#IndirectTCP

[nileshpnj]

What is Indirect TCP (I-TCP) ? | Mobile Computing

In this video, we will understand how traditional TCP in improvised with Indirect TCP (I-TCP). I-TCP segments a TCP connection into a fixed part and wireless part. MH (Mobile Host) connected wirelessly with Access Point (AP). 

 CH (correspondent Host) connected wired with AP. Standard TCP is used between CH and AP. In the same way, Wireless TCP is used between MH and AP. Here, AP can act as proxy, i.e.  AP will behave here MH for CH, and CH for MH. 

This AP can relay data on both sides and act as a proxy. 

If CH send packet, the AP will take it and ACK to CH, and later will try to forward these packet to MH. If MH receives the packet, it ACK the packet to AP. If packet lost in wireless link, due to transmission error, the CH will notice this, and tries to retransmit it. 

Similarly, if MH wants to send packet, the AP will ACK it and tries to forward the packet to CH. If packet lost in wireless link, the MH will notice this, and immediately retransmit it. 

 Socket and State Migration. 

 After the handover of MH to a new FA, the old FA must forward the buffered data to a new FA.  After the registration to a new FA by MH, this new FA responsibility to inform the old FA, about the current location to enable packet forwarding. Sockets and buffer content must migrate to  new FA. In sockets, there is a current state of TCP resides - sequence no., address, port. 

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