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What does this image represent?
Its the TCP Header
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Describe the meaning of the different fields in the TCP Header.
- Source Port (16 bits): Holds the port number of the source point.
- Destination Port (16 bits):
Holds the port number of the destination point.- Sequence Number (32 bits):
- (i) if SYN flag = 0, this is the sequence number of the first data byte.
- (ii) if SYN flag = 1, this is the initial sequence number (ISN) and the seq. # of the actual first data byte is ISN+1.
- Acknowledgement Number (32 bits):
If the ACK flag=1, this fields holds the sequence number of the next data byte the receiver is expecting. - Header Length (4 bits):
Specifies the size of the TCP Header in 32-bit words
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Continue... Describe the meaning of different fields in the TCP Header.
- Reserved (6 bits): Reserved for future use.
- Flags (6 bits):
Holds the control bits used to- identify the purpose of the segment.
- (i)URG: Indicates Urgent Pointer field is valid
- (ii)ACK: Indicates Acknowledgement field is valid
- (iii)PSH: Segment requests a PUSH
- (iv)RST: Resets the connection
- (v)SYN: Synchonizes sequence numbers
- (vi)FIN: No more data from sender
- Window (16 bits):
Contains the size of hte receive window, wich specifies the # of bytes destination is willing to accept.
Checksum (16 bits): Used for error detection of the header and data.
Urgent Pointer (16 bits): Specifies the position where urgent data (data delivered as quickly as possible) ends.
- Options + Padding (variable): Options have 3 fields
- (i) Option-Kind: type of option, not optional
- (ii)Option-Length: total length of the option
- (iii)Option-Data: cotains value of option, if applicable
- Padding: field composed of zeros that are used to ensure that the TCP header ends and data begins.
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What does the image represent?
This is the UDP Header!
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Describe the meaning of the different fields in a UDP header.
Source Port (16 bits): Holds the port number of the source point.
Destination Port (16 bits): Holds the port number of the destination point.
Segment Length (16 bits): Contains the length of the entire UDP segment, including header and data.
Checksum (16 bits): Used for error detection.
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What does this image represent?
This is the IPv4 Header!
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Mention briefly the significance of different fields in the IPv4 Header.
- Version (4 bits): Indicates the version number.
- InternetHeader Length (IHL) (4 bits):
Length of the header in 32-bit words.
Type of Service (8 bits): Specifies reliability, precedence, delay and throughput parameters.
Total length (16 bits): Total datagram length in bytes.
Identification (16 bits): Sequence number that identifies a datagram.
- Flags (3 bits): used to control/identify fragments.
- (i) Bit 0: Reserved
- (ii) Bit 1: Dont Fragment (DF)
- (iii) Bit 2: More Fragments (MF)
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Continue...Mention briefly the significance of different fields in the IPv4 Header.
Fragment Offset (13 bits): byte count that indicates where in the original datagram this fragment belongs.
Time to Live (TTL): Number of hops a packet may be routed over that limits its lifetime to prevent routing loops.
Protocol (8 bits): Defines the next protocol that is to receive the data field.
Header Checksum (16 bits): Error detector for the header only.
Source Address (32 bits): IP address indicating the sender of the packet.
Destination Address (32 bits): IP address indicating the receiver of the packet.
- Options Padding (variable): The Options part holds the options requested by the sender.
- The Padding part is used to ensure that the header is a multiple of 32 bits.
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Mention 3 significant differences between IPv4 and IPv6 protocol.
- Address Space: IPv4 addresses are 32 bits (4bytes) in length while IPv6 are 128-bits (16 bytes) in length.
- Header format: IPv6 has simplifier header format than Ipv4
- Security Capabilities: IPv6 includes features that support authentication and privacy.
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How many unique IP addresses can be supported by IPv4 and IPv6?
- IPv4: 232=4,294,967,296
- IPv6: 2128= ~ 3.4×1038
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Briefly mention the significance of IEEE LLC/SNAP header.
- This header allows the upper layers to know where to find the data.
- * LLC-Logical Link Control (24 bits):
- (i) DSAP-Destination Service Access Point (1byte): Acts as a pointer to memory buffer in the receiver.
- (ii) SSAP-Source Service Access Point (1byte): specifies the source of hte sending process.
- (iii) Control Byte (1byte): indicates the type of LLC frame.
*OUI-Organizationally Unique ID (24 bits): number that identifies a vendor, manufacturer, or other organization.
*Type (16 bits)
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Find how computers on LAN use CSMA/CD Protocol for transfer of Ethernet
Packets. (IEEE Standard 802.3)
- a. Nodes listen to the network to check if it is
- free.
- b. If no other transmission is detected, a node
- starts transmitting.
- c. If more than one node senses that no
- transmission is occurring, both can start transmitting at the same time.
- d. When two nodes start transmitting at the same
- time, the transmissions overlap and cause a collision.
- e. If a collision occurs, one of the nodes
- recognizes the interference and transmits a bit sequence (jam) that ensures the
- other node recognizes the collision too.
- f. After a random delay, the nodes attempt to
- retransmit the information and the process begins again.
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