draft-ietf-tewg-diff-te-mar-05.txt   draft-ietf-tewg-diff-te-mar-06.txt 
Network Working Group Jerry Ash Network Working Group Jerry Ash
Internet Draft AT&T Internet Draft AT&T
Category: Experimental Category: Experimental
<draft-ietf-tewg-diff-te-mar-05.txt> <draft-ietf-tewg-diff-te-mar-06.txt>
Expiration Date: June 2005 Expiration Date: June 2005
December, 2004 December, 2004
Max Allocation with Reservation Bandwidth Constraints Model for Max Allocation with Reservation Bandwidth Constraints Model for
DiffServ-aware MPLS Traffic Engineering & Performance Comparisons DiffServ-aware MPLS Traffic Engineering & Performance Comparisons
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware have applicable patent or other IPR claims of which he or she is aware have
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3. bandwidth isolation, i.e., a CT cannot hog the bandwidth of another 3. bandwidth isolation, i.e., a CT cannot hog the bandwidth of another
CT under overload conditions, CT under overload conditions,
4. protection against QoS degradation, at least of the high-priority CTs 4. protection against QoS degradation, at least of the high-priority CTs
(e.g. high-priority voice, high-priority data, etc.), and (e.g. high-priority voice, high-priority data, etc.), and
5. reasonably simple, i.e., does not require additional IGP extensions 5. reasonably simple, i.e., does not require additional IGP extensions
and minimizes signaling load processing requirements. and minimizes signaling load processing requirements.
In Appendix A modeling analysis is presented which shows that the MAR In Appendix A modeling analysis is presented which shows that the MAR
Model meets all these objectives, and provides good network performance Model meets all these objectives, and provides good network performance
relative to MAM and full sharing models, under normal and abnormal relative to MAM and full sharing models, under normal and abnormal
operating conditions. It is demonstrated that simultaneously achieves operating conditions. It is demonstrated that MAR simultaneously
bandwidth efficiency, bandwidth isolation, and protection against QoS achieves bandwidth efficiency, bandwidth isolation, and protection
degradation without preemption. against QoS degradation without preemption.
In Section 3 we give the assumptions and applicability, in Section 4 a In Section 3 we give the assumptions and applicability, in Section 4 a
functional specification of the MAR Bandwidth Constraints Model, and in functional specification of the MAR Bandwidth Constraints Model, and in
Section 5 we give examples of its operation. In Appendix A, MAR Section 5 we give examples of its operation. In Appendix A, MAR
performance is analyzed relative to the criteria for selecting a performance is analyzed relative to the criteria for selecting a
Bandwidth Constraints Model, in order to provide guidance to user Bandwidth Constraints Model, in order to provide guidance to user
implementation of the model in their networks. In Appendix B, implementation of the model in their networks. In Appendix B,
bandwidth prediction for path computation is discussed. bandwidth prediction for path computation is discussed.
2. Definitions 2. Definitions
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1. connection admission control (CAC) allocates bandwidth for network 1. connection admission control (CAC) allocates bandwidth for network
flows/LSPs according to the traffic load assigned to each CT, based on flows/LSPs according to the traffic load assigned to each CT, based on
traffic measurement and forecast. traffic measurement and forecast.
2. CAC could allocate bandwidth per flow, per LSP, per traffic trunk, or 2. CAC could allocate bandwidth per flow, per LSP, per traffic trunk, or
otherwise. That is, no specific assumption is made on a specific CAC otherwise. That is, no specific assumption is made on a specific CAC
method, only that CT bandwidth allocation is related to the method, only that CT bandwidth allocation is related to the
measured/forecast traffic load, as per assumption #1. measured/forecast traffic load, as per assumption #1.
3. CT bandwidth allocation is adjusted up or down according to 3. CT bandwidth allocation is adjusted up or down according to
measured/forecast traffic load. No specific time period is assumed for measured/forecast traffic load. No specific time period is assumed for
this adjustment, it could be short term (hours), daily, weekly, monthly, this adjustment, it could be short term (seconds, minutes, hours),
or otherwise. daily, weekly, monthly, or otherwise.
4. Capacity management and CT bandwidth allocation thresholds (e.g., 4. Capacity management and CT bandwidth allocation thresholds (e.g.,
BCc) are designed according to traffic load, and are based on traffic BCc) are designed according to traffic load, and are based on traffic
measurement and forecast. Again, no specific time period is assumed for measurement and forecast. Again, no specific time period is assumed for
this adjustment, it could be short term (hours), daily, weekly, monthly, this adjustment, it could be short term (hours), daily, weekly, monthly,
or otherwise. or otherwise.
5. No assumption is made on the order in which traffic is allocated to 5. No assumption is made on the order in which traffic is allocated to
various CTs, again traffic allocation is assumed to be based only on various CTs, again traffic allocation is assumed to be based only on
traffic load as it is measured and/or forecast. traffic load as it is measured and/or forecast.
6. If link bandwidth is exhausted on a given path for a flow/LSP/traffic 6. If link bandwidth is exhausted on a given path for a flow/LSP/traffic
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Hence, in the above example, in the current state of the link and the Hence, in the above example, in the current state of the link and the
current CT loading, CT0 and CT1 can no longer increase their bandwidth current CT loading, CT0 and CT1 can no longer increase their bandwidth
on the link, since they are above their BCc values and there is only on the link, since they are above their BCc values and there is only
RBW_THRES=10 units of spare bandwidth left on the link. But CT2 can RBW_THRES=10 units of spare bandwidth left on the link. But CT2 can
take the additional bandwidth (up to 10 units) if the demand arrives, take the additional bandwidth (up to 10 units) if the demand arrives,
since it is below its BCc value. since it is below its BCc value.
7. Summary 7. Summary
The proposed MAR Bandwidth Constraints Model includes the following: a) The proposed MAR Bandwidth Constraints Model includes the following:
allocate bandwidth to individual CTs, b) protect allocated bandwidth by
bandwidth reservation methods, as needed, but otherwise fully share 1. allocate bandwidth to individual CTs,
bandwidth, c) differentiate high-priority, normal-priority, and 2. protect allocated bandwidth by bandwidth reservation methods, as
best-effort priority services, and d) provide admission control to needed, but otherwise fully share bandwidth,
reject connection requests when needed to meet performance objectives. 3. differentiate high-priority, normal-priority, and best-effort
priority services, and
4. provide admission control to reject connection requests when needed
to meet performance objectives.
Modeling results presented in Appendix A show that MAR bandwidth Modeling results presented in Appendix A show that MAR bandwidth
allocation a) achieves greater efficiency in bandwidth sharing while allocation a) achieves greater efficiency in bandwidth sharing while
still providing bandwidth isolation and protection against QoS still providing bandwidth isolation and protection against QoS
degradation, and b) achieves service differentiation for high-priority, degradation, and b) achieves service differentiation for high-priority,
normal-priority, and best-effort priority services. normal-priority, and best-effort priority services.
8. Security Considerations 8. Security Considerations
Security considerations related to the use of DS-TE are discussed in Security considerations related to the use of DS-TE are discussed in
[DSTE-PROTO]. Those apply independently of the Bandwidth Constraints [DSTE-PROTO]. Those apply independently of the Bandwidth Constraints
Model, including MAR specified in this document. Model, including MAR specified in this document.
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allocation rules now described. allocation rules now described.
MAR bandwidth allocation is done on a per-CT basis, in which aggregated MAR bandwidth allocation is done on a per-CT basis, in which aggregated
CT bandwidth is managed to meet the overall bandwidth requirements of CT CT bandwidth is managed to meet the overall bandwidth requirements of CT
service needs. Individual flows/LSPs are allocated bandwidth in the service needs. Individual flows/LSPs are allocated bandwidth in the
corresponding CT according to CT bandwidth availability. A fundamental corresponding CT according to CT bandwidth availability. A fundamental
principle applied in MAR bandwidth allocation methods is the use of principle applied in MAR bandwidth allocation methods is the use of
bandwidth reservation techniques. bandwidth reservation techniques.
Bandwidth reservation gives preference to the preferred traffic by Bandwidth reservation gives preference to the preferred traffic by
allowing it to seize any idle bandwidth on a link, while allowing the allowing it to seize idle bandwidth on a link more easily than the
non-preferred traffic to only seize bandwidth if there is a minimum
level of idle bandwidth available called the reservation bandwidth non-preferred traffic. Burke [BUR] first analyzed bandwidth reservation
threshold RBW_THRES. Burke [BUR] first analyzed bandwidth reservation
behavior from the solution of the birth-death equations for the behavior from the solution of the birth-death equations for the
bandwidth reservation model. Burke's model showed the relative bandwidth reservation model. Burke's model showed the relative
lost-traffic level for preferred traffic, which is not subject to lost-traffic level for preferred traffic, which is not subject to
bandwidth reservation restrictions, as compared to non-preferred bandwidth reservation restrictions, as compared to non-preferred
traffic, which is subject to the restrictions. Bandwidth reservation traffic, which is subject to the restrictions. Bandwidth reservation
protection is robust to traffic variations and provides significant protection is robust to traffic variations and provides significant
dynamic protection of particular streams of traffic. It is widely used dynamic protection of particular streams of traffic. It is widely used
in large-scale network applications [ASH1, MUM, AKI, KRU, NAK]. in large-scale network applications [ASH1, MUM, AKI, KRU, NAK].
Bandwidth reservation is used in MAR bandwidth allocation to control Bandwidth reservation is used in MAR bandwidth allocation to control
sharing of link bandwidth across different CTs. On a given link, a sharing of link bandwidth across different CTs. On a given link, a
small amount of bandwidth RBW_THRES is reserved (say 1% of the total small amount of bandwidth RBW_THRES is reserved (say 1% of the total
link bandwidth), and the reservation bandwidth can be accessed when a link bandwidth), and the reservation bandwidth can be accessed when a
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