RFC 7792

RSVP-TE Signaling Extensions in Support of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks

📅 published March 2016, from ietf

RSVP-TE Signaling Extensions in Support of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks 🎀

okay so this is RFC 7792 🦋 It's dated March 2016 and it's a Standards Track doc from the IETF, so it's a real Internet standard and not just somebody's opinion 💅 The authors are F. Zhang and X. Zhang (Huawei), A. Farrel (Old Dog Consulting), O. Gonzalez de Dios (Telefonica), and D. Ceccarelli (Ericsson) 🫶 It's ISSN 2070-1721, and the header doesn't list anything it obsoletes or updates, so no drama there ✨

Abstract 🌸

This memo describes the extensions to the Resource Reservation Protocol - Traffic Engineering (RSVP-TE) signaling protocol to support Label Switched Paths (LSPs) in a GMPLS-controlled network that includes devices using the flexible optical grid.

Status of This Memo 📜

This is an Internet Standards Track document.

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). Further information on Internet Standards is available in 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/rfc7792.

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. Terminology .....................................................3
   2.1. Conventions Used in This Document ..........................3
3. Requirements for Flexible-Grid Signaling ........................4
   3.1. Slot Width .................................................4
   3.2. Frequency Slot .............................................5
4. Protocol Extensions .............................................6
   4.1. Traffic Parameters .........................................6
        4.1.1. Applicability to Fixed-Grid Networks ................7
   4.2. Generalized Label ..........................................7
   4.3. Signaling Procedures .......................................7
5. IANA Considerations .............................................8
   5.1. Class Types for RSVP Objects ...............................8
6. Manageability Considerations ....................................8
7. Security Considerations .........................................8
8. References ......................................................9
   8.1. Normative References .......................................9
   8.2. Informative References .....................................9
Acknowledgments ...................................................11
Contributors ......................................................11
Authors' Addresses ................................................12

1. Introduction 🧚

okay so [G.694.1] defines the Dense Wavelength Division Multiplexing (DWDM) frequency grids for Wavelength Division Multiplexing (WDM) applications 💖 A frequency grid is a reference set of frequencies used to denote allowed nominal central frequencies that may be used for defining applications that utilize WDM transmission. The channel spacing is the frequency spacing between two allowed nominal central frequencies. All of the wavelengths on a fiber use different central frequencies and occupy a designated range of frequencies.

Fixed-grid channel spacing is selected from 12.5 GHz, 25 GHz, 50 GHz, 100 GHz, and integer multiples of 100 GHz. Additionally, [G.694.1] defines "flexible grids", also known as "flexi-grid". The terms "frequency slot" (i.e., the frequency range allocated to a specific channel and unavailable to other channels within a flexible grid) and "slot width" (i.e., the full width of a frequency slot in a flexible grid) are introduced in [G.694.1] to define a flexible grid. 🌈

[RFC7698] defines a framework and the associated control-plane requirements for the GMPLS-based [RFC3945] control of flexi-grid DWDM networks.

[RFC6163] provides a framework for GMPLS and Path Computation Element (PCE) control of Wavelength Switched Optical Networks (WSONs), and [RFC7689] describes the requirements and protocol extensions for signaling to set up Label Switched Paths (LSPs) in WSONs.

This document describes the additional requirements and protocol extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) [RFC3473] to set up LSPs in networks that support the flexi-grid. ✨

2. Terminology 📖

For terminology related to flexi-grid, please refer to [RFC7698] and [G.694.1].

2.1. 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].

3. Requirements for Flexible-Grid Signaling 🎯

The architecture for establishing LSPs in a flexi-grid network is described in [RFC7698].

An optical-spectrum LSP occupies a specific frequency slot, i.e., a range of frequencies. The process of computing a route and the allocation of a frequency slot is referred to as "Routing and Spectrum Assignment" (RSA). [RFC7698] describes three architectural approaches to RSA: combined RSA, separated RSA, and distributed SA. The first two approaches are referred to as "centralized SA", because routing (i.e., path determination) and spectrum assignment (i.e., selection of frequency slots) are both performed by a centralized entity prior to the signaling procedure.

In the case of centralized SA, the assigned frequency slot is specified in the RSVP-TE Path message during LSP setup. In the case of distributed SA, the slot width of the flexi-grid LSP is specified in the Path message, allowing the network elements to select the frequency slot to be used when they process the RSVP-TE messages. 🦋

If the capability to switch or convert the whole optical spectrum allocated to an optical-spectrum LSP is not available at some nodes along the path of the LSP, the LSP is subject to the Optical "spectrum continuity constraint" as described in [RFC7698].

The remainder of this section states the additional requirements for signaling in a flexi-grid network.

3.1. Slot Width 📏

The slot width is an end-to-end parameter representing how much frequency resource is requested for a flexi-grid LSP. It is the equivalent of optical bandwidth, although the amount of bandwidth associated with a slot width will depend on the signal encoding.

Different LSPs may request different amounts of frequency resource in flexible-grid networks, so the slot width MUST be carried in the signaling message during LSP establishment. This enables the nodes along the LSP to know how much frequency resource has been requested (in a Path message) and how much has been allocated (by a Resv message) for the LSP. 💅

3.2. Frequency Slot 🌸

The frequency slot information identifies which part of the frequency spectrum is allocated on each link for an LSP in a flexi-grid network.

This information MUST be present in a Resv message to indicate, hop by hop, the central frequency of the allocated resource. In combination with the slot width indicated in a Resv message (see Section 3.1), the central frequency carried in a Resv message identifies the resources reserved for the LSP (known as the frequency slot).

The frequency slot can be represented by two parameters, as follows:

   Frequency slot = [(central frequency) - (slot width)/2] ~
                    [(central frequency) + (slot width)/2]

As is common with other resource identifiers (i.e., labels) in GMPLS signaling, it must be possible for the head-end node, when sending a Path message, to suggest or require the central frequency to be used for the LSP. Furthermore, for bidirectional LSPs, the Path message MUST be able to specify the central frequency to be used for reverse-direction traffic. 🫶

As described in [G.694.1], the allowed frequency slots for the flexible DWDM grid have a nominal central frequency (in THz), defined by:

   193.1 + n * 0.00625

      where n is zero or a positive or negative integer.

The slot width (in GHz) is defined as:

   12.5 * m

      where m is a positive integer.

It is possible that an implementation supports only a subset of the possible slot widths and central frequencies. For example, an implementation can be built that is:

  1. limited to have a nominal central frequency granularity of 12.5 GHz, by only allowing values of n that are even, and
  2. further limited to only support slot widths of 25 GHz, by only allowing values of m that are even.

Further details can be found in [RFC7698]. 🔍

4. Protocol Extensions 🔧

This section defines the extensions to RSVP-TE signaling for GMPLS [RFC3473] to support flexible-grid networks.

4.1. Traffic Parameters 🎀

In RSVP-TE, the SENDER_TSPEC object in the Path message indicates the requested resource reservation. The FLOWSPEC object in the Resv message indicates the actual resource reservation. As described in Section 3.1, the slot width represents how much frequency resource is requested for a flexi-grid LSP. That is, it describes the end-to-end traffic profile of the LSP. Therefore, the traffic parameters for a flexi-grid LSP encode the slot width.

This document defines new Class Types (C-Types) for the SENDER_TSPEC and FLOWSPEC objects to carry Spectrum-Switched Optical Network (SSON) traffic parameters:

   SSON SENDER_TSPEC: Class = 12, C-Type = 8.

   SSON FLOWSPEC: Class = 9, C-Type = 8.

The SSON traffic parameters carried in both objects MUST have the format shown in Figure 1.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              m                |            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 1: The SSON Traffic Parameters
      m (16 bits): a positive integer; the slot width is specified by
                   m * 12.5 GHz.

The Reserved bits MUST be set to zero and ignored upon receipt.

🧚 part 1 is done bestie, part 2 is coming with the rest of section 4 and everything after it! 💜

4.1.1. Applicability to Fixed-Grid Networks ✨

okay bestie, quick heads up: the slot width of a fixed grid from [G.694.1] can ALSO be described using the SSON traffic parameters 🧚 the fixed-grid channel spacings (12.5 GHz, 25 GHz, 50 GHz, 100 GHz, and integer multiples of 100 GHz) are all multiples of 12.5 GHz, so the m parameter can represent those slot widths too. it's giving unity 💜

so yes, it's possible to think about using the new traffic parameter object types in common signaling messages for flexi-grid AND legacy DWDM networks. one set of messages, both worlds 🌈 iconic.

4.2. Generalized Label 🎀

okay so in a flexible-grid network, the labels that get requested or allocated (as signaled in the RSVP-TE objects) are encoded the way [RFC7699] describes. this new label encoding can show up in any RSVP-TE object or sub-object that can carry a label 🦋

as noted in Section 4.2 of [RFC7699], the m parameter is part of the label AND part of the traffic parameters. it's in both places, bestie, which is so iconic of it 💅

and as described in Section 4.3 of [RFC7699], a "compound label" (built by concatenating the flexi-grid labels) is used when signaling an LSP that uses multiple flexi-grid slots. stacking slots like a pro 👑

4.3. Signaling Procedures 🌸

ngl this part is kinda chill. the signaling procedures for LSP control in [RFC7698] have no differences from the ones needed for a fixed-grid network in [RFC7689]. no plot twist here 🙈

obviously the TSpec, FlowSpec, and label formats from Sections 4.1 and 4.2 are used. and the signaling procedures for distributed SA and centralized SA can both be applied 🫶

5. IANA Considerations 🍓

5.1. Class Types for RSVP Objects 💖

this document introduces two new Class Types for existing RSVP objects. IANA made the following allocations from the "Resource Reservation Protocol (RSVP) Parameters" registry, using the "Class Names, Class Numbers, and Class Types" sub-registry. the tea is in the table, so here it is verbatim:

    Class Number  Class Name                            Reference
    ------------  -----------------------               ---------
    9             FLOWSPEC                              [RFC2205]

                  Class Type (C-Type):

                  (8) SSON FLOWSPEC                     RFC 7792

    Class Number  Class Name                            Reference
    ------------  -----------------------               ---------
    12            SENDER_TSPEC                          [RFC2205]

                  Class Type (C-Type):

                  (8) SSON SENDER_TSPEC                 RFC 7792

6. Manageability Considerations 🧚

this document makes minor modifications to GMPLS signaling, but it does NOT change the manageability considerations for those networks. (sorry for the caps, that's just the vibe I'm getting 💀) clearly, protocol analysis tools and other diagnostic aids (including logging systems and MIB modules) will need to be upgraded to support the new traffic parameters and label formats. the tooling glow-up is coming 🌈

7. Security Considerations 🔥

⚠️ bestie, listen up. this document introduces no new security considerations to [RFC3473]. but do not skip the reading: see also [RFC5920] for a discussion of security considerations for GMPLS signaling. 🔐

8. References 📚

8.1. Normative References 💜

8.2. Informative References 🦋

Acknowledgments 🌷

this work was supported in part by the FP-7 IDEALIST project under grant agreement number 317999. thank you, FP-7 IDEALIST 🫶

Contributors 💜

Here are the contributors' details, verbatim:

Ramon Casellas
CTTC
Av. Carl Friedrich Gauss n7
Castelldefels, Barcelona  08860
Spain

Email: ramon.casellas@cttc.es


Felipe Jimenez Arribas
Telefonica Investigacion y Desarrollo
Emilio Vargas 6
Madrid  28045
Spain

Email: felipej@tid.es


Yi Lin
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen  518129
China

Phone: +86 755-28972914
Email: yi.lin@huawei.com


Qilei Wang
ZTE

Email: wang.qilei@zte.com.cn


Haomian Zheng
Huawei Technologies

Email: zhenghaomian@huawei.com

Authors' Addresses 🎀

and finally, the authors' addresses, verbatim so you can reach out to them 💌

Fatai Zhang
Huawei Technologies

Email: zhangfatai@huawei.com


Xian Zhang
Huawei Technologies

Email: zhang.xian@huawei.com


Adrian Farrel
Old Dog Consulting

Email: adrian@olddog.co.uk


Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
Ronda de la Comunicacion S/N
Madrid  28050
Spain

Phone: +34 913129647
Email: oscar.gonzalezdedios@telefonica.com


Daniele Ceccarelli
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy

Email: daniele.ceccarelli@ericsson.com
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