Requirements for Very Fast Setup of GMPLS Label Switched Paths (LSPs)

Internet Engineering Task Force (IETF)                     A. Malis, Ed.
Request for Comments: 7709                           Huawei Technologies
Category: Informational                                        B. Wilson
ISSN: 2070-1721                           Applied Communication Sciences
                                                                G. Clapp
                                                      AT&T Labs Research
                                                               V. Shukla
                                                  Verizon Communications
                                                           November 2015


 Requirements for Very Fast Setup of GMPLS Label Switched Paths (LSPs)

Abstract

   Establishment and control of Label Switch Paths (LSPs) have become
   mainstream tools of commercial and government network providers.  One
   of the elements of further evolving such networks is scaling their
   performance in terms of LSP bandwidth and traffic loads, LSP
   intensity (e.g., rate of LSP creation, deletion, and modification),
   LSP set up delay, quality-of-service differentiation, and different
   levels of resilience.

   The goal of this document is to present target scaling objectives and
   the related protocol requirements for Generalized Multi-Protocol
   Label Switching (GMPLS).

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7709.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Driving Applications and Their Requirements . . . . . . . . .   5
     4.1.  Key Application Requirements  . . . . . . . . . . . . . .   5
   5.  Requirements for Very Fast Setup of GMPLS LSPs  . . . . . . .   6
     5.1.  Protocol and Procedure Requirements . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Generalized Multi-Protocol Label Switching (GMPLS) [RFC3471]
   [RFC3945] includes an architecture and a set of control-plane
   protocols that can be used to operate data networks ranging from
   packet-switch-capable networks, through those networks that use Time
   Division Multiplexing, to WDM networks.  The Path Computation Element
   (PCE) architecture [RFC4655] defines functional components that can
   be used to compute and suggest appropriate paths in connection-
   oriented traffic-engineered networks.  Additional wavelength switched
   optical networks (WSON) considerations were defined in [RFC6163].

   This document refers to the same general framework and technologies,
   but it adds requirements related to expediting LSP setup under heavy
   connection churn scenarios, while achieving low blocking under an
   overall distributed control plane.  This document focuses on a
   specific problem space -- high-capacity and highly dynamic connection
   request scenarios -- that may require clarification and or extensions
   to current GMPLS protocols and procedures.  In particular, the
   purpose of this document is to address the potential need for
   protocols and procedures that enable expediting the setup of LSPs in
   high-churn scenarios.  Both single-domain and multi-domain network
   scenarios are considered.

   This document focuses on the following two topics: 1) the driving
   applications and main characteristics and requirements of this
   problem space, and 2) the key requirements that may be novel with
   respect to current GMPLS protocols.

   This document presents the objectives and related requirements for
   GMPLS to provide the control for networks operating with such
   performance requirements.  While specific deployment scenarios are
   considered part of the presentation of objectives, the stated
   requirements are aimed at ensuring the control protocols are not the
   limiting factor in achieving a particular network's performance.
   Implementation dependencies are out of scope of this document.

   Other documents may be needed to define how GMPLS protocols meet the
   requirements laid out in this document.  Such future documents may
   define extensions or simply clarify how existing mechanisms may be
   used to address the key requirements of highly dynamic networks.

2.  Background

   The Defense Advanced Research Projects Agency (DARPA) Core Optical
   Networks (CORONET) program [Chiu] is an example target environment
   that includes IP and optical commercial and government networks, with
   a focus on highly dynamic and resilient multi-terabit core networks.

   It anticipates the need for rapid (sub-second) setup and SONET/SDH-
   like restoration times for high-churn (up to tens of requests per
   second network wide and holding times as short as one second) on-
   demand wavelength, sub-wavelength, and packet services for a variety
   of applications (e.g., grid computing, cloud computing, data
   visualization, fast data transfer, etc.).  This must be done while
   meeting stringent call-blocking requirements and while minimizing the
   use of resources such as time slots, switch ports, wavelength
   conversion, etc.

3.  Motivation

   The motivation for this document, and envisioned related future
   documents, is two-fold:

   1.  The anticipated need for rapid setup, while maintaining low
       blocking, of large bandwidth and highly churned on-demand
       connections (in the form of sub-wavelengths, e.g., OTN ODUx, and
       wavelengths, e.g., OTN OCh) for a variety of applications
       including grid computing, cloud computing, data visualization,
       and intra- and inter-datacenter communications.

   2.  The ability to set up circuit-like LSPs for large bandwidth flows
       with low setup delays provides an alternative to packet-based
       solutions implemented over static circuits that may require tying
       up more expensive and power-consuming resources (e.g., router
       ports).  Reducing the LSP setup delay will reduce the minimum
       bandwidth threshold at which a GMPLS circuit approach is
       preferred over a layer 3 (e.g., IP) approach.  Dynamic circuit
       and virtual circuit switching intrinsically provide guaranteed
       bandwidth, guaranteed low-latency and jitter, and faster
       restoration, all of which are very hard to provide in packet-only
       networks.  Again, a key element in achieving these benefits is
       enabling the fastest possible circuit setup times.

   Future applications are expected to require setup times that are as
   fast as 100 ms in highly dynamic, national-scale network environments
   while meeting stringent blocking requirements and minimizing the use
   of resources such as switch ports, wavelength converters/
   regenerators, and other network design parameters.  Of course, the
   benefits of low setup delay diminish for connections with long
   holding times.  For some specific applications, a trade-off may be
   required, as the need for rapid setup may be more important than
   their requirements for other features currently provided in GMPLS
   (e.g., robustness against setup errors).

   With the advent of data centers, cloud computing, video, gaming,
   mobile and other broadband applications, it is anticipated that
   connection request rates may increase, even for connections with
   longer holding times, either during limited time periods (such as
   during the restoration from a data center failure) or over the longer
   term, to the point where the current GMPLS procedures of path
   computation/selection and resource allocation may not be timely, thus
   leading to increased blocking or increased resource cost.  Thus,
   extensions of GMPLS signaling and routing protocols (e.g., OSPF-TE)
   may also be needed to address heavy churn of connection requests
   (i.e., high-connection-request arrival rate) in networks with high-
   traffic loads, even for connections with relatively longer holding
   times.

4.  Driving Applications and Their Requirements

   There are several emerging applications that fall under the problem
   space addressed here in several service areas such as provided by
   telecommunication carriers, government networks, enterprise networks,
   content providers, and cloud providers.  Such applications include
   research and education networks / grid computing, and cloud
   computing.  Detailing and standardizing protocols to address these
   applications will expedite the transition to commercial deployment.

   In the target environment, there are multiple Bandwidth-on-Demand
   service requests per second, such as might arise as cloud services
   proliferate.  It includes dynamic services with connection setup
   requirements that range from seconds to milliseconds.  The aggregate
   traffic demand, which is composed of both packet (IP) and circuit
   (wavelength and sub-wavelength) services, represents a five to
   twenty-fold increase over today's traffic levels for the largest of
   any individual carrier.  Thus, the aggressive requirements must be
   met with solutions that are scalable, cost effective, and power
   efficient, while providing the desired quality of service (QoS).

4.1.  Key Application Requirements

   There are two key performance-scaling requirements in the target
   environment that are the main drivers behind this document:

   1.  Connection request rates ranging from a few requests per second
       for high-capacity (e.g., 40 Gb/s, 100 Gb/s) wavelength-based LSPs
       to around 100 requests per second for sub-wavelength LSPs (e.g.,
       OTN ODU0, ODU1, and ODU2).

   2.  Connection setup delay of around 100 ms across a national or
       regional network.  To meet this target, assuming pipelined cross-
       connection and worst-case propagation delay and hop count, it is
       estimated that the maximum processing delay per hop is around 700
       microseconds [Lehmen].  Optimal path selection and resource
       allocation may require somewhat longer processing (up to 5
       milliseconds) in either the destination or source nodes and
       possibly tighter processing delays (around 500 microseconds) in
       intermediate nodes.

   The model for a national network is that of the continental US with
   up to 100 nodes and LSPs with distances up to ~3000 km and up to 15
   hops.

   A connection setup delay is defined here as the time between the
   arrival of a connection request at an ingress edge switch -- or more
   generally a Label Switch Router (LSR) -- and the time at which
   information can start flowing from that ingress switch over that
   connection.  Note that this definition is more inclusive than the LSP
   setup time defined in [RFC5814] and [RFC6777], which do not include
   PCE path computation delays.

5.  Requirements for Very Fast Setup of GMPLS LSPs

   This section lists the protocol requirements for very fast setup of
   GMPLS LSPs in order to adequately support the service characteristics
   described in the previous sections.  These requirements may be the
   basis for future documents, some of which may be simply
   informational, while others may describe specific GMPLS protocol
   extensions.  While some of these requirements may have implications
   on implementations, the intent is for the requirements to apply to
   GMPLS protocols and their standardized mechanisms.

5.1.  Protocol and Procedure Requirements

   R1  The portion of the LSP establishment time related to protocol
       processing should scale linearly based on the number of traversed
       nodes.

   R2  End-to-end LSP data path availability should be bounded by the
       worst-case single-node data path establishment time.  In other
       words, pipelined cross-connect processing as discussed in
       [RFC6383] should be enabled.

   R3  LSP establishment time shall depend on the number of nodes
       supporting an LSP and link propagation delays and not on any off
       (control) path transactions, e.g., PCC-PCE and PCC-PCC
       communications at the time of connection setup, even when PCE-
       based approaches are used.

   R4  LSP holding times as short as one second must be supported.

   R5  The protocol aspects of LSP signaling must not preclude LSP
       request rates of tens per second.

   R6  The above requirements should be met even when there are failures
       in connection establishment, i.e., LSPs should be established
       faster than when crank-back is used.

   R7  These requirements are applicable even when an LSP crosses one or
       more administrative domains/boundaries.

   R8  The above are additional requirements and do not replace existing
       requirements, e.g., alarm-free setup and teardown, recovery, or
       inter-domain confidentiality.

6.  Security Considerations

   Being able to support very fast setup and a high-churn rate of GMPLS
   LSPs is not expected to adversely affect the underlying security
   issues associated with existing GMPLS signaling.  If encryption that
   requires key exchange is intended to be used on the signaled LSPs,
   then this requirement needs to be included as a part of the protocol
   design process, as the usual extra round-trip time (RTT) for key
   exchange will have an effect on the setup and churn rate of the GMPLS
   LSPs.  It is possible to amortize the costs of key exchange over
   multiple exchanges (if those occur between the same peers) so that
   some exchanges need not cost a full RTT and operate in so-called
   zero-RTT mode.

7.  Acknowledgements

   The authors would like to thank Ann Von Lehmen, Joe Gannett, Ron
   Skoog, and Haim Kobrinski of Applied Communication Sciences for their
   comments and assistance on this document.  Lou Berger provided
   editorial comments on this document.

8.  References

8.1.  Normative References

   [RFC3471]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Functional Description",
              RFC 3471, DOI 10.17487/RFC3471, January 2003,
              <http://www.rfc-editor.org/info/rfc3471>.

   [RFC3945]  Mannie, E., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Architecture", RFC 3945,
              DOI 10.17487/RFC3945, October 2004,
              <http://www.rfc-editor.org/info/rfc3945>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <http://www.rfc-editor.org/info/rfc4655>.

   [RFC5814]  Sun, W., Ed. and G. Zhang, Ed., "Label Switched Path (LSP)
              Dynamic Provisioning Performance Metrics in Generalized
              MPLS Networks", RFC 5814, DOI 10.17487/RFC5814, March
              2010, <http://www.rfc-editor.org/info/rfc5814>.

   [RFC6163]  Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
              "Framework for GMPLS and Path Computation Element (PCE)
              Control of Wavelength Switched Optical Networks (WSONs)",
              RFC 6163, DOI 10.17487/RFC6163, April 2011,
              <http://www.rfc-editor.org/info/rfc6163>.

   [RFC6383]  Shiomoto, K. and A. Farrel, "Advice on When It Is Safe to
              Start Sending Data on Label Switched Paths Established
              Using RSVP-TE", RFC 6383, DOI 10.17487/RFC6383, September
              2011, <http://www.rfc-editor.org/info/rfc6383>.

   [RFC6777]  Sun, W., Ed., Zhang, G., Ed., Gao, J., Xie, G., and R.
              Papneja, "Label Switched Path (LSP) Data Path Delay
              Metrics in Generalized MPLS and MPLS Traffic Engineering
              (MPLS-TE) Networks", RFC 6777, DOI 10.17487/RFC6777,
              November 2012, <http://www.rfc-editor.org/info/rfc6777>.

8.2.  Informative References

   [Chiu]     Chiu, A., et al., "Architectures and Protocols for
              Capacity Efficient, Highly Dynamic and Highly Resilient
              Core Networks", Journal of Optical Communications and
              Networking vol. 4, No. 1, pp. 1-14, 2012,
              DOI 10.1364/JOCN.4.000001,
              <http://dx.doi.org/10.1364/JOCN.4.000001>.

   [Lehmen]   Von Lehmen, A., et al., "CORONET: Testbeds, Demonstration,
              and Lessons Learned", Journal of Optical Communications
              and Networking Vol. 7, Issue 3, pp. A447-A458, 2015,
              DOI 10.1364/JOCN.7.00A447,
              <http://dx.doi.org/10.1364/JOCN.7.00A447>.

Authors' Addresses

   Andrew G. Malis (editor)
   Huawei Technologies

   Email: agmalis@gmail.com


   Brian J. Wilson
   Applied Communication Sciences

   Email: bwilson@appcomsci.com


   George Clapp
   AT&T Labs Research

   Email: clapp@research.att.com


   Vishnu Shukla
   Verizon Communications

   Email: vishnu.shukla@verizon.com