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.Protocol, IPng / IPv6 (InternetThe document also listed 16 issuesProtocol, next generation / version 6)considered relevant when designing and cre-ating the new protocol.These issues are aIPng refers to the proposed successor to IPv4combination of technical issues relating to(Internet Protocol version 4) as the network-features and (current or imminent) short-layer protocol in the Internet s TCP/IP pro-comings in IPv4, policy and administrativetocol suite.This is the protocol responsibleissues, and practical issues having to do withfor routing or delivering packets to theirimplementation and transition.Exampledestination.issues include:The phenomenal growth of the Internethas begun to push IP to its limits.BecauseScalability: The next version should beof this, an IETF (Internet Engineering Taskable to provide addresses for up to 1012Force) working group was formed to plan(that s right, a trillion) hosts! Protocol, IPng / IPv6 (Internet Protocol, next generation / version 6) 819Transition and deployment: The details threatening IPv6, note that 128 bits areaand considerations of how to switch enough for almost a trillion trillionfrom one protocol to the next must be nonhierarchical addresses for everybplanned out.square meter of surface area on ourcplanet.This ratio drops to about just aMobile hosts: Whether to make it easierfew thousand per square meter oncefor hosts to connect from mobile loca- dbits are allocated for hierarchicaltions.If so, how to do it?groupings still more than ampleeRobustness and Fault Tolerance: How to room for growth.) IPv6 addresses actu-fensure that the new version is at least ally identify interfaces rather than net-as robust and fault tolerant as the cur- work nodes.A single node can havegrent one.multiple interfaces, so can be reachedthrough any of multiple addresses.hThe solicitation garnered almost 20 RFCsIPv6 also supports a new type ofin response mostly from representatives ofiaddress an anycast address.Suchdifferent industries or organizations whoan address is used when sending ajmight be affected by the new protocol.packet to any of a group of interfaces,Respondents came from high-tech compa-kand it ensures that only one copy ofnies, universities, research centers, consortia,the packet is sent to a node that isltelecommunications and entertainmentassociated with multiple addressesindustries, etc.on the anycast list.mBased on this and other feedback, theIETF working group released a draft specifi- Address notation: 128 bits provide a lotncation in June of 1995.In this document, the of possibilities for addresses.IPv6 will,oprotocol is called IPv6 (IP version 6).This in fact, support several addressingis just a draft and is not yet a standard.In schemes for back compatibility andpfact, people and groups are still working on to increase the likelihood of a smoothqalternatives to the IETF specifications, and transition to IPv6.The notation forone of those may actually end up becoming specifying addresses will change, how-rthe actual next version of IP.ever.IPv6 will use colons (:) instead ofIPv6 differs from the current version in periods to separate address elements.sthe following areas: Special notation will make it easy torepresent addresses that are encapsu- tAddressing capabilities: IPv6 uses 16lated in the longer format for exam-uoctets (128 bits) for addresses (asple, current (32-bit) addresses, whichopposed to 4 octets, or 32 bits, inwill have many leading zeros whenvIPv4).This is more than enoughrepresented as IPv6 addresses.address space for a trillion hosts and isweven enough to use different address- Header format: The header format hasxing schemes and hierarchies.(To allay been simplified by dropping someany fears of another address shortage fields or making them optional.This isyz 820 Protocol, IPng / IPv6 (Internet Protocol, next generation / version 6)to reduce the overhead from the packet The value in the priority field specifiesheaders.what kind of traffic is in the packet.Thetable Priority Values shows the possibleHeader extensions and options: IPv6types of traffic.provides for several types of optionalextension headers, which can provide PRIORITY VALUESspecial instructions for handling a VALUE MEANINGpacket.Currently, six extensions are0 uncharacterized trafficsupported: hop-by-hop, routing, frag-1 filler traffic (e.g., news)ment, destination options, authenti-cation, and encapsulating security2 unattended datapayload.All extensions except hop-transfer (e.g., e-mail)by-hop are processed only at the final3 reserveddestination.A hop-by-hop extensionis processed at every stop.4 attended bulk transfer (e.g [ Pobierz całość w formacie PDF ] |
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