| 词条 | IP header |
| 释义 |
An IP header is header information at the beginning of an IP packet which contains information about IP version, source IP address, destination IP address, time-to-live, etc. Two different versions of IP are used in practice today: IPv4 and IPv6. The IPv6 header uses IPv6 addresses and thus offers a much bigger address space, but is not backwards compatible with IPv4. IPv4{{main|IPv4 header}}IPv4 is the fourth version in the development of the Internet Protocol (IP), and routes most traffic on the Internet.[1] The IPv4 header includes 13 mandatory fields and is as small as 20 bytes. A 14th optional and infrequently used options field can increase the header size. IPv6{{main|IPv6 header}}IPv6, the successor to IPv4, has been defined and is in various stages of production deployment, and has a different header layout. An IPv6 packet is the smallest message entity exchanged via the Internet Protocol across an IPv6 network. Packets consist of control information for addressing and routing, and a payload consisting of user data. The control information in IPv6 packets is subdivided into a mandatory fixed header and optional extension headers. The payload of an IPv6 packet is typically a datagram or segment of the higher-level Transport Layer protocol, but may be data for an Internet Layer (e.g., ICMPv6) or Link Layer (e.g., OSPF) instead. References1. ^{{cite web |url=http://bgp.potaroo.net/index-bgp.html |title=BGP Analysis Reports |accessdate=2013-01-09}} 1 : Internet Protocol |
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