2. Overview 2.1. Relation to other protocols below show the status of the Internet protocol in the protocol level: ---- ----- - --- --- | Telnet | | FTP | | TFTP | ... | | ------ ----- ---- --- | | | | ----- --- ----- | TCP | | UDP | ... | ... | --- - ---- --- | | | -------------------------- - - | Internet protocol & icmp | -------------------------- - | ------ --------------------- | Local Network protocol | ---------------------- ----- Protocol Relationships Figure 1. Internet protocol interface is the high-level host to the host's protocol, downward is the Local Network Protocol. Here, the local area network ("Local Network") can be inside a building A small network can also be a large network like Arpanet.
2.2. Operation Model (Model Of Operation) Transfer Datress Operation Model from an application to other applications can be displayed in the following example: Assuming transfer includes a middle gateway. After the sender is ready to send the local area network module to send that Data (this data is a datagram), deliver destination address and other parameters when calling the interface. The Internet module assembles the header and gives him a data. Internet module determines a local area network address for this Internet address. Here, it is the address of a gateway. It sends this datagram and local area network address to the local area network interface. The local area network interface creates a local area network header and attacked it with a datagram, and then passes through local area network. The host's datagram is encapsulated (wrappe) in the local area network header. Local area network interface Remove the header, then transfer the data report to the Internet module .INTERNET module determines the data report from the Internet address to the second Online other hosts .INTERNET module determines the local area network address of the destination host. Call the local area network interface to send a datagram. This LAN address creates a local area header and is assembled together, and then sends the assembly to the destination host. In this On the destination host, the LAN interface removes the Data News's LAN head and then handed over to the Internet module. The Internet module determines the application to be delivered by the data. Then transmit the data as a responsive response to the application, transfer the source when calling Address and other parameters. Application Application Program Program / / Internet Module Internet Module Internet Module / / / LNI-1 LNI-1 LNI-2 LNI-2 / / / / LOCAL NETWORK 1 Local Network 2 Transmission Path Figure 22.3. The function and purpose of the Function Description Internet protocol is to transmit datagram via an internet. This is from an Internet module to another The Internet module passes the data to the destination address to implement. Internet module is located on the host or the gateway on the Internet system. Date reported from an Internet module to another from an Internet module. So, one of the Internet protocol Important features are Internet addressing.
In information addresses from an Internet module to another Internet module, the datagram may need to transmit on a network of a maximum package size than the data report size. For the customer service, the slice mechanism is provided in the Internet protocol (Fragmentation) Mechanism.
Addressing Name (Addresses) and Routes are different. The name indicates what we have to find. The address tells us where it is. Routing tells us how to reach the .InterNet protocol Address. Mapping from domain names is a high-level protocol (such as host to host or application) task .INTERNET module maps the Internet address as a local area network address. Map the local network address to the routing is the underlying program (such as local area network) Or the gateway is task. The address is fixed to the address of 4 segments (32 bits). Start with the network number, next is the local address (called "other" part). There are three forms or types of Internet addresses: a Class address, the highest bit of the first paragraph is 0, the other 7 is the network address. The remaining 24-bit bit local address .b class Address, the first two paragraphs are the network address, where the first two byypons 10, other 14 Bytes are network addresses, the next two sections are local addresses. The first three sections of Class address are the network address, the last segment is the local address. In the first three sections, the first three bits are 110, the other 21 is the network address. Must note when the Internet address is transformed into a local area network address: a single physical host must be considered several different hosts, by using a different Internet address. Some hosts may have multiple physical interfaces (Multi-homing). That is, for a host, there must be a physical interface for multiple networks, each interface that can have multiple logical Internet addresses.
Examples of address mapping can refer to "Address mapings" [5]
Fragmentation When generated on a local area network that allows the large size of the Internet datagram, the fragmentation must be required when the package size is transmitted on a smaller local area network. A data report can be marked "Does not slide". If you mark it, if you mark it, in any case, it cannot be shardd. If the data tagged as "unbearable", unless the fragmentation cannot reach the destination, it will discard it. That is in the Internet The protocol module is not visible to the local area network, transmission, and recombination, it is called intranet sharpening, which can be used. Internet shards and reorganization programs require a data report to be divided into any number of blocks, which can be reorganized later. Split recipients use the Identification head to ensure that different fractions are not mixed together. Fragment offset headers tell the recipient slide in the original datagram, fragmentation offset and fragmentation length (Frament Length) Determines the block of the original datagram covered by this fragment. The More-Fragments flag (by reset) indicates the last slice. These heads provide enough information to reorganize the datagram. Identification head Different fractional pieces of datagrams are distinguished by a datagram, the originating protocol module sets the Identification header as a value, which must be the survival of the source address and destination address pair and protocol. During the period is unique (the translator Note: This value is unique to the same source, destination, protocol during survival). For a complete datagram packet generation protocol module (Originating protocol module) Set the more-fragments flag 0, at the same time, set the fragmentation offset to 0. In order to make a long Internet datagram, the Internet protocol module (such as gateway) creates two new Internet datagrams, copy the Internet header content from long data report To two new Internet headers. Data reported data in 8 OCTET's integer double boundary is divided into two parts (the second part does not have to be an integer multiple of 8 OCTETs, but the first part must be). Put the first part 8 OCTET block The number is NFB (Number of Fragment Blocks: Split Block). The first part of the data is placed in the first new Internet datagram, the total length of the head is set to the first datagram. MORE-FRAGMENTS logo Set it to 1. The second part of the data is placed in the second new Internet datagna inside The length of the total length is set to the second datagram. The More-Fragments flag is set to be the same value as the same length. The second new Internet datagram has set the film offset head value to the grown data. The head value plus NFB and. This process can be genericized to n-segmentation, which is two points. To recombinant Internet datagram, the Internet protocol module (such as destination host) will be identified, destination address The Internet datagram is combined with the four head values of the source address and the protocol. This combination is achieved by placing the data block of each fragment on the position of the slice of the INTENET header. The fractional offset value of the first fragment is 0, and the last piece of the more-fragments mark is 0.
