CS610 - Computer Network
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Q103: With help of the diagram below, explain TCP Segment Format.


TCP uses single format for all messages. TCP uses the term segment to refer to a message. Each message sent from TCP on one machine to TCP on another machine uses this format including data and acknowledgement.

SourcePort: 2 bytes
Ephemeral (client) port number Source Port: The 16-bit port number of the process that originated the TCP segment on the source device. This will normally be an for a request sent by a client to a server

DestinationPort: 2 bytes
The 16-bit port number of the process that is the ultimate intended recipient of the message on the destination device.

Sequence Number: 4 bytes
For normal transmissions, the sequence number of the first byte of data in this segment. In a connection request (SYN) message, this carries the initial sequence number (ISN) of the source TCP.

Acknowledgment Number: 4 bytes
When the ACK bit is set, this segment is serving as an acknowledgment (in addition to other possible duties) and this field contains the sequence number the source is next expecting the destination to send.

Window: 2 bytes
Indicates the number of octets of data the sender of this segment is willing to accept from the receiver at one time. This normally corresponds to the current size of the buffer allocated to accept data for this connection.

Checksum: 2 bytes
16-bit checksum for data integrity protection Checksum: A , computed over the entire TCP datagram plus a special “pseudo header” of fields. It is used to protect the entire TCP segment against not just errors in transmission, but also errors in delivery.

Urgent Pointer: 2 bytes
Used in conjunction with the URG control bit for priority data transfer. This field contains the sequence number of the last byte of urgent data.

Options Variable:
TCP includes a generic mechanism for including one or more sets of optional data in TCP segment. Each of the options can be either one byte in length or variable length. The first byte if the option kind subfield and its value specify the type of option, which in turn indicates whether the option is just a single byte or multiple bytes. Options that are many bytes consist of three fields.

Note this table is also included in options column. options may vary

Option-kind: 1 byte
specifies the option type

Option-length: 1byte
the length of the entire option in bytes, including the option-kind and option-length fields.

Option-data: Variable
The option data itself in at least one oddball case, this field is omitted(making option length equal to 2)
Q104: Define special IP.
Special IP’s are those IP’s which are not assigned to any machine; these are reserve IP’s, used for special purpose, for example:
Q105: What is meant by the Client-Server Paradigm?
It is used by all network applications. The passive program is called a server and the active program is called a client.
Q106: Write a note on Address Resolution and what is mean by address resolution with centralization message exchange?
Mapping between a protocol address and a hardware address is called Address Resolution. A host or router uses address resolution when it needs to send a packet to another computer on the same physical network. A computer never resolves the address of a computer that attaches to a remote network. A network includes one or more servers that are assigned the task of answering address resolution requests. It has an advantage that resolution is easier to configure, manage and control.
Q107: To solve the problem the routers and networks in the internet are divided into groups, how large do you think are these groups?
There is no limit to determine the size of group, it can be large or small depends upon network administrator.
Q108: How does a packet pass across an internet?
A source creates the packet and places the destination address in a packet header. The packet is sent to the nearest router. The router uses the destination address to select the next router on the path to the destination, and then transmits the packet. The packet reaches the router that can deliver the packet to its final destination.
Q109: What are some of the metrics used by routing protocols?
Path length, reliability, delay, bandwidth, load, and communication cost.
Q110: What are the problem that IP does not guarantee and how to handle these problems?
IP does not guarantee the following problems: Delivery of packets, Delivery of packets in sequence.
Course Instructor

Mr. Hammad Khalid Khan
M.S Electrical Engineering
(Telecommunication)
Oklahoma State University USA
Books

Computer Networks & Internets with Internet Applications by Douglas E.Comer

Computer Networks by Andrew S. Tanenbaum

Networking: A Top-Down Approach Featuring the Internet by James F. Kurose and Keith W. Ross