In December 1998, the IETF published RFC 2474 - Definition of the Differentiated services field (DS field) in the IPv4 and IPv6 headers, which replaced the IPv4 TOS field with the DS field.
Mix profiles exist for IPv4, TCP, VPN (IPsec) and IPv6 traffic, distributions are similar but frame sizes vary given the different overhead and upper layer limitations on MTU.
In a case where a router receives a protocol data unit (PDU) larger than the next hop's MTU, it has two options if the transport is IPv4: drop the PDU and send an Internet Control Message Protocol (ICMP) message which indicates the condition Packet too Big, or fragment the IP packet and send it over the link with a smaller MTU.
The unicast IPv4 address of the cluster is linked to a multicast MAC address.
Also available to run on NicheStack are a number of security modules, including SSH, IPsec/IKE and SSL.
In theory, under IPv4, time to live is measured in seconds, although every host that passes the datagram must reduce the TTL by at least one unit.
For example, compartment boundaries can be defined by a certain type of network technology (e.g., a specific wireless access network) or based on a particular communication protocol and/or addressing space (e.g., an IPv4 or and IPv6 network), but also based on a policy domain (e.g., a national health network that requires a highly secure boundary).
XORP, a routing suite implementing RFC2328 (OSPFv2) and RFC2740 (OSPFv3) for both IPv4 and IPv6
The practical limit for the data length which is imposed by the underlying IPv4 protocol is 65,507 bytes (65,535 − 8 byte UDP header − 20 byte IP header).