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Versions: 00 01 02 03 draft-ietf-isis-te-metric-extensions

Network Working Group                                        S. Previdi
Internet Draft                                            Cisco Systems
Intended status: Proposed Standard
Expires: April 2012                                        S. Giacalone
                                                        Thomson Reuters

                                                                D. Ward
                                                       Juniper Networks

                                                               J. Drake
                                                       Juniper Networks

                                                               A. Atlas
                                                       Juniper Networks

                                                             C.Filsfils
                                                          Cisco Systems

                                                       October 10, 2011


             IS-IS Traffic Engineering (TE) Metric Extensions
              draft-previdi-isis-te-metric-extensions-00.txt




   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 TE [RFC5305] such that
   network performance information can be distributed and collected in a
   scalable fashion. The information distributed using ISIS TE Express
   Path 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.







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Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on April 10, 2011.



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   described in the Simplified BSD License.



Table of Contents




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   1. Introduction...................................................3
   2. Conventions used in this document..............................4
   3. Express Path Extensions to IS-IS TE............................4
   4. Sub TLV Details................................................6
      4.1. Unidirectional Link Delay Sub-TLV.........................6
      4.2. Unidirectional Delay Variation Sub-TLV....................6
      4.3. Unidirectional Link Loss Sub-TLV..........................7
      4.4. Unidirectional Residual Bandwidth Sub-TLV.................8
      4.5. Unidirectional Available Bandwidth Sub-TLV................9
   5. Announcement Thresholds and Filters...........................10
   6. Announcement Suppression......................................11
   7. Network Stability and Announcement Periodicity................11
   8. Compatibility.................................................11
   9. Security Considerations.......................................11
   10. IANA Considerations..........................................11
   11. References...................................................12
      11.1. Normative References....................................12
      11.2. Informative References..................................12
   12. Acknowledgments..............................................12
   13. Author's Addresses...........................................12



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
   [RFC5305](hereafter called "IS-IS TE Express Path"), 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 IS-IS TE Express Path 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


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   CSPF, or for other uses such as supplementing the data used by an
   Alto server [Alto]. With respect to CSPF, the data distributed by IS-
   IS TE Express Path 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 [Frost], or acting on it once it is
   distributed are outside the scope of this document.



2. Conventions used in this document

   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.



3. Express Path Extensions to IS-IS TE

   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 (TLV-22) defined in [RFC5305] has
   nested sub-TLVs which permit the ISIS Reachability TLV to be readily
   extended. This document proposes several additional sub-TLVs:

   Type  Length   Value

   TBD1  6        Unidirectional Link Delay

   TBD2  6        Unidirectional Delay Variation

   TBD3  6        Unidirectional Packet Loss

   TBD4  6        Unidirectional Residual Bandwidth Sub TLV

   TBD5  6        Unidirectional Available Bandwidth Sub TLV



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   As can be seen in the list above, the sub-TLVs described in this
   document carry different types of network performance information.
   Many (but not all) of the 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.

   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.


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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           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  RESERVED   |                       Delay                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV has a type of TBD1.
   The length is 6.
   Where:

   "A" 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.

   The "Reserved" field is reserved for future use. It MUST be set to 0
   when sent and MUST be ignored when received.

   "Delay Value" is a 24-bit field carries the average link delay 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.



4.2. 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



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   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        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   RESERVED  |              Delay Variation                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This sub-TLV has a type of TBD2.
   The length is 6.

   Where:

   "A" 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 The "Reserved" field is
   reserved for future use. It MUST be set to 0 when sent and MUST be
   ignored when received.

   "Delay Variation" is a 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.









4.3. 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:



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   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          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  RESERVED   |                 Link Loss                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This sub-TLV has a type of TBD3.
   The length is 6.

   Where:

   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" field is reserved for future use. It MUST be set to 0 when
   sent and MUST be ignored when received.

   "Link Loss" is a 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.  When set to a value of all 1s (2^24 -
   1), the link packet loss has not been measured.



4.4. Unidirectional Residual Bandwidth Sub-TLV

   This TLV advertises the residual bandwidth (defined in section Error!
   Reference source not found.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 sub-TLV to its
   neighbor.

   The format of this sub-TLV is shown in the following diagram:




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    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                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This sub-TLV has a type of TBD4.
   The length is 6.

   "Reserved" field is reserved for future use. It MUST be set to 0 when
   sent and MUST be ignored when received.

   "Residual Bandwidth" is a 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
   Link 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.

   Note that although it may seem possible to calculate Residual
   Bandwidth using the existing sub-TLVs in RFC 5305, this is not a
   consistently reliable approach and hence the Residual Bandwidth sub-
   TLV has been added here. For example, because the Maximum Reservable
   Bandwidth [RFC5305] can be larger than the capacity of the link,
   using it as part of an algorithm to determine the value of the
   Maximum Link Bandwidth [RFC5305] minus the bandwidth currently
   allocated to RSVP-TE Label Switched Paths cannot be considered
   reliably accurate.







4.5. Unidirectional Available Bandwidth Sub-TLV

   This TLV advertises the available bandwidth (defined in section
   Error! Reference source not found.between two directly connected IS-
   IS neighbors. The available bandwidth advertised by this sub-TLV MUST
   be the available bandwidth from the system originating the Sub-TLV to



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   its neighbor. 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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Available Bandwidth                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This sub-TLV has a type of TBD5.
   The length is 6.

   Where:

   "Reserved" field is reserved for future use. It MUST be set to 0 when
   sent and MUST be ignored when received.

   "Available Bandwidth" is a field that 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 4.4. 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.



5. Announcement Thresholds and Filters

   The values advertised in all sub-TLVs MUST be controlled using an
   exponential filter (i.e. a rolling average) with a configurable
   measurement interval and filter coefficient.

   Implementations are expected to provide separately configurable
   advertisement thresholds. All thresholds MUST be configurable on a
   per sub-TLV basis.

   The announcement of all sub-TLVs that do not include the A bit SHOULD
   be controlled by variation thresholds that govern when they are sent.

   Sub-TLV that include the A bit are governed by several thresholds.
   Firstly, a threshold SHOULD be implemented to govern the announcement


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   of sub-TLVs that advertise a change in performance, but not an SLA
   violation (i.e. when the A bit is not set). Secondly, implementations
   MUST provide configurable thresholds that govern the announcement of
   sub-TLVs with the A bit set (for the indication of a performance
   violation).  Thirdly, implementations SHOULD provide reuse
   thresholds. These thresholds govern sub-TLV re-announcement with the
   A bit cleared to permit fail back.



6. Announcement Suppression

   When link performance average values change, but fall under the
   threshold that would cause the announcement of a sub-TLV with the A
   bit set, implementations MAY suppress or throttle sub-TLV
   announcements. All suppression features and thresholds SHOULD be
   configurable.

7. Network Stability and Announcement Periodicity

   To mitigate concerns about stability, all values (except residual
   bandwidth) MUST be calculated as rolling averages where the averaging
   period MUST be a configurable period of time, rather than
   instantaneous measurements.

   Announcements MUST also be able to be throttled using configurable
   inter-update throttle timers. The minimum announcement periodicity is
   1 announcement per second.



8. Compatibility

   As per (RFC5305), unrecognized TLVs should be silently ignored



9. Security Considerations

   This document does not introduce security issues beyond those
   discussed in [RFC3630] and [RFC5329].








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10. IANA Considerations

   IANA maintains the registry for the sub-TLVs. IS-IS TE Express Path
   will require one new type code per sub-TLV defined in this document.



11. References



11.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5305] Li, T., Smit, H., "IS-IS Extensions for Traffic
             Engineering", RFC 3630, September 2003.



11.2. Informative References

   [RFC3031] Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol
             Label Switching Architecture", January 2001

   [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.

   [Frost]   D. Frost, S. Bryant"A Packet Loss and Delay Measurement
             Profile for MPLS-based Transport Networks"

   [Alto]    R. Alimi R. Penno Y. Yang, "ALTO Protocol"



12. Acknowledgments

   The authors would like to recognize Ayman Soliman and Les Ginsberg
   for their contributions.


   This document was prepared using 2-Word-v2.0.template.dot.





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13. Author's Addresses

   Stefano Previdi
   Cisco Systems
   Via Del Serafico 200
   00142 Rome
   Italy

   Email: sprevidi@cisco.com


   Spencer Giacalone
   Thomson Reuters
   195 Broadway
   New York NY 10007, USA

   Email: Spencer.giacalone@thomsonreuters.com


   Dave Ward
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089, USA

   Email: dward@juniper.net


   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


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   Cisco Systems
   Brussels, Belgium

   Email: cfilsfil@cisco.com













































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