Information Technology Reference
In-Depth Information
In IPv6, the main header is a fixed 40 bytes in length. Additional extension headers and
routing headers can be added after the main IPv6 header. The fixed header lengths provide
simplified header formats and more efficient forwarding of IPv6 packets. This design also
lets extensions to the IPv6 protocol be handled gracefully instead of hacking into the main
header.
Security Enhancements
IPv4 does not contain built-in authentication or data encryption. The IPv4 protocol provides
the ability to include checksum information to allow validation of data integrity. The ability
to perform payload encryption is not inherent and is managed above the network layer.
IPv6 provides an Authentication Header (AH) to perform authentication, with the use of
IPSec for data encryption using the Encapsulating Security Payload (ESP) Header. The
ESP Header also can provide authentication, removing the need for both an AH and ESP
Header when performing encryption and authentication. The ability to provide IPSec-based
encryption is required for IPv6-capable hosts. The ability to carry a checksum is maintained
at the transport layer with TCP or UDP. This provides authentication, encryption, and data
integrity validation.
QoS Capabilities
IPv4 allows limited QoS information to be carried in the IP header. This QoS information
is contained primarily in the 3 Precedence bits and 3 type of service (TOS) bits. The com-
bined use of Precedence bits and TOS bits is called Differentiated Services Code Points
(DSCPs), allowing a maximum of 64 DSCPs.
IPv6 provides 8 bits to store differentiated services information, which allows for 256
different classifications. This increased granularity for differentiating traffic improves
traffic classification and more specialized data handling for advanced queuing and packet
discard schemes.
IPv6 also provides a 20-bit Flow Identifier field, which can be combined with the IP source
address to uniquely identify a particular data flow. This allows routers in the forwarding
path to provide specialized treatment to an entire data flow without having to delve deeply
into the packet headers to obtain enough information to differentiate between data flows. In
IPv4, several fields at the network and transport layers are required to uniquely identify a
data flow, increasing data processing in the forwarding path.
IPv6 Addressing
IPv4's addressing format is very simple compared to IPv6. IPv4 has unicast, multicast, and
broadcast addresses. Unicast addresses are divided into classes, which are defined by the
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