SCTP Extension: Unreliable Streams

1
SCTP Extension Unreliable Streams
ltdraft-xie-usctp-sigtran-01.txtgt Qiaobing
Xie Motorola, Inc. Email ltQXIE1_at_email.mot.comgt
2
Combining Reliable and Unreliable Data
Endpoint A
Endpoint Z
association
Stream 0
Stream 1
Stream 2
Stream 0
3
Advantages

• Bringing unreliable data traffic under congestion
  control.
• Unreliable media streams getting link-level fault
  tolerance from SCTP multi-homing.
• Bundling reliable and unreliable contents into a
  single association, potentially simplifying
  multi-media app session set up and control.
• Automatic muxing and de-muxing independent media
  streams as a result of SCTP chunk bundling.
• New service 1 ordered delivery and loss
  detection withinunreliable streams.
• New service 2 limited reliability capability.
• New service 3 partial payload checksum
  capability.

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Unreliable Streams Parameter in INIT and INIT ACK
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
3 4 5 6 7 8 9 0 1 ---------------
-----------------
Parameter Type 0xC000 Parameter Length
------------------
-------------- u-stream
start 1 US1 u-stream end 1 UE1
-----------------------
--------- /
/ \
. . . .
\ /
/ ------------
--------------------
u-stream start k USk u-stream end k
UEk -------------------
-------------
Example -----------------------
typexxxx length12 Streams
Mode ----------------------- gt
--------------------- u-start 3
u-end 4 0 - 2 reliable
----------------------- 3 - 4
unreliable u-start 6 u-end 9
5 reliable -------------------
---- 6 - 9 unreliable
5
Forward Cumulative TSN Chunk (FWD TSN)
0 1 2
3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4
5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-------------------------
------- 1 1 0 0 0 0 0 0 Chunk Flags
0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
-------------------------
------- New
Cumulative TSN
-------------------------
-------
6
r_data (TSN101)
data (TSN102)
SACK (cTSN102)
data (TSN103)
T3 timeout, update local cTSN to 103
data (TSN104)
Report 103 missing and hold up 104
SACK (cTSN102, g104)
Fwd TSN(104)
deliver 104 and update local cTSN to 104
SACK (cTSN105)
7
Partial Checksum Parameter
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
3 4 5 6 7 8 9 0 1 ---------------
-----------------
Parameter Type 0xc004 Parameter
Length4 ---------------
-----------------
8
Partial Checksum Data Chunk (P-DATA)
0 1 2
3 0 1 2 3 4 5 6 7 8 9 0 1 2 3
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-------------------------
------- 1 1 0 0 0 0 1 1
ReservedU11 Length
------------------------
--------
TSN
-------------------------
------- Stream Identifier S
Stream Sequence Number n
-------------------------
------- Checksum Coverage
Payload Protocol Identifier
-------------------------
------- \
\ /
User Data (seq n of Stream S)
/ \
\ ------------
--------------------