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Why does the TCP header have a header length field and UDP header does not?
Wiki User
∙ 15y ago
in tcp header (32 bits) we have a field that is called options and padding that has variable in length and the header length shows the actual header size
i.e size of 20 octets+size of options and padding field
and in UDP we dont have any field like that and its header is fixed of 8 OCTETS (32 bits header size)
refrence: WIRELESS COMMUNICATIONS AND NETWORKS by William Stallings
Second Edition pg 91(see fig)
Wiki User
∙ 15y ago
Chandan Bhagam
TCP header size is not fixed due to it havving an optional OPTIONS field, so the header length field is used by the application to know where the data part of the packet starts from. This is not the case in UDP where header size is always fixed
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IS TCP is unreliable Protocol?
No TCP a reliable protocol whereas UDP is unreliable.
Which processes does TCP but not UDP use?
Aknowlagement
Which OSI layer does TCP operate?
TCP and UDP are transport layer protocols; the OSI layer is layer 4 (transport)
What are the pieces of communication in UDP called?
UDP, or User Datagram Protocol is a very simple communication protocol. It is a part of the Transport Layer of the OSI model - the same as the well known TCP. UDP is very straight forward, containing very few features. There is no hand shaking, no security, no ordering of packets and very little error detection (if any at all). The structure of a UDP packet is as follows: Bits 0-15: Source Port Number (optional - leave as all zeros if unused) Bits 16-31: Destination Port Number Bits 32-47: The length of the entire UDP datagram (note that the maximum size is 2^16-1) Bits 48-63: The checksum (optional under IPv4 - leave as all zeros if unused) Bits 64-??: The actual data. About the checksum: this is the confusing part about UDP. When a checksum is computed, the UDP software creates a fake header to include in the checksum calculation - but this fake header is not actually transmitted. The structure of this fake header (officially called the "pseudo header") is: For IPv4: Bits 0-31: Source IP address (taken from the IP header) Bits 32-63: Destination IP address (taken from the IP header) Bits 64-71: Reserved - leave as all zeros Bits 72-79: Protocol (taken from the IP header) Bits 80-95: Length (taken from the UDP datagram) Bits 96-??: The UDP datagram described above. For IPv6: Bits 0-127: Source IP address Bits 128-255: Destination IP Address Bits 256-287: Length Bits 288-311: Reserved (leave as all zeros) Bits 312-319: Next header Bits 320-???: The UDP datagram described above NOTES: -this is only the structure of the UDP packet - and does not include the IP header. -Since it is possible for the checksum to end up as 0, the standard dictates that a checksum of zero be changed to 0xFFFF in order not to confuse with a checksum field which is disabled. This is true even under IPv6, where the checksum MUST be used. A checksum field value of zero is an error and the datagram should be discarded. -UDP makes no guarantees that the datagram will arrive, nor does it make any guarantees about the order that the datagram arrives in. If the user wants these features, then these will need to be implemented by the applications using UDP to communicate, or use a different communication protocol such as TCP.
What protocol uses both TCP and UDP?
DNS does.
What is a layer four header?
In the commonly used TCP/IP communications, that would either be a TCP header, or a UDP header.In the commonly used TCP/IP communications, that would either be a TCP header, or a UDP header.In the commonly used TCP/IP communications, that would either be a TCP header, or a UDP header.In the commonly used TCP/IP communications, that would either be a TCP header, or a UDP header.
What has port numbers in its header?
both tcp and udp
The fields in TCP header that are missing from UDP header?
The sequence number, acknowledge number, and Window fields.
Compare the TCP header and the UDP header?
Both TCP and UDP have origin and destination ports - and that is about all the similarity there is between the two. TCP has several other fields that UDP doesn't have, including window size; a consecutive byte numbering (to figure out where to place a TCP segment in a data stream); the bytes that the other side is expected to send; and others.
If the Protocol field in the IP header has a decimal value of 17 it means that the higher level protocol using the services of IP is TCP?
no, service of UDP
What information is found in both the TCP and UDP header information?
souce and destination ports
Which information is found in both the udp and the tcp header information?
source and destination port
Which information is found in both the TCP and UDP header imformation?
The host and destination ports.
What is udp format?
UDP protocol is a means of transporting data in an unreliable (but speedy) manner. Packets are sent without regard for listening to see if they arrive. The header of a UDP packet is much smaller than a TCP header because it doesn't have all of the overhead that TCP has, namely, checking for packet receipt, error detection and correction, flow control, etc.
What is fastest udp or tcp?
UDP
IP TCP and UDP all discard a packet that arrives with a checksum error and do not?
Only TCP will automatically discard a packet with a bad checksum. UDP packets have a checksum field, but it is rarely used, and then only by the application (not UDP itself)
When is UDP preferred to TCP?
UDP and TCP both are transport layer protocols. UDP is connection less and TCP is connection oriented. UDP is preferred over TCP when large amount data is to be sent like on skype or video conferencing .
