What are advantages and disadvantages of dns?

Answer 1

DNS-based redirection - advantages and disadvantagesAdvantages of DNS-based redirection

DNS-based redirection has several advantages. The most visible one is that it achieves transparency without losing scalability.

It is transparent because the clients are obliged to use the addresses provided by the authoritative DNS server, and cannot establish whether these addresses belong to the home machine of the service or to any of its replicas.

DNS as a distributed name resolution service proved to be very efficient, even though the amount of people using it has increased tremendously with the growth of the internet.

Another vital advantage of using DNS to redirect clients is that it is a natural way of informing the clients about the service addresses. It is used by many existing network services, and is very likely to be used by those to come as well.

Moreover, DNS is supported by a huge infrastructure of millions of DNS servers, capable of caching the answers our redirector generates. Once we make this infrastructure work for us, both efficiency and availability of our redirector considerably increase.

One more important advantage of DNS is that it allows multiple replica addresses to be returned, enabling the client to choose one from them.

The last advantage of DNS-based redirection is its good maintainability. Deployment of the complete redirection mechanism boils down to launching a single modified DNS server, and subsequently delegating a service domain to this server.

From this moment on this server is responsible for answering requests for the service address. No other modification of the DNS infrastructure is necessary.

Disadvantages of DNS-based redirection

On the other hand, using DNS-based redirection leads to a few difficulties. The first of them is caused by the fact that DNS queries carry no information about the client that triggered the name resolution.

All that the service-side DNS server knows is the network address of the DNS server that asks about the service location.

Therefore, we have to assume that clients always use a DNS server that is close to them, and approximate a client's location to that of its DNS server. Whether we consider it to be a drawback or not depends on the accuracy we want to achieve.

Studies show that 64% of clients are located in the same network as their DNS servers. Thus, as long as we do not need strict per-client redirection, the location of the client DNS server approximates the client well enough.