Chapter 2 Internet Protocol (IP) (Recommended reading: Comer, Vol 1, Chapters 4, 7)

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Don't hesitate to comment below if you have any questions or additional phrases Chapter 2Internet Protocol (IP)(Recommended reading: Comer, Vol 1, Chapters 4, 7) Internet Protocol (IP): a protocol used in the internet layer. IP makes use of the existing networks to deliver information, where these networks may use a variety of protocols. IP Addresses Hardware Address and Protocol Address Each network adopts its own addressing scheme. Different networks may adopt different hardware addresses with different sizes and different formats. E.g, Ethernet address: 48 bits When these networks are interconnected, there must be a uniform addressing scheme for all the computers and routers. Each computer / router is assigned a unique protocol address. Dr. Y.W. Leung ,Remarks Each computer has two addresses: hardware address: used by the underlying network protocol; protocol address: used by the internetworking protocols. Hardware address is also known as physical address. IP Addressing Scheme Each computer / router is assigned a unique IP address having 32 bits. Each IP address has two parts: The prefix specifies the network to which the computer is attached. (network id or netid) The suffix specifies a particular computer on a network. (hostid) Problem Given only 32 bits, how many bits should be allocated to the prefix and the suffix? Considerations If the prefix has many bits, the internet can accommodate many networks but each network can only have a few computers. If the prefix has a few bits, the internet can only accommodate a few networks although each network can have many computers. Dr. Y.W. Leung ,The IP addressing scheme defines three primary classes, where each class has a distinct prefix/suffix size. (The Classful Addressing Scheme) The internet can accommodate large networks, medium networks, and small networks. Classes A, B, C are the primary classes. The IP addresses of computers and routers belong to these classes. Class D is used for multicasting. When a packet is sent to an IP multicast address, all the computers sharing this address will receive this packet. Dr. Y.W. Leung ,In each primary class, the number of networks and the number of computers per network are as follows: Each packet sent across the internet contains: the IP address of the source, and the IP address of the destination. Dotted Decimal Notation Commonly we use the dotted decimal notation to represent the 32-bit IP address. more convenient for human to manipulate Each octet (8-bit) is expressed as a decimal value, and adjacent decimal values are separated by a dot. Example: Dr. Y.W. Leung ,The first decimal value defines the class of the IP address as follows: Loopback address 127.x.x.x intended for use in testing TCP/IP and for inter-process communication on the local computer Dr. Y.W. Leung ,Assigning IP Addresses Assigning Prefix Address Each network must have a unique prefix address throughout an internet. The prefix must be coordinated globally. To connect a network to the global internet, an organization obtains a unique prefix address from the Internet Service Provider (ISP). In turn, the ISP coordinates with a central organization (the Internet Assigned Number Authority (IANA, on or before 1998); the Internet Corporation for Assigned Names and Numbers (ICANN, after 1998)) to ensure the uniqueness of the prefix. To connect a network to a private internet (Intranet), the organization can determine the prefix while ensuring its uniqueness. Dr. Y.W. Leung ,Assigning Suffix Address Each computer must have a unique suffix address in the same network; while two computers in two different networks can have identical suffix address. Assign any unique suffix to each computer / router within a network without considering the addresses in the other networks. If the suffix is 00…0 or 11…1, the corresponding IP addresses have special meaning. Do not assign these suffixes. An IP address with suffix equal to 00…0 is used to refer to the network itself. An IP address with suffix equal to 11…1