Next Generation: IPv6 and ICMPv6 Objectives Upon completion you will be able to: Understand the shortcomings of IPv4 Know the IPv6 address format, address types, and abbreviations Be familiar with the IPv6 header format Know the extension header types Know the differences between ICMPv4 and ICMPv6 Know the strategies for transitioning from IPv4 to IPv6 TCP/IP Protocol Suite

27.1 IPv6 TCP/IP Protocol Suite IPv6 has these advantages over IPv4: 1. larger address space 2. better header format 3. new options 4. allowance for extension 5. support for resource allocation 6. support for more security The topics discussed in this section include: IPv6 Addresses Address Space Assignment Packet Format Comparison between IPv4 and IPv6 TCP/IP Protocol Suite

Figure 27.1 IPv6 address TCP/IP Protocol Suite

Figure 27.2 Abbreviated address TCP/IP Protocol Suite

Figure 27.3 Abbreviated address with consecutive zeros TCP/IP Protocol Suite

Figure 27.4 CIDR address TCP/IP Protocol Suite

Figure 27.5 Address structure TCP/IP Protocol Suite

Table 27.1 Type prefixes for IPv6 addresses TCP/IP Protocol Suite

Figure 27.6 Provider-based address TCP/IP Protocol Suite

Figure 27.7 Address hierarchy TCP/IP Protocol Suite

Figure 27.8 Unspecified address TCP/IP Protocol Suite

Figure 27.9 Loopback address TCP/IP Protocol Suite

Figure 27.10 Compatible address TCP/IP Protocol Suite

Figure 27.11 Mapped address TCP/IP Protocol Suite

Figure 27.12 Link local address TCP/IP Protocol Suite

Figure 27.13 Site local address TCP/IP Protocol Suite

Figure 27.14 Multicast address TCP/IP Protocol Suite

IPV6 Datagram Better header format:options are seperated from base header and inserted when needed between the base header and the data. New options:New options for additional functionalities. Allowance for extention:Allows extention of the protocol if required by new technologies or applications. Support for resource allocation:In IPV6 TOS field is removed,but two new fields,traffic class and flow label,have been added to enable the source to request special handling of the packet. Support from more security:The encryption and authentication options in IPV6 provide confidentility and integrity of the packet. TCP/IP Protocol Suite

Figure 27.15 IPv6 datagram TCP/IP Protocol Suite

IPV6 Datagram Better header format:options are seperated from base header and inserted when needed between the base header and the data. New options:New options for additional functionalities. Allowance for extention:Allows extention of the protocol if required by new technologies or applications. Support for resource allocation:In IPV6 TOS field is removed,but two new fields,traffic class and flow label,have been added to enable the source to request special handling of the packet. Support from more security:The encryption and authentication options in IPV6 provide confidentility and integrity of the packet. TCP/IP Protocol Suite

Figure 27.16 Format of an IPv6 datagram TCP/IP Protocol Suite

IPV6 Datagram header format Version:Version 6. Traffic Class:The 8 bit traffic class field is used to differentiate the type of payload. Flow label:20 bit field designed to provide special handling to perticular flow of data. Payload length:2-byte payload length field defines the length of the Ip datagram excluding the header.In IPV6 length of header is fixed(40 bytes). Next header:8 bit field defining type of the first extension header or the type of the data that follows the base header in the datagram. Hop Limit:Same as TTL in Ipv4. Source and destination address:Source and Destination 16 byte (128 bit) address. TCP/IP Protocol Suite

IPV6 Datagram header format Payload:Compared to Ipv4 the payload field in Ipv6 has a different format . It is a combination of zero or more extension headers followed by the data from other protocols.In Ipv6 options ,which are part of header in Ipv4,are designed as extension headers. The payload can have as many extention headers as requred by situation. Each extention header has two mendatory fields next header and header length. Fragmentation and reasembly:IPv6 datagrams can be fragmented only by the source and not by the intermediate routers. The reasembly takes place at the destination. When a router receives a packet,it can ckeck the size of the packet and drop it if the size is larger that MTU of the network ahead and sends packet-too-big ICMPv6 message to source. TCP/IP Protocol Suite

Figure 27.17 Extension header format TCP/IP Protocol Suite

IPV6 Datagram extention header format Up to 6 extention headers. many of these extentions are options in Ipv4. Hop by Hop option: used when the source needs to pass information to all routers visited by the datagram. Pad1:some options need to start at a specific bit of the 32 bit word.If an option falls short of exactby 1 byte ,Pad 1 is added. PanN:used for 2 or more bytes are needed for padding. Jumbo payload:Defines longer length of datagrams. Destination option:USed when the source needs to pass the information to destionation only.Intermediate routers are not permitted to access this information. TCP/IP Protocol Suite

Source routing :uses the concept of srtict source route and loose source route option of Ipv4. Fragmentation:The concept is same as Ipv4 but in Ipv6 only the origenal source can fragment the Datagram.Sourve must use Path MTU Discovery technique to find the smallest MTU of the Networkand then faragments the datagram by using this knowledge. Authetication:Validated the message sender and ensures the integrity of data. ESP(Encrypted security Payload):Provides confidentility and guards against eavesdropping. TCP/IP Protocol Suite

Figure 27.18 Extension header types TCP/IP Protocol Suite

Table 27.2 Next header codes TCP/IP Protocol Suite

Table 27.5 Comparison between IPv4 and IPv6 packet header TCP/IP Protocol Suite

Figure 27.26 Fragmentation TCP/IP Protocol Suite

Figure 27.27 Authentication TCP/IP Protocol Suite

Figure 27.29 Encrypted security payload TCP/IP Protocol Suite

Table 27.6 Comparison between IPv4 options and IPv6 extension headers TCP/IP Protocol Suite

27.2 ICMPv6 TCP/IP Protocol Suite ICMPv6, while similar in strategy to ICMPv4, has changes that makes it more suitable for IPv6. ICMPv6 has absorbed some protocols that were independent in version 4. The topics discussed in this section include: Error Reporting Query TCP/IP Protocol Suite

Figure 27.32 Comparison of network layers in version 4 and version 6 TCP/IP Protocol Suite

Figure 27.33 Categories of ICMPv6 messages TCP/IP Protocol Suite

Error Reporting Messages: 4 types of errors are handled 1.Destination unreachable 2.Packet Too Big 3.Time Exceeded and 4.parameter Problem Note:Source quench message is elimininated because priority and flow lables fields in IPV6 are supposed to take care of congestion. The redirection message has moved from error reporting catagory to the neighbour discovery catagory Packet Too Big: since IPv6 doesnot fragment at router ,when a packet larger than MTU of a network comes to router ,it generates this message and sends it to source TCP/IP Protocol Suite

Figure 27.34 General format of ICMP messages TCP/IP Protocol Suite

Figure 27.35 Error-reporting messages TCP/IP Protocol Suite

Table 27.7 Comparison of error-reporting messages in ICMPv4 and ICMPv6 TCP/IP Protocol Suite

Figure 27.36 Destination-unreachable message format TCP/IP Protocol Suite

Figure 27.37 Packet-too-big message format TCP/IP Protocol Suite

Figure 27.38 Time-exceeded message format TCP/IP Protocol Suite

Figure 27.39 Parameter-problem message format TCP/IP Protocol Suite

Figure 27.40 Redirection message format TCP/IP Protocol Suite

Figure 27.41 Query messages TCP/IP Protocol Suite

Host use neighbour discovery protocol to find routers in the neighbourhood that will forward packets for them. Router Solicitation message:A host uses this message to find routers in the neighbourhood that will forward packets for them. Router Advertisement Message:is a responce to Router Solicitation message Neighbour Solicitation message:In Ipv6 Arp protocol is illiminated and its duties are included in ICMPv6. Neighbour Solicitation message has same duty as ARP request Neighbour advertisement message:Responce to Neighbour Solicitation message. Redirection Message: same duty as ICMPv6. TCP/IP Protocol Suite

Table 27.8 Comparison of query messages in ICMPv4 and ICMPv6 TCP/IP Protocol Suite

Figure 27.42 Echo request and reply messages TCP/IP Protocol Suite

Figure 27.43 Router-solicitation and advertisement message formats TCP/IP Protocol Suite

Figure 27.44 Neighbor-solicitation and advertisement message formats TCP/IP Protocol Suite

Figure 27.45 Group-membership messages TCP/IP Protocol Suite

Figure 27.46 Group-membership message formats TCP/IP Protocol Suite

Figure 27.47 Four situations of group-membership operation TCP/IP Protocol Suite

27.3 TRANSITION FROM IPv4 TO IPv6 Three strategies have been devised by the IETF to provide for a smooth transition from IPv4 to IPv6. The topics discussed in this section include: Dual Stack Tunneling Header Translation TCP/IP Protocol Suite

Figure 27.48 Three transition strategies TCP/IP Protocol Suite

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 all the Internet uses IPv6. 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. TCP/IP Protocol Suite

Figure 27.49 Dual stack TCP/IP Protocol Suite

Tunneling Tunneling is a strategy used when two computers using IPv6 want to communicate with each other and the packet must pas through a region that uses IPv4. 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. To make it clear that the IPv4 packet is carrying an IPv6 packet as data, the protocol value is set to 41. TCP/IP Protocol Suite

Figure 27.50 Automatic tunneling TCP/IP Protocol Suite

Figure 27.51 Configured tunneling TCP/IP Protocol Suite

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 con- verted to an IPv4 header. TCP/IP Protocol Suite

Figure 27.52 Header translation TCP/IP Protocol Suite

Header Translation Procedure 1. The IPv6 mapped address is changed to an IPv4 address by extracting the rightmost 32 bits. 2. The value of the IPv6 priority field is discarded. 3. The type of service field in IPv4 is set to zero. 4. The checksum for IPv4 is calculated and inserted in the corresponding field. 5. The IPv6 flow label is ignored. 6. Compatible extension headers are converted to options and inserted in the IPv4 header. Some may have to be dropped. 7. The length of IPv4 header is calculated and inserted into the corresponding field. 8. The total length of the IPv4 packet is calculated and inserted in the corresponding field. TCP/IP Protocol Suite

Table 27.9 Header translation TCP/IP Protocol Suite