Review of local IP subnet configuration and address resolution protocols

IPv4 was originally deployed in the absence of any local IP subnet  protocol.Because and nothing else a smallnumber of terminals were related to the Internet, IP address and access router were by hand. As the numerate of terminalsgrew, and especially with the ushering in of wireless terminals, a server-basedprotocol, DHCP, was developed to take hold of  of IP addresses and other limited
subnet parameters. Address resolution in IPv4 uses ARP. Though this protocol dealswith IP addresses, ARP is actually a link stratum protocol. ARP was standardized in theearly days of the Internet progress to maturity, and consequently has changed little from that time.Because it is so widely deployed, changes to ARP would have existence hard to propagate.

IPv6 was originally designed with both local IP subnet  and addressresolution handled by Neighbor Discovery, to promote better scalability. Neighbor Discoveryallows terminals and routers to their IP discourse without any humanintervention. In particular, Neighbor Discovery does not insist upon a server, reducing theadministrative overhead of server livelihood. However, since many network administratorswere friendly with DHCP and wanted to keep possession of control over IP address, local IP subnet with DHCP was added to IPv6. DHCP canalso be used in IPv6 to  other parameters of the like kind as the name of a DNS server.In IPv6,  of the IP place by the post with Neighbor Discovery is called statelessauto though  using DHCP is called stateful .

ARP wasin the at daybreak days of the Internet in RFC 826 (RFC 826, 1982). In thosedays, it was one unsolved problem about how to make over an IP packet that had been routedacross the Internet to the expiration terminal on the last hop. When the package arrived at theaccess router, the router had the IP direct of the destination terminal but it needed theEthernet indite to deliver the packet. ARP allows the entrance router to obtain a mappingbetween the IP pay court to and the Ethernet address of the reticulated interface card that hasbeenured with the IP ingenuity. The access router caches the mapping in the ARPcache against some period of time, allowing the admission router to perform address resolutionfor farther on incoming packets without having to sustain a part ARP. After the cache times away,however, the access router must bring about ARP again to he mapping. ARP canalso be used by terminals on the final hop to deliver packets directly to a different terminal,rather than having to tolerate through the access router. Figure 5.1 illustrates the protocol.