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Q: What is the IP protocol ?
IP is the acronym of "Internet Protocol". This protocol was designed in 70's with the purpose of connecting computers that were in separate networks. Since then, computers were connected each other by means of local networks, but theses local networks were separated, representing information island.

Internet, as a name to designate the protocol, and later the worldwide information network, just means "inter network", that is, connection between networks. At the beginning, the protocol had an only military use, but computers from universities, users and enterprises were quickly added.

Internet as worldwide information network is the result of the practical application of the IP protocol, that is, the result of the interconnection of all information networks existing in the world.


Q. What are the IP addresses ?

The IP address is an only identifier that is applied to each device connected to an IP network. This way, different elements taking part in the network (servers, routers, user computers, etc) communicate among them using their IP address as identifier.

In version 4 of the IP protocol (used nowadays) addresses consist of 4 numbers of 8 bits (an 8 bits number take a value from 0-255 range) that they use to be represented separated by points, for example:

A version 4 IP address has 32 bits, which is equivalent to 232 different IP addresses (4 billions more or less).


Q.What is IPv6?
IPv6 is the acronym of "Internet Protocol Version 6". IPv6 is the Internet next generation protocol, which was firstly designated IPng, that is, "Internet Next Generation".

IPv6 is the update of data network protocol in which Internet is based on. The IETF (Internet Engineering Task Force) developed the basic specifications during 90's to substitute the actual version of Internet protocol, IP version 4 (IPv4), at last 70´s.


Q.What happened to IPv5?
The "version 5" reference was employed for another use. An experimental real time streaming protocol was designed. To avoid any confusion, it was decided not using this name.


Q.Why is necessary a new IP protocol (IPv6)?
IPv4 has demonstrated, by means of its long life, a flexible and powerful design, but it's starting to present problems, as the increase of the IP address demand, the major of all.

New users in so inhabited countries like China or India and new technologies with always connected devices (xDSL, cable, PLC, PDAs, UMTS mobile telephones, etc) are causing the quick disappearance, in a practical way, of available IPv4 addresses.

IPv6 resolves this problem by means of creating a new IP address format, so the number of IP addresses will not extinguish although each device we are able to imagine could connect to Internet.

IPv6 also adds a lot of improvements in areas such as routing and network autoconfiguration. New devices that connect to Internet will be plug and play devices. With IPv6 is not precise to configure DNS IPs, the gateway, the subnetwork mask or any other parameters. The equipment is plugged to the network and gets, the same way, all configuration data.


Q.Is there another easier solution than IPv6?
There is an obvious solution, the renumbering and the reallocation of the IPv4 addressing space. However, it isn't as simple as it seems, even unthinkable in some networks, since it requires worldwide coordination efforts, absolutely unimaginable. Moreover, it would be still limited for the population and the quantity of devices that will be connected to Internet next years


Q.How is the IPv6 address format?
Let's see an IPv6 address example:


The address consists of 128 bits, versus the 32 bits of currently IPv4 addresses. It is represented as 8 groups of 16 bits each one, separated by the ":" character.

Each 16 bits group is represented by means of 4 hexadecimal ciphers, that is, each cipher has a value between 0 and 15 (0,1,2, ... a,b,c,d,e,f being a=10, b=11, etc to f=15).

An abbreviated format exists to designate IPv6 addresses when all endings are 0, for example:


Is the abbreviated form of the following address:


The same way, an only 0 can be written, removing 0's in the left side and 4 0's in the middle of the address can be abbreviated (only once in each address), so:


Is the abbreviated form of the following address:



Q: What is different between IPng and IPv6? Are they different or same?
 In short, they are different. IPng is rather a conceptual name for "revised IP". There's no specific protocol called IPng. IPv6 is a name of a protocol, which was choosed in IPng protocol competition from several candidates.
(see chapter 1 in huitema's book, for details)


Q: What is the status of IPv6 spec? Has it been fixed?
Partly yes, partly no. Basic specs are out as RFC (Request For Comments) documents. Related upper-layer specs are now being discussed at IETF ipng working group, and some of the documents are accessible as internet-draft. Proceed to for details.


Q: What are the major advantages of IPv6?
Major advantages are given below:

1. Scalability:- IPv6 has 128-bit address space, which is 4 times wider in bits in compared to IPv4's 32-bit address space.
2. Security:- IPv6 includes security in the basic spec. It includes encryption of packets (ESP: Encapsulated Security Payload) and authentication of the sender of packets (AH: Authentication Header).

3. Consideration to realtimeness:- To implement better support for realtime traffic (such as videoconference), IPv6 includes flowlabel in the spec. With flowlabel mechanism, routers can recognize to which end-to-end flow the packets belongs.

4. Plug and play:- IPv6 includes plug and play in the standard spec. It therefore must be easier for novice users to connect their machines to the network --- it will be done automatically!

5. Clearer spec and optimization:- IPv6 follows good practices of IPv4, and rejects minor flaws/obsolete items of IPv4.


Q: What is "6bone"?
The word "6bone" stands for "IPv6 backbone". The 6bone is experimental worldwide network for testing interconnectivity of IPv6 implementations, checking if IPv6 really works well or not in actual situation, and so forth. The world 6bone is made up by several regional 6bones. For example, there's a 6bone for Japan region called the WIDE 6bone, which is connected to the world 6bone. Although most of the regional 6bones are made possible by using IPv6-over-v4 tunnelling technology, some part of them are made of IPv6-dedicated leased line. (one of them is the WIDE 6bone operated by WIDE project in Japan)


Q: Features of IPv6 has been added to IPv4, as optional feature such as DHCP. Why do we need to move to IPv6?
It is a problem that thease features are optional for IPv4, and it is very important to include features of IPv6 into the basic spec. If you don't see why, imagine the following story: You are very novice user of the internet, who can hardly do ifconfig or routing setup. You carry along your laptop, and visited some university for presentation. Just after you connected your laptop to the local network, the chairman said that there is no DHCP server available in the university, and administrator took a day-off.


Q: Why NAT is not enough to compete with address space problems?

First of all, IPv6 is not only address space expansion. It is more than that. IPv4 has been used for more than 20 years, and there are various gap and strain found between spec sheet and actual usage. IPv6 tries to include technologies that are up-to-date, and inevitable for 21st century.
Also, there are many trials to interconnect home electronic devices such as washing machines, TV box, audio set, elevators and so forth, by using internet protocols. It would be very hard to follow this trend with NAT only. We need new IP protocol.


Q: Why it is IPv6, not IPv5?
The version number "5" has already been used for ST-II protocol.Transition


Q: How IPv6 host communicate with existing IPv4 hosts?
For first years of IPv6, IPv6 host must be able to speak IPv4 hosts. Therefore, the IPv6/v4 host will communicate by IPv4 with IPv4 hosts, and by IPv6 with IPv6 (to be precise, IPv6/v4) hosts.