Mobile race condition
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How the hell is it possible for me to call someone at the very moment they are calling me? I heard the ringing tone already, and then I received a call and had an option to decline call or hang up and receive call. Why haven't one of us hit the voicemail? This never happened to me in Europe.
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@gąska where were you when this happened? In the U.S., different phone companies service different areas, and some areas have multiple competing carriers (especially for cellular services, with some locations covered by multiple towers and others only one or even have no coverage at all).
While most of these play well with others, this isn't always the case, and inconsistencies in equipment, standards, compliance, deployment models, and service models mean edge cases are inevitable. Results can be different by a distance of 100m or less. It works 99% of the time, but that 1% can make for really weird effects.
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@gąska said in Mobile race condition:
How the hell is it possible for me to call someone at the very moment they are calling me? I heard the ringing tone already, and then I received a call and had an option to decline call or hang up and receive call. Why haven't one of us hit the voicemail? This never happened to me in Europe.
Is it possible that you actually called each other at the same time?
I've had that happen to me quite a few times.
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@scholrlea said in Mobile race condition:
@gąska where were you when this happened? In the U.S., different phone companies service different areas, and some areas have multiple competing carriers (especially for cellular services, with some locations covered by multiple towers and others only one or even have no coverage at all).
I was in Chicago. The other person in San Francisco. This might explain what happened. Plus maybe some new feature silently activated by my operator that lets me have several active calls on a single line.
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@gąska said in Mobile race condition:
Plus maybe some new feature silently activated by my operator that lets me have several active calls on a single line.
Call waiting has been around for a long time. I remember when it was the bane of dial up internet.
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@boomzilla said in Mobile race condition:
Call waiting has been around for a long time. I remember when it was the bane of dial up internet.
That was simple - I took that feature off my phone line. If I didn't answer, I was on the computer!
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@boomzilla said in Mobile race condition:
@gąska said in Mobile race condition:
Plus maybe some new feature silently activated by my operator that lets me have several active calls on a single line.
Call waiting has been around for a long time. I remember when it was the bane of dial up internet.
Well, coming from Europe, it's new to me. At least it's new that I have it on by default.
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@gąska said in Mobile race condition:
@boomzilla said in Mobile race condition:
@gąska said in Mobile race condition:
Plus maybe some new feature silently activated by my operator that lets me have several active calls on a single line.
Call waiting has been around for a long time. I remember when it was the bane of dial up internet.
Well, coming from Europe, it's new to me. At least it's new that I have it on by default.
Yeah, the only way it's going to Voicemail is if you don't respond, or you use the option to "do not answer", which immediately sends them to voicemail.
Otherwise it's going to let you know you have another call.
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@xaade said in Mobile race condition:
@gąska said in Mobile race condition:
@boomzilla said in Mobile race condition:
@gąska said in Mobile race condition:
Plus maybe some new feature silently activated by my operator that lets me have several active calls on a single line.
Call waiting has been around for a long time. I remember when it was the bane of dial up internet.
Well, coming from Europe, it's new to me. At least it's new that I have it on by default.
Yeah, the only way it's going to Voicemail is if you don't respond, or you use the option to "do not answer", which immediately sends them to voicemail.
Otherwise it's going to let you know you have another call.
Call waiting is popular here in Poland too, I’m just not sure how it plays out when both callers call each other at the same time.
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@kt_ said in Mobile race condition:
@xaade said in Mobile race condition:
@gąska said in Mobile race condition:
@boomzilla said in Mobile race condition:
@gąska said in Mobile race condition:
Plus maybe some new feature silently activated by my operator that lets me have several active calls on a single line.
Call waiting has been around for a long time. I remember when it was the bane of dial up internet.
Well, coming from Europe, it's new to me. At least it's new that I have it on by default.
Yeah, the only way it's going to Voicemail is if you don't respond, or you use the option to "do not answer", which immediately sends them to voicemail.
Otherwise it's going to let you know you have another call.
Call waiting is popular here in Poland too, I’m just not sure how it plays out when both callers call each other at the same time.
For me. Exactly like above.
I start ringing their number, I hear the rings, and then I see their number is calling me. If I'm quick, I can switch to answering them. If I'm not, I go to their voicemail, and I suspect they go to mine.
Given that the original behavior is that we both automatically go to voicemail, I'd count this as an improvement.
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@kt_ said in Mobile race condition:
I’m just not sure how it plays out when both callers call each other at the same time.
If both call each other at the same time, neither can be connected as it is impossible to determine which party is to be billed. The phone system relies on this being relatively rare.
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@dkf said in Mobile race condition:
@kt_ said in Mobile race condition:
I’m just not sure how it plays out when both callers call each other at the same time.
If both call each other at the same time, neither can be connected as it is impossible to determine which party is to be billed. The phone system relies on this being relatively rare.
Wouldn't it just bill both parties because both started separate calls?
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@ben_lubar Don't give them ideas.
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When 2 people call each other simultaneously, then obviously a call between them should be established.
It is quite clear they want to talk, after all.
Come on, telephone industry, you have only had decades to figure that out.
(As for payment: split the bill in half, no problem)
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@ben_lubar said in Mobile race condition:
@dkf said in Mobile race condition:
@kt_ said in Mobile race condition:
I’m just not sure how it plays out when both callers call each other at the same time.
If both call each other at the same time, neither can be connected as it is impossible to determine which party is to be billed. The phone system relies on this being relatively rare.
Wouldn't it just bill both parties because both started separate calls?
Theoretically, yes. Practically, no. It tells both parties to try again (or lets them send a voicemail).
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@gąska this happened to me ages ago when mobile phones were pretty much non-existent. It's possible even with old analog lines.
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@adynathos said in Mobile race condition:
When 2 people call each other simultaneously, then obviously a call between them should be established.
If that were the case it would be, with spoofed ANI, an interesting way to intercept an outgoing call.
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@greybeard said in Mobile race condition:
@adynathos said in Mobile race condition:
When 2 people call each other simultaneously, then obviously a call between them should be established.
If that were the case it would be, with spoofed ANI, an interesting way to intercept an outgoing call.
How do you mean?
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@kt_ Alice initiates a call to Bob. Mallory then initiates a call to Alice spoofed as coming from Bob. The calls are joined together. Alice thinks she called Bob but is instead connected to Mallory.
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@greybeard said in Mobile race condition:
@kt_ Alice initiates a call to Bob. Mallory then initiates a call to Alice spoofed as coming from Bob. The calls are joined together. Alice thinks she called Bob but is instead connected to Mallory.
That won't work because the phone company won't use the spoofed number but the real one (which they know for billing purposes but won't tell you because spoofing is a good thing, obviously).
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@planar said in Mobile race condition:
@greybeard said in Mobile race condition:
@kt_ Alice initiates a call to Bob. Mallory then initiates a call to Alice spoofed as coming from Bob. The calls are joined together. Alice thinks she called Bob but is instead connected to Mallory.
That won't work because the phone company won't use the spoofed number but the real one (which they know for billing purposes but won't tell you because spoofing is a good thing, obviously).
Pretty sure that would work, actually, because the "phone company" is more than one company...
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@sloosecannon said in Mobile race condition:
@planar said in Mobile race condition:
@greybeard said in Mobile race condition:
@kt_ Alice initiates a call to Bob. Mallory then initiates a call to Alice spoofed as coming from Bob. The calls are joined together. Alice thinks she called Bob but is instead connected to Mallory.
That won't work because the phone company won't use the spoofed number but the real one (which they know for billing purposes but won't tell you because spoofing is a good thing, obviously).
Pretty sure that would work, actually, because the "phone company" is more than one company...
Do phones not have an equivalent of
SYN
SYN ACK
ACK
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@ben_lubar said in Mobile race condition:
@sloosecannon said in Mobile race condition:
@planar said in Mobile race condition:
@greybeard said in Mobile race condition:
@kt_ Alice initiates a call to Bob. Mallory then initiates a call to Alice spoofed as coming from Bob. The calls are joined together. Alice thinks she called Bob but is instead connected to Mallory.
That won't work because the phone company won't use the spoofed number but the real one (which they know for billing purposes but won't tell you because spoofing is a good thing, obviously).
Pretty sure that would work, actually, because the "phone company" is more than one company...
Do phones not have an equivalent of
SYN
SYN ACK
ACKNot in the specific scenario we're discussing, no...
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@ben_lubar The phone system use the SS7 protocol, which was not designed with security in mind.
Example :
After years of warnings, mobile network hackers exploit SS7 flaws to drain bank accounts