Routing, URLs and Domain Names

Overview

Recall questions on how a router chooses a route, the parts of a URL and what a fully qualified domain name is.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What information does a router use to choose between two possible routes?

   Model answer

   It compares the cost, or metric, of each route as recorded in its routing table. Metrics may include the number of hops to the destination, the bandwidth of the links, the current level of congestion or delay on them, and any administrative preference set by the network operator. The route with the lowest cost is chosen for that packet.

2. 2

   Describe what a uniform resource locator is.

   Model answer

   A URL is the full text address that identifies where a particular resource is located on the Internet and how to retrieve it. It names the protocol to be used, the host holding the resource, and the path and name of the resource on that host — for example the protocol, then the fully qualified domain name of the web server, then the folder path, then the file name.

3. 3

   Break down the parts of a URL such as https://www.example.co.uk/revision/networks.html

   Model answer

   'https' is the protocol or scheme, which tells the browser how to fetch the resource. 'www.example.co.uk' is the fully qualified domain name of the host holding it: 'www' is the host name and 'example.co.uk' is the domain name. '/revision/' is the path, the folder structure on that host. 'networks.html' is the name of the resource itself. A URL may also carry a port number after the host and a query string after the resource name.

4. 4

   Explain the term 'fully qualified domain name'.

   Model answer

   A fully qualified domain name is the complete, unambiguous name of a particular host on the Internet. It gives the host name together with the whole domain name it belongs to, all the way up to the top-level domain — for example a name whose first part identifies the individual machine or service, such as a web server or a mail server, and whose remaining parts identify the domain that machine belongs to. Because it is complete, it identifies exactly one host and cannot be ambiguous.

5. 5

   Explain the term 'domain name'.

   Model answer

   A domain name is the human-readable name identifying an area of the Internet under one organisation's control — for example the name registered by a company or a school. It is easier for people to remember and to type than the numeric address of a machine, and it can be kept even if the organisation moves its servers to different numeric addresses. It does not by itself identify one particular machine; the host name in front of it does that.

6. 6

   Explain the term 'IP address'.

   Model answer

   An IP address is the numeric address that identifies a device on a network so that packets can be routed to it. It is what routers actually use to deliver traffic. It is split into a network identifier part, identifying which network the device is on, and a host identifier part, identifying the particular device within that network.

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