SS-Drop: A Novel Message Drop Policy to Enhance Buffer Management in Delay Tolerant Networks

Table 1

Summary of common message drop policies.

Message drop policy	Policy type	Major contributions
Drop front (DF) [16]	Policy without network knowledge	Drop front (DF) uses the first-in first-out (FIFO) strategy to drop messages in case of buffer overflow.
Drop last (DL) [16]	Policy without network knowledge	Unlike drop front (DF), drop last (DL) uses the last in first-out (LIFO) technique to drop.
Drop random (DR) [17]	Policy without network knowledge	Randomly select messages for drop to show unbiasedness.
Drop youngest (DY) [18]	Policy without network knowledge	Dropping of messages whose TTL is long.
Drop oldest (DOA) [16]	Policy without network knowledge	DOA selects the message with maximum residential time in the buffer for dropping.
Drop largest (DLA) [19] [20],	Policy without network knowledge	DLA policy drops the message with the largest size from the buffer as the buffer gets overflow.
Evict most forwarded first (MOFO) [21]	Policy with network knowledge	MOFO keeps the message sent counter for the sent messages, and the message with the highest sent counter value is dropped first.
RAPID’s utility-based drop [22]	Policy with network knowledge	RAPID or resource allocation problem is a policy that considers network wide information. The schemes emphasize on a locally optimizing variable which is the expected delay in utility per message used.
Global knowledge-based drop (GBD) [23]	Policy with network knowledge	This policy focuses on the overall statistical information of messages. Moreover, GBD requires global knowledge of the network state.
History-based drop (HBD) [22]	Policy with network knowledge	The history-based message drop policy uses local information to calculate a comprehensive value for the selection of message to be dropped.
Evict most probable first (MOPR) [23]	Policy with network knowledge	A forwarding predictability (FP) value is assigned to every message. MOPR selects those messages for dropping that possesses the highest FP value.
Evict least probable first (LEPR) [24, 25]	Policy with network knowledge	LEPR selects a message to drop which has the minimum FP value.