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How is a packet received by a wireless devices with thousands of users/devices connected to the same network?

If we are using UDP, will it send the packets to all the devices such that only the authenticated devices will accept the packets and others would reject?

How does the situation change if we use TCP instead of UDP?

Jonathan Leffler
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Rohith Gowda
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3 Answers3

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UDP and TCP are the same as they are higher layer protocols.

Majorly simplified, but the device opens a tunnel to a GSN (Gateway Serving Node) which is a server installed at the carrier. Which GSN to use is based on the APN (Access Point Name) supplied when the tunnel (PDP context) is requested. The tunnel is assigned an IP address at the GSN and that is the address used for IP communication. Packets will be filtered at the GSN and routed to the specific device. Traffic is tunneled between the GSN and the device using telecom specific protocols. Packets are not broadcast out to all devices and then filtered there.

Ps. I phrased the answer using GPRS terms. Other 2.5/3/4G protocols use the same structure but sometimes have different names.

DrC
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  • Not sure what you mean by dedicated. The tunnel is assigned an ID and that ID is used to communicate. It is not like a switched protocol though where there are dedicated resources reserved for the communication. – DrC Feb 27 '13 at 05:42
  • what happens if we are using wi-fi – Rohith Gowda Feb 27 '13 at 14:50
  • Probably best to ask that as a new question. Personally, I'm not familiar enough with the lower layers of those protocols. – DrC Feb 27 '13 at 15:33
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what you mean by authenticated user? are you concentrating in application level ? or at lower layers of the n/w? even it is UDP , it should be thought of sending it to specific IP.even in complex n/w each s/m is an unique entity

internals-in
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    my doubt was, whether packets are recieved by all the end users and filtered there or it will be directed to a specific user. – Rohith Gowda Feb 27 '13 at 05:38
  • Packets are sent to a specific device (more accurately a specific context on the device - like a logical NIC). "User" really isn't a concept at this layer. – DrC Feb 27 '13 at 05:45
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Rohith Gowda , actually if you are concentrating on udp packets at Application level (either java, c# ...) u creates the packets for specific ip and sends to an IP,( which is the recivers ip) and the reciver have to grab it , i think you actually want this right? and no need to fear about others with different ip than what you are sending to, because you are in abstracted APP Layer, your doubt will be look after by lower layers.if you want an additional snooping proof just encode the data that you want to send
one Example is (in java)
DatagramPacket (UDP) can be created by invoking a new instance of 

 DatagramPacket(packet data [],offset ,length ,address* ,port* )

look at the last 2 params they specify the SeverAddress and the Port of transmit to the server i think you are now clear that the destination server with the ip (Sever-address) listening at the particular port can grab it.

internals-in
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