Network Address Translation

By Raul Bernardino

Introduction:
The internet protocol (IP) authorization body ICANN which is given away a block of IPs to the ISPs around the world and coordinate them. The ICANN is an abbreviation of Internet Corporation for Assigned Names and Numbers. The ICANN exist since 1998 has dedication to manage and control IPs with the participation from all over the world. The ICANN is not controlling the internet contains but it is coordinating the IP Management and top levels domain names. The main roles are developing policies for the unique identifier of the internet.  There are three main tasks besides developing the policies. They are allocating IP addresses, manage DNSs, and assigning domainnmes, and resolve the disputes. Below is diagram of the ICANN organization structure.

Without this organization, I do think today internet might not exist. The ICANN makes world connect and share the information.

How do ICANN manage the IPs throughout the world? Since IP4 is not enough to every devices that willing to connect, the ICANN manages the IPs through regional registers such as APNIC for Asia Pacific internet register, through government such as gTLD internet register, ISPs, etc as it shows in above diagram.

The internet server provider will allocate a block of IP to the companies and institution that are willing to share information over the internet. To maximize the IP allocation, the companies, institutions, or agencies are organizing themselves internally with the private IPs either use class A, B or C to accommodate the needs and put router as a gateway to translate the private IPs to public IP or from public IP to the local/private IP. Below is Network Address Translation diagram.

NATs are one of security plus for the network why is that? The local area network (LAN) users just use one internet protocol address to communication to the rest of the world. The internet services provider just need to give one IP to the agencies for all their devices in that agency. If there is a changing IP internal it does not need to tell rest of the world. The changing ISP also does not affect with the internal IP communication. NATs will responsible to make it works or translating from public to private. Below diagram will show us how it translating from public to private and from private to public.

What router does?

The outgoing data-grams will be replacing source IP and port number with new IP and new port number. And the remote client or server will be respond with NAT IP address and new port number as a destination address. In the NAT table, it remembers the NATs as a translation pairs. Therefore the incoming data-grams can be forwarded to the destination address bases on the pair translation address in the NAT table. NAT works in the 16-bit port number field, 60,000 simultaneous connections in the single LAN. NAT also controversial in which the router only works up to layer 3 and it is violated the end to end argument.

In order to overcome the shortage of the IPv4 address with NATs, the IPv6 can be a solution. The IPv6 has 32 bit address. It will be permitting more devices and users on the internet end to end communication. It will be reducing network traffic on the router site. Simplify the internet address assignment. The IPv6 also support network layer security and it is allowing network motilities.

References list:

1. Kurose J.F., Ross K.W., 2010: Computer Networking; A Top-Down Approach: 5^th Edition’; Boston, Addison-Wesley
2. Lecture notes, CPCOMM_week4_lecture
3. ICANN, [on-line]. Available from: http://www.icann.org/en/about/   (Accessed date: August 27, 2011)
4. Pasho, A. (June 2, 2011), June 8 is World IPv6 Day – Is Your Organization IPv6 Aware?, [on-line]. Available from: http://blog.getcs.com/2011/06/june-8-is-world-ipv6-day-is-your-organization-ipv6-aware/ (Accessed date: August 27, 2011)