Performance of Stream Control Transmission Protocol (SCTP)atiq/Pres/sctp-multistreaming.pdf ·...
Transcript of Performance of Stream Control Transmission Protocol (SCTP)atiq/Pres/sctp-multistreaming.pdf ·...
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1Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Performance of Stream Control Transmission Protocol
(SCTP)
Mohammed Atiquzzaman, Ph.D.School of Computer Science
University of Oklahoma.Email: [email protected]
Web: www.cs.ou.edu/~atiq
Tohoku University, Sendai, Japan.Aug 6, 2002.
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2Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Introduction
! TCP is the main transport protocol in the Internet protocol suite! Original TCP performed poorly in satellite networks
" errors " long propagation delay.
! Many schemes for enhancing TCP for satellite networks.! IETF developing Stream Control Transmission Protocol (SCTP)
for PSTN signaling over IP.
Open question: How good is multistreaming?
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3Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Objectives
! Evaluate the performance of SCTP multistreaming.! Suitability of SCTP for wireless networks! Performance comparison of SCTP and TCP.
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4Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Outline
! SCTP" Multistreaming" Multihoming
! Performance of multistreaming
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5Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Stream Control Transmission Protocol
! SCTP (RFC 2960) being developed by IETF as a transport protocol for PSTN signaling." Reliable: retransmission of lost packets, ack of packets. " Non-duplicated service: uses sequence numbers." In-order delivery: re-sequencing at the destination.
! Transport layer protocol which operates on top of an unreliable connectionless network layer such as IP." Transparent to IPv4 or IPv6
! Key features:" Multistreaming – multiple streams per association" Multihoming – multiple IP addresses per host
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6Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
SCTP in the protocol stack
Upper layer applications
TCP, UDP, SCTP
IP
Link Layer
Physical Layer
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7Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Multistreaming
! SCTP accomplishes multistreaming by creating independence between " data transmission (uses Transport Sequence Number) " data delivery (uses Stream Sequence Number)
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8Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Multihoming
! Supports multiple IP addresses in an association.! Requires multiple Network Interface Cards – already quite
common in laptops !!
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9Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
SCTP Packets
Chunk Type
•Payload
•SACK, etc.
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10Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Chunk Type: Payload
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| Type = 0 | Reserved|U|B|E| Length |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| TSN |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| Stream Identifier S | Stream Sequence Number n |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| Payload Protocol Identifier |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ // User Data (seq n of Stream S) // /+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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11Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Chunk Type: SACK
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 3 |Chunk Flags | Chunk Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cumulative TSN Ack | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertised Receiver Window Credit (a_rwnd) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Number of Gap Ack Blocks = N | Number of Duplicate TSNs = X | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Gap Ack Block #1 Start | Gap Ack Block #1 End | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / ... / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Gap Ack Block #N Start | Gap Ack Block #N End | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Duplicate TSN 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / ... / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Duplicate TSN X | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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12Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
SCTP Congestion Control
! SCTP congestion control is similar to TCP congestion control." Enables seamless introduction of SCTP into IP networks.
! SCTP is rate adaptive similar to TCP.# Slow Start, Congestion Avoidance, Fast Retransmit# Fast Recovery is implemented, but in a slightly different way
than TCP.! Differences with TCP
" Number of bytes acknowledged is used to increase cwnd." SACK is mandatory
# Unlimited number of Gap Ack Blocks in SACK" No explicit fast recovery phase
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13Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Performance/Advantages of
SCTP Multistreaming
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14Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
ns-2 Simulation Setup
! Ftp traffic.! Packets of fixed length (one
MTU).! Upper layer at destination is
always ready to accept data.! Association consists of a number
of streamsLink Delay: L1+L2 = 260 msec
Receiver buffer size = B
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15Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Performance Metrics
! Goodput! Optimal receiver buffer size
" as a function of packet error probability (e).
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16Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Packet Plot: No loss
s = 4, e = 0, B = 15K
! No packet loss $no blocking at receiver.
! cwnd increases until B.
! Goodput limited to B/MTUpackets per RTT.
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17Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Goodput: No loss
s = 4, e = 0
! Since goodput is limited to B/MTUpackets every RTT; it increases linearly with B.
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18Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Packet plot: Congestion Control limited
! Poor goodput when receiver buffer is not a constraint" Long delays in
Retx while waiting for DupAcks
+ " drop in cwnd due
to Retx
s = 4, e = 0.01, B=35K
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19Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
cwnd and a_rwnd with errors: Receiver buffer limited
s = 4, e = 0.01, B = 15K
cwnd is restricted to 15K
! B=15K $throughput constrained by receiver buffer
a_rwnd frequently drops below 1 MTU
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20Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
cwnd and a_rwnd with errors: Congestion control limited
s = 4, e = 0.01, B = 35K
a_rwnd usually does not drop below 1
MTU
! B=35K $throughput constrained by congestion control of SCTP
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21Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Goodput with errors
s = 4, e > 0
Congestion control limited:!Goodput is limited by the congestion control of SCTP. ! Goodput can only be increased by lowering the error rate
Receiver buffer limited:! Goodput increases as B increases when the goodput is constrained by B (a_rwnd frequently drops below 1 MTU)
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22Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Goodput vs. Buffer size: One and four streams
! For small BMutlistreaming results in “less” HOL blocking" goodput of 4-
streams is higher than 1-stream.
! For large BGoodput is limited by congestion control
Multistreaming increases goodput for small receiver buffers.
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23Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Advantage of Multistreaming: High Throughput
B = 15K
! “Small” Buffer size of 15K shows advantage of multistreaming. HOL blocking is eliminated
as evidenced by the fact that a_rwnd is, not a
limiting factor
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24Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Optimal Buffer Size
Optimal Receiver Buffer Size
Buffer size beyond which a_rwnd never falls below 1 MTU
Multistreaming reduces receiver buffer requirements.
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25Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Conclusions
! Performance of SCTP multistreaming has been studied! Multistreaming increases transport level performance for small
receiver buffer size." Wireless handheld devices, ex. Mobile and satellite networks.
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26Mohammed Atiquzzaman, University of Oklahoma, USA.
Presentation at Tohoku University, JapanAug 6, 2002.
Further information
! Acknowledgements" National Aeronatics and Space Administration (NASA)
! Further InformationDr. Mohammed [email protected], (405) 325 8077
! These slides are available atwww.cs.ou.edu/~atiq