I pv6
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The document discusses the development of IPv6 and its key features compared to IPv4. IPv6 was developed by IETF in the 1990s to address limitations in IPv4, including running out of addresses. It features a longer 128-bit address size, simplified header, improved security, and support for more devices. The header structure was streamlined by removing fields like fragmentation information and checksum. IPv6 also defines extension headers for features like routing, fragmentation, authentication and encryption.
I pv6
- 2. 1/29/2015 2 STARTING • It was in 1990 that (Internet Engineering Task Force) IETF started working on a new version of Internet Protocol (IP), one which would never run out of address, would solve a variety of other problems, and be more flexible and efficient as well. Its major goals were to:- 1) Support billions of hosts 2) Reduce the size of the routing tables 3) Simplify the protocols 4) Provide better security and authentication. 5) Pay more attention to type of services 6) Add multicasting 7) Allow the protocol to evolve in future 8) Permit the old and new protocol to coexist for years…
- 3. 1/29/2015 3 • From a large number of proposals ,a modified combined version by now called SIPP (Simple Internet Protocol Plus) was selected and given the designation IPv6. • IPv6 meets the goals fairly well. It maintains the good features of IP, discards the bad ones and add new ones when needed. In general IPv6 is not compatible with IPv4 but is compatible with all other Internet protocols including TCP,DNS,UDP etc… • MAIN FEATURES IPv6 has longer address than IPv4. Simplification of header. Better support for options Big advance in security. More attention to the type of services
- 4. 1/29/2015 4 MAIN IPv6 HEADER • The Version field is always 6 for IPv6 and 4 for IPv4. • The Priority Field is used to distinguish between packets whose sources can be flow controlled and those that cannot. Values 0 to 7 are for transmissions that are capable of slowing down in view of congestion. Values 8 to 15 are for real time traffic whose sending rate is constant, even if all the packets are lost. This distinction allows the router to deal with packets better in event of congestion. Within each group, low-numbered are less important than high numbered. The IPv6 standard suggests to use 1 News 4 FTP 6 Telnet
- 5. 1/29/2015 5 CONTD….. o The Flow label field is under experimentation and will be used to allow a source and destination to set up a pseudoconnection with particular properties and connections. The flow can be set up in advance and given an identifier. • Each flow is designated by the source address, destination address and flow numbers. Even if 2 flows coming from different hosts but with the same flow number pass thru the same router, the router will be able to tell them apart with the help of source and destination address. Flow numbers will be chosen randomly rather than assigned sequentially starting from 1. • The Payload length field tells how many bytes follow the 40- byte header..
- 6. 1/29/2015 6 FOLLOWED BY….. • The Next header field tells which of the currently 6 extension header follows this one. If this header is the last IP header, the next header field tells which transport protocol handler (e.g. TCP,UDP) to pass the packet to. • The Hop limit field is used to keep packets from living forever. It is same as the Time to live field in IPv4 a field that is decremented on each hop.. • Next is the Source address and Destination address fields. In the original proposal, SIP used 8-byte address. But during many process reviews it was felt that with 8-byte address IPv6 would run out of address within a span of time and 16-byte address would never. So the latter was fixed.
- 7. 1/29/2015 7 IPv6 ADDRESS SPACES Prefix (Binary) Usage Fraction 0000 0000 Reserved (Including IPv4) 1/256 0000 0001 Unassigned 1/256 0000 001 OSI NSAP addresses 1/128 0000 010 Novell Netware IPX addresses 1/128 0000 011 Unassigned 1/128 0000 1 Unassigned 1/32 0001 Unassigned 1/16 001 Unassigned 1/8 010 Provider based addresses 1/8 011 Unassigned 1/8
- 8. 1/29/2015 8 Prefix (Binary) Usage Fraction 100 Geographic base address 1/8 101 Unassigned 1/8 110 Unassigned 1/8 1110 Unassigned 1/16 11110 Unassigned 1/32 1111 10 Unassigned 1/64 1111 110 Unassigned 1/128 1111 1110 0 Unassigned 1/512 1111 1110 10 Link Local use address 1/1024 1111 1110 11 Site Local use address 1/1024 1111 1111 Multicast 1/256
- 9. 1/29/2015 9 DETAILS… • The IPv6 address space is divided as shown above. Addresses beginning with 80 zeroes are reserved for IPv4 addresses. Two variants are supported, distinguished by the next 16 bits. These variants relate to how IPv6 packets will be tunneled over the existing IPv4 infrastructure… • Multicast address have a 4 bit flag field and a 4 bit scope field following the prefix, then a 112-bit group identifier. One of the flag bits in it distinguishes permanent from transient groups. The scope field allows multicast to be limited to the current link, site ,organization or planet. These 4 scopes are spread out over the 16 values to allow new scopes to be added later… • In addition to supporting standard unicast (point-to-point) and multicast addresses, IPv6 also supports new kind of addressing, anycast which is like multicasting, in that the destination is a group of addresses, but instead of trying to deliver the packet to all of them, it tries to deliver it to just one, usually the nearest one…
- 10. 1/29/2015 10 COMPARISON OF IPv4 HEADER & IPv6 HEADER
- 11. 1/29/2015 11 • Purpose of comparing the IPv4 header with the IPv6 Header is to see what has been left out of IPv6.:- ☻ The IHL Field in IPv4 is gone as the Next Header field in IPv6 tells what follows the last IP header. ☻ All the fields relating to fragmentation in IPv4 were removed bcoz IPv6 takes a different approach to fragmentation. All IPv6 hosts and routers must support packets of 576 bytes. This rule makes fragmentation less likely to occur. ☻ Finally the Checksum field in IPv4 is gone bcoz it greatly reduces performance. Removing all these features has resulted in lean and mean network layer protocol which is IPv6…
- 12. 1/29/2015 12 EXTENSION HEADERS • Each of the extension headers are optional, but if more than one is present, they must appear directly after the fixed header. Some of the headers have a fixed format while others contain a variable number of variable length fields. Each item is encoded as a tuple (Type, Length, Value)… • The Type is a 1-byte field telling which option is chosen. Its values have been chosen so that the first 2 bits tell the routers how to process the options when they do not know. The choices are skip the option, discard the packet and send back an ICMP packet, discard the packet and do not send back an ICMP packet, to multicast addresses. • The Length is a 1-byte field. It tells how long the value is (0 to 255 bytes). • The Value is any information required upto 255 bytes… • The different kinds of extension headers defined at present are listed in detail below….
- 13. 1/29/2015 13 Extension header Description Hop-by-hop options Miscellaneous information for routers Routing Full or partial route to follow Fragmentation Management of datagram packets Authentication Verification of sender’s identity Encrypted security payload Information about the encrypted contents Destination options Additional information for destination
- 14. 1/29/2015 14 HOP-BY-HOP • Used for information that all routers along the path must examine. • Format Next Header 0 194 0 Jumbo payload length •Like all extension headers, this one starts out with a byte telling what kind of header comes the next. This byte is then followed by another one which tells the duration for which the hop-by-hop header is in bytes. The next 2 bytes defines the datagram size as a 4-byte number. The last 4-byte gives the size of the datagram. Sizes less than 65,536 are not permitted and will Result in router discarding the packet and sending back an ICMP error message. The datagram's using this header are called Jumbograms. Its use is important for supercomputer applications…
- 15. 1/29/2015 15 ROUTING HEADER • It lists one or more routers that must be visited on the way to the destinations. Two types of routing are available. • Strict routing The full path is supplied • Loose routing Only selected routers are supplied • Format Next Header 0 Number of address Next Address Bit Map 1-24 Addresses
- 16. 1/29/2015 16 CONTD… • The first 4 bytes contains four 1-byte integers: the next header type, the routing type (currently 0), the number of addresses present in the header (1 to 24) and the index of the next address to visit. The latter field starts at 0 and is incremented as each address is visited. • Then comes a reserved byte followed by the bit map with bits which tells whether each address must follow strict source routing or loose source routing. • The fragment header deals with fragmentation. In IPv6 only the source host can fragment a packet. • The Authentication header provides a mechanism by which the receiver of a packet can be sure of who send it. These headers use cryptographic techniques to accomplish their missions. It contains 3 parts. First part has 4- bytes holding the next header number, length of authentication header and 16 zero bits. Then comes the 32-bit key number. Finally the checksum. The payload of authentication header is sent unencrypted.
- 17. 1/29/2015 17 • Encrypted security payload extension header is used for packets that must be sent secretly. It starts out with a 32-bit key number followed by the encrypted payload. • The Destination option header is intended for fields that needs to be interpreted at the destination host.