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Little question

Community Veteran
Posts: 38,308
Thanks: 972
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Registered: 15-06-2007

Little question

If someone is on a variable IP address would there be any noticeable difference to the user or could some protocols be expected to be affected. I know that this is probably part of the trial but presumably some prior testing has taken pace
16 REPLIES
Plusnet Staff
Plusnet Staff
Posts: 12,169
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Registered: 04-04-2007

Re: Little question

It depends what they do. The most likely candidates for problems are applications that require inbound connections. The obvious things are hosting a webserver or mail server on your connection, but will also include accessing your PC via remote desktop/VPN, uploading via BitTorrent or hosting a game. Services like DynDNS (which will also be affected) make these kind of things easier when you have a dynamic IP address as you have a static host name that follows your IP.
We'd expect most things to work fine, most websites, streaming servers, file downloads will be fine. We've tested a number of things to see if they work or not but there's an awful lot of different applications out there and we've not tested everything so it's the things that aren't so obvious that people use we need to look at as well as the obvious.
VileReynard
Seasoned Pro
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Registered: 01-09-2007

Re: Little question

Doesn't FTP (Active mode) make an inbound connection?

Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Re: Little question

Yes, I think so. But certain protocols have helpers (application layer gateways) within CGNAT to allow them to continue to work, there's examples on Cisco's documentation here:
http://www.cisco.com/en/US/docs/routers/crs/software/crs_r3.9.1/cg_nat/configuration/guide/cgc391cgn...
camlin
Newbie
Posts: 3
Registered: 16-01-2013

Re: Little question

I am sorry, but I don't think ALGs are a good solution:
1 - First of all they only work if the messages are sent in clear (does not work when they are encrypted)
2 - They typically only know about a few protocols (usually: only SIP)
3 - They are often quite buggy and implemented as an after thought: For example most SIP ALG, just change the IP in the SDP payload but they often forget to adjust the message size, meaning it will get rejected by most server if the internal and external IP are not the same length (for example: going from 10.10.1.10 to 192.168.200.100).
Community Veteran
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Registered: 10-04-2007

Re: Little question

Surely both 10.10.1.10 and 192.168.200.100 are 4 bytes long!
jelv (a.k.a Spoon Whittler)
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camlin
Newbie
Posts: 3
Registered: 16-01-2013

Re: Little question

Except when they appear in the SDP payload of a SIP message they appear in their textual form (not binary).
And in that case, no their length is not the same... Meaning the SIP length header would have to change...
VileReynard
Seasoned Pro
Posts: 10,648
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Registered: 01-09-2007

Re: Little question

Unreliable FTP is sufficient to make CGNAT a non-starter.
I bet P2P uploads will fail.
So Linux bit torrents will at best be download only.
I believe uPNP can be used for Port Forwarding and NAT Traversal - so even if it works now,
I might install a program or game in the next few years - which will fail unexpectedly.

Community Veteran
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Registered: 10-04-2007

Re: Little question

FTP will only fail if PASV isn't used. Anybody who is using a router and not connecting direct to the modem is highly likely to be using PASV already.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
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Community Veteran
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Registered: 10-06-2010

Re: Little question

You will be able to upload as much as you like on bittorrent or any other P2P protocol, just not to other IPs that can't receive an incoming connection for whatever reason.
VileReynard
Seasoned Pro
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Re: Little question

Quote from: jelv
FTP will only fail if PASV isn't used. Anybody who is using a router and not connecting direct to the modem is highly likely to be using PASV already.

I'm not. Grin

Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: 18-07-2007

Re: Little question

This is just more reasons for testing though surely? What will work, and how? What won't, and why? Even if it's not suitable for everyone, will it still be suitable for some users who maybe don't have to use active FTP connections?
Just some of the things we're hoping to find out with this trial.
VileReynard
Seasoned Pro
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Re: Little question

I wonder how many applications download updates using FTP?
My question would be:-
How many different IP4 addresses will non-Plusnet users see during the course of the trial?
I wouldn't want my bank logging just one IP address for multiple users.
A claim against misuse of my account or identity theft would be very hard to defend if IPV4 logs show a lot of duplicates.

Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: 18-07-2007

Re: Little question

Surely that depends on the information we have regarding internal traffic? It's not something I can answer right now, but I will ask about that. Can see your concern, but as long as we can identify how the routing is in our network there shouldn't be an issue there.
xS9
Dabbler
Posts: 20
Registered: 26-01-2013

Re: Little question

What is the aim of this trial?
If the aspiration of the business is to cull the IPV4 footprint for the entire userbase, then it's not worth the time as it's not a viable mitigation. It does not provide a 100% like for like service.
Alternatively, if this is to create a "basic/limited" surfing product for purely surfing/email users, then does the projected business case add up?
My opinion currently is that PlusNet are trying to achieve the former and will face the latter, which will in-turn be deemed not cost effective.