Transport layer Congestion control Reliable transport Data from

Transport layer Congestion control Reliable transport Data from sensors/ from sink should be reliably transferred (De)multiplexing Many applications may exist, transport layer should (de)multiplex from/to network/application layer

Reliable Multi-Segment Transport (RMST) Protocol Has two modes of operation: Non-caching mode Reliability is provided using source and destination only Caching mode Nodes on the path are involved in providing reliability Packets in a data flow are labelled by a unique sequence number

RMST Non-caching mode Packet losses are detected by the sink and requested from the source in an end-to-end fashion through NACK packets requires no involvement from intermediate nodes => less processing and storage

RMST Caching mode Some sensors on the path cache the packets They may detect packet losses and can resend lost packets reliable segments are created between intermediate nodes with caching capabilities

Pump Slowly, Fetch Quickly (PSFQ) Protocol Slow data distribution (Pump slowly) Quick error recovery (Fetch quickly) NACK based

PSFQ Data dostribution Two timers are used: Tmin and Tmax A node transmits packets every Tmin A node relays packets at random time (Tmin, Tmax) Random time reduces redundant broadcasts

PSFQ Error recovery is done by sending NACK packets whenever a packet lost is detected A node sends NACK every Tr < Tmax time.

PSFQ PSFQ may not work if the last packet is lost To solve this, PSFQ uses Tpro timer If a node does not receive a packet for Tpro time, the node sends NACK packet.

Congestion Detection and Avoidance Protocol (CODA) Aim is to detect and avoid congestion If a node detects the congestion, it sends a suppression message towards the source. The nodes on the path reduce the packet rate or drop.

CODA