computer networking Mobile Ip

1. Unit -2:Next Generation IP
Total Marks-10
Topics and Sub-topics
2.1 IPv6 Addressing : Representation, address space, address space
allocation, Autoconfiguration, Renumbering.
2.2 Transition from IPv4 to IPv6: Dual stack, Tunneling, Header
Translation.
2.3 IPv6 Protocol : Packet format, Extension Header.

2. 2.1 IPv6 Addressing:
• An Ipv6 address is 128 bits or 16 bytes (octet) long.
• Notations for IPv6: a) Hexadecimal colon notation b) binary notation
Figure 2.1 IPv6 address in binary and hexadecimal colon notation

3. Figure 2.2 Abbreviated IPv6 addresses

4. 19.4
Expand the address 0:15::1:12:1213 to its original.
Example 19.11
Solution
We first need to align the left side of the double colon to the
left of the original pattern and the right side of the double
colon to the right of the original pattern to find how many
0s we need to replace the double colon.
This means that the original address is.

5. 2.2 Address Space:
• IPv6 has a much larger address space; 2128 addresses are available.
• If we compare it with the address space of IPv4, then it can be seen that the
address space of IPv6 is 296 times bigger than that of IPv4.
• 3 types of addresses:
1. Unicast : A unicast address defines a single computer. The packet sent to a
unicast address must be delivered to that specific computer defined by the
address.
2. Multicast : Multicast addresses are used to define a group of hosts instead of
just one. A packet sent to a multicast address must be delivered to each member
of the group.
3. Anycast : An anycast address, like a multicast address, also defines a group of
nodes that all share a single address. However, a packet destined for an anycast
address is delivered to only one of the member of the anycast group, the nearest
one (the one with the shortest route).

6. 2.3 TRANSITION FROM IPv4 TO IPv6
• Because of the huge number of systems on the Internet, the transition from IPv4
to IPv6 cannot happen suddenly.
• It takes a considerable amount of time before every system in the Internet can
move from IPv4 to IPv6.
• The transition must be smooth to prevent any problems between IPv4 and IPv6
systems.
Figure 2.3.1 Transition Strategies.

7. 2.3 TRANSITION FROM IPv4 TO IPv6 Continue….
1. Dual Stack :
• Dual Stack It is recommended that all hosts, before migrating completely to version 6, have
a dual stack of protocols. In other words, a station must run IPv4 and IPv6 simultaneously
until allthe Internet uses IPv6. The layout of dual stack configuration is as shown in fig.2.3.2
Figure 2.3.2 Dual Stack Strategy
• To determine which version to use when sending a packet to a destination, the source host
queries the DNS. If the DNS returns an IPv4 address, the source host sends an IPv4 packet.
If the DNS returns an IPv6 address, the source host sends an IPv6 packet.

8. 2.3 TRANSITION FROM IPv4 TO IPv6 Continue….
2. Tunneling :
• Tunneling is a strategy used when two computers using IPv6 want to
communicate with each other and the packet must pass through a region that
uses IPv4.
• To pass through this region, the packet must have an IPv4 address. So the IPv6
packet is encapsulated in an IPv4 packet when it enters the region, and it leaves
its capsule when it exits the region.
• It seems as if the IPv6 packet goes through a tunnel at one end and emerges at
the other end. To make it clear that the IPv4 packet is carrying an IPv6 packet as
data, the protocol value is set to 41.
• Tunneling is shown in Figure 2.3.3.

9. 2.3 TRANSITION FROM IPv4 TO IPv6 Continue….
Figure 2.3.3 Tunneling Strategy

10. 2.3 TRANSITION FROM IPv4 TO IPv6 Continue….
3. Header Translation:
• Header translation is necessary when the majority of the Internet has moved to IPv6 but
some systems still use IPv4.
• The sender wants to use IPv6, but the receiver does not understand IPv6.
• Tunneling does not work in this situation because the packet must be in the IPv4 format to
be understood by the receiver.
• In this case, the header format must be totally changed through header translation. The
header of the IPv6 packet is converted to an IPv4 header. Figure 2.3.4 shows Header
translation strategy.
Figure 2.3.4 Header Translation Strategy

11. 2.4 Advantages of IPv6:
1. Larger address space :
An IPv6 address is 128 bits long, Compared with the 32-bit address of IPv4, this is a huge
(296) increase in the address space.
2. Better header format :
IPv6 uses a new header format in which options are separated from the base header and
inserted, when needed, between the base header and the upper-layer data. This simplifies
and speeds up the routing process because most of the options do not need to be
checked by routers.
3. New options :
IPv6 has new options to allow for additional functionalities.
4. Allowance for extension :
IPv6 is designed to allow the extension of the protocol if required by new technologies or
applications.

12. 2.4 Advantages of IPv6: Continue……
5. Support for resource allocation :
To implement better support for real time traffic (such as video conference), IPv6 includes
flow label in the specification. With flow label mechanism, routers can recognize to which
end-to-end flow the given packet belongs to.
6. Support for more security :
The encryption and authentication options in IPv6 provide confidentiality and integrity of
the packet
7. Plug and Play :
IPv6 includes plug and play in specification. It therefore must be easier for novice users to
connect their machines to the network, it will be done automatically.
8. Clearer Specification and Optimization :
IPv6 follows good practices of IPv4, and omits flaws/obsolete items of IPv4.

13. 2.5 IPv6 Packet Format :
• Figure 2.5.1 shows IPv6 packet.
• Each packet is composed of a mandatory base header followed by the payload.
The payload consists of two parts: optional extension headers and data from an
upper layer. The base header occupies 40 bytes, whereas the extension headers
and data from the upper layer contain up to 65,535 bytes of information.
Figure 2.5.1 IPv6 Packet.

14. • IPv6 Base Header :
• Figure 2.5.2 shows the base header with its eight fields. These fields are as follows:
1. Version - This 4-bit field defines the version number of the IP. For IPv6, the value is 6.
2. Priority - The 4-bit priority field defines the priority of the packet with respect to traffic
congestion.
3. Flow label - The flow label is a 3-byte (24-bit) field that is designed to provide special
handling for a particular flow of data.
4. Payload length - The 2-byte payload length field defines total length of the IP datagram
excluding the base header, including the extension headers and the upper layer protocol
data. This field is used to tell the routers how much information a particular packet
contains in its payload.
5. Next header - The next header is an 8-bit field defining the header that follows the base
header in the datagram.
6. Hop limit - This 8-bit hop limit field serves the same purpose as the TIL field in IPv4. This
field shows the maximum number of routers the IPv6 packet can travel.

15. Figure 2.5.2 Base Header of IPv6 Datagram
Version
0-3
Traffic Class
4-11
Flow Label
12-31
Payload Length
32-47
Next Header
48-55
Hop Limit
56-63
Source Address (128-bit)
64-191
Destination Address (128-bit)
192-288
Data

16. 2.5 IPv6 Base Header : Continue…
7. Source address - The source address field is a 16-byte (128-bit) Internet address that
identifies the original source of the datagram.
8. Destination address - The destination address field is a 16-byte (128-bit) Internet address
that usually identifies the final destination of the datagram. However, if source routing is
used, this field contains the address of the next router.
9. Data – the data to be transmitted in the datagram, either an entire higher layer message
or a fragment of one.

17. 2.5.1 IPv6 Extension Header :
• In IPv6, the Fixed Header contains only that much information which is
necessary, avoiding those information which is either not required or is rarely
used.
• All such information is put between the Fixed Header and the Upper layer header
in the form of Extension Headers. Each Extension Header is identified by a
distinct value.
• When Extension Headers are used, IPv6 Fixed Header’s Next Header field points
to the first Extension Header. If there is one more Extension Header, then the
first Extension Header’s ‘Next-Header’ field points to the second one, and so on.
The last Extension Header’s ‘Next-Header’ field points to the Upper Layer
Header. Thus, all the headers points to the next one in a linked list manner.

18. 2.5.1 IPv6 Extension Header : Continue…
• If the Next Header field contains the value 59, it indicates that there are no
headers after this header, not even Upper Layer Header.
• Extension Headers are arranged one after another in a linked list manner, as
depicted in the following diagram:
• Figure Extension Header Connected Format

19. 2.5.1 IPv6 Extension Header : Continue…
• Some next header codes are listed in following Table:
Sr. No. Code Next Header Code
1. 00 HOP by HOP Option
2. 02 ICMPv6
3. 06 TCP
4. 17 UDP
5. 43 Source Routing Option
6. 44 Fragmentation Option
7. 50 Encrypted Security Payload
8. 51 Authentication Header
9. 59 Null (No Next Header)
10. 60 Destination Option.

20. 2.5.1 IPv6 Extension Header : Continue…
• The sequence of Extension Headers should be:
• These headers:
1. should be processed by First and subsequent destinations.
2. should be processed by Final Destination.