sensitive but not Time-critical will benefit from interleaving as the number of actually errors received is greatly reduced by interleaving while not effecting timeliness of the data greatly.

Examples of such are

most forms of downloading:
FTP
Torrents
VPN's
etc.etc.

If the reverse is true ie they application is Time-critical but Not particularly error sensitive. you MAY benefit from non-interleaved connection depending on the actual number of errors being recieved.

A primary example of this is FPS online Gaming

-the game processes world data posted to you by the server and the faster you recieve that data the better because you get a more up to date picture of what is actually occouring on the server at any given point.

But wont it ******** up my leet aim if i get errors.

-If the errors are few and far between, no it wont. Is is more important knowing the location of an object in a timely fashion rather than knowing if the information is %100 correct. because that information is likely to be superceeded by new information coming from the server very quickly. 'cos objects move lots'.

If you get large burst errors and the occur frequently, which can be common on NZADSL.

You will more than likely experience frequent time-outs disconnections and/or poor rego.

If you want to know the error rate of your connection this can 'generally' be found by looking though your ADSL routers report/logs.

Questions feedback? Corrections.

The interleaving examples are cited from the Wiki Topic.

The Implications is all me.

If anyone wants to know more PM me to save cluttering the thread.

Massive Wall o' Text Alert!

anyway I think the mods should sticky this to make it more obvious to some of the noobs

That was an excellent explanation of Interleaving, thanks Jebus77.

I didn't fully appreciate the way that Interleaving reshuffles the packets, thereby mitigating the effects of burst errors to some extent. Rather I thought it was just a means of FEC, but in fact it is quite a lot more than that, and if latency is of no concern, it would always be a good idea to have interleaving turned on.

However, with the increase in popularity of Online Gaming and VoIP, I can see that most internet users would like to be given the choice of whether interleaving is enabled or not, depending on their particular type of usage.

One scenario in which this freedom of choice approach falls down is where customers have a line which has a high error rate. In this case, there are going to be problems if interleaving is turned off.

It is worthy of note that Xtra see fit to deny their customers the freedom of choice regarding interleaving, I would imagine so as to save on support calls. Kind of a "one size fits all" approach, which is not really the way to impress discerning customers

GrantK wrote: That was an excellent explanation of Interleaving, thanks Jebus77. I didn't fully appreciate the way that Interleaving reshuffles the packets, thereby mitigating the effects of burst errors to some extent. Rather I thought it was just a means of FEC, but in fact it is quite a lot more than that, and if latency is of no concern, it would always be a good idea to have interleaving turned on. However, with the increase in popularity of Online Gaming and VoIP, I can see that most internet users would like to be given the choice of whether interleaving is enabled or not, depending on their particular type of usage. One scenario in which this freedom of choice approach falls down is where customers have a line which has a high error rate. In this case, there are going to be problems if interleaving is turned off. It is worthy of note that Xtra see fit to deny their customers the freedom of choice regarding interleaving, I would imagine so as to save on support calls. Kind of a "one size fits all" approach, which is not really the way to impress discerning customers

Thanks

As far as I'm aware Xtra were of the opinion that for all intensive purposes interleaving was NEEDED on NZ ADSL networks because of (Along with a million other reasons) the physical state of the Copper connections.

While the state of the physical side of the network is not perfect in most cases the connection is reliable enough to be handled in a non-interleaved state. (dont get this wrong interleaving is a wonderful tool but people should be given options based on a line to line basis, which is probably too difficult for telecom to deal with given their client base and average experience of a help desk operator)

But i think your right they just didnt want to deal with cases where some guy had turned off his interleaving and was having a **** time on ADSL because of it. creating more work for their ADSL teams.

Nice work thanks for that

More importantly interleaving off affects your connection stability by decreasing SNR Margin. If you're shitloads away from the exchange and have a poor line like I am then chances are your noise margin is low enough as it is, but I had interleaving turned off and all of a sudden would get rapid disconnects left right centre. Although it wouldn't disconnect all the time and for the most part made gaming a hell of a lot easier it comes down to what you prefer.

Great thread - nice to see a coherent explanation
Another vote for a sticky..

Just so we all understand what this actually means in real life as I understand it,

* Xtra have opted leave it on.
* Most ISPs (including Maxnet) have the option to turn it off if requested.
* Orcon has taken interleaving off for all customers.

While I do not have definite figures, I would say that for 10-20% of lines Interleaving will help to make things more stable when left on. While it can be turned off, Maxnet only have a small number of people that have requested it to be turned off.

It is important also to understand the relationship between Attenuation and SNR, and how this relates to Interleaving:

Attenuation is in simple terms what happens to a signal over distance. This is how much "quieter" the signal gets after distance (you can think of this as getting quieter the further away you get).

Signal to noise ratio is exactly that - the ratio of Signal in proportion to the background noise. (You can think of this as a person talking in a noisy room. It is fine, but as long as the speech is louder than the background noise).

What people sometimes miss is the relation between these 2 figures. Obviously if you are further away from the exchange, then the signal will be less, so then a smaller amount of noise will then impact the overall quality of the line. (does that make sense?)

Also when you reach the outer reaches of what these 2 measurements, then the signal can drop off and that is where disconnections kick in.

Interleaving helps out those that have poor line quality. At the end of the day, if it is because of distance, then no one will be able to help that (other than the real estate agent ;-). But if it is a line quality issue, then typically you are able to call your ISP, they have access to new line test tools from Telecom (that pretty much measure the same figures as the modem Attenuation/SNR, but just a bit more accurately) and whenever the ISP pulls up a faulty line report, then that is typically a simple dispatch of a tech.

Telecom only charges the $81 if they go out on site, and it turns out that it was because of a faulty modem / customer equipment.

Awesome Addition thanks Jaybest!

why not put this on the gpwiki? Saves stickying everything

because no one reads it

jaybest wrote: Great thread - nice to see a coherent explanation Another vote for a sticky.. Just so we all understand what this actually means in real life as I understand it, * Xtra have opted leave it on. * Most ISPs (including Maxnet) have the option to turn it off if requested. * Orcon has taken interleaving off for all customers. While I do not have definite figures, I would say that for 10-20% of lines Interleaving will help to make things more stable when left on. While it can be turned off, Maxnet only have a small number of people that have requested it to be turned off. It is important also to understand the relationship between Attenuation and SNR, and how this relates to Interleaving: Attenuation is in simple terms what happens to a signal over distance. This is how much "quieter" the signal gets after distance (you can think of this as getting quieter the further away you get). Signal to noise ratio is exactly that - the ratio of Signal in proportion to the background noise. (You can think of this as a person talking in a noisy room. It is fine, but as long as the speech is louder than the background noise). What people sometimes miss is the relation between these 2 figures. Obviously if you are further away from the exchange, then the signal will be less, so then a smaller amount of noise will then impact the overall quality of the line. (does that make sense?) Also when you reach the outer reaches of what these 2 measurements, then the signal can drop off and that is where disconnections kick in. Interleaving helps out those that have poor line quality. At the end of the day, if it is because of distance, then no one will be able to help that (other than the real estate agent ;-). But if it is a line quality issue, then typically you are able to call your ISP, they have access to new line test tools from Telecom (that pretty much measure the same figures as the modem Attenuation/SNR, but just a bit more accurately) and whenever the ISP pulls up a faulty line report, then that is typically a simple dispatch of a tech. Telecom only charges the $81 if they go out on site, and it turns out that it was because of a faulty modem / customer equipment.

I might just have to point this one to Mike for the next evo upgrade...

Nice info

Orcon have taken interleaving off for ALL customers???

SWEET I JUST ORDERED ORCON

Domitian wrote: Orcon have taken interleaving off for ALL customers??? SWEET I JUST ORDERED ORCON

Most other ISPs can turn it off if asked.

tl;dr version please

i dont understand any of that shit

PoPo wrote: tl;dr version please i dont understand any of that shit

Interleaving makes your ping higher.

Don't be a chump boof.

It makes your ping lower popo

uber munksies wrote: Don't be a chump boof. It makes your ping lower popo

LOL if you are going to reply in this thread atleast read it! Boof is correct interleaving increases your ping, Turning it off MAY decrease it. It may also cause connection instability(turning it off that is).

itey wrote: because no one reads it

I read it

Can you get interleaving turned off on adsl2+ ?

yes

always wondered what that inteleaving business in my router was all about.
cheers for explaining

Hi can requiest for interleaving for telecom customers to be turned off?

Not on xtra.

Very nice explaination dude.
Keep up the good shit!

I was on Xtra a while back then I switched to Orcon (because interleaving being off by default) and had really good speeds (for my ancient phone line) of about 2800kbs/700kbps.

Then I was upset to find that they throttle torrents... So then I switched to Xnet (that doesn't throttle torrents) but now I'm getting speeds of 1300kbs/600kbps and experience quite a few drop outs.

I thought turning off interleaving would lower my pings on Xbox Live but obviously not because XBL mostly uses P2P connections and aren't server based.

So my question, Should I turn my interleaving back on considering i only use XBL for online gaming? or leave it turned off?