IS-IS Traffic Engineering (TE) Metric Extensions
draft-ietf-isis-te-metric-extensions-09
The information below is for an old version of the document.
Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7810.
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Authors | Stefano Previdi , Spencer Giacalone , David Ward , John Drake , Qin Wu | ||
Last updated | 2016-02-04 (Latest revision 2016-01-20) | ||
Replaces | draft-previdi-isis-te-metric-extensions | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Formats | |||
Reviews | |||
Additional resources | Mailing list discussion | ||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Hannes Gredler | ||
Shepherd write-up | Show Last changed 2015-12-11 | ||
IESG | IESG state | Became RFC 7810 (Proposed Standard) | |
Consensus boilerplate | Yes | ||
Telechat date |
(None)
Needs a YES. Needs 10 more YES or NO OBJECTION positions to pass. |
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Responsible AD | Alvaro Retana | ||
Send notices to | "Hannes Gredler" <hannes@gredler.at>, aretana@cisco.com | ||
IANA | IANA review state | IANA OK - Actions Needed |
draft-ietf-isis-te-metric-extensions-09
Networking Working Group S. Previdi, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track S. Giacalone Expires: July 23, 2016 Unaffiliated D. Ward Cisco Systems, Inc. J. Drake Juniper Networks Q. Wu Huawei January 20, 2016 IS-IS Traffic Engineering (TE) Metric Extensions draft-ietf-isis-te-metric-extensions-09 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 IS-IS 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 July 23, 2016 [Page 1] Internet-Draft IS-IS TE Metric Extensions January 2016 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 July 23, 2016. Copyright Notice Copyright (c) 2016 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 . . . . . . . . . . . . 8 4.5. Unidirectional Residual Bandwidth Sub-TLV . . . . . . . . 9 4.6. Unidirectional Available Bandwidth Sub-TLV . . . . . . . 10 4.7. Unidirectional Utilized Bandwidth Sub-TLV . . . . . . . . 11 5. Announcement Thresholds and Filters . . . . . . . . . . . . . 12 6. Announcement Suppression . . . . . . . . . . . . . . . . . . 13 7. Network Stability and Announcement Periodicity . . . . . . . 13 Previdi, et al. Expires July 23, 2016 [Page 2] Internet-Draft IS-IS TE Metric Extensions January 2016 8. Enabling and Disabling Sub-TLVs . . . . . . . . . . . . . . . 14 9. Static Metric Override . . . . . . . . . . . . . . . . . . . 14 10. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 14 11. Security Considerations . . . . . . . . . . . . . . . . . . . 14 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 15.1. Normative References . . . . . . . . . . . . . . . . . . 16 15.2. Informative References . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 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 (hereafter called "IS-IS TE Metric Extensions") to IS-IS Extended Reachability TLV defined in [RFC5305], 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 IS-IS 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 [RFC7285]. With respect to CSPF, the data distributed by IS-IS TE Metric Extensions can be used to setup, fail over, and fail back data paths using protocols such as RSVP-TE [RFC3209]. 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 mechanisms to measure latency, delay variation, and loss in an MPLS network are given in [RFC6374]. While this document does not specify Previdi, et al. Expires July 23, 2016 [Page 3] Internet-Draft IS-IS TE Metric Extensions January 2016 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 TLVs 22, 141, 222, and 223 in order 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-ISIS 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 ---------------------------------------------------- 33 (Suggested) Unidirectional Link Delay 34 (Suggested) Min/Max Unidirectional Link Delay 35 (Suggested) Unidirectional Delay Variation 36 (Suggested) Unidirectional Packet Loss 37 (Suggested) Unidirectional Residual Bandwidth 38 (Suggested) Unidirectional Available Bandwidth 39 (Suggested) 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 performance topology for initial tunnel path computation, or to verify alternative failover paths. Previdi, et al. Expires July 23, 2016 [Page 4] Internet-Draft IS-IS TE Metric Extensions January 2016 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 specification [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 IS-IS TE Metric Extensions sub-TLVs is not confined to the TE context. In other words, IS-IS TE Metric Extensions sub-TLVs defined in this document can also be used for computing paths in the absence of a TE subsystem. Previdi, et al. Expires July 23, 2016 [Page 5] Internet-Draft IS-IS TE Metric Extensions January 2016 However, as for the TE case, Interface Address and Neighbor Address sub-TLVs (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 (suggested value: 33). 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. Previdi, et al. Expires July 23, 2016 [Page 6] Internet-Draft IS-IS TE Metric Extensions January 2016 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 | Min Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESERVED | Max Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 2 Type: TBA (suggested value: 34). 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. Min Delay. This 24-bit field carries minimum measured link delay value (in microseconds) over a configurable interval, encoded as an integer value. Max 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 an offset value (in microseconds) to be added to the measured delay value, to facilitate the communication of operator specific delay constraints. It is possible for the Min and Max delay to be the same value. Previdi, et al. Expires July 23, 2016 [Page 7] Internet-Draft IS-IS TE Metric Extensions January 2016 When the delay value (Min or Max) 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESERVED | Delay Variation | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 3 Type: TBA (suggested value: 35). Length: 4. 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 microseconds, 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. 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: Previdi, et al. Expires July 23, 2016 [Page 8] Internet-Draft IS-IS TE Metric Extensions January 2016 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 (suggested value: 36). 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. 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 encoded as the maximum value. 4.5. Unidirectional Residual Bandwidth Sub-TLV This sub-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. Previdi, et al. Expires July 23, 2016 [Page 9] Internet-Draft IS-IS TE Metric Extensions January 2016 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 | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Residual Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Type: TBA (suggested value: 37). Length: 4. 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 [RFC5305] 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 [RFC5305]. Residual Bandwidth subtracts tunnel reservations from Maximum Bandwidth (i.e. the link capacity) [RFC5305] and provides an aggregated remainder across priorities. Unreserved Bandwidth, on the other hand, is subtracted from the Maximum Reservable Bandwidth (the bandwidth that can theoretically be reserved) and provides per priority remainders. Residual Bandwidth and Unreserved Bandwidth [RFC5305] 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: Previdi, et al. Expires July 23, 2016 [Page 10] Internet-Draft IS-IS TE Metric Extensions January 2016 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 | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Available Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 4 Type: TBA (suggested value: 38). Length: 4. 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 (see Section 4.5 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 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: Previdi, et al. Expires July 23, 2016 [Page 11] Internet-Draft IS-IS TE Metric Extensions January 2016 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 | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Utilized Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Figure 5 Type: TBA (suggested value: 39). Length: 4. RESERVED. This field is reserved for future use. It MUST be set to 0 when sent and MUST be ignored when received. 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 represents the actual utilization of the link (i.e., as measured by the advertising node). For a bundled link, bandwidth utilization is defined to be the sum of the component link bandwidth utilizations. 5. Announcement Thresholds and Filters The values advertised in all sub-TLVs (except Min/Max 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. Min and max 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 min and max 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: Previdi, et al. Expires July 23, 2016 [Page 12] Internet-Draft IS-IS TE Metric Extensions January 2016 1. If the measured parameter falls outside a configured upper bound for all but the min delay metric (or lower bound for min 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 min/max 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. 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 described in Section 5 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. Previdi, et al. Expires July 23, 2016 [Page 13] Internet-Draft IS-IS TE Metric Extensions January 2016 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 for each sub-TLV in order to simplify migration and to mitigate scenarios where dynamic measurements are not possible. 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 [RFC5305]. Section 7 describe a mechanism in order to ensure network stability when the new sub-TLVs defined in this document are advertised. Implementation SHOULD follow the described guidelines in order to mitigate the instability risk. [RFC5304] describes an authentication method for IS-IS LSP that allows cryptographic authentication of IS-IS LSPs. It is anticipated that in most deployments, IS-IS protocol is used within an infrastructure entirely under control of the dame operator. However, it is worth to consider that the effect of sending IS-IS Traffic Engineering sub-TLVs over insecure links could result in a man-in-the-middle attacker delaying real time data to a given site (or destination), which could negatively affect the value of the data Previdi, et al. Expires July 23, 2016 [Page 14] Internet-Draft IS-IS TE Metric Extensions January 2016 for that site/destination. The use of LSP cryptographic authentication allows to mitigate the risk of man-in-the-middle attack. 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 in the following sub-TLV registry: TLVs 22, 23, 141, 222, and 223: Type Value ---------------------------------------------------- 33 (Suggested) Unidirectional Link Delay 34 (Suggested) Min/Max Unidirectional Link Delay 35 (Suggested) Unidirectional Delay Variation 36 (Suggested) Unidirectional Packet Loss 37 (Suggested) Unidirectional Residual Bandwidth 38 (Suggested) Unidirectional Available Bandwidth 39 (Suggested) Unidirectional Bandwidth Utilization 13. Contributors The following people gave a substantial contribution to the content of this document and should be considered as co-authors: Alia Atlas Juniper Networks US akatlas@juniper.net Clarence Filsfils Cisco Systems Inc. Belgium Email: cfilsfil@cisco.com Previdi, et al. Expires July 23, 2016 [Page 15] Internet-Draft IS-IS TE Metric Extensions January 2016 14. Acknowledgements The authors would like to recognize Ayman Soliman, Nabil Bitar, David McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk, Hannes Gredler, Uma Chunduri, Alvaro Retana and Brian Weis for their contribution and review of this document. The authors also recognize Curtis Villamizar for significant comments and direct content collaboration. 15. References 15.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)", RFC 4206, DOI 10.17487/RFC4206, October 2005, <http://www.rfc-editor.org/info/rfc4206>. [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, <http://www.rfc-editor.org/info/rfc5120>. [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008, <http://www.rfc-editor.org/info/rfc5304>. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, <http://www.rfc-editor.org/info/rfc5305>. [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, December 2008, <http://www.rfc-editor.org/info/rfc5316>. [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, February 2011, <http://www.rfc-editor.org/info/rfc6119>. Previdi, et al. Expires July 23, 2016 [Page 16] Internet-Draft IS-IS TE Metric Extensions January 2016 15.2. Informative References [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, <http://www.rfc-editor.org/info/rfc3209>. [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, <http://www.rfc-editor.org/info/rfc4203>. [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay Measurement for MPLS Networks", RFC 6374, DOI 10.17487/RFC6374, September 2011, <http://www.rfc-editor.org/info/rfc6374>. [RFC6375] Frost, D., Ed. and S. Bryant, Ed., "A Packet Loss and Delay Measurement Profile for MPLS-Based Transport Networks", RFC 6375, DOI 10.17487/RFC6375, September 2011, <http://www.rfc-editor.org/info/rfc6375>. [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., Previdi, S., Roome, W., Shalunov, S., and R. Woundy, "Application-Layer Traffic Optimization (ALTO) Protocol", RFC 7285, DOI 10.17487/RFC7285, September 2014, <http://www.rfc-editor.org/info/rfc7285>. Authors' Addresses Stefano Previdi (editor) Cisco Systems, Inc. Via Del Serafico 200 Rome 00191 IT Email: sprevidi@cisco.com Spencer Giacalone Unaffiliated Email: spencer.giacalone@gmail.com Previdi, et al. Expires July 23, 2016 [Page 17] Internet-Draft IS-IS TE Metric Extensions January 2016 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 Qin Wu Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: sunseawq@huawei.com Previdi, et al. Expires July 23, 2016 [Page 18]