intSrvGuaranteedIfSlack

If a network element uses a certain amount  of
slack,  Si,  to  reduce the amount of resources
that it has reserved for a particular flow,  i,
the  value  Si  should be stored at the network
element.   Subsequently,  if  reservation   re-
freshes  are  received  for flow i, the network
element must use the same slack Si without  any
further computation. This guarantees consisten-
cy in the reservation process.
              
As an example for the use of  the  slack  term,
consider the case where the required end-to-end
delay, Dreq, is larger than the  maximum  delay
of the fluid flow system.  In this, Ctot is the
              
sum of the Backlog terms end to end,  and  Dtot
is the sum of the delay terms end to end.  Dreq
is obtained by setting R=r in the  fluid  delay
formula, and is given by
              
             b/r + Ctot/r + Dtot.
              
In this case the slack term is
              
       S = Dreq - (b/r + Ctot/r + Dtot).
              
The slack term may be used by the network  ele-
ments  to  adjust  their local reservations, so
that they can admit flows that would  otherwise
have been rejected. A service element at an in-
termediate network element that can  internally
differentiate between delay and rate guarantees
can now take advantage of this  information  to
lower the amount of resources allocated to this
flow. For example, by taking an amount of slack
s  <= S, an RCSD scheduler [5] can increase the
local delay bound, d, assigned to the flow,  to
d+s. Given an RSpec, (Rin, Sin), it would do so
by setting Rout = Rin and Sout = Sin - s.
              
Similarly,  a  network  element  using  a   WFQ
scheduler  can  decrease  its local reservation
from Rin to Rout by using some of the slack  in
the  RSpec.  This  can be accomplished by using
the transformation rules given in the  previous
section,  that ensure that the reduced reserva-
tion level will not increase the  overall  end-
to-end delay.

MIB

INTEGRATED-SERVICES-GUARANTEED-MIB

OID

.1.3.6.1.2.1.52.5.1.1.1.3

Type

column

Access

readwrite

Status

current

Parent

intSrvGuaranteedIfEntry

Table

intSrvGuaranteedIfTable

Siblings

3