Names, Identifiers and Addresses Tejaswi Eerpina(002311509)

Names A string of bits or characters that is used to refer to an entity. Need names in computer system to refer to and operate on entities such as hosts, printers, disks, and files etc. Used to share resources, to uniquely identify entities, to refer to locations. Example: A resource such as a printer offers an interface containing operations for printing a document, requesting the status of a print job

Addresses Access point is a special kind of entity in distributed system. Need an access point to operate on an entity. Name of an access point is called an address. The address of an access point of an entity is also simply called an address of that entity. Entity can offer more than one access point. Eg: Telephone can be viewed as an access point of a person. The telephone number corresponds to an address.

Identifiers An identifier refers to at most one entity. To check if the processes are referring to the same entity, it is sufficient to test if the two identifiers are equal. if an address can be reassigned to a different entity, we cannot use an address as an identifier.

Human-friendly name is generally represented as a character string. For example, files in UNIX systems have character-string names that can be as long as 255 characters, and which are defined entirely by the user. Name is decomposed into several parts such as jtp.cs.vu.nl and that name resolution takes place through recursive look up of those parts. For example, a client needing to know the address of the FTP server named by jtp.cs.vu.nl the resolution request would be as: NS(.) ~ NS(nl) ~ NS(vu.nl) ~ address ofjtp.cs.vu.nl