08-10-2016, 09:23 AM
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Features of SCTP
g Acked error-free non duplicated user data transfer
g Data fragmentation conforming to discovered path MTU (max
transmission unit)
g Sequenced delivery of user messages within each stream (but
have multiple streams)
g Option for out-of-order delivery of a user message
g Bundling of multiple user messages into a single SCTP packet
g Fault-tolerance (at network level) by supporting multi-homing at
either/both ends of an association and heart-beat/keep alive
messages
g Message boundaries preserved
g SACK
Need for SCTP (why not use TCP?)
g Head of line blocking in TCP; not good in
many situations
g Applications must add their own recordmaking;
TCP is stream (or byte) oriented
g Fault-tolerance: What if NIC with destination
IP address fails?
g TCP vulnerable to Denial of Service attacks
g Main motivator:
– Carrying SS7 signaling on IP Networks
(Packet switched) SS7 Networks’s Needs
g Reliability:
– Multiple parallel links; nodes in mated pairs
g Packet sequencing (between two switches) needed
only within each call; not across all calls between
two switches
g In VoIP, need to do signaling in IP networks. (Both
voice and signaling messages on IP networks)
SCTP Components
1. Association startup and teardown
2. Sequenced delivery within streams
3. User data fragmentation
4. Sack, congestion avoidance
5. Chunk bundling
6. Packet validation
7. Path management
Congestion Control
g Slow start and congestion avoidance per association
g Uses:
1. Receiver advertised window size
2. Congestion control window- adjusted by sender based on
observed network conditions
3. Slow start threshold
Need these for each IP address (multi-homed)
Four NACKS (by SACK) => immediate transmission of missing
packet (fast retransmit)