TCP Transfer Rate

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Topic # 119011 17-May-2013 03:20

I was directed to this thread by another person while discussing transfer speed across the internet today and was wondering if anyone has any comment on it.

Some specific posts made by a FileZilla developer piqued my interest. See here and here.

I remember reading a thread here recently discussing how theoretically impossible it was for a single TCP stream to go faster than a particular speed due to constraints like latency among other things.

I would imagine that the developer was likely testing in perfect conditions, a completely uncontested link both locally and at the destination as well as good routing in between but the distance was still transatlantic (20+ hops)...

Has anyone here seen speeds like that using a single TCP thread of any kind, not just FTP?

The best I have achieved is with sftp and was ~2.9MiB/s. Is this developer smoking something odd or is he correct that there is an underlying problem with congestion globally?

A well routed VPS I test with based in the US is roughly 10 hops from me and even taking in to account an ISP with plenty of capacity and a good home network configuration there is no hope I would even reach 2Mbit/s for a single stream via FTP/sftp/HTTP.

PeterReader

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Reply # 820905 17-May-2013 03:20

Hello... Our robot found some keywords in your post, so here is an automated reply with some important things to note regarding broadband speeds.

If you are posting regarding DSL speeds please check that

- you have reset your modem and router

- your PC (or other PCs in your LAN) is not downloading large files when you are testing

- you are not being throttled by your ISP due to going over the monthly cap

- your tests are always done on an ethernet connection to the router - do not use wireless for testing

- you read this topic and follow the instructions there.

Make sure you provide information for other users to help you. If you have not already done it, please EDIT your post and add this now:

- Your ISP and plan

- Type of connection (ADSL, ADSL2, VDSL)

- Your modem DSL stats (do not worry about posting Speedtest, we need sync rate, attenuation and noise margin)

- Your general location (or street)

- If you are rural or urban

- If you know your connection is to an exchange, cabinet or conklin

- If your connection is to a ULL or wholesale service

- If you have done an isolation test as per the link above

Most of the problems with speed are likely to be related to internal wiring issues. Read this discussion to find out more about this. Your ISP is not intentionally slowing you down today (unless you are on a managed plan). Also if this is the school holidays it's likely you will notice slower than usual speed due to more users online.

A master splitter is required for VDSL2 and in most cases will improve speeds on DSL connections. Regular disconnections can be a monitored alarm or a set top box trying to connect. If there's an alarm connected to your line even if you don't have an alarm contract it may still try to connect so it's worth checking.

I recommend you read these two blog posts:

- Is your premises phone wiring impacting your broadband performance? (very technical)

- Are you receiving a substandard ULL ADSL2+ connection from your ISP?

I am the Geekzone Robot and I am here to help. I am from the Internet. I do not interact. Do not expect other replies from me.

1080p

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Reply # 820910 17-May-2013 03:20

PeterReader: Hello... Our robot found some keywords in your post, so here is an automated reply with some important things to note regarding broadband speeds.

If you are posting regarding DSL speeds please check that

- you have reset your modem and router

- your PC (or other PCs in your LAN) is not downloading large files when you are testing
- you are not being throttled by your ISP due to going over the monthly cap

- your tests are always done on an ethernet connection to the router - do not use wireless for testing

- you read this topic and follow the instructions there.

Make sure you provide information for other users to help you. If you have not already done it, please EDIT your post and add this now:

- Your ISP and plan

- Type of connection (ADSL, ADSL2, VDSL)

- Your modem DSL stats (do not worry about posting Speedtest, we need sync rate, attenuation and noise margin)

- Your general location (or street)

- If you are rural or urban

- If you know your connection is to an exchange, cabinet or conklin

- If your connection is to a ULL or wholesale service

- If you have done an isolation test as per the link above

Most of the problems with speed are likely to be related to internal wiring issues. Read this discussion to find out more about this. Your ISP is not intentionally slowing you down today (unless you are on a managed plan). Also if this is the school holidays it's likely you will notice slower than usual speed due to more users online.

A master splitter is required for VDSL2 and in most cases will improve speeds on DSL connections. Regular disconnections can be a monitored alarm or a set top box trying to connect. If there's an alarm connected to your line even if you don't have an alarm contract it may still try to connect so it's worth checking.

I recommend you read these two blog posts:

- Is your premises phone wiring impacting your broadband performance? (very technical)

- Are you receiving a substandard ULL ADSL2+ connection from your ISP?

Shaddup PeterRetard.

mercutio

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Reply # 820918 17-May-2013 06:07

<root@am:~>
zsh 3005 # curl -4O http://proof.ovh.net/files/100Mio.dat
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 100M 100 100M 0 0 74.7M 0 0:00:01 0:00:01 --:--:-- 74.9M

74.9 megabytes/sec single threaded throughput :/ but that's amsterdam, which is quite close to france...

whereas from chicago i only get:

<root@bch:~>
zsh 1335 [127] # curl -4O http://proof.ovh.net/files/100Mio.dat
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 100M 100 100M 0 0 7664k 0 0:00:13 0:00:13 --:--:-- 9878k

adsl single threaded throughput internationally can be a bit degraded by small queues on connections if the isp doesn't add it's own queueing. although this manifests on faster connections more, and slow connections have too much queueing. they're not scaling based on adsl sync rate, ..

dwl

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Reply # 820968 17-May-2013 09:08

TCP can support a single thread at high rates over high delays (e.g. > 100 Mbps for 240 ms RTT) but only if the window sizes are set high enough (tuning issue) and there is low loss for that thread (beyond the average Internet user's control). Multiple threads may well be additive provided there is not shaping on a per user basis.

These graphics show both window size and loss effects:

The loss requirement should often not be so onerous as shown in the graph with better error recovery like SACK (often enabled) as more errors can be recovered for each segment. Different TCP algorithms may get a greater share of bandwidth when contending with other users.

Recent threads here on Geekzone suggest typical limits around 2-3MB/s to the US on UFB but faster speeds are seen with some providers or at certain times of day.

Regs

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Reply # 821103 17-May-2013 12:42

I stuffed around with tcp packet and window sizes etc quite successfully once. got ftp streams running 5x better to some destinations. others it didn't make a difference - likely because of the network between here and there.

the 'easy' solution is multi-threading (http or torrent etc). the 'correct' solution is an optimised network.

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Reply # 821249 17-May-2013 16:13

Regs: I stuffed around with tcp packet and window sizes etc quite successfully once. got ftp streams running 5x better to some destinations. others it didn't make a difference - likely because of the network between here and there.

the 'easy' solution is multi-threading (http or torrent etc). the 'correct' solution is an optimised network.

I think this is the point made by the developer, he thought that applying the 'quick fix' of segmented downloads would end up breaking the internet overall by encouraging users to no fix their systems.

The problem is that almost no one has a network of sufficient quality to make this viable and short of renting your own dedicated pipe no one ever will.

Nice to see some decent TCP transfer though. The transatlantic throughput seemed unbelievable to me.