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Old 05-22-2008, 11:03 PM   #1
citiz3n
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Receiving Packets Simultaneously in Two Different Network Interface ?


Hi guys.

Is it possible to have to connections established using two network device (ie. ethernet and wlan) .. at the same time in Linux.

And assuming im connected to an IPTV streaming server from both the connections... will i be able to get SAME packets simultaneously from the different network interface (of course its actually duplicate packets).


Please enlighten me.


Thank you in advance.


Citiz3n
 
Old 05-23-2008, 12:36 AM   #2
dkm999
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It is certainly possible to be receiving packets on two different interfaces at the same instant. There is dedicated hardware attached to each Ethernet port that will hold the packet until the CPU can pay attention to it.

If you make two connections to some server, and somehow arrange to have them assigned to different interfaces (more on this below), you have no guarantee that the two copies of a packet will arrive at the same time, however. The Internet is a probabilistic delivery system; each packet will be delayed by an apparently random amount as it passes through each segment of a path from server to client. These delays will very likely not be the same along two different paths, so your chances of seeing copies of the same packet appear at the same instant are pretty small.

Furthermore, the way we normally set up computers to talk over the Internet is to have them use the best route from point A to point B. This means that, if your machine has two interfaces, it will choose one of them to reach a remote server, not both. There are some tricky ways around this, but they are not for the faint of heart.
 
Old 05-23-2008, 02:44 AM   #3
citiz3n
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Quote:
Originally Posted by dkm999 View Post
It is certainly possible to be receiving packets on two different interfaces at the same instant. There is dedicated hardware attached to each Ethernet port that will hold the packet until the CPU can pay attention to it.

If you make two connections to some server, and somehow arrange to have them assigned to different interfaces (more on this below), you have no guarantee that the two copies of a packet will arrive at the same time, however. The Internet is a probabilistic delivery system; each packet will be delayed by an apparently random amount as it passes through each segment of a path from server to client. These delays will very likely not be the same along two different paths, so your chances of seeing copies of the same packet appear at the same instant are pretty small.

Furthermore, the way we normally set up computers to talk over the Internet is to have them use the best route from point A to point B. This means that, if your machine has two interfaces, it will choose one of them to reach a remote server, not both. There are some tricky ways around this, but they are not for the faint of heart.
Oh okay...

So it is possible. Then lets consider this situation. Im viewing an IPTV streaming via interface A from server Z. Then i swap connection (handoff) to interface B but still from server z. Will there be a loss in transmission in between that?

Also consider this.... It's a connectionless protocol since its IPTV and when i making the handoff its a (make-and-break handoff).


Thank You.

Citiz3n
 
Old 05-24-2008, 02:18 AM   #4
dkm999
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As with so many things, the answer is "it depends". In this case, it depends on everything in the two paths from your IPTV server to the receiver. Packets can get congested at any router point along the way, and can arrive either A before B or B before A. In addition, packets have been known to get damaged or lost due to noise, collisions on Ethernet links, etc.

But, given that there is reasonable bandwidth between the source and destination, it seems unlikely that any significant loss of data will occur. If a packet or two is missing, the IPTV stream will recover (otherwise, it would not be using UDP, which does not guarantee delivery).
 
Old 05-25-2008, 08:38 PM   #5
citiz3n
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Originally Posted by dkm999 View Post
As with so many things, the answer is "it depends". In this case, it depends on everything in the two paths from your IPTV server to the receiver. Packets can get congested at any router point along the way, and can arrive either A before B or B before A. In addition, packets have been known to get damaged or lost due to noise, collisions on Ethernet links, etc.

But, given that there is reasonable bandwidth between the source and destination, it seems unlikely that any significant loss of data will occur. If a packet or two is missing, the IPTV stream will recover (otherwise, it would not be using UDP, which does not guarantee delivery).
Oh.. alright.. thank you for the reply.

Best Regards,

Citiz3n
 
  


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