7 ms·

How Android knows it's on an expensive connection

84 points by sadiq 13y ago

sehugg 13y ago
I'd love to see this sort of thing standardized -- a "how much does this connection cost?" function. I get twitchy whenever I hook up my laptop to any sort of metered hotspot. And when using a gateway with wifi-over-wan there is no way to communicate the metered connection status to the client (well, I guess you could reverse DNS lookup your IP and guess based on the name) Alternatively, I'd just like unmetered bandwidth everywhere...
- remosi 13y ago
  Well, this scheme at least lets you announce "This is an (relatively) expensive connection, please avoid doing things you don't need to.".
- russellsprouts 13y ago
  I know Windows 8 lets you allow or disallow (Windows 8) apps from downloading over metered connections.
Tichy 13y ago
Couldn't Android just ask for the DHCP option? It sounds to me as if this is a case of Android as a DHCP client talking to Android as a DHCP host, so making Android ask as a client seems feasible.
- remosi 13y ago
  Yeah, it could. It doesn't tho. So you have to remember to force it if you want android to listen to you setting the attribute.
  - Tichy 13y ago
    Ah, is the article written for other platforms who want to emulate Android in automatically limiting Hotspots on mobile plans? Then it makes sense.
    - remosi 13y ago
      That was why I wrote it yes. I wanted to know how I could ask android phones politely to avoid slamming the bandwidth on an AP that really didn't have the backhaul for everyone's photos and kept these notes in case I needed to do it again (or someone asked me how to do it.) I wasn't expecting it to be read by more than about 3 people who were trying to figure this out :)
PeterisP 13y ago
Why should my phone send out strange flags (that disable sync features) just because it's used as a hotspot? At least for me, phone traffic is free, and if some device needs to sync some photos the software shouldn't disturb it because somewhere (USA?) has nonfunctioning competition in mobile connectivity. For example, for my Android tablet the usual network connection is my phone hotspot - how would I even know if some feature is waiting for "nonexpensive connection" that is not going to come any time soon?
- kllrnohj 13y ago
  > At least for me, phone traffic is free What magical land do you live in that has truly unlimited cell data? And how much does it cost? > how would I even know if some feature is waiting for "nonexpensive connection" that is not going to come any time soon? The feature is typical used for things like when you enable "only do this on WiFi" type options, it knows that although it is connected to a wifi hotspot, that hotspot itself is using cell data so don't do that expensive thing that you said to only do on wifi. Typically the worst thing that'll happen is you will get a few "are you sure?" style dialogs when you go to install a large game or similar.
  - tadfisher 13y ago
    T-Mobile (US) has never gotten rid of their unlimited data option. Up until recently, they had a 5GB cap whereafter they would throttle the connection to EDGE speeds; they have since replaced this with a generic "don't abuse the network" policy, which I have yet to trigger (some months I have gone over 10GB of usage).
    - MacsHeadroom 13y ago
      This unlimited LTE and HSPDA+ 4G plan by T-Mobile is $30/month, for those interested. But only if you buy the start up kit from Walmart. The plan is $70/month otherwise.
  - buro9 13y ago
    > What magical land do you live in that has truly unlimited cell data? And how much does it cost? Three in the UK. GBP 15 per month for an unlimited data plan. It's only 3G, but they've committed to provide 4G for no price bump once they've finished their rollout later this year. What else? Hmm... I used 7GB last month. Spotify mostly, some Ted talks too. No-one's complaining, it really is unlimited cell data.
lukashed 13y ago
I love it how simple the tethering works. I thought it would be some kind of rocket science, but in fact Android is simply enabling IP forwarding by writing a 1 into /proc/sys/net/ipv4/ip_forward and running a dhcp server. Sometimes it's the simple solution that works best.
- rca 13y ago
  It should also have to add some iptables rules no? At least one for the natting and one for the filtering.

84 points by sadiq 13y ago

I'd love to see this sort of thing standardized -- a "how much does this connection cost?" function. I get twitchy whenever I hook up my laptop to any sort of metered hotspot. And when using a gateway with wifi-over-wan there is no way to communicate the metered connection status to the client (well, I guess you could reverse DNS lookup your IP and guess based on the name) Alternatively, I'd just like unmetered bandwidth everywhere...

remosi 13y ago
Well, this scheme at least lets you announce "This is an (relatively) expensive connection, please avoid doing things you don't need to.".
russellsprouts 13y ago
I know Windows 8 lets you allow or disallow (Windows 8) apps from downloading over metered connections.

Tichy 13y ago

Couldn't Android just ask for the DHCP option? It sounds to me as if this is a case of Android as a DHCP client talking to Android as a DHCP host, so making Android ask as a client seems feasible.

remosi 13y ago
Yeah, it could. It doesn't tho. So you have to remember to force it if you want android to listen to you setting the attribute.
- Tichy 13y ago
  Ah, is the article written for other platforms who want to emulate Android in automatically limiting Hotspots on mobile plans? Then it makes sense.
  - remosi 13y ago
    That was why I wrote it yes. I wanted to know how I could ask android phones politely to avoid slamming the bandwidth on an AP that really didn't have the backhaul for everyone's photos and kept these notes in case I needed to do it again (or someone asked me how to do it.) I wasn't expecting it to be read by more than about 3 people who were trying to figure this out :)

PeterisP 13y ago

Why should my phone send out strange flags (that disable sync features) just because it's used as a hotspot? At least for me, phone traffic is free, and if some device needs to sync some photos the software shouldn't disturb it because somewhere (USA?) has nonfunctioning competition in mobile connectivity. For example, for my Android tablet the usual network connection is my phone hotspot - how would I even know if some feature is waiting for "nonexpensive connection" that is not going to come any time soon?

kllrnohj 13y ago
> At least for me, phone traffic is free What magical land do you live in that has truly unlimited cell data? And how much does it cost? > how would I even know if some feature is waiting for "nonexpensive connection" that is not going to come any time soon? The feature is typical used for things like when you enable "only do this on WiFi" type options, it knows that although it is connected to a wifi hotspot, that hotspot itself is using cell data so don't do that expensive thing that you said to only do on wifi. Typically the worst thing that'll happen is you will get a few "are you sure?" style dialogs when you go to install a large game or similar.
- tadfisher 13y ago
  T-Mobile (US) has never gotten rid of their unlimited data option. Up until recently, they had a 5GB cap whereafter they would throttle the connection to EDGE speeds; they have since replaced this with a generic "don't abuse the network" policy, which I have yet to trigger (some months I have gone over 10GB of usage).
  - MacsHeadroom 13y ago
    This unlimited LTE and HSPDA+ 4G plan by T-Mobile is $30/month, for those interested. But only if you buy the start up kit from Walmart. The plan is $70/month otherwise.
- buro9 13y ago
  > What magical land do you live in that has truly unlimited cell data? And how much does it cost? Three in the UK. GBP 15 per month for an unlimited data plan. It's only 3G, but they've committed to provide 4G for no price bump once they've finished their rollout later this year. What else? Hmm... I used 7GB last month. Spotify mostly, some Ted talks too. No-one's complaining, it really is unlimited cell data.

lukashed 13y ago

I love it how simple the tethering works. I thought it would be some kind of rocket science, but in fact Android is simply enabling IP forwarding by writing a 1 into /proc/sys/net/ipv4/ip_forward and running a dhcp server. Sometimes it's the simple solution that works best.

rca 13y ago
It should also have to add some iptables rules no? At least one for the natting and one for the filtering.