A quick summary on SCTP and how it's different from conventional protocols such as TCP.

1. CHANWOO JEONG
20122473

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• Unicast, Full Duplex, Connection-oriented
• Reliable, Acknowledgements
• In-sequence transport (or not)
• , etc.
• Message oriented
• Supports Multiple Streams
• Supports Multi homing
• , etc.
“Next gen TCP”

6. For example:
(text message) works on top of MAP

7. • An IETF workgroup to design a series of interworking
protocols allowing SS7 traffic to be carried over IP
• They found existing protocols (mostly TCP) to have
several drawbacks
• Made another protocol(sctp), suited to the purpose.
• SCTP is part of this protocol suite

8. lists several
limitations of TCP, such as:
1. Being In-order (the HOL problem)
2. Not being message-oriented
3. Not supporting multi-homed hosts
4. Being vulnerable to several DoS
“Transport of PSTN signaling(SS7) across the IP network is an application
for which all of these limitations of TCP are relevant. While this
application directly motivated the development of SCTP, other
applications may find SCTP a good match to their requirements.“
-- TCP provides both reliable data transfer and strict order-of-
transmission delivery of data. Some applications need reliable
transfer without sequence maintenance, while others would be
satisfied with partial ordering of the data. In both of these
cases the head-of-line blocking offered by TCP causes unnecessary
delay.
-- The stream-oriented nature of TCP is often an inconvenience.
Applications must add their own record marking to delineate their
messages, and must make explicit use of the push facility to
ensure that a complete message is transferred in a reasonable
time.
-- The limited scope of TCP sockets complicates the task of
providing highly-available data transfer capability using multi-
homed hosts.
-- TCP is relatively vulnerable to denial of service attacks, such
as SYN attacks.

10. • Full Duplex, Unicast protocol
• Reliable transmission
• In sequence packet delivery
• Congestion Control (cwnd)
• Flow Control (rwnd)
• Selective ACK, Cumulative ACK

11. • Data chunk
• Init chunk
• Init-ACK chunk
• SACK chunk
• Heartbeat chunk
• Cookie chunk
• etc

12. TCP
Endpoint:
Destination
TCP
Endpoint:
Source

13. With failure detecting and recovery features,
Improvement in Survivability/Resilience was made.

14. send() appends a byte chunk onto the TCP
internal buffer to be sent
From recv() users only get a consecutive
stream of bytes.
Users must implement a way to separate
messages from the byte stream
• By fixing the length of messages
• By specifying each length of messages
• By putting a delimiter in between messages
SCTP sends and receives data
per-message basis
Once a user sends a message thru
sctp_sndmsg(),
sctp_recvmsg() won’t return until SCTP
receives the whole message. And will
return only the message.

15. sctp_sndmsg()
sctp_recvmsg()
TSN 1 TSN 2 TSN 3‘A MESSAGE’

16. sctp_sndmsg()
sctp_recvmsg()
TSN 1 TSN 2 TSN 3

17. sctp_sndmsg()
sctp_recvmsg()
TSN 2 TSN 3

18. sctp_sndmsg()
sctp_recvmsg()
TSN 3

19. sctp_sndmsg()
sctp_recvmsg()

20. sctp_sndmsg()
sctp_recvmsg()
‘A MESSAGE’

21. “…, so that message loss in any one stream will only
initially affect delivery within that stream, and not
delivery in other streams.”

27. serverclient
ACK

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• Google is thinking of replacing it with their QUIC protocol 

33. • TCP already took over the world and it just works fine
• Applications should be rewritten to use this
• It doesn’t go well with IPv6
• It also doesn’t go well with NAT
• And Microsoft is not being cooperative  (no windows support)

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