Hi, My answer wasn't incorrect... you are simply misunderstanding what "end-to-end" means in this context. This is getting a bit off topic, but it's interesting stuff.
TCP/IP begins and ends at the edge of the cell network, on the network providers Internet gateway. Between the gateway and the phone itself there is no TCP/IP. This is the exact reason why you CANNOT build TCP/ IP connections from a server to a phone. You can ONLY build connections from a phone to a server. For further clarification see http://en.wikipedia.org/wiki/Packet_Data_Protocol#PDP_Context When the gateway receives the outgoing request from the phone, the gateway assigns its own IP address and a port number to the request and puts it on to the Internet as a standard TCP/IP data packet. This context may exist for some time on the gateway, or it may be flushed very quickly, there is no way to predict. It's not even possible for the application on the phone to know what IP address is being used on its behalf. The packet coming back to the phone is stripped of its TCP/IP envelope at the gateway and then put on the cell network using whatever packet technology the cell network uses. This is the very meaning of the word "gateway"... it is a gateway between two completely different networks that work in completely different ways, it is a protocol converter. - Mike NAVTEQ Network for Developers http://NN4D.com Disclaimer: I work for NAVTEQ and these are my personal opinions which do not necessarily reflect NAVTEQ’s views On 4 Feb, 07:13, Bob Kerns <[email protected]> wrote: > This isn't correct, or is misleading. It's kind of like saying > "ethernet doesn't use TCP/IP" or "WiFi doesn't use TCP/IP" or "dialup > modems don't use TCP/IP" or "DSL doesn't use TCP/IP" or "Cable doesn't > use TCP/IP". > > If you drop below the level of TCP/IP, to how the data is physically > moved, then yes, you are below TCP/IP, and in that sense, cell > networks don't use TCP/IP. > > However, they CARRY TCP/IPtraffic. And that's what thoseIPaddresses > are --IPaddresses. You can establish TCP connections. > > TCP/IPis actually two protocols.IPis the lower-level of the two, > handling addressing and routing. It is completely agnostic as to how > the packets are transported. You could use carrier pigeons. Really! > > http://www.rfc-editor.org/rfc/rfc1149.txt > > I don't know if anybody's done it -- but it wouldn't surprise me. > > TCP is on top ofIP, and gives you reliable transmission and end-to- > end connection semantics. > > Now, perhaps you meant to contrast the situation with VOIP, where > voice is carried overIP. Indeed, voice data is not (normally) carried > over cell networks as TCP/IP, though it's possible. (Not necessarily > acceptable, but possible). > > But every phone with a data plan is using the cell networks to carry > TCP/IP. > > Your gatewayaddresswill be theaddressof the gateway server, but > yourIPaddresswill be yourIPaddressthat your server uses to send > traffic to you. > > I don't know the current state of the art for how stable your > phone'sIPaddresswill be. I can tell you that my phone switches cell sites > surprisingly often, but I've not watched theIPaddresses > simultaneously. > > But you don't switchIPaddresses when you move from Access Point to > Access Point on the same WiFi network. In theory, you could retain the > sameIPaddressfor the life of your phone, with a sufficiently clever > and powerful cell network. > > In practice, however, that's unreasonable. But perhaps someone can > tell me just when it changes. And why, after rebooting, I have TWO? > One for each tower? We're at the limits of my networking knowledge > when we come to the specifics of how it's layered on top of the > cellular network. > > BTW, Vertifi, this "Class B/Class C" terminology is long obsolete; > addresses have not been allocated by that scheme for many years. It > consumed too much IPv4addressspace. Instead, the number of prefix > bits is specified, like 192.168.0.0/24 -- where 24 is not necessarily > a multiple of 8. I don't know if your server farm people are expecting > "Class C" to refer to distinct networks, or simply using the term as a > holdover, but treating it as the arbitrary distinction that it is. But > certainly we should not import any significance to thoseIPaddresses > being allocated from some larger block than /24. They could all be > from the same subnet, so far as the cellular network is concerned. > This would be some network in some bunker somewhere, with a bunch of > NAT servers, with multiple hot connections to various pieces of the > backbone. > > TheIPaddressassigned to the phone will be anaddressspecific to > the link between you and the next piece of equipment that actually > treats your data as TCP/IPtraffic. My iPhone reports it as > 10.135.130.117; I've never seen it other than a 10.0.0.0/8 non- > routable privateaddress. This is translated via NAT further upstream, > so servers on the other end see a routableIPaddress; at the moment, > mine is 98.210.255.162. > > In theory, this can be different for every TCP connection! But there > are a few things that care about connections with the same originating > system -- active FTP being one. So normally, this syntheticIPaddress > doesn't change, so long as you have one active TCP or recent > connection, or recent UDP traffic, but after you've been idle or a > bit, it purges its mapping tables, and on your next connection, you > appear to come from a newIPaddress. > > This is really no different than any large enterprise NAT networking > environment. Just bigger. > > Anyway -- while there are holes in my explanation, I don't think > there's anything inaccurate. But I hate being wrong, so please jump > in with any corrections or additions! > > On Feb 3, 7:38 am, Mike <[email protected]> wrote: > > > > > The simple answer is that cell networks don't use TCP/IP. What you > > see is theIPaddressof the gateway server that happens to have > > generated the request. This could change on every request and is not > > time based. > > > Hope it helps. > > > - Mike > > NAVTEQ Network for Developershttp://NN4D.com > > > On 3 Feb, 15:35, Vertifi <[email protected]> wrote: > > > > Hello, > > > > I have an app which performs some online functions to a web server > > > farm we operate using URLConnection. I'm finding that theclientIP > > >addressof the phone seems to change after a fairly brief period of > > > inactivity. > > > > For example, please see these timestamps and the correspondingclient > > >IPaddresses: > > > > 2010-02-03 09:46:47 / 32.152.30.98 > > > 2010-02-03 09:47:05 / 32.152.30.98 > > > 2010-02-03 09:57:21 / 32.152.218.197 > > > 2010-02-03 09:59:53 / 32.152.23.19 > > > > This is sitting in a stationary location (on an AT&T EDGE network) in > > > my office. Is there some reason for this behavior? > > > > Any advice would be greatly appreciated > > > > Regards, > > > Chris @ Vertifi- Hide quoted text - > > - Show quoted text - -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
