draft-ietf-rap-signaled-priority-v2-01.txt   rfc3181.txt 
Internet Draft S. Herzog Network Working Group S. Herzog
Expiration: January 2001 IPHighway Request for Comments: 3181 PolicyConsulting.Com
File: draft-ietf-rap-signaled-priority-v2-01.txt July 2000 Obsoletes: 2751 October 2001
Replaces: RFC 2751 Category: Standards Track
Signaled Preemption Priority Policy Element Signaled Preemption Priority Policy Element
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with all This document specifies an Internet standards track protocol for the
provisions of Section 10 of RFC2026. Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract Abstract
This document describes a preemption priority policy element for use This document describes a preemption priority policy element for use
by signaled policy based admission protocols (such as [RSVP] and by signaled policy based admission protocols (such as the Resource
[COPS]). ReSerVation Protocol (RSVP) and Common Open Policy Service (COPS).
Preemption priority defines a relative importance (rank) within the Preemption priority defines a relative importance (rank) within the
set of flows competing to be admitted into the network. Rather than set of flows competing to be admitted into the network. Rather than
admitting flows by order of arrival (First Come First Admitted) admitting flows by order of arrival (First Come First Admitted)
network nodes may consider priorities to preempt some previously network nodes may consider priorities to preempt some previously
admitted low priority flows in order to make room for a newer, high- admitted low priority flows in order to make room for a newer, high-
priority flow. priority flow.
This memo corrects an RSVP POLICY_DATA P-Type codepoint assignment This memo corrects an RSVP POLICY_DATA P-Type codepoint assignment
error in RFC 2751. error in RFC 2751.
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5 Priority Merging Issues ..........................................5 5 Priority Merging Issues ..........................................5
5.1 Priority Merging Strategies ...................................6 5.1 Priority Merging Strategies ...................................6
5.1.1 Take priority of highest QoS .................................6 5.1.1 Take priority of highest QoS .................................6
5.1.2 Take highest priority ........................................7 5.1.2 Take highest priority ........................................7
5.1.3 Force error on heterogeneous merge ...........................7 5.1.3 Force error on heterogeneous merge ...........................7
5.2 Modifying Priority Elements ...................................7 5.2 Modifying Priority Elements ...................................7
6 Error Processing .................................................8 6 Error Processing .................................................8
7 IANA Considerations ..............................................8 7 IANA Considerations ..............................................8
8 Security Considerations ..........................................8 8 Security Considerations ..........................................8
9 References .......................................................9 9 References .......................................................9
10 Author Information .............................................9 10 Author's Address ...............................................9
Appendix A: Example ...............................................10 Appendix A: Example ...............................................10
A.1 Computing Merged Priority ....................................10 A.1 Computing Merged Priority ....................................10
A.2 Translation (Compression) of Priority Elements ...............11 A.2 Translation (Compression) of Priority Elements ...............11
Full Copyright Statement ..........................................12 Full Copyright Statement ..........................................12
1 Introduction 1 Introduction
This document describes a preemption priority policy element for use
by signaled policy based admission protocols (such as [RSVP] and
[COPS]).
Traditional Capacity based Admission Control (CAC) indiscriminately Traditional Capacity based Admission Control (CAC) indiscriminately
admits new flows until capacity is exhausted (First Come First admits new flows until capacity is exhausted (First Come First
Admitted). Policy based Admission Control (PAC) on the other hand Admitted). Policy based Admission Control (PAC) on the other hand
attempts to minimize the significance of order of arrival and use attempts to minimize the significance of order of arrival and use
policy based admission criteria instead. policy based admission criteria instead.
One of the more popular policy criteria is the rank of importance of One of the more popular policy criteria is the rank of importance of
a flow relative to the others competing for admission into a network a flow relative to the others competing for admission into a network
node. Preemption Priority takes effect only when a set of flows node. Preemption Priority takes effect only when a set of flows
attempting admission through a node represents overbooking of attempting admission through a node represents overbooking of
resources such that based on CAC some would have to be rejected. resources such that based on CAC some would have to be rejected.
Preemption priority criteria help the node select the most important Preemption priority criteria help the node select the most important
flows (highest priority) for admission, while rejecting the low flows (highest priority) for admission, while rejecting the low
priority ones. priority ones.
Network nodes which support preemption should consider priorities to Network nodes which support preemption should consider priorities to
preempt some previously admitted low-priority flows in order to make preempt some previously admitted low-priority flows in order to make
room for a newer, high-priority flow. room for a newer, high-priority flow.
This document describes the format and applicability of the This document describes the format and applicability of the
preemption priority represented as a policy element in [RSVP-EXT]. preemption priority represented as a policy element in [RSVP-EXT].
2 Scope and Applicability 2 Scope and Applicability
The Framework document for policy-based admission control [RAP] The Framework document for policy-based admission control [RAP]
describes the various components that participate in policy decision describes the various components that participate in policy decision
making (i.e., PDP, PEP and LDP). The emphasis of PREEMPTION_PRI making (i.e., PDP, PEP and LDP). The emphasis of PREEMPTION_PRI
elements is to be simple, stateless, and light-weight such that they elements is to be simple, stateless, and light-weight such that they
could be implemented internally within a node's LDP (Local Decision could be implemented internally within a node's LDP (Local Decision
Point). Point).
Certain base assumptions are made in the usage model for Certain base assumptions are made in the usage model for
PREEMPTION_PRI elements: PREEMPTION_PRI elements:
- They are created by PDPs - They are created by PDPs
In a model where PDPs control PEPs at the periphery of the policy In a model where PDPs control PEPs at the periphery of the policy
domain (e.g., in border routers), PDPs reduce sets of relevant domain (e.g., in border routers), PDPs reduce sets of relevant
policy rules into a single priority criterion. This priority as policy rules into a single priority criterion. This priority as
expressed in the PREEMPTION_PRI element can then be communicated expressed in the PREEMPTION_PRI element can then be communicated
to downstream PEPs of the same policy domain, which have LDPs but to downstream PEPs of the same policy domain, which have LDPs but
no controlling PDP. no controlling PDP.
- They can be processed by LDPs - They can be processed by LDPs
PREEMPTION_PRI elements are processed by LDPs of nodes that do not PREEMPTION_PRI elements are processed by LDPs of nodes that do not
have a controlling PDP. LDPs may interpret these objects, forward have a controlling PDP. LDPs may interpret these objects, forward
them as is, or perform local merging to forward an equivalent them as is, or perform local merging to forward an equivalent
merged PREEMPTION_PRI policy element. LDPs must follow the merging merged PREEMPTION_PRI policy element. LDPs must follow the
strategy that was encoded by PDPs in the PREEMPTION_PRI objects. merging strategy that was encoded by PDPs in the PREEMPTION_PRI
(Clearly, a PDP, being a superset of LDP, may act as an LDP as objects. (Clearly, a PDP, being a superset of LDP, may act as an
well). LDP as well).
- They are enforced by PEPs - They are enforced by PEPs
PREEMPTION_PRI elements interact with a node's traffic control PREEMPTION_PRI elements interact with a node's traffic control
module (and capacity admission control) to enforce priorities, and module (and capacity admission control) to enforce priorities, and
preempt previously admitted flows when the need arises. preempt previously admitted flows when the need arises.
3 Stateless Policy 3 Stateless Policy
Signaled Preemption Priority is stateless (does not require past Signaled Preemption Priority is stateless (does not require past
history or external information to be interpreted). Therefore, when history or external information to be interpreted). Therefore, when
carried in COPS messages for the outsourcing of policy decisions, carried in COPS messages for the outsourcing of policy decisions,
these objects are included as COPS Stateless Policy Data Decision these objects are included as COPS Stateless Policy Data Decision
objects (see [COSP, COPS-RSVP]). objects (see [COPS, COPS-RSVP]).
4 Policy Element Format 4 Policy Element Format
The format of Policy Data objects is defined in [RSVP-EXT]. A single The format of Policy Data objects is defined in [RSVP-EXT]. A single
Policy Data object may contain one or more policy elements, each Policy Data object may contain one or more policy elements, each
representing a different (and perhaps orthogonal) policy. representing a different (and perhaps orthogonal) policy.
The format of preemption priority policy element is as follows: The format of preemption priority policy element is as follows:
+-------------+-------------+-------------+-------------+ +-------------+-------------+-------------+-------------+
| Length (12) | P-Type = PREEMPTION_PRI | | Length (12) | P-Type = PREEMPTION_PRI |
+------+------+-------------+-------------+-------------+ +------+------+-------------+-------------+-------------+
| Flags | M. Strategy | Error Code | Reserved(0) | | Flags | M. Strategy | Error Code | Reserved(0) |
+------+------+-------------+-------------+-------------+ +------+------+-------------+-------------+-------------+
| Preemption Priority | Defending Priority | | Preemption Priority | Defending Priority |
+------+------+-------------+-------------+-------------+ +------+------+-------------+-------------+-------------+
Length: 16 bits Length: 16 bits
Always 12. The overall length of the policy element, in bytes. Always 12. The overall length of the policy element, in bytes.
P-Type: 16 bits P-Type: 16 bits
PREEMPTION_PRI = 1 PREEMPTION_PRI = 1
This value is registered with IANA, see Section 7. This value is registered with IANA, see Section 7.
Flags: 8 bits Flags: 8 bits
Reserved (always 0). Reserved (always 0).
Merge Strategy: 8 bit Merge Strategy: 8 bit
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Error code: 8 bits Error code: 8 bits
0 NO_ERROR Value used for regular PREEMPTION_PRI elements 0 NO_ERROR Value used for regular PREEMPTION_PRI elements
1 PREEMPTION This previously admitted flow was preempted 1 PREEMPTION This previously admitted flow was preempted
2 HETEROGENEOUS This element encountered heterogeneous merge 2 HETEROGENEOUS This element encountered heterogeneous merge
Reserved: 8 bits Reserved: 8 bits
Always 0. Always 0.
Preemption Priority: 16 bit (unsigned) Preemption Priority: 16 bit (unsigned)
The priority of the new flow compared with the defending priority The priority of the new flow compared with the defending priority
of previously admitted flows. Higher values represent higher of previously admitted flows. Higher values represent higher
Priority. Priority.
Defending Priority: 16 bits (unsigned) Defending Priority: 16 bits (unsigned)
Once a flow was admitted, the preemption priority becomes Once a flow was admitted, the preemption priority becomes
irrelevant. Instead, its defending priority is used to compare irrelevant. Instead, its defending priority is used to compare
with the preemption priority of new flows. with the preemption priority of new flows.
For any specific flow, its preemption priority must always be less For any specific flow, its preemption priority must always be less
than or equal to the defending priority. A wide gap between than or equal to the defending priority. A wide gap between
preemption and defending priority provides added stability: moderate preemption and defending priority provides added stability: moderate
preemption priority makes it harder for a flow to preempt others, but preemption priority makes it harder for a flow to preempt others, but
once it succeeded, the higher defending priority makes it easier for once it succeeded, the higher defending priority makes it easier for
the flow to avoid preemption itself. This provides a mechanism for the flow to avoid preemption itself. This provides a mechanism for
balancing between order dependency and priority. balancing between order dependency and priority.
5 Priority Merging Issues 5 Priority Merging Issues
Consider the case where two RSVP reservations merge: Consider the case where two RSVP reservations merge:
F1: QoS=High, Priority=Low F1: QoS=High, Priority=Low
F2: QoS=Low, Priority=High F2: QoS=Low, Priority=High
F1+F2= F3: QoS=High, Priority=??? F1+F2= F3: QoS=High, Priority=???
The merged reservation F3 should have QoS=Hi, but what Priority The merged reservation F3 should have QoS=Hi, but what Priority
should it assume? Several negative side-effects have been identified should it assume? Several negative side-effects have been identified
that may affect such a merger: that may affect such a merger:
Free-Riders: Free-Riders:
If F3 assumes Priority=High, then F1 got a free ride, assuming high If F3 assumes Priority=High, then F1 got a free ride, assuming high
priority that was only intended to the low QoS F2. If one associates priority that was only intended to the low QoS F2. If one associates
costs as a function of QoS and priority, F1 receives an "expensive" costs as a function of QoS and priority, F1 receives an "expensive"
priority without having to "pay" for it. priority without having to "pay" for it.
Denial of Service: Denial of Service:
If F3 assumes Priority=Low, the merged flow could be preempted or If F3 assumes Priority=Low, the merged flow could be preempted or
fail even though F2 presented high priority. fail even though F2 presented high priority.
Denial of service is virtually the inverse of the free-rider problem. Denial of service is virtually the inverse of the free-rider problem.
When flows compete for resources, if one flow receives undeserving When flows compete for resources, if one flow receives undeserving
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blockade state [RSVP] may increase the instability of admitted flows blockade state [RSVP] may increase the instability of admitted flows
where a reservation may be preempted, reinstated, and preempted again where a reservation may be preempted, reinstated, and preempted again
periodically. periodically.
5.1 Priority Merging Strategies 5.1 Priority Merging Strategies
In merging situations LDPs may receive multiple preemption elements In merging situations LDPs may receive multiple preemption elements
and must compute the priority of the merged flow according to the and must compute the priority of the merged flow according to the
following rules: following rules:
a. Preemption priority and defending priority are merged and computed a. Preemption priority and defending priority are merged and computed
separately, irrespective of each other. separately, irrespective of each other.
b. Participating priority elements are selected. b. Participating priority elements are selected.
All priority elements are examined according to their merging All priority elements are examined according to their merging
strategy to decide whether they should participate in the merged strategy to decide whether they should participate in the merged
result (as specified bellow). result (as specified bellow).
c. The highest priority of all participating priority elements is c. The highest priority of all participating priority elements is
computed. computed.
The remainder of this section describes the different merging The remainder of this section describes the different merging
strategies the can be specified in the PREEMPTION_PRI element. strategies the can be specified in the PREEMPTION_PRI element.
5.1.1 Take priority of highest QoS 5.1.1 Take priority of highest QoS
The PREEMPTION_PRI element would participate in the merged The PREEMPTION_PRI element would participate in the merged
reservation only if it belongs to a flow that contributed to the reservation only if it belongs to a flow that contributed to the
merged QoS level (i.e., that its QoS requirement does not constitute merged QoS level (i.e., that its QoS requirement does not constitute
a subset another reservation.) A simple way to determine whether a a subset another reservation.) A simple way to determine whether a
flow contributed to the merged QoS result is to compute the merged flow contributed to the merged QoS result is to compute the merged
QoS with and without it and to compare the results (although this is QoS with and without it and to compare the results (although this is
clearly not the most efficient method). clearly not the most efficient method).
The reasoning for this approach is that the highest QoS flow is the The reasoning for this approach is that the highest QoS flow is the
one dominating the merged reservation and as such its priority should one dominating the merged reservation and as such its priority should
dominate it as well. This approach is the most amiable to the dominate it as well. This approach is the most amiable to the
prevention of priority distortions such as free-riders and denial of prevention of priority distortions such as free-riders and denial of
service. service.
This is a recommended merging strategy. This is a recommended merging strategy.
5.1.2 Take highest priority 5.1.2 Take highest priority
All PREEMPTION_PRI elements participate in the merged reservation. All PREEMPTION_PRI elements participate in the merged reservation.
This strategy disassociates priority and QoS level, and therefore is This strategy disassociates priority and QoS level, and therefore is
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The reasoning for this approach assumes that the heterogeneous case The reasoning for this approach assumes that the heterogeneous case
is relatively rare and too complicated to deal with, thus it better is relatively rare and too complicated to deal with, thus it better
be prohibited. be prohibited.
This strategy lends itself to denial of service, when a single This strategy lends itself to denial of service, when a single
receiver specifying a non-compatible QoS level may cause denial of receiver specifying a non-compatible QoS level may cause denial of
service for all other receivers of the merged reservation. service for all other receivers of the merged reservation.
Note: The determination of heterogeneous flows applies to QoS level Note: The determination of heterogeneous flows applies to QoS level
only (FLOWSPEC values), and is a matter for local (LDP) definition. only (FLOWSPEC values), and is a matter for local (LDP) definition.
Other types of heterogeneous reservations (e.g. conflicting Other types of heterogeneous reservations (e.g., conflicting
reservation styles) are handled by RSVP and are unrelated to this reservation styles) are handled by RSVP and are unrelated to this
PREEMPTION_PRI element. PREEMPTION_PRI element.
This is a recommended merging strategy when reservation homogeneity This is a recommended merging strategy when reservation homogeneity
is coordinated and enforced for the entire multicast tree. It is more is coordinated and enforced for the entire multicast tree. It is
restrictive than Section 5.1.1, but is easier to implement. more restrictive than Section 5.1.1, but is easier to implement.
5.2 Modifying Priority Elements 5.2 Modifying Priority Elements
When POLICY_DATA objects are protected by integrity, LDPs should not When POLICY_DATA objects are protected by integrity, LDPs should not
attempt to modify them. They must be forwarded as-is or else their attempt to modify them. They must be forwarded as-is or else their
security envelope would be invalidated. In other cases, LDPs may security envelope would be invalidated. In other cases, LDPs may
modify and merge incoming PREEMPTION_PRI elements to reduce their modify and merge incoming PREEMPTION_PRI elements to reduce their
size and number according to the following rule: size and number according to the following rule:
Merging is performed for each merging strategy separately. Merging is performed for each merging strategy separately.
There is no known algorithm to merge PREEMPTION_PRI element of There is no known algorithm to merge PREEMPTION_PRI element of
different merging strategies without loosing valuable information different merging strategies without loosing valuable information
that may affect OTHER nodes. that may affect OTHER nodes.
- For each merging strategy, the highest QoS of all participating - For each merging strategy, the highest QoS of all participating
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6 Error Processing 6 Error Processing
A PREEMPTION_PRI error object is sent back toward the appropriate A PREEMPTION_PRI error object is sent back toward the appropriate
receivers when an error involving PREEMPTION_PRI elements occur. receivers when an error involving PREEMPTION_PRI elements occur.
PREEMPTION PREEMPTION
When a previously admitted flow is preempted, a copy of the When a previously admitted flow is preempted, a copy of the
preempting flow's PREEMPTION_PRI element is sent back toward the PDP preempting flow's PREEMPTION_PRI element is sent back toward the PDP
that originated the preempted PREEMPTION_PRI object. This PDP, having that originated the preempted PREEMPTION_PRI object. This PDP,
information on both the preempting and the preempted priorities may having information on both the preempting and the preempted
construct a higher priority PREEMPTION_PRI element in an effort to priorities may construct a higher priority PREEMPTION_PRI element in
re-instate the preempted flow. an effort to re-instate the preempted flow.
Heterogeneity Heterogeneity
When a flow F1 with Heterogeneous Error merging strategy set in its When a flow F1 with Heterogeneous Error merging strategy set in its
PREEMPTION_PRI element encounters heterogeneity the PREEMPTION_PRI PREEMPTION_PRI element encounters heterogeneity the PREEMPTION_PRI
element is sent back toward receivers with the Heterogeneity error element is sent back toward receivers with the Heterogeneity error
code set. code set.
7 IANA Considerations 7 IANA Considerations
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The integrity of PREEMPTION_PRI is guaranteed, as any other policy The integrity of PREEMPTION_PRI is guaranteed, as any other policy
element, by the encapsulation into a Policy Data object [RSVP-EXT]. element, by the encapsulation into a Policy Data object [RSVP-EXT].
Further security mechanisms are not warranted, especially considering Further security mechanisms are not warranted, especially considering
that preemption priority aims to provide simple and quick guidance to that preemption priority aims to provide simple and quick guidance to
routers within a trusted zone or at least a single zone (no zone routers within a trusted zone or at least a single zone (no zone
boundaries are crossed). boundaries are crossed).
9 References 9 References
[RFC2751] Herzog, S., "Signaled Preemption Priority
Policy Element", RFC 2751, January 2000.
[RSVP-EXT] Herzog, S., "RSVP Extensions for Policy [RSVP-EXT] Herzog, S., "RSVP Extensions for Policy
Control", RFC 2750, January 2000. Control", RFC 2750, January 2000.
[COPS-RSVP] Boyle, J., Cohen, R., Durham, D., Herzog, S., [COPS-RSVP] Boyle, J., Cohen, R., Durham, D., Herzog, S.,
Raja, R. and A. Sastry, "COPS usage for RSVP", Raja, R. and A. Sastry, "COPS usage for RSVP",
RFC 2749, January 2000. RFC 2749, January 2000.
[RAP] Yavatkar, R., et al., "A Framework for Policy [RAP] Yavatkar, R., Pendarakis, D. and R. Guerin, "A
Based Admission Control", RFC 2753, January Framework for Policy Based Admission Control",
2000. RFC 2753, January 2000.
[COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S., [COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S.,
Raja, R. and A. Sastry, "The COPS (Common Open Raja, R. and A. Sastry, "The COPS (Common Open
Policy Service) Protocol", RFC 2748, January Policy Service) Protocol", RFC 2748, January
2000. 2000.
[RSVP] Braden, R., ed., et al., "Resource ReSerVation [RSVP] Braden, R., Zhang, L., Berson, S., Herzog, S.
Protocol (RSVP) - Functional Specification", and S. Jamin, "Resource ReSerVation Protocol
RFC 2205, September 1997. (RSVP) - Functional Specification", RFC 2205,
September 1997.
[IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for [IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for
Writing an IANA Considerations Section in Writing an IANA Considerations Section in
RFCs", BCP 26, RFC 2434, October 1998. RFCs", BCP 26, RFC 2434, October 1998.
10 Author Information 10 Author's Address
Shai Herzog Shai Herzog
IPHighway, Inc. PolicyConsulting.Com
55 New York Avenue 200 Clove Rd.
Framingham, MA 01701 New Rochelle, NY 10801
Phone: (508) 620-1141 EMail: herzog@policyconsulting.com
EMail: herzog@iphighway.com
Appendix A: Example Appendix A: Example
The following examples describe the computation of merged priority The following examples describe the computation of merged priority
elements as well as the translation (compression) of PREEMPTION_PRI elements as well as the translation (compression) of PREEMPTION_PRI
elements. elements.
A.1 Computing Merged Priority A.1 Computing Merged Priority
r1 r1
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\ \ QoS=Low (Pr=7, St=Highest QoS) \ \ QoS=Low (Pr=7, St=Highest QoS)
r4 r3 r4 r3
QoS=Low (Pr=9, St=Error) QoS=Low (Pr=9, St=Error)
Example 1: Merging preemption priority elements Example 1: Merging preemption priority elements
Example one describes a multicast scenario with one sender and four Example one describes a multicast scenario with one sender and four
receivers each with each own PREEMPTION_PRI element definition. receivers each with each own PREEMPTION_PRI element definition.
r1, r2 and r3 merge in B. The resulting priority is 4. r1, r2 and r3 merge in B. The resulting priority is 4.
Reason: The PREEMPTION_PRI of r3 doesn't participate (since r3 is not Reason: The PREEMPTION_PRI of r3 doesn't participate (since r3 is not
contributing to the merged QoS) and the priority is the highest of contributing to the merged QoS) and the priority is the highest of
the PREEMPTION_PRI from r1 and r2. the PREEMPTION_PRI from r1 and r2.
r1, r2, r3 and r4 merge in A. The resulting priority is again 4: r4 r1, r2, r3 and r4 merge in A. The resulting priority is again 4: r4
doesn't participate because its own QoS=Low is incompatible with the doesn't participate because its own QoS=Low is incompatible with the
other (r1) QoS=High. An error PREEMPTION_PRI should be sent back to other (r1) QoS=High. An error PREEMPTION_PRI should be sent back to
r4 telling it that its PREEMPTION_PRI element encountered r4 telling it that its PREEMPTION_PRI element encountered
heterogeneity. heterogeneity.
A.2 Translation (Compression) of Priority Elements A.2 Translation (Compression) of Priority Elements
Given this set of participating PREEMPTION_PRI elements, the Given this set of participating PREEMPTION_PRI elements, the
following compression can take place at the merging node: following compression can take place at the merging node:
From: From:
(Pr=3, St=Highest QoS) (Pr=3, St=Highest QoS)
(Pr=7, St=Highest QoS) (Pr=7, St=Highest QoS)
(Pr=4, St=Highest PP) (Pr=4, St=Highest PP)
(Pr=9, St=Highest PP) (Pr=9, St=Highest PP)
(Pr=6, St=Highest PP) (Pr=6, St=Highest PP)
To: To:
(Pr=7, St=Highest QoS) (Pr=7, St=Highest QoS)
(Pr=9, St=Highest PP) (Pr=9, St=Highest PP)
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
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