1. Naming Chapter - 5 Presenter: Venkatesh Javvaji
Advisor: Dr. Yanqing Zhang

2. Outline
Names
Identifiers
Addresses

3. 5.1 Names, Identifiers, And Addresses
In a Distributed System Name is defined as a string of bits or characters, which is used to refer an entity.
Entity can be anything in a Distributed System like hosts, printers, disks and files.
Explicitly named entities are processes, users, mailboxes, newsgroups, webpages, graphical windows, messages, network connections…

4. Entities can be operated on
Entities can be operated on. For example, a resource such as printer offers an interface.
To operate on an entity, it is necessary to access it, for which we need an access point.
An access point is yet another, but special, kind of entity in a distributed system. The name of an access point is called an address.
An entity can offer more than one access point like example telephone number.
In distributed systems example of access point is host.

5. Address is just a special kind of name: it refers to an access point of an entity.
Address of an access point is used as a regular name as it is tightly associated with an entity.
If an address is used to refer to an entity, we will have an invalid reference at the instant when access point changes or is reassigned to another entity.

6. Likewise, if an entity offers more than one access point, it is not clear which address to use as a reference.
Better solution is to have a single name, such a name is called location independent.
In addition to addresses, there are other types of names that are used to uniquely identify an entity.

7. A true Identifier is a name that has the following properties:
1. An identifier refers to at most one entity.
2. Each entity is referred to by at most one identifier.
3. An identifier always refers to the same entity

8. There is a close relationship between name resolution in distributed systems and message routing.
In principle, a naming system maintains a name- to-address binding which in its simplest form is just a table of (name, address) pairs.
In distributed Systems a centralized table is not going to work.

9. Instead, Name is decomposed into several parts such as jtp. cs. vu
Instead, 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