ルーティング面でのIPv6移行(基礎的なアプローチの詳細)

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最終更新
2006-11-09T05:13:00+09:00
この記事のURI参照
http://www.7key.jp/rfc/2185/rfc2185_3.html#source

ルーティング面でのIPv6移行(和訳)

最終更新
2006-11-09T00:00:00+09:00
この記事のURI参照
http://www.7key.jp/rfc/2185/rfc2185_3.html#translation

3. 基礎的なアプローチの詳細

3.1 基礎的な2重IP層処理

   In the basic dual-IP-layer transition scheme, routers may
   independently support IPv4 and IPv6 routing. Other parts of the
   transition, such as DNS support, and selection by the source host of
   which packet format to transmit (IPv4 or IPv6) are discussed in [1].
   Forwarding of IPv4 packets is based on routes learned through running
   IPv4-specific routing protocols. Similarly, forwarding of IPv6
   packets (including IPv6-packets with IPv4-compatible addresses) is
   based on routes learned through running IPv6-specific routing
   protocols. This implies that separate instances of routing protocols
   are used for IPv4 and for IPv6 (although note that this could consist
   of two instances of OSPF and/or two instances of RIP, since both OSPF
   and RIP are capable of supporting both IPv4 and IPv6 routing).

   A minor enhancement would be to use an single instance of an
   integrated routing protocol to support routing for both IPv4 and
   IPv6.  At the time that this is written there is no protocol which
   has yet been enhanced to support this. This minor enhancement does
   not change the basic dual-IP-layer nature of the transition.

   For initial testing of IPv6 with IPv4-compatible addresses, it may be
   useful to allow forwarding of IPv6 packets without running any IPv6-
   compatible routing protocol. In this case, a dual (IPv4 and IPv6)
   router could run routing protocols for IPv4 only. It then forwards
   IPv4 packets based on routes learned from IPv4 routing protocols.
   Also, it forwards IPv6 packets with an IPv4-compatible destination
   address based on the route for the associated IPv4 address. There are
   a couple of drawbacks with this approach: (i) It does not
   specifically allow for routing of IPv6 packets via IPv6-capable
   routers while avoiding and routing around IPv4-only routers; (ii) It
   does not produce routes for "non-compatible" IPv6 addresses. With
   this method the routing protocol does not tell the router whether
   neighboring routers are IPv6-compatible. However, neighbor discovery
   may be used to determine this. Then if an IPv6 packet needs to be
   forwarded to an IPv4-only router it can be encapsulated to the
   destination host.

3.2 手動設定の静的なトンネル

   Tunneling techniques are already widely deployed for bridging non-IP
   network layer protocols (e.g. AppleTalk, CLNP, IPX) over IPv4 routed
   infrastructure. IPv4 tunneling is an encapsulation of arbitrary
   packets inside IPv4 datagrams that are forwarded over IPv4
   infrastructure between tunnel endpoints. For a tunneled protocol, a
   tunnel appears as a single-hop link (i.e. routers that establish a
   tunnel over a network layer infrastructure can inter-operate over the
   tunnel as if it were a one-hop, point-to-point link). Once a tunnel
   is established, routers at the tunnel endpoints can establish routing
   adjacencies and exchange routing information.  Describing the
   protocols for performing encapsulation is outside the scope of this
   paper (see [1]).  Static point-to-point tunnels may also be
   established between a host and a router, or between two hosts. Again,
   each manually configured point-to-point tunnel is treated as if it
   was a simple point-to-point link.

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Copyright (C) 2006 七鍵 key@do.ai 初版:2006年11月09日 最終更新:2006年11月09日