In the case of Singapore, the number of internet user has
raised from 1.2 million users in 2000 to 3.7 million users in 2010 (“Singapore
internet,” 2010). This shows that the number internet users have risen
significantly.
Hence to slow down IPv4 depletion, Network Address
Translation (NAT) and Port Address Translation (PAT) come into play. In NAT
(dynamic), a group of private addresses can be mapped to a set of public
addresses. Normally, that set of private addresses is more than that set of
public addresses. While PAT will be referring to mapping of a set of private
addresses to one public address. As a result, it helps to slows down the
depletion IP address (Tyson, n.d.) .
Figure 1 (Using NAT
(Dynamic) (Tyson, n.d.) )
Figure 2 (Using PAT (Tyson, n.d.) )
There are several benefits of using NAT/PAT. This includes
conservation of IP address. Secondly, NAT/PAT will allow greater scalability
since adding a new host will not affect the addressing a scheme of the public
address. Lastly, NAT/PAT provides an additional layer of security since query
can only be initiated by the internal host. Therefore it makes it difficult for
people with malicious motive to enter the network (Kozierok,
2005) .
However NAT/PAT also has disadvantage, this includes
performance issue. It is because when address translation takes place, there is
a need to recalculate the header checksum. As a result some time is lost to
perform this task (Kozierok, 2005) . Secondly, there is
also problem in security protocol. For instance, IPSec might flag address
translation process as datagram “hacking” since it has the capability of
detecting header modification (Kozierok, 2005) .
In conclusion, although NAT/PAT might have its disadvantage,
it also brought many advantage such as scalability in private network. As a
result, many organizations decide to use NAT/PAT because they feel that the
advantages have outweighed the disadvantages.
Reference
Kozierok, C. M. (2005, September 20). IP NAT
overview, motivation, advantages and disadvantages. Retrieved May 2, 2012,
from The TCP/IP Guide: http://www.tcpipguide.com/free/t_IPNATOverviewMotivationAdvantagesandDisadvantages.htm
Singapore internet statistic and telecommunications. (2010, June 24). Retrieved May 2, 2012, from
Internet World Stats: http://www.internetworldstats.com/asia/sg.htm
Tyson, J. (n.d.). How Network Address Translation
Works. Retrieved May 2, 2012, from howstuffworks:
http://computer.howstuffworks.com/nat1.htm
Hi Kim Chye, I have read your post on NAT/PAT and found it to be quite intriguing and informative.
ReplyDeleteIn fact, up until before I read your post, I did not know that NAT might trigger IPSec flags, and also didn't knew that recalculating the header checksum during address translation would cause a performance loss.
Thanks for the great post. Keep up the good work! :)
JunRong:
ReplyDeleteYo KC. After reading your post on Network / Port Address Translation , i found it quite education and easy to understand with the help of the pictures.
You had include the disadvantages such as performance issue and how it comes out about , which is all new to me. You have also explain very detailedly and making me learn so much more on PAT and NAT.
Thanks for the hardwork on making this post. Good job =D