IPv4 addresses were originally split up into separate classes to partition them
ID: 3907592 • Letter: I
Question
IPv4 addresses were originally split up into separate classes to partition them into different size blocks for use by different organisations. This system was then replaced with a more flexible mechanism to partition the addresses of IPv4.
Describe the original class based addresses that were, used detailing what they were, and what problems were caused by adopting that approach.
Describe the new system that was put in place to replace that mechanism. How did the partitioning work?
What are the advantages of the new approach?
Explanation / Answer
IPv4 uses 32 bits for addressing. The 32 bit bits are split into 4 bytes and each byte is separated by a dot(.). So it looks like this:
a.b.c.d
where the value of a,b,c,d is between 0-255. Hence a typical IP address would appear like this: 192.168.0.1
IPv4 has four different address classes. There are:
class A - used by large organisations which had lots of computer and used 8 bits for network address and 24 bits for node addresses.
class B - used by medium sized organisations and used 2 bytes for the network and 1 byte for node addresses
class C - used by small organisations and used 3 bytes for the network and 1 byte for node addresses
The problem with IPv4
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There are two main problems associated with IPv4. Firstly, today there are 7+ billion people in this world. Half of them own a computer and 6 billions have access to mobile phones. If we handed out just one IPv4 address to every person we would be 3 billion IP addresses short. This makes reclaiming lost address space essentially pointless. It is obvious that more addresses are needed for a modern internet. This lead to the evolution of IPv6. Secondly, IPv4 is network address translation (NAT). Overloaded NAT - one IP with multiple private IPs behind it breaks quite a few applications and provides no extra security against internet threats. This results in cost increase with no counter benefits.
How IPv6 solves the problem?
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1.IPv6 eliminates the need for NAT by having more IP addresses than can possibly be used and assigning them sparsely.
2.Since the Ip addresses are no longer a scarce commodity, giant blocks can be handed out for only a few devices without a risk of exhaustion. For example, a network that once had 254 usable IP address (an IPv4/24) might now get an IPv6/64 with 2^64 addresses
3.IPv6 has 128 bits of IP space. This is 2^128 which is a huge number. So if you mask all but 64 bits you still have 2^64 or 18 quintillion, addresses for 254 hosts. That's more address than on the entire IPv4 network which means that attacks that depends on sequential scanning for vulnerable hosts such as worms, are obsolete on IPv6.
4.It would take 2 billion years for a worm to scan a /64, scanning 10,000 hosts per second.
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