why is range 6881-6889 not recommended?

[jrmarino]

I did make an attempt at a search for this question. I see on the FAQ that the standard incoming port range of 6881-6889 is not recommended, but the FAQ does not say why it is not recommended.

I was suffering from a download speeds much lower than I am used to with BitTornado. I had the default utorrent port selected (no randomization) with uPNP option. I didn't pay attention to it at the time, but I think the NAT bad message was lit. When I turned of uPNP and changed the port to 6881, the download speed that I am used to returned.

Since it's working now, my tendency is to leave it alone. Is the standard port range not recommended due to some possible port blocking attempt? What's the reason this range is not recommended by utorrent?

[Redleer]

mayby some isp:s likes to block standard bittorrent ports. havent readed alot about port settings so dont know for sure

[Inf]

This standard port range is not recommended because some ISP-s still seems to throttle the traffic on those specific ports (while many other autodetect the bittorent protocol and throttle it on any port :-( ).

[ColdArmor]

ISP's know these are standard ports for BitTorrent and they will throttle you speeds.

[sixshot]

As others have said, some ISP either block those ports or throttle them. So using a random other port would be more beneficial to both the peers and to you as they won't know precisely what port you're using while using BitTorrent. The IANA has a listing of a variety of ports used by what protocol service (ie. MySQL and anything else in between), a lot of which spans beyond the usual 1024 port that is mostly not restricted (in *nix world, any service using ports below (or at?) 1024 requires the service software to be run as a super-user (ie. root)). IANA suggests that for any software requiring the use of ports to utilize a port or a range of ports that is/are deemed as for general use (49152 to 65535).

Another reason to not use the default BitTorrent port is to work around the ISP's peering eyes. They might have those ports monitored for illegal activities. But who knows...

[splintax]

This standard port range is not recommended because some ISP-s still seems to throttle the traffic on those specific ports

Most ISPs don't do that anymore; if they throttle it at all they use packet inspection as you mentioned...

Most people that are causing a significant drain on the ISP's system are clued-up enough to know how to change ports..

[joecool]

use ports 6881-6999, how can you use random when you have to foreward with a router, huh

[Firon]

Not everyone's behind a router. And for the ones that are, they can use UPnP.

[Ultima]

That's assuming that their router supports IGD (I personally don't know how many/what routers support this though; for all I know, most routers might =P)

[Firon]

That and the fact that UPnP support is pretty hit and miss... (Linksys routers are great example of this: either it works for you, or it doesn't)

[slayers]

Some trackers would ban peers using those ports because they assumed ISP's would be throtling and hurt the swarm. So it's become somewhat of a no-no in bittorrent land. Better play safe than sorry.

[ColdArmor]

Some trackers would ban peers using those ports because they assumed ISP's would be throtling and hurt the swarm.

Back in the day that was one of my problems

[jrmarino]

Slayers, I'm not saying some trackers weren't/aren't configured to ban standard port peers as I don't know, but I will say that logic certainly doesn't make sense to me.

It seems to me that a swarm with X throttled peers is better than a swarm without those same X peers, meaning the swarm still benefits from the packets the peers can distribute, even if it's at a reduced rate. As I understand the algorithm, it takes into account the transfer capability of the peers, giving higher throughput peers preference, but the X peers still significantly contribute.

I can't see how a swarm would EVER be better off banning peers that distribute good packets.

As for me personally, I max out my DSL limit, so if I am throttled (I doubt it), the threshold is higher than what I'm paying for. So I have no reason to switch my port number from 6881.

[slayers]

Your reasoning is correct. What I meant to say was blocking instead of throtling. When ISPs block those ports, peers make no contribution and only overload already overloaded trackers. If they have to make a choice (and many poorly funded trackers do) they would prefer to not support those peers. This was very true in the earlier days I can't say how much of it still stands. ISPs have gone into protocol throtling which is much more efficient (albeit more expensive since it requires specific hardware) than port blocking (which is trivial to implement) so port jumping becomes obsolete. Ratio enforced trackers (which only became popular afterwards) couldn't care less if you're blocked or not, if your ratio doesn't hold your banned.

So you see, the original premise for avoiding those ports have softened through time. But it's a big world out there so who knows what trackers and ISPs are doing exactly with ports. It's just better to avoid them because there is a chance that your ISP might be doing it the easy way (port blocking) or that your tracker is avoiding those peers.

[splintax]

A lot of trackers ban 6881-9 and tell you in the tracker response.

I personally see no problem with it, as it encourages people to avoid any throttling that may occur should their ISP be using such an unreliable method, as well as get people to learn something about ports which would hopefully decrease the number of unconnectables..

As far as UPnP goes, Firon is right; and there is no real reason to randomize the port each time..