Download - S CTP
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP
Stream Control Transmission Protocol (SCTP) is a new reliable, message-oriented transport layer protocol. SCTP, however, is mostly designed for Internet applications that have recently been introduced. These new applications need a more sophisticated service than TCP can provide.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP
SCTP is a message-oriented, reliable protocol that combines the best
features of UDP and TCP.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Services
1. Process-to-process Communication
Table 23.4 Some SCTP applications
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Services (Cont..)
2. Multiple Streams
Figure 23.27 Multiple-stream concept
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Services (Cont..)
An association in SCTP can involve multiple streams.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Services (Cont..)
3. Multihoming
Figure 23.28 Multihoming concept
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Services (Cont..)
4. Full-Duplex Communication
5. Connection-Oriented Service
6. Reliable Service
SCTP association allows multiple IP addresses for each end.
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features
1. Transmission Sequence Number
In SCTP, a data chunk is numbered using a TSN.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
2. Stream Identifier
To distinguish between different streams, SCTP uses an SI.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
3. Stream Sequence Number
To distinguish between different data chunks belonging to the same stream,
SCTP uses SSNs.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
4. Packets
TCP has segments; SCTP has packets.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
Figure 23.29 Comparison between a TCP segment and an SCTP packet
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
In SCTP, control information and data information are carried in separate
chunks.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
Figure 23.30 Packet, data chunks, and streams
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
Data chunks are identified by three items: TSN, SI, and SSN.
TSN is a cumulative number identifying the association; SI defines the stream; SSN defines the chunk in
a stream.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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SCTP Features (Cont..)
5. Acknowledgment Number
6. Flow Control
7. Error Control
8. Congestion Control
In SCTP, acknowledgment numbers are used to acknowledge only data
chunks;control chunks are acknowledged by
other control chunks if necessary.
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Packets Format
Figure 23.31 SCTP packet format
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Packets Format (Cont..)
In an SCTP packet, control chunks come before data chunks.
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Packets Format (Cont..)
1. General Header
Figure 23.32 General header
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Packets Format (Cont..)
2. Chunks
Table 23.5 Chunks
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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An SCTP Association
A connection in SCTP is called an association (to emphasize
multihoming).
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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An SCTP Association (Cont..)
1. Association Establishment
Figure 23.33 Four-way handshaking
• Cookie: To solve SYN flooding kind of attacks.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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An SCTP Association (Cont..)
No other chunk is allowed in a packet carrying an INIT or INIT ACK chunk.A COOKIE ECHO or a COOKIE ACK
chunk can carry data chunks.
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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An SCTP Association (Cont..)
2. Data Transfer
In SCTP, only DATA chunks consume TSNs;
DATA chunks are the only chunks that are acknowledged.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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An SCTP Association (Cont..)
Figure 23.34 Simple data transfer
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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An SCTP Association (Cont..)
• Multihoming Data Tranfer
• Multistream Delivery
• Fragmentation
The acknowledgment in SCTP defines the cumulative TSN, the TSN of the last data chunk received in order.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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An SCTP Association (Cont..)
3. Association Termination
Figure 23.35 Association termination
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Flow Control
In SCTP, we need to handle to units of data, the byte and the chunk. The values of rwnd and cwnd are expressed in bytes; The values of TSN and acknowledgments are expressed in chunks.
Some assumptions to ease understanding:• There is never congestion in the network
• The network is error-free
• Data transfer is unidirectional
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Flow Control (Cont..)
Figure 23.36 Flow control, receiver site
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Flow Control (Cont..)
Figure 23.37 Flow control, sender site (Assumption: each chunk is 100 bytes long)
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Flow Control (Cont..)
Figure 23.38
Flow control
scenario
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Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Error Control
SCTP uses a SACK chunk to report the state of the receiver buffer to the sender.
Aseel Alturki
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Error Control (Cont..)
Figure 23.39 Error control, receiver site
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Error Control (Cont..)
Figure 23.40 Error control, sender site (Assumption: each chunk is 100 bytes long)
Aseel AlturkiBased on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
Based on Data Communications and Networking, 4th Edition. by Behrouz A. Forouzan, McGraw-Hill Companies, Inc., 2007
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Error Control (Cont..)
1. Sending Data Chunks
The total size of the data chunk or chunks included in the packet must not exceed rwnd – inTransit
AND
The total size of the frame must not exceed the MTU (Maximum Transmission Unit) size
• Retransmission
2. Generation SACK Chunks
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