![]() Interface ID: identifies a device's interface.Ī unique local address is an IPv6 private address and can only be used on the intranet. Subnet ID: used by an organization to construct a local network. Currently, the first three bits of every assigned global routing prefix are 001. Generally, the prefix is at least 48 bits. Global routing prefix: assigned by a provider to an organization. Generally, the IPv6 address space obtained from a carrier is /48, which can be further planned as required. ![]() Unicast address: aggregatable global unicast addressĪn aggregatable global unicast address is globally unique, and is similar to an IPv4 public address.In IPv6, an interface may have multiple IPv6 addresses. A packet sent to a unicast address is delivered to the interface identified by that address. Interface ID: consists of (128 – n) bits and is parallel to the host ID of an IPv4 address.Īn identifier for a single interface.Network prefix: consists of n bits and has the same function as the network ID of an IPv4 address.However, this substitution can only be applied once in the IPv6 address.Īn IPv6 address is composed of two parts: If one or more consecutive 16-bit fields contain 0s, they can be replaced using two consecutive colons (::). However, if all bits of a 16-bit field are 0s, at least one 0 must be reserved. Leading 0s in each 16-bit field can be suppressed. Each IPv6 address contains eight fields, and each field consists of 16 bits.Īn IPv6 address can be compressed using two methods. Instead, they are represented in colon hexadecimal notation. IPv6 addresses are not represented in dotted decimal notation as with IPv4 addresses. IPv6 contains 128 bits and supports 340 undecillion (340 x 10 36) hosts. IPv4 contains 32 bits and supports 4 billion (4 x 10 9) hosts. One of the most obvious differences between IPv4 and IPv6 is the size of address space. The Flow Label field is added to improve QoS efficiency.IPv6 provides optimal support for IPsec, allowing the upper-layer protocols to omit many security options. The intermediate node can skip processing, saving a large amount of resources. The fixed-length IPv6 header is defined to facilitate fast hardware processing.The path maximum transmission unit (PMTU) mechanism is used to determine the MTU of a path. Fragmentation and reassembly are performed by the source and destination, respectively. Fragmentation is removed from the intermediate node.The checksums at Layer 2 and Layer 4 are sufficiently robust, removing the need for a checksum at Layer 3.When compared with IPv4, IPv6 offers the following improvements: When more than one extension header is used in the same IPv6 packet, those headers must appear in the following order:įigure 1-1 shows the IPv6 header and extension headers. RFC 2460 defines six IPv6 extension headers.
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