Explicit loss notification with ACK

Wireless connection to not use TCP
o Complicates mobility, and is vulnerable to failures
o Violates end-to-end semantics
Snoop protocol
o One of the most recent enhancements to TCP in wireless environments
o Uses snoop agent at base station
Monitors TCP packet transmission
Caches all packets sent to a mobile, and re-transmits lost packets locally
Avoids lengthy TCP retransmission by sender
Mainly used in direction of fixed host to mobile
Works like link layer solutions
TCP/IP for satellite
o Choice of orbit (LEO, MEO, GEO) relates to performance of TCP if over IP
o Data transfer is short compared with delay-bandwidth product
o Slow start algorithm is inefficient
o Performance degrades when data rate and RTT product exceeds available memory
o Potential solution:
Spoofing TCP with premature ACK in order to have TCP continue transmission
Selective ACK (SACK) to improve protocol efficiency and congestion control over long delay
links
o Explicit loss notification with ACK
Explicitly notifies TCP sender with reason for packet loss
Eliminates adverse interactions between protocol layers
Congestion control only when a real congestion occurs
Changes ACK format to add information bit whether it is congestion or wireless error
Base station stores information of lost packet