20. Protocol stack of tcp/ip. Protocol ip
The historical and technical open standard of the Internet is the TCP/IP protocol stack.
The TCP/IP protocol stack has four layers:
Application layer— The application layer handles high-level protocols, including issues of representation, encoding, and dialog control. The TCP/IP model combines all application-related issues into one layer and ensures that this data is properly packaged for the next layer.
Transport layer—deals with quality of service (QoS) issues of reliability, flow control, and error correction. One of its protocols, Transmission Control Protocol (TCP), provides for reliable network communications.
Internet layer—sending source datagrams from any network on the internetwork and have them arrive at the destination, regardless of the path
Network access layer—includes the LAN and WAN protocols, and all the details in the OSI physical and data link layers.
Internet Protocol (IP)— a network-layer (Layer 3) protocol, contains addressing information and some control information that enables packets to be routed. It provides connectionless, best-effort delivery routing of datagrams. IP is not concerned with the content of the datagrams. Instead, it looks for a way to move the datagrams to their destination. The protocol is connectionless and unreliable.
IP packets are treated independently, with each packet carrying the addresses of the receiver and the sender.
The IP service does not guarantee packet delivery. A packet can be misdirected, duplicated, or lost on the way to its destination.
The IP protocol does not provide any special features that recover lost or corrupted packets. These services are instead provided by the end systems
21. Classes of ip addresses
The IP addresses are 32 bits long, consist of four eight-bit octets. Each octet - one byte. IP-address consists of two parts. The first part identifies the network and the second network node. Five IP address classes are used:
Class A— The Class A address category was designed to support extremely large networks. BUT! The 127.0.0.0 network is reserved for loopback testing (routers or local machines can use this address to send packets to themselves). Therefore, it cannot be assigned to a network.
Class B— The Class B address category was designed to support the needs of moderate- to large-sized networks.
Class C— The Class C address category is the most commonly used of the original address classes. This address category was intended to support a lot of small networks.
Class D— The Class D address category was created to enable multicasting in an IP address. A multicast address is a unique network address that directs packets with that destination address to predefined groups of IP addresses. Therefore, a single station can simultaneously transmit a single stream of datagrams to multiple recipients.
Class E- IETF reserves the addresses in this class for its own research. Therefore, no Class E addresses have been released for use in the Internet.
