udemy computer networks

In the early days of network history, the International Organization for Standardization (ISO) and the International Telegraph Telephone Advisory Committee CCITT has jointly published a layer-7 Reference Model for Open System Interconnection. Network processes in a computer operating system include application requests (at the top of the protocol stack) to network media (bottom) The OSI reference model divides functions into seven discrete layers. Fig

mask, so that it is convenient to obtain the IP address of the network address, and do not need to find the routing table. A subnet mask is an important property of a network or a subnet. In each item of the router's routing table, in addition to giving the destination network address, you must also give the subnet mask for the network. If a router is connected to two subnets, two IP addresses and subnet masks are given 、、。 Forwarding by using subnet time group

. The main protocol for the Internet is collectively known as the TCP/IP protocol , but not only TCP and two protocols.Internet standards are developed by IETF, an IETF standard document called RFC. The public Internet generally refers specifically to the Internet. Many private networks, through firewalls, restrict incoming and outgoing network messages, called Intranet intranets.Applications that provide services over the Internet are called distribu

socket descriptor is required, and each socket descriptor has a pointer to the address where the socket is stored. When the socket is created, its port number and IP address are empty, so the application process calls bind (BIND) to indicate the local address of the socket. When BIND is invoked on the server side, the well-known port number and local IP address are filled into the created socket. This is called binding the local address to the socket . After the server calls bind, it must a

differentiation. When the connection is disconnected, this port can be reused. Note that most IP stacks will not immediately reuse the port after it is released. Instead, they will re-use the port until the temporary port is used. This explains why every time a client program is run, it does not obtain the same port. In addition, different operating systems have different limits on the temporary port range. The number of temporary port numbers is limited by the number of independent connections