Ipv6_Versus_Ipv4

BACKGROUND In computer networking, particularly when discussing TCP/IP, IP addressing is very paramount. An IP address is a numeric identifier assigned to each machine on an IP network. An IP address is a software address, not an hardware address- the latter is hard-coded on a network Interface Card(NIC) and used for finding hosts on a local network. IP addressing was designed to allow host on one network to communicate with a host on a different network, regardless of the type of the LANs the hosts are participating in. The Internet Protocol version 4(IPv4) has been used for many years in IP addressing , but recently specifically in December 1998, the Internet Protocol Version 6(IPv6) was defined and born with the intention of making it a replacement for IPV4. THE NEED FOR IPv6 The main driving force for the redesign of Internet Protocol is the foreseeable IPv4 address exhaustion. IPv6 was defined in December 1998 by the Internet Engineering Task Force (IETF) with the publication of an Internet standard specification, RFC 2460. The first publicly used version of the Internet Protocol, Version 4 (IPv4), provides an addressing capability of about 4 billion addresses (232). This was deemed sufficient in the early design stages of the Internet when the explosive growth and worldwide proliferation of networks was not anticipated. During the first decade of operation of the TCP/IP-based Internet, by the late 1980s, it became apparent that methods had to be developed to conserve address space. In the early 1990s, even after the introduction of classless network redesign, it became clear that this would not suffice to prevent IPv4 address exhaustion and that further changes to the Internet infrastructure were needed. By the beginning of 1992, several proposed systems were being circulated, and by the end of 1992, the IETF announced a call for white papers (RFC 1550) and the creation of the "IP Next Generation" (IPng) area of working groups. Estimates of the time frame until complete exhaustion of IPv4 addresses used to vary widely. In 2003, Paul Wilson (director of APNIC) stated that, based on then-current rates of deployment, the available space would last for one or two decades. In September 2005, a report by Cisco Systems suggested that the pool of available addresses would dry up in as little as 4 to 5 years. As of May 2009, a daily updated report projected that the IANA pool of unallocated addresses would be exhausted in June 2011, with the various Regional Internet Registries using up their allocations from IANA in March 2012. There is now consensus among Regional Internet Registries that final milestones of the exhaustion process will be passed in 2010 or 2011 at the latest, and a policy process has started for the end-game and post-exhaustion era IPv4 and IPv6: COMPARISON Admittedly, for the most part, IPv6 is a conservative extension of IPv4. Most transport- and application-layer protocols need little or no change to operate over IPv6; exceptions are application protocols that embed network-layer addresses, such as FTP or NTPv3. IPv6 specifies a new packet format, designed to minimize packet-header processing. Since the headers of IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable. Below we highlight the notable differences between the two(IPv4 and IPv6) IP versions. Larger Address Space in IPv6 The most important feature of IPv6 is a much larger address space than that of IPv4: addresses in IPv6 are 128 bits long, compared to 32-bit addresses in IPv4. The very large IPv6 address space supports a total of 2128 (about 3.4×1038) addresses—or approximately 5×1028 (roughly 295) addresses for each of the roughly 6.5 billion (6.5×109) people alive in 2006.[10] In another perspective, there is the same number of IP addresses per person as the number of atoms in a metric ton of carbon. While these numbers are impressive, it was not the intent of the designers of the IPv6 address space to assure geographical saturation with usable addresses. Rather, the longer addresses allow a better, systematic, hierarchical allocation of addresses and efficient route aggregation. With IPv4, complex Classless Inter-Domain Routing (CIDR) techniques were developed to make the best use of the small address space. Renumbering an existing network for a new connectivity provider with different routing prefixes is a major effort with IPv4, as discussed in RFC 2071 and RFC 2072. With IPv6, however, changing the prefix announced by a few routers can in principle renumber an entire network since the host identifiers (the least-significant 64 bits of an address) can be independently self-configured by a host. Stateless address auto-configuration IPv6 hosts can configure themselves automatically when connected to a routed IPv6 network using ICMPv6 router discovery messages. When first connected to a network, a host sends a link-local multicast router solicitation request for its configuration parameters; if configured suitably, routers respond to such a request with a router advertisement packet that contains network-layer configuration parameters. If IPv6 stateless address auto-configuration is unsuitable for an application, a network may use stateful configuration with the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) or hosts may be configured statically. Multicast Multicast, the ability to send a single packet to multiple destinations, is part of the base specification in IPv6. This is unlike IPv4, where it is optional (although usually implemented). IPv6 does not implement broadcast, which is the ability to send a packet to all hosts on the attached link. The same effect can be achieved by sending a packet to the link-local all hosts multicast group. It therefore lacks the notion of a broadcast address—the highest address in a subnet (the broadcast address for that subnet in IPv4) is considered a normal address in IPv6. IPv6 multicast shares common features and protocols with IPv4 multicast, but also provides changes and improvements. When even the smallest IPv6 global routing prefix is assigned to an organization, the organization is also assigned the use of 4.2 billion globally routable source-specific IPv6 multicast groups to assign for inner-domain or cross-domain multicast applications [RFC 3306]. In IPv4 it was very difficult for an organization to get even one globally routable cross-domain multicast group assignment and implementation of cross-domain solutions was very arcane [RFC 2908]. IPv6 also supports new multicast solutions, including Embedded Rendezvous Point [RFC 3956] which simplifies the deployment of cross domain solutions. Mobility Unlike mobile IPv4, Mobile IPv6 (MIPv6) avoids triangular routing and is therefore as efficient as normal IPv6. IPv6 routers may also support Network Mobility (NEMO) [RFC 3963] which allows entire subnets to move to a new router connection point without renumbering. However, since neither MIPv6 nor MIPv4 or NEMO are widely deployed today, this advantage is mostly theoretical. Addressing in IPv4 and IPv6 The increased length of network addresses emphasizes a most important change when moving from IPv4 to IPv6. IPv6 addresses are 128 bits long, whereas IPv4 addresses are 32 bits; where the IPv4 address space contains roughly 4.3×109 (4.3 billion) addresses, IPv6 has enough room for 3.4×1038 (340 trillion trillion trillion) unique addresses. IPv6 addresses are normally written with hexadecimal digits and colon separators like 2001:db8:85a3::8a2e:370:7334, as opposed to the dot-decimal notation of the 32 bit IPv4 addresses. IPv6 addresses are typically composed of two logical parts: a 64-bit (sub-)network prefix, and a 64-bit host part. IPv6 addresses are classified into three types: unicast addresses which uniquely identify network interfaces, anycast addresses which identify a group of interfaces—mostly at different locations—for which traffic flows to the nearest one, and multicast addresses which are used to deliver one packet to many interfaces. Broadcast addresses are not used in IPv6. Each IPv6 address also has a 'scope', which specifies in which part of the network it is valid and unique. Some addresses have node scope or link scope; most addresses have global scope (i.e. they are unique globally). Mandatory network layer security Internet Protocol Security (IPsec), the protocol for IP encryption and authentication, forms an integral part of the base protocol suite in IPv6. IPsec support is mandatory in IPv6; this is unlike IPv4, where it is optional (but usually implemented). IPsec, however, is not widely used at present except for securing traffic between IPv6 Border Gateway Protocol routers. Options extensibility IPv4 has a fixed size (40 octets) of option parameters. In IPv6, options are implemented as additional extension headers after the IPv6 header, which limits their size only by the size of an entire packet. The extension header mechanism allows IPv6 to be easily 'extended' to support future services for QoS, security, mobility, etc. without a redesign of the basic protocol. Simplified processing by routers A number of simplifications have been made to the packet header, and the process of packet forwarding has been simplified, in order to make packet processing by routers simpler and hence more efficient. The packet header in IPv6 is simpler than that used in IPv4, with many rarely used fields moved to separate options; in effect, although the addresses in IPv6 are four times larger, the (option-less) IPv6 header is only twice the size of the (option-less) IPv4 header. IPv6 routers do not perform fragmentation. IPv6 hosts are required to either perform PMTU discovery, perform end-to-end fragmentation, or to send packets smaller than the IPv6 minimum MTU size of 1280 octets. The IPv6 header is not protected by a checksum; integrity protection is assumed to be assured by both a link layer checksum and a higher layer (TCP, UDP, etc.) checksum. In effect, IPv6 routers do not need to re-compute a checksum when header fields (such as the TTL or Hop Count) change. This improvement may have been made less necessary by the development of routers that perform checksum computation at link speed using dedicated hardware, but it is still relevant for software based routers. The table overleaf summarizes the differences between IPv4 and IPv6 and the advantages of the latter over the former. SUBJECTS IPv4 IPv6 IPv6 ADVANTAGES Address Space 4Billion Addresses 2^128 79 Octillion times the IPv4 address space Configuration Manual or use DHCP Universal Plug and Play (UPnP) with or without DHCP Lower Operation Expenses and reduce error Broadcast/ Multicast Uses both No broadcast and has different forms of multicast Better bandwidth efficiency Anycast support Not part of the original protocol Explicit support of anycast Allows new applications in mobility, data center Network Configuration Mostly manual and labor intensive Facilitate the re-numbering of hosts and routers Lower operation expenses and facilitate migration QoS support ToS using DIFFServ Flow classes and flow labels More Granular control of QoS Security Uses IPsec for Data packet protection IPsec becomes the key technology to protect data and control packets Unified framework for security and more secure computing environment Mobility Uses Mobile IPv4 MobileIPv6 provides fasthandover, better router optimization and hierarchical mobility Better efficiency and scalability; Work with latest 3G mobile technologies and beyond. References IPv6 (IPng) versus IPv4 (www.networkdictionary.com) CCNA COURSE MATERIAL, HIIT (Ikeja, Lagos) IPv6 Stateless Address Autoconfiguration, S. Thomson, T. Narten, T. Jinmei, September 2007. Global IPv6 Statistics - Measuring the current state of IPv6 for ordinary users, S.H. Gunderson (Google), RIPE 57 (Dubai, Oct 2008) Welcome to your IPv6 enabled transit network. Whether you like it, or not. Rob Isaac (2008).