IP layer
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... host system implementations of the Internet protocol
suite. This RFC covers the communication protocol layers: link
layer, IP layer, and transport layer. Its companion RFC,
"Requirements ...
... gateway
function within the host IP layer will force host system
maintainers to track these (more frequent) changes. Also,
...
... coordinating the changes more difficult. Finally, the
complexity of a gateway IP layer is somewhat greater than
that of a host, making the implementation and operation
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... calls themselves. For example, many implementations reflect
the coupling between the transport layer and the IP layer by
giving them shared access to common data structures. These
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The packet receive interface between the IP layer and the link
layer MUST include a flag to indicate whether the incoming packet
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...
Although the IP layer does not generally know link layer
addresses (since every different network medium typically has
...
... and IEEE 802 nets |2.3.3 |x| | | | |
Link layer report b'casts to IP layer |2.4 |x| | | | |
IP layer pass TOS to ...
... Link layer report b'casts to IP layer |2.4 |x| | | | |
IP layer pass TOS to link layer |2.4 |x| | | | |
...
... IP datagrams, ICMP
processing is considered to be (and is typically implemented
as) part of the IP layer. See Section 3.2.2.
...
... IP datagrams and (2) reassemble
incoming IP datagrams. The IP layer may also (3) implement
intentional fragmentation of outgoing datagrams ...
... intentional fragmentation of outgoing datagrams. Finally, the IP
layer must (4) provide diagnostic and error functionality. We
expect that IP layer functions may increase somewhat in the
...
... datagrams. Finally, the IP
layer must (4) provide diagnostic and error functionality. We
expect that IP layer functions may increase somewhat in the
future, as further Internet control and management ...
... IP source address that is invalid by the rules of this
section. This validation could be done in either the IP
layer or by each protocol in the transport layer.
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...
The IP layer must not crash as the result of an option
length that is outside the possible range. For
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If a Source Quench message is received, the IP layer MUST
report it to the transport layer (or ICMP processing ...
...
A mechanism has been proposed [IP:14] to make the IP
layer respond directly to Source Quench by controlling
the rate at which datagrams are sent, however, this
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...
The host IP layer MUST operate correctly in a minimal
network environment, and in particular, when there are no
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... network environment, and in particular, when there are no
gateways. For example, if the IP layer of a host insists on
finding at least one gateway ...
... destination is not on the connected
network), the IP layer MUST pick a gateway from its list of
"default" gateways ...
... gateway from its list of
"default" gateways. The IP layer MUST support multiple
default gateways.
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...
As an extra feature, a host IP layer MAY implement a table
of "static routes". Each such static route MAY include a
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... handle on the appropriate cache entry, to be passed to
the IP layer with each subsequent datagram.
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...
The IP layer MUST be able to detect the failure of a "next-
hop" gateway that is listed in its route cache ...
... While advice might be passed using required arguments
in all interfaces to the IP layer, some transport and
application layer ...
... timer. If the timer had expired (reached
zero), the IP layer would send a ping to the
gateway ...
...
If the failed gateway is not the current default, the IP
layer can immediately switch to a default gateway. If it is
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... switch to a default gateway. If it is
the current default that failed, the IP layer MUST select a
different default gateway (assuming more than one default is
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The IP layer MUST implement reassembly of IP datagrams.
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... along the path. In the absence of actual knowledge of the
minimum MTU along the path, the IP layer SHOULD use
EMTU_S <= 576 whenever the destination address is not on a
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... application does not specify it, the transport layer
must ask the IP layer to perform the conceptual
mapping:
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... hosts" group (224.0.0.1) when the IP layer is initialized and
remain a member for as long as the IP layer is active ...
... group (224.0.0.1) when the IP layer is initialized and
remain a member for as long as the IP layer is active.
...
...
The interface between the IP layer and the transport layer MUST
provide full access to all the mechanisms of the IP layer ...
... IP layer and the transport layer MUST
provide full access to all the mechanisms of the IP layer,
including options, Type-of-Service, and Time-to-Live ...
... interface between the transport layer
and the IP layer, as a set of procedure calls. This is an
extension of the information in Section 3.3 of RFC-791std5 [IP:1 ...
... 791std5).
The IP layer MUST pass certain ICMP messages up to the
appropriate transport-layer ...
... layer |3.2.1.8 |x| | | | |
IP layer silently ignore unknown options |3.2.1.8 |x| | | | |
Security option |3.2.1.8a| | |x| | |
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... datagram service of the
IP layer. UDP is used by applications that do not require the
level of service ...
... UDP MUST pass any IP option that it receives from the IP
layer transparently to the application layer.
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... UDP MUST pass to the application layer all ICMP error
messages that it receives from the IP layer. Conceptually
at least, this may be accomplished with an upcall to the
ERROR_REPORT routine (see Section 4.2.4.1).
...
... UDP datagram,
and these values must be passed transparently to the IP layer.
UDP MAY pass the received TOS ...
... layer may not have the
appropriate information to make this decision, so it is
preferable to leave to the IP layer the task of
determining a suitable MTU for the Internet ...
... therefore recommend that TCP always send the option (if
not 536) and that the IP layer determine MMS_R as
specified in 3.3.3 and 3.4. A proposed IP-layer
mechanism ...
... specified in 3.3.3 and 3.4. A proposed IP-layer
mechanism to measure the MTU would then modify the IP
layer without changing TCP.
...
... threshold R1, pass negative advice
(see Section 3.3.1.4) to the IP layer, to trigger
dead-gateway diagnosis.
...
... TCP connection,
then the TCP MUST ask the IP layer to select a local IP
address before sending the (first) SYN. See the function
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...
When received options are passed up to TCP from the IP
layer, TCP MUST ignore options that it does not understand.
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... TCP MUST act on an ICMP error message passed up from the IP
layer, directing it to the connection that created the
...
... TCP SHOULD
pass the current TOS value without change to the IP layer,
when it sends segments on the connection ...
... IP LAYER REFERENCES ...