Networking Working Group S. Previdi, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track S. Giacalone Expires: October 27, 2014 Thomson Reuters D. Ward Cisco Systems, Inc. J. Drake A. Atlas Juniper Networks C. Filsfils Cisco Systems, Inc. Q. Wu Huawei April 25, 2014 IS-IS Traffic Engineering (TE) Metric Extensions draft-ietf-isis-te-metric-extensions-03 Abstract In certain networks, such as, but not limited to, financial information networks (e.g. stock market data providers), network performance criteria (e.g. latency) are becoming as critical to data path selection as other metrics. This document describes extensions to IS-IS Traffic Engineering Extensions (RFC5305) such that network performance information can be distributed and collected in a scalable fashion. The information distributed using ISIS TE Metric Extensions can then be used to make path selection decisions based on network performance. Note that this document only covers the mechanisms with which network performance information is distributed. The mechanisms for measuring network performance or acting on that information, once distributed, are outside the scope of this document. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying RFC-2119 significance. Previdi, et al. Expires October 27, 2014 [Page 1] Internet-Draft IS-IS TE Metric Extensions April 2014 Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on October 27, 2014. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. TE Metric Extensions to IS-IS . . . . . . . . . . . . . . . . 4 3. Interface and Neighbor Addresses . . . . . . . . . . . . . . 5 4. Sub TLV Details . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. Unidirectional Link Delay Sub-TLV . . . . . . . . . . . . 6 4.2. Min/Max Unidirectional Link Delay Sub-TLV . . . . . . . . 7 4.3. Unidirectional Delay Variation Sub-TLV . . . . . . . . . 8 4.4. Unidirectional Link Loss Sub-TLV . . . . . . . . . . . . 9 4.5. Unidirectional Residual Bandwidth Sub-TLV . . . . . . . . 10 4.6. Unidirectional Available Bandwidth Sub-TLV . . . . . . . 11 4.7. Unidirectional Utilized Bandwidth Sub-TLV . . . . . . . . 12 5. Announcement Thresholds and Filters . . . . . . . . . . . . . 13 6. Announcement Suppression . . . . . . . . . . . . . . . . . . 14 7. Network Stability and Announcement Periodicity . . . . . . . 14 Previdi, et al. Expires October 27, 2014 [Page 2] Internet-Draft IS-IS TE Metric Extensions April 2014 8. Enabling and Disabling Sub-TLVs . . . . . . . . . . . . . . . 14 9. Static Metric Override . . . . . . . . . . . . . . . . . . . 14 10. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 15 11. Security Considerations . . . . . . . . . . . . . . . . . . . 15 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 14.1. Normative References . . . . . . . . . . . . . . . . . . 15 14.2. Informative References . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction In certain networks, such as, but not limited to, financial information networks (e.g. stock market data providers), network performance information (e.g. latency) is becoming as critical to data path selection as other metrics. In these networks, extremely large amounts of money rest on the ability to access market data in "real time" and to predictably make trades faster than the competition. Because of this, using metrics such as hop count or cost as routing metrics is becoming only tangentially important. Rather, it would be beneficial to be able to make path selection decisions based on performance data (such as latency) in a cost-effective and scalable way. This document describes extensions to IS-IS Extended Reachability TLV defined in [RFC5305] (hereafter called "IS-IS TE Metric Extensions"), that can be used to distribute network performance information (such as link delay, delay variation, packet loss, residual bandwidth, and available bandwidth). The data distributed by the TE Metric Extensions proposed in this document is meant to be used as part of the operation of the routing protocol (e.g. by replacing cost with latency or considering bandwidth as well as cost), by enhancing Constrained-SPF (CSPF), or for other uses such as supplementing the data used by an ALTO server [I-D.ietf-alto-protocol]. With respect to CSPF, the data distributed by ISIS TE Metric Extensions can be used to setup, fail over, and fail back data paths using protocols such as RSVP-TE [RFC3209]; [I-D.atlas-mpls-te-express-path] describes some methods for using this information to compute Label Switched Paths (LSPs) at the LSP ingress. Note that the mechanisms described in this document only disseminate performance information. The methods for initially gathering that performance information, such as [RFC6375], or acting on it once it is distributed are outside the scope of this document. Example Previdi, et al. Expires October 27, 2014 [Page 3] Internet-Draft IS-IS TE Metric Extensions April 2014 mechanisms to measure latency, delay variation, and loss in an MPLS network are given in [RFC6374]. While this document does not specify how the performance information should be obtained, the measurement of delay SHOULD NOT vary significantly based upon the offered traffic load. Thus, queuing delays SHOULD NOT be included in the delay measurement. For links, such as Forwarding Adjacencies, care must be taken that measurement of the associated delay avoids significant queuing delay; that could be accomplished in a variety of ways, including either by measuring with a traffic class that experiences minimal queuing or by summing the measured link delays of the components of the link's path. 2. TE Metric Extensions to IS-IS This document proposes new IS-IS TE sub-TLVs that can be announced in ISIS Extended Reachability TLV (TLV-22) to distribute network performance information. The extensions in this document build on the ones provided in IS-IS TE [RFC5305] and GMPLS [RFC4203]. IS-IS Extended Reachability TLV 22 (defined in [RFC5305]), Inter-AS reachability information TLV 141 (defined in [RFC5316]) and MT-ISN TLV 222 (defined in [RFC5120]) have nested sub-TLVs which permit the TLVs to be readily extended. This document proposes several additional sub-TLVs: Type Value ----------------------------------------------- TBA Unidirectional Link Delay TBA Low/High Unidirectional Link Delay TBA Unidirectional Delay Variation TBA Unidirectional Packet Loss TBA Unidirectional Residual Bandwidth TBA Unidirectional Available Bandwidth TBA Unidirectional Bandwidth Utilization As can be seen in the list above, the sub-TLVs described in this document carry different types of network performance information. The new sub-TLVs include a bit called the Anomalous (or "A") bit. When the A bit is clear (or when the sub-TLV does not include an A bit), the sub-TLV describes steady state link performance. This information could conceivably be used to construct a steady state Previdi, et al. Expires October 27, 2014 [Page 4] Internet-Draft IS-IS TE Metric Extensions April 2014 performance topology for initial tunnel path computation, or to verify alternative failover paths. When network performance violates configurable link-local thresholds a sub-TLV with the A bit set is advertised. These sub-TLVs could be used by the receiving node to determine whether to fail traffic to a backup path, or whether to calculate an entirely new path. From an MPLS perspective, the intent of the A bit is to permit LSP ingress nodes to: A) Determine whether the link referenced in the sub-TLV affects any of the LSPs for which it is ingress. If there are, then: B) Determine whether those LSPs still meet end-to-end performance objectives. If not, then: C) The node could then conceivably move affected traffic to a pre- established protection LSP or establish a new LSP and place the traffic in it. If link performance then improves beyond a configurable minimum value (reuse threshold), that sub-TLV can be re-advertised with the Anomalous bit cleared. In this case, a receiving node can conceivably do whatever re-optimization (or failback) it wishes to do (including nothing). Note that when a sub-TLV does not include the A bit, that sub-TLV cannot be used for failover purposes. The A bit was intentionally omitted from some sub-TLVs to help mitigate oscillations. See Section 5 for more information. Consistent with existing IS-IS TE specifications [RFC5305], the bandwidth advertisements defined in this draft MUST be encoded as IEEE floating point values. The delay and delay variation advertisements defined in this draft MUST be encoded as integer values. Delay values MUST be quantified in units of microseconds, packet loss MUST be quantified as a percentage of packets sent, and bandwidth MUST be sent as bytes per second. All values (except residual bandwidth) MUST be calculated as rolling averages where the averaging period MUST be a configurable period of time. See Section 5 for more information. 3. Interface and Neighbor Addresses The use of TE Metric Extensions SubTLVs is not confined to the TE context. In other words, IS-IS TE Metric Extensions SubTLVs defined in this document can also be used for computing paths in the absence of a TE subsystem. Previdi, et al. Expires October 27, 2014 [Page 5] Internet-Draft IS-IS TE Metric Extensions April 2014 However, as for the TE case, Interface Address and Neighbor Address SubTLVs (IPv4 or IPv6) MUST be present. The encoding is defined in [RFC5305] for IPv4 and in [RFC6119] for IPv6. 4. Sub TLV Details 4.1. Unidirectional Link Delay Sub-TLV This sub-TLV advertises the average link delay between two directly connected IS-IS neighbors. The delay advertised by this sub-TLV MUST be the delay from the local neighbor to the remote one (i.e. the forward path latency). The format of this sub-TLV is shown in the following diagram: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| RESERVED | Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 1 Type: TBA Length: 4 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. Delay. This 24-bit field carries the average link delay over a configurable interval in micro-seconds, encoded as an integer value. When set to the maximum value 16,777,215 (16.777215 sec), then the delay is at least that value and may be larger. If there is no value to send (unmeasured and not statically specified), then the sub-TLV should not be sent or be withdrawn. Previdi, et al. Expires October 27, 2014 [Page 6] Internet-Draft IS-IS TE Metric Extensions April 2014 4.2. Min/Max Unidirectional Link Delay Sub-TLV This sub-TLV advertises the minimum and maximum delay values between two directly connected IS-IS neighbors. The delay advertised by this sub-TLV MUST be the delay from the local neighbor to the remote one (i.e. the forward path latency). The format of this sub-TLV is shown in the following diagram: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| RESERVED | Low Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESERVED | High Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 2 Type: TBA Length: 8 A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. Low Delay. This 24-bit field carries minimum measured link delay value (in microseconds) over a configurable interval, encoded as an integer value. High Delay. This 24-bit field carries the maximum measured link delay value (in microseconds) over a configurable interval, encoded as an integer value. Implementations MAY also permit the configuration of a static (non dynamic) offset value (in microseconds) to be added to the measured delay value, to facilitate the communication of operator specific delay constraints. Previdi, et al. Expires October 27, 2014 [Page 7] Internet-Draft IS-IS TE Metric Extensions April 2014 It is possible for the high delay and low delay to be the same value. When the delay value (Low or High) is set to maximum value 16,777,215 (16.777215 sec), then the delay is at least that value and may be larger. 4.3. Unidirectional Delay Variation Sub-TLV This sub-TLV advertises the average link delay variation between two directly connected IS-IS neighbors. The delay variation advertised by this sub-TLV MUST be the delay from the local neighbor to the remote one (i.e. the forward path latency). The format of this sub- TLV is shown in the following diagram: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| RESERVED | Delay Variation | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 3 Type: TBA. Lenght: 4. A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. Delay Variation. This 24-bit field carries the average link delay variation over a configurable interval in micro-seconds, encoded as an integer value. When set to 0, it has not been measured. When set to the maximum value 16,777,215 (16.777215 sec), then the delay is at least that value and may be larger. Previdi, et al. Expires October 27, 2014 [Page 8] Internet-Draft IS-IS TE Metric Extensions April 2014 4.4. Unidirectional Link Loss Sub-TLV This sub-TLV advertises the loss (as a packet percentage) between two directly connected IS-IS neighbors. The link loss advertised by this sub-TLV MUST be the packet loss from the local neighbor to the remote one (i.e. the forward path loss). The format of this sub-TLV is shown in the following diagram: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| RESERVED | Link Loss | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ This sub-TLV has a type of TBD3. The length is 4. where: Type: TBA. Length: 4. A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. Link Loss. This 24-bit field carries link packet loss as a percentage of the total traffic sent over a configurable interval. The basic unit is 0.000003%, where (2^24 - 2) is 50.331642%. This value is the highest packet loss percentage that can be expressed (the assumption being that precision is more important on high speed links than the ability to advertise loss rates greater than this, and that high speed links with over 50% loss are unusable). Therefore, measured values that are larger than the field maximum SHOULD be Previdi, et al. Expires October 27, 2014 [Page 9] Internet-Draft IS-IS TE Metric Extensions April 2014 encoded as the maximum value. When set to a value of all 1s (2^24 - 1), the link packet loss has not been measured. 4.5. Unidirectional Residual Bandwidth Sub-TLV This TLV advertises the residual bandwidth between two directly connected IS-IS neighbors. The residual bandwidth advertised by this sub-TLV MUST be the residual bandwidth from the system originating the LSA to its neighbor. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length |A| RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Residual Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Type: TBA. Length: 4. A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. Residual Bandwidth. This field carries the residual bandwidth on a link, forwarding adjacency [RFC4206], or bundled link in IEEE floating point format with units of bytes per second. For a link or forwarding adjacency, residual bandwidth is defined to be Maximum Bandwidth [RFC3630] minus the bandwidth currently allocated to RSVP- TE LSPs. For a bundled link, residual bandwidth is defined to be the sum of the component link residual bandwidths. The calculation of Residual Bandwidth is different than that of Unreserved Bandwidth [RFC3630]. Residual Bandwidth subtracts tunnel reservations from Maximum Bandwidth (i.e. the link capacity) [RFC3630] and provides an aggregated remainder across QoS classes. Unreserved Bandwidth [RFC3630], on the other hand, is subtracted from the Maximum Reservable Bandwidth (the bandwidth that can theoretically be reserved) [RFC3630] and provides per-QoS-class Previdi, et al. Expires October 27, 2014 [Page 10] Internet-Draft IS-IS TE Metric Extensions April 2014 remainders. Residual Bandwidth and Unreserved Bandwidth [RFC3630] can be used concurrently, and each has a separate use case (e.g. the former can be used for applications like Weighted ECMP while the latter can be used for call admission control). 4.6. Unidirectional Available Bandwidth Sub-TLV This Sub-TLV advertises the available bandwidth between two directly connected IS-IS neighbors. The available bandwidth advertised by this sub-TLV MUST be the available bandwidth from the system originating this Sub-TLV. The format of this Sub-TLV is shown in the following diagram: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length |A| RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Available Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 4 Type: TBA. Length: 4. A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. Available Bandwidth. This field carries the available bandwidth on a link, forwarding adjacency, or bundled link in IEEE floating point format with units of bytes per second. For a link or forwarding adjacency, available bandwidth is defined to be residual bandwidth minus the measured bandwidth used for the actual forwarding of non- RSVP-TE LSP packets. For a bundled link, available bandwidth is defined to be the sum of the component link available bandwidths minus the measured bandwidth used for the actual forwarding of non- RSVP-TE Label Switched Paths packets. For a bundled link, available Previdi, et al. Expires October 27, 2014 [Page 11] Internet-Draft IS-IS TE Metric Extensions April 2014 bandwidth is defined to be the sum of the component link available bandwidths. 4.7. Unidirectional Utilized Bandwidth Sub-TLV This Sub-TLV advertises the bandwidth utilization between two directly connected IS-IS neighbors. The bandwidth utilization advertised by this sub-TLV MUST be the bandwidth from the system originating this Sub-TLV. The format of this Sub-TLV is shown in the following diagram: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length |A| RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bandwidth Utilization | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 5 Type: TBA. Length: 4. A-bit. The A-bit represents the Anomalous (A) bit. The A-bit is set when the measured value of this parameter exceeds its configured maximum threshold. The A bit is cleared when the measured value falls below its configured reuse threshold. If the A-bit is clear, the sub-TLV represents steady state link performance. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. Bandwidth Utilization. This field carries the bandwidth utilization on a link, forwarding adjacency, or bundled link in IEEE floating point format with units of bytes per second. For a link or forwarding adjacency, bandwidth utilization represent the actual utilization of the link (i.e.: as measured in the router). For a bundled link, bandwidth utilization is defined to be the sum of the component link bandwidth utilization. Previdi, et al. Expires October 27, 2014 [Page 12] Internet-Draft IS-IS TE Metric Extensions April 2014 5. Announcement Thresholds and Filters The values advertised in all sub-TLVs (except Low/High delay and residual bandwidth) MUST represent an average over a period or be obtained by a filter that is reasonably representative of an average. For example, a rolling average is one such filter. Low or High delay MAY be the lowest and/or highest measured value over a measurement interval or MAY make use of a filter, or other technique to obtain a reasonable representation of a low and high value representative of the interval with compensation for outliers. The measurement interval, any filter coefficients, and any advertisement intervals MUST be configurable per sub-TLV. In addition to the measurement intervals governing re-advertisement, implementations SHOULD provide per sub-TLV configurable accelerated advertisement thresholds, such that: 1. If the measured parameter falls outside a configured upper bound for all but the low delay metric (or lower bound for low-delay metric only) and the advertised sub-TLV is not already outside that bound or, 2. If the difference between the last advertised value and current measured value exceed a configured threshold then, 3. The advertisement is made immediately. 4. For sub-TLVs which include an A-bit (except low/high delay), an additional threshold SHOULD be included corresponding to the threshold for which the performance is considered anomalous (and sub-TLVs with the A-bit are sent). The A-bit is cleared when the sub-TLV's performance has been below (or re-crosses) this threshold for an advertisement interval(s) to permit fail back. To prevent oscillations, only the high threshold or the low threshold (but not both) may be used to trigger any given sub-TLV that supports both. Additionally, once outside of the bounds of the threshold, any readvertisement of a measurement within the bounds would remain governed solely by the measurement interval for that sub-TLV. Previdi, et al. Expires October 27, 2014 [Page 13] Internet-Draft IS-IS TE Metric Extensions April 2014 6. Announcement Suppression When link performance values change by small amounts that fall under thresholds that would cause the announcement of a sub-TLV, implementations SHOULD suppress sub-TLV readvertisement and/or lengthen the period within which they are refreshed. Only the accelerated advertisement threshold mechanism may shorten the re-advertisement interval. All suppression and re-advertisement interval backoff timer features SHOULD be configurable. 7. Network Stability and Announcement Periodicity Section 5 and Section 6 provide configurable mechanisms to bound the number of re-advertisements. Instability might occur in very large networks if measurement intervals are set low enough to overwhelm the processing of flooded information at some of the routers in the topology. Therefore care SHOULD be taken in setting these values. Additionally, the default measurement interval for all sub-TLVs SHOULD be 30 seconds. Announcements MUST also be able to be throttled using configurable inter-update throttle timers. The minimum announcement periodicity is 1 announcement per second. The default value SHOULD be set to 120 seconds. Implementations SHOULD NOT permit the inter-update timer to be lower than the measurement interval. Furthermore, it is RECOMMENDED that any underlying performance measurement mechanisms not include any significant buffer delay, any significant buffer induced delay variation, or any significant loss due to buffer overflow or due to active queue management. 8. Enabling and Disabling Sub-TLVs Implementations MUST make it possible to individually enable or disable each sub-TLV based on configuration. 9. Static Metric Override Implementations SHOULD permit the static configuration and/or manual override of dynamic measurements data on a per sub-TLV, per metric basis in order to simplify migrations and to mitigate scenarios where measurements are not possible across an entire network. Previdi, et al. Expires October 27, 2014 [Page 14] Internet-Draft IS-IS TE Metric Extensions April 2014 10. Compatibility As per [RFC5305], unrecognized Sub-TLVs should be silently ignored 11. Security Considerations This document does not introduce security issues beyond those discussed in [RFC3630] and [RFC5329]. 12. IANA Considerations IANA maintains the registry for the sub-TLVs. IS-IS TE Metric Extensions will require one new type code per sub-TLV defined in this document. 13. Acknowledgements The authors would like to recognize Ayman Soliman, Nabil Bitar, David McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk and Hannes Gredler for their contributions. The authors also recognize Curtis Villamizar for significant comments and direct content collaboration. 14. References 14.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. Previdi, et al. Expires October 27, 2014 [Page 15] Internet-Draft IS-IS TE Metric Extensions April 2014 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, February 2008. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, October 2008. [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5316, December 2008. [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, "Traffic Engineering Extensions to OSPF Version 3", RFC 5329, September 2008. [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic Engineering in IS-IS", RFC 6119, February 2011. [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay Measurement for MPLS Networks", RFC 6374, September 2011. 14.2. Informative References [I-D.atlas-mpls-te-express-path] Atlas, A., Drake, J., Giacalone, S., Ward, D., Previdi, S., and C. Filsfils, "Performance-based Path Selection for Explicitly Routed LSPs using TE Metric Extensions", draft- atlas-mpls-te-express-path-04 (work in progress), September 2013. [I-D.ietf-alto-protocol] Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol", draft- ietf-alto-protocol-27 (work in progress), March 2014. [RFC6375] Frost, D. and S. Bryant, "A Packet Loss and Delay Measurement Profile for MPLS-Based Transport Networks", RFC 6375, September 2011. Authors' Addresses Stefano Previdi (editor) Cisco Systems, Inc. Via Del Serafico 200 Rome 00191 IT Email: sprevidi@cisco.com Previdi, et al. Expires October 27, 2014 [Page 16] Internet-Draft IS-IS TE Metric Extensions April 2014 Spencer Giacalone Thomson Reuters 195 Broadway New York, NY 10007 USA Email: Spencer.giacalone@thomsonreuters.com Dave Ward Cisco Systems, Inc. 3700 Cisco Way SAN JOSE, CA 95134 US Email: wardd@cisco.com John Drake Juniper Networks 1194 N. Mathilda Ave. Sunnyvale, CA 94089 USA Email: jdrake@juniper.net Alia Atlas Juniper Networks 1194 N. Mathilda Ave. Sunnyvale, CA 94089 USA Email: akatlas@juniper.net Clarence Filsfils Cisco Systems, Inc. Brussels Belgium Email: cfilsfil@cisco.com Previdi, et al. Expires October 27, 2014 [Page 17] Internet-Draft IS-IS TE Metric Extensions April 2014 Qin Wu Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: sunseawq@huawei.com Previdi, et al. Expires October 27, 2014 [Page 18]