type of service
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... Layer about how the
tradeoffs should be made for the particular packet. This facility is
the "Type of Service" facility, abbreviated as the "TOS facility" in
this memo.
...
... IS-IS [7]) have been developed which can compute
routes separately for each type of service. These new routing
protocols make it practical for routers to consider the requested
...
... routing
protocols make it practical for routers to consider the requested
type of service when making routing decisions.
...
... TOS facility. Section 2 introduces the primary considerations that
motivated the design choices in this specification. Sections 3 and 4
describe the Type of Service octet in the IP header and the values
which the TOS ...
... hosts and routers should be able to handle a
new type of service correctly without having to understand its
semantics.
...
... Specification of the Type of Service Octet ...
...
The TOS facility is one of the features of the Type of Service octet
in the IP datagram header ...
... host unreachable
11 -- network unreachable for type of service
12 -- host unreachable for type of service ...
... (redirect datagrams for the network and type of service) Redirects
as if they were code 3 (redirect datagrams for the host ...
... as if they were code 3 (redirect datagrams for the host and type
of service) Redirects. Readers considering violating these
assumptions should be aware that long and careful consideration of
the way in which Redirects are treated is necessary to avoid
...
... code 3 (redirect datagrams for hosts and type of service)
Redirects. This alternative allows the host to have only type 1
...
... and a non-infinite metric then code 11 (Network unreachable for
type of service) or code 12 (Host unreachable for type of service)
...
... type of service
12 -- host unreachable for type of service
These codes were defined in RFC-1122std3 ...
... TOS field and the specification of that field's values:
(1) To define a new type of service requesting that the network
"minimize monetary cost"
...
... IP header currently has only three unused bits, so
at most three new type of service bits could be defined without
resorting to the impractical step of changing the IP header ...
... TOS field to
1000 (minimize delay) sets bit 3 of the Type of Service octet; bit
3 is defined as the Low Delay bit ...
... Requirements Working Group. Much of the
specification of the treatment of Type of Service by hosts is merely
a restatement of the ideas of the IETF ...