Deck 16: Stream Control Transmission Protocol Sctp

Question 1

A packet is carrying two DATA chunks, each containing 22 bytes of user data. What is the size of each DATA chunk? What is the total size of the packet?

Answer 1

Data Chunks:
• Data chunks is carry the user data and this is also a control data.
• The SCTP (Stream Control Transmission Protocol) packet has made up of data chunks and the headers and this will vary by the content
• Data chunks has discussed in RFC4960(Request For Comment) and the modified version has discussed in RFC2690 and RFC 3309.
• Chunk has the content types which is as follows:
• Chunk Type: The IETF (Internet Engineering Task Force) has predetermined the value of chunk type is 8 bits.
• Chunk Flags: This has the 8 bits flag value defined by the chunk type and this has the default value 0.
• Chunk Length: This has the unsigned (only positive value) 16 bits without padding.
• Chunk value: This can be used for general purpose value defined by the chunk type.
There are 2 data chunks and each contains the 22 bytes of user data. Therefore, Now, find the size of chunk. Hence, the packet size is .and each chunk size is .

Question 2

A SACK chunk reports the receipt of three out-of-order data chunks and five duplicate data chunks. What is the total size of the chunk in bytes?

Answer 2

SACK:
• The term SACK stands for Selective ACK.
• In the SACK, the receiver explicitly tells that which packet or segment or messages are acknowledged in a stream (it may be positively or negatively). Fig: SACK contents message format
Chunk:
• Chunk is also known as data chunk. It is defined in RFC 2690(Request For Comment) SCTP (Stream Control Transmission Protocol) standards.
• This is a type of term that can be used to describe the section of information within SCTP packets that contains either the control information and user data.
Data Chunks:
• Data chunks is carry the user data and this is also a control data.
• The SCTP (Stream Control Transmission Protocol) packet has made up of data chunks and the headers and this will vary by the content
• Data chunks has discussed in RFC4960(Request For Comment) and the modified version has discussed in RFC2690 and RFC 3309.
• Chunk has the content types which is as follows:
• Chunk Type: The IETF (Internet Engineering Task Force) has predetermined the value of chunk type is 8 bits.
• Chunk Flags: This has the 8 bits flag value defined by the chunk type and this has the default value 0.
• Chunk Length: This has the unsigned (only positive value) 16 bits without padding.
• Chunk value: This can be used for general purpose value defined by the chunk type.
As per given details there is 3 out-of-order of the packets and there are 5 duplicate data chunks.
• There is the SACK chunk, according to the SACK chunk there will be general header, SACK header, 3 out-of-order of the packets and 5 duplicate data.
• As per given details there is 3 out-of-order of the packet that means 1 out-of-order will take 4 bytes that means it will take .
• As per given details there is 5 duplicate data that means 1 duplicate packet will take also 4 bytes that means it will take .
• General header it will take .
• SACK header it will take .
• Performing the addition of all the details in order to get the total size of the packets which is as follows: Hence, the total size of the packet is .

Question 3

A packet is carrying a COOKIE ECHO message and a DATA chunk. If the size of the cookie is 200 bytes and that of the user data is 20 bytes, what is the size of the packet?

Answer 3

Data Chunks:
• Data chunks is carry the user data and this is also a control data.
• The SCTP (Stream Control Transmission Protocol) packet has made up of data chunks and the headers and this will vary by the content
• Data chunks has discussed in RFC4960(Request For Comment) and the modified version has discussed in RFC2690 and RFC 3309.
• Chunk has the content types which is as follows:
• Chunk Type: The IETF (Internet Engineering Task Force) has predetermined the value of chunk type is 8 bits.
• Chunk Flags: This has the 8 bits flag value defined by the chunk type and this has the default value 0.
• Chunk Length: This has the unsigned (only positive value) 16 bits without padding.
• Chunk value: This can be used for general purpose value defined by the chunk type.
Cookie Echo:
• Cookie Echo is a type of state that has the description that this will wait for cookie acknowledgement.
Cookie ACK:
• This is the last chunk that has forwarded during join establishment.
• The Cookie ACK has the table which is as follows: • In this the chunk has the length 4 bytes in the cookies and this is a type of simple chunk 11.
Consider the following detail: Since, the value General header is 12 Bytes, Cookies Ack length is 4 bytes, and data padding information is 16 Bytes in Data chunk.
To find the size of packet, sum the general header, cookie ack length, data padding information, user data, and cookies size. Hence, the size of packet is .

Question 4

A packet is carrying a COOKIE ACK message and a DATA chunk. If the user data is 20 bytes, what is the size of the packet?

Question 5

Four DATA chunks have arrived carrying the following information:
a. Which data chunk is a fragment?
b. Which data chunk is the first fragment?
c. Which data chunk is the last fragment?
d. How many middle fragments are missing?

Question 6

The value of the cumulative TSN in a SACK is 23. The value of the previous cumulative TSN in the SACK was 29. What is the problem?

Question 7

An SCTP association is in the ESTABLISHED state. It receives a SHUTDOWN chunk. If the host does not have any outstanding or pending data, what does it need to do?

Question 8

An SCTP association is in the COOKIE-WAIT state. It receives an INIT chunk; what does it need to do?

Question 9

The following is a dump of a DATA chunk in hexadecimal format.
a. Is this an ordered or unordered chunk?
b. Is this the first, the last, the middle, or the only fragment?
c. How many bytes of padding are carried by the chunk?
d. What is the TSN?
e. What is the SI?
f. What is the SSN?
g. What is the message?

Question 10

The following is a dump of an SCTP general header in hexadecimal format.
a. What is the source port number?
b. What is the destination port number?
c. What is the value of the verification tag?
d. What is the value of the checksum?

Question 11

The state of a receiver is as follows:
a. The receiving queue has chunks 1 to 8, 11 to 14, and 16 to 20.
b. There are 1800 bytes of space in the queue.
c. The value of lastAck is 4.
d. No duplicate chunk has been received.
e. The value of cum TSN is 5.

Question 12

Show the contents of the SACK message sent by the receiver in Exercise 11.

Question 13

The state of a sender is as follows:
a. The sending queue has chunks 18 to 23.
b. The value of curTSN is 20.
c. The value of the window size is 2000 bytes.
d. The value of inTransit is 200.

Question 14

An SCTP client opens an association using an initial tag of 806, an initial TSN of 14534, and a window size of 20000. The server responds with an initial tag of 2000, an initial TSN of 670, and a window size of 14000. Show the contents of all four packets exchanged during association establishment. Ignore the value of the cookie.

Question 15

If the client in the previous exercise sends 7600 data chunks and the server sends 570 data chunks, show the contents of the three packets exchanged during association termination.