** ** [RFC2210]
All of the sub-parameters on the right hand side of the equal sign
MUST be included in the parameter. Note that the Path
MTU Discovery (PMTUD) working group is currently specifying a robust
method for determining the MTU supported over an end-to-end path.
This new method is expected to update RFC1191 and RFC1981, the
current standards track protocols for this purpose.
=
Any one of the sub-parameter on the right hand side of the equal sign
can be included in the parameter.
An application MAY like to reserve resources for packets with a
particular QoS class, e.g. a DiffServ per-hop behavior (PHB)
[RFC2475], DiffServ-aware MPLS traffic engineering (DSTE) class
type [RFC3564, RFC4124], or Y.1541 QoS class [Y.1541].
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=
Any subset of the sub-parameter on the right hand side of the equal
sign can be included in the parameter.
is the priority of the new flow compared with
the defending priority of previously admitted flows. Once a flow is
admitted, the preemption priority becomes irrelevant. is used to compare with the preemption priority of new
flows. For any specific flow, its preemption priority MUST always be
less than or equal to the defending priority.
and provide an essential way to differentiate flows
for emergency services, ETS, E911, etc., and assign them a higher
admission priority than normal priority flows and best-effort
priority flows.
Appropriate security measures need to be taken to prevent abuse of
the parameters, see Section 8 on Security Considerations.
[Y.1540] defines packet transfer outcomes, as follows:
Successful: packet arrives within the preset waiting time with no
errors
Lost: packet fails to arrive within the waiting time
Errored: packet arrives in time, but has one or more bit errors
in the header or payload
Packet Loss Ratio (PLR) = total packets lost/total packets sent
Packet Error Ratio (PER) = total errored packets/total packets sent
, , , and are QSPEC-2
parameters describing the desired path latency, path jitter and path
bit error rate respectively. Since these parameters are cumulative,
an individual QNE cannot decide whether the desired path latency,
etc., is available, and hence they cannot decide whether a
reservation fails. Rather, when these parameters are included in
, the QNI SHOULD also include corresponding parameters
in a QSPEC object in order to facilitate collecting
this information.
5.2.2
=
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Any subset of the QSPEC parameters on the right hand side of the
equal sign can be included in the object.
When used in the object, refers to traffic
resources available at a QNE in the network.
The Object collects information on the resources
currently available on the path when it travels in a RESERVE or QUERY
message and hence in this case this QSPEC object is read-write. Each
QNE MUST inspect all parameters of this QSPEC object, and if
resources available to this QNE are less than what a particular
parameter says currently, the QNE MUST adapt this parameter
accordingly. Hence when the message arrives at the recipient of the
message, reflects the bottleneck of the resources
currently available on a path. It can be used in a QUERY message,
for example, to collect the available resources along a data path.
When travels in a RESPONSE message, it in fact just
transports the result of a previous measurement performed by a
RESERVE or QUERY message back to the initiator. Therefore in this
case, is read-only.
The parameters and provide information,
for example, about the bandwidth available along the path followed by
a data flow. The local parameter is an estimate of the bandwidth the
QNE has available for packets following the path. Computation of the
value of this parameter SHOULD take into account all information
available to the QNE about the path, taking into consideration
administrative and policy controls on bandwidth, as well as physical
resources. The composition rule for this parameter is the MIN
function. The composed value is the minimum of the QNE's value and
the previously composed value. This quantity, when composed
end-to-end, informs the QNR (or QNI in a RESPONSE message) of the
minimal bandwidth link along the path from QNI to QNR.
The parameter accumulates the latency of the packet
forwarding process associated with each QNE, where the latency is
defined to be the mean packet delay added by each QNE. This delay
results from speed-of-light propagation delay, from packet processing
limitations, or both. The mean delay reflects the variable queuing
delay that may be present. Each QNE MUST add the propagation delay
of its outgoing link, if this link exists. Furthermore, the QNI MUST
add the propagation delay of the ingress link, if this link exists.
The composition rule for the parameter is summation
with a clamp of (2**32 - 1) on the maximum value. This quantity,
when composed end-to-end, informs the QNR (or QNI in a RESPONSE
message) of the minimal packet delay along the path from QNI to QNR.
The purpose of this parameter is to provide a minimum path latency
for use with services which provide estimates or bounds on additional
path delay [RFC2212].
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The parameter accumulates the jitter of the packet
forwarding process associated with each QNE, where the jitter is
defined to be the nominal jitter added by each QNE. IP packet
jitter, or delay variation, is defined in [RFC3393], Section 3.4
(Type-P-One-way-ipdv), and where the selection function includes the
packet with minimum delay such that the distribution is equivalent to
2-point delay variation in [Y.1540]. The suggested evaluation
interval is 1 minute. This jitter results from packet processing
limitations, and includes any variable queuing delay which may be
present. Each QNE MUST add the jitter of its outgoing link, if this
link exists. Furthermore, the QNI MUST add the jitter of the ingress
link, if this link exists. The composition method for the parameter is the combination of several statistics describing
the delay variation distribution with a clamp on the maximum value
(note that the methods of accumulation and estimation of nominal QNE
jitter are specified in clause 8 of [Y.1541]). This quantity, when
composed end-to-end, informs the QNR (or QNI in a RESPONSE message)
of the nominal packet jitter along the path from QNI to QNR. The
purpose of this parameter is to provide a nominal path jitter for use
with services that provide estimates or bounds on additional path
delay [RFC2212].
The parameter accumulates the packet loss rate (PLR) of
the packet forwarding process associated with each QNE, where the PLR
is defined to be the PLR added by each QNE. Each QNE MUST add the
PLR of its outgoing link, if this link exists. Furthermore, the QNI
MUST add the PLR of the ingress link, if this link exists. The
composition rule for the parameter is summation with a
clamp on the maximum value (this assumes sufficiently low PLR values
such that summation error is not significant, however a more accurate
composition function is specified in clause 8 of [Y.1541]). This
quantity, when composed end-to-end, informs the QNR (or QNI in a
RESPONSE message) of the minimal packet PLR along the path from QNI
to QNR.
The parameter accumulates the packet error rate (PER) of
the packet forwarding process associated with each QNE, where the PER
is defined to be the PER added by each QNE. Each QNE MUST add the
PER of its outgoing link, if this link exists. Furthermore, the QNI
MUST add the PER of the ingress link, if this link exists. The
composition rule for the parameter is summation with a
clamp on the maximum value (this assumes sufficiently low PER values
such that summation error is not significant, however a more accurate
composition function is specified in clause 8 of [Y.1541]). This
quantity, when composed end-to-end, informs the QNR (or QNI in a
RESPONSE message) of the minimal packet PER along the path from QNI
to QNR.
, , , : Error terms C and D represent how the
element's implementation of the guaranteed service deviates from the
fluid model. These two parameters have an additive composition rule.
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The error term C is the rate-dependent error term. It represents the
delay a datagram in the flow might experience due to the rate
parameters of the flow. The error term D is the rate-independent,
per-element error term and represents the worst case non-rate-based
transit time variation through the service element. If the
composition function is applied along the entire path to compute the
end-to-end sums of C and D ( and ) and the resulting
values are then provided to the QNR (or QNI in a RESPONSE message).
and are the sums of the parameters C and D between the
last reshaping point and the current reshaping point.
5.2.3
= ~~
Any subset of the QSPEC parameters on the right hand side of the
equal sign can be included in the object. These
parameters describe the QoS reserved by the QNEs along the data path.
, and are defined above.
~~~~ = slack term, which is the difference between desired delay and
delay obtained by using bandwidth reservation, and which is used to
reduce the resource reservation for a flow [RFC2212]. This is an
QSPEC-2 parameter.
5.2.4
=
Any subset of the QSPEC parameters on the right hand side of the
equal sign can be included in the object.
does not have an equivalent in RSVP. It allows the QNI
to define a range of acceptable QoS levels by including both the
desired QoS value and the minimum acceptable QoS in the same message.
It is a read-only QSPEC object. The desired QoS is included with a
and/or a QSPEC object seeded to the
desired QoS value. The minimum acceptable QoS value MAY be coded in
the ~~