gateway
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... IP implementations have used
wired-in lists (for example, addresses of "Prime" gateways.)
Fortunately, broadcasting provides a fast and simple way for a host ...
... broadcast to provide all of its neighbors
with some information; for example, a gateway might announce its
presence to other gateways.
...
... with some information; for example, a gateway might announce its
presence to other gateways.
...
... broadcasts and non-broadcasts, especially in
gateways. This is the most useful case of broadcast; it allows
a host ...
... broadcast; it allows
a host to discover gateways without wired-in tables, it is the
basis for address resolution protocols, and it is also useful
...
... broadcasts; the datagram is
routed by normal mechanisms until it reaches a gateway attached
to the destination hardware ...
... For reasons of performance or security, a gateway may choose not to
forward broadcasts; especially, it may be a good idea to ban
...
... that the best known algorithms require no additional complexity in
non-gateway hosts. A good broadcast method ...
... Minimization of gateway modification, in both code and data
space. ...
... reliability, it is
quite good, and is extremely simple to implement, requiring no
additional data space in a gateway.
...
... Gateways and Broadcasts ...
...
Most of the complexity in supporting broadcasts lies in gateways. If
a gateway receives a directed broadcast ...
... broadcasts lies in gateways. If
a gateway receives a directed broadcast for a network to which it is
...
... not sufficient simply to avoid repeating datagram that a
gateway has heard from itself; this still allows loops if
there are several gateways on a hardware ...
... gateway has heard from itself; this still allows loops if
there are several gateways on a hardware network.
...
... network to which
it is addressed, then it should not be forwarded. However,
the gateway should consider itself to be a destination of the
datagram ...
... hardware network
to which the gateway is connected, it should be sent as a
(data link layer) broadcast ...
... broadcast on that network. Again, the
gateway should consider itself a destination of the datagram.
...
... Otherwise, the gateway should use its normal routing
procedure to choose a subsequent gateway ...
... gateway should use its normal routing
procedure to choose a subsequent gateway, and send the
datagram along to it.
...
... algorithm to
decide what to do. The method is simple: the gateway should
forward copies of the datagram along all connected links ...
... link which is part of the best
route between the gateway and the source of the datagram.
Otherwise, the datagram ...
...
This algorithm may be improved if some or all of the gateways
exchange among themselves additional information; this can be done
transparently from the point of view of other hosts ...
... transparently from the point of view of other hosts and even other
gateways. See [4, 3] for details.
...
... pseudo-Algol description of the routing algorithm a
gateway should use. The algorithm is shown in figure 1. Some
definitions are:
...
... Examine packet for possible internal use;
END
ELSE /* duplicate from another gateway, discard */
Discard;
END
...