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Subnet Mask
Subnet Mask is used to segment a network into 2, 4, 8, etc sub-networks.
For example, take a Class B network with network number 172.16.0.0 and
subnet mask 255.255.244.0. The first two numbers represents network
number after segmentation. The first 3 bits of the third number is the Subnet
Number. There are 2^3= 8 sub networks. The remaining five bits plus the
eight bits of fourth number, thirteen bits in total, are the networks addresses
available for each sub-network. Each sub-network can have 2^13=8192
networks addresses. Example addresses are as follows:
TCP Protocol
TCP is a connection-oriented protocol, it establishes a logical connection
between two computers. Before transferring data, the two computers
exchange control messages to make sure a connection has been
established, this process is called handshaking. TCP sets up control
functions in the Flag field of the Segment Header. Compared to UDP, TCP is
a very reliable protocol, and uses PAR(Positive Acknowledgment with Re-
transmission) to guarantee that data from one host computer can reach the
other host computer safely and correctly.
TCP/IP Protocol
TCP/IP consists of two protocols:
! ! ! ! !
TCP, Transmission Control Protocol
!
IP, Internet Protocol
TCP/IP features:
!
Open communication standard, it is free and does not depend on any
Operating systems or hardware.
!
Not restricted to any network hardware, Ethernet, Token Ring, Leased
Line, X.25 or Frame Relay can all be integrated and operate under TCP/
IP.
!
Widely accepted addressing method. It is used to assign network
equipments a unique IP address.
!
Many standardized high-level protocols provide user with wide and
consistent services
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