Connected: An Internet Encyclopedia
5.2.1.1 General
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Connected: An Internet Encyclopedia
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RFC 1812
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5. INTERNET LAYER - FORWARDING
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5.2 FORWARDING WALK-THROUGH
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5.2.1 Forwarding Algorithm
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5.2.1.1 General
5.2.1.1 General
This section covers the general forwarding algorithm. This algorithm
applies to all forms of packets to be forwarded: unicast, multicast,
and broadcast.
- The router receives the IP packet (plus additional information
about it, as described in Section [3.1]) from the Link Layer.
- The router validates the IP header, as described in Section
[5.2.2]. Note that IP reassembly is not done, except on IP
fragments to be queued for local delivery in step (4).
- The router performs most of the processing of any IP options. As
described in Section [5.2.4], some IP options require additional
processing after the routing decision has been made.
- The router examines the destination IP address of the IP
datagram, as described in Section [5.2.3], to determine how it
should continue to process the IP datagram. There are three
possibilities:
- The IP datagram is destined for the router, and should be
queued for local delivery, doing reassembly if needed.
- The IP datagram is not destined for the router, and should be
queued for forwarding.
- The IP datagram should be queued for forwarding, but (a copy)
must also be queued for local delivery.
Next: 5.2.1.2 Unicast
Connected: An Internet Encyclopedia
5.2.1.1 General