datagram
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... router) chooses appropriate values to insert into the
TOS fields of the IP datagrams it originates. Sections 6 and 7
describe the ICMP Destination Unreachable and Redirect messages ...
... TOS facility is one of the features of the Type of Service octet
in the IP datagram header. The Type of Service octet consists of
...
... the importance or priority of the datagram. This field is not
discussed in detail in this memo.
...
...
The last field, labeled "MBZ" (for "must be zero") above, is
currently unused. The originator of a datagram sets this field to
zero (unless participating in an Internet protocol experiment which
...
... makes use of that bit). Routers and recipients of datagrams ignore
the value of this field. This field is copied on fragmentation.
...
... example, setting the TOS field to 1000 (minimize delay) does not
guarantee that the path taken by the datagram will have a delay that
the user considers "low". The network will attempt to choose the
...
... information about path delay. The network will not discard the
datagram simply because it believes that the delay of the available
paths is "too high" (actually, the network manager can override this
...
... TCP [13] should use the same TOS for datagrams containing only TCP
control information as it does for datagrams ...
... datagrams containing only TCP
control information as it does for datagrams which contain user
data. Although it might seem intuitively correct to always
request that the network ...
... Redirect message also includes a code, which specifies
the class of datagrams to which the Redirect applies. There are
currently four codes defined:
...
... currently four codes defined:
0 -- redirect datagrams for the network
1 -- redirect datagrams ...
... routers should consider the value of the TOS field of
a datagram when choosing an appropriate path to get the datagram to
its destination ...
... TOS field of
a datagram when choosing an appropriate path to get the datagram to
its destination. The mechanisms for doing so are discussed in this
...
... routers to choose different paths based up the TOS field in a
datagram. Inside such a routing domain, the network manager ...
... 1]) the
host treats code 0 (redirect datagrams for the network) Redirects
as if they were code 1 (redirect datagrams ...
... datagrams for the network) Redirects
as if they were code 1 (redirect datagrams for the host)
Redirects. Similarly, it is assumed that the host ...
... Redirects. Similarly, it is assumed that the host treats code 2
(redirect datagrams for the network and type of service) Redirects
...
... network and type of service) Redirects
as if they were code 3 (redirect datagrams for the host and type
of service) Redirects. Readers considering violating these
...
... As an alternative, a host may treat all Redirects as if they were
code 3 (redirect datagrams for hosts and type of service)
...
... table. The value can be any of the possible values of the TOS
field in an IP datagram (including those values whose semantics
are yet to be defined). Any routes learned using routing
protocols ...
...
The TOS field in a datagram primarily affects the path chosen through
the network, but an implementor ...
... implementor may choose to have TOS also affect
other aspects of how the datagram is handled. For example, a host or
router ...
... network output
queues to datagrams which have requested that delay be minimized.
Similarly, a router forced by overload ...
... TOS exactly matches the TOS
in the datagram being routed. If there is no route with the
requested TOS ...