RFC 8363

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

📅 published May 2018, from ietf

GMPLS OSPF-TE Extensions in Support of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks 🌈

  • RFC number: 8363 🎀
  • Authors: X. Zhang (Huawei), H. Zheng (Huawei), R. Casellas (CTTC), O. Gonzalez de Dios (Telefonica), D. Ceccarelli (Ericsson) 💖
  • Category: Standards Track ✨
  • Date: May 2018 🦋
  • ISSN: 2070-1721
  • Obsoletes / Updates: the header doesn't list anything this one obsoletes or updates 🫶

Abstract

okay so the ITU-T (the International Telecommunication Union Telecommunication standardization sector) extended its Recommendations G.694.1 and G.872 to add a new DWDM grid 🌸 It defines channel spacings, a set of nominal central frequencies, and the idea of the "frequency slot." The data-plane techniques that go with it are called "flexi-grid" ✨

Building on flexi-grid as defined in G.694.1 and in RFCs 7698 and 7699, this document describes OSPF-TE extensions (Open Shortest Path First - Traffic Engineering) that support GMPLS control of networks with devices using this new flexible optical grid 💅

Status of This Memo

this one is an Internet Standards Track document 👑

it's a product of the Internet Engineering Task Force (IETF), so it reflects the consensus of the IETF community. it got public review and was approved for publication by the Internet Engineering Steering Group (IESG). if you want more on Internet Standards, check Section 2 of RFC 7841 📚

for the current status, any errata, and how to send feedback, go to https://www.rfc-editor.org/info/rfc8363 🔗

Copyright (c) 2018 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 (https://trustee.ietf.org/license-info) as they stand on the publication date. read those carefully, because they spell out your rights and restrictions for this document 🧾

if you pull Code Components out of this document, they have to include Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions. they come without warranty, as the Simplified BSD License describes 🫶

Table of Contents 🗺️

1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
  2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
    2.1.  Conventions Used in This Document . . . . . . . . . . . .   4
  3.  Requirements for Flexi-Grid Routing . . . . . . . . . . . . .   4
    3.1.  Available Frequency Ranges  . . . . . . . . . . . . . . .   4
    3.2.  Application Compliance Considerations . . . . . . . . . .   5
    3.3.  Comparison with Fixed-Grid DWDM Links . . . . . . . . . .   6
  4.  Extensions  . . . . . . . . . . . . . . . . . . . . . . . . .   7
    4.1.  Interface Switching Capability Descriptor (ISCD)
          Extensions for Flexi-Grid . . . . . . . . . . . . . . . .   7
      4.1.1.  Switching Capability Specific Information (SCSI)  . .   8
      4.1.2.  An SCSI Example . . . . . . . . . . . . . . . . . . .  10
    4.2.  Extensions to the Port Label Restrictions Field . . . . .  11
  5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
    5.1.  New ISCD Switching Type . . . . . . . . . . . . . . . . .  13
    5.2.  New SCSI Type . . . . . . . . . . . . . . . . . . . . . .  13
  6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
  7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
    7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
    7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  16
  Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  16
  Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1. Introduction 🦋

okay so [G.694.1] defines the DWDM frequency grids for WDM (Wavelength Division Multiplexing) applications 🌈 a frequency grid is a reference set of frequencies, and it's used to mark which nominal central frequencies are allowed for defining applications ✨ the channel spacing is the frequency gap between two allowed nominal central frequencies 💅 and all the wavelengths on a fiber need different central frequencies and need to fit into a fixed chunk of frequency bandwidth 🫶

fixed-grid channel spacing is one of 12.5 GHz, 25 GHz, 50 GHz, or 100 GHz, or an integer multiple of 100 GHz 🍓 but [G.694.1] also defines a "flexible grid," aka "flexi-grid" 🔥 two terms are used to describe it: "frequency slot" (the frequency range given to one channel, which no other channel can use inside the flexible grid) and "slot width" (the full width of one frequency slot in the flexible grid) 🧚

[RFC7698] sets out a framework and the control-plane requirements for GMPLS-based control of flexi-grid DWDM networks 👑

[RFC6163] gives a framework for GMPLS and PCE (Path Computation Element) control of WSONs (Wavelength Switched Optical Networks) 💜 and [RFC7688] defines the requirements and OSPF-TE extensions that support GMPLS control of a WSON 🌸

[RFC7792] describes requirements and protocol extensions for signaling to set up LSPs (Label Switched Paths) in networks that support flexi-grid ✨ this document complements [RFC7792] by describing the requirements and extensions for OSPF-TE routing in a flexi-grid network 💖

this document is part of the wider effort to extend OSPF-TE so it can support GMPLS control of flexi-grid networks 🎀

2. Terminology 🍓

for flexi-grid terms, check [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", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be read as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they show up in all capitals, just like here 🫶 (lowercase versions are just regular words, so they don't count 🙈)

3. Requirements for Flexi-Grid Routing 🌷

the architecture for setting up LSPs in a Spectrum Switched Optical Network (SSON) is described in [RFC7698] 🦋

a flexi-grid LSP takes up one or more specific frequency slots 💖 the process of computing a route and allocating a frequency slot is called "RSA" (Routing and Spectrum Assignment) ✨ [RFC7698] describes three architectural approaches to RSA: combined RSA, separated RSA, and routing and distributed SA 🧠 the first two are sort of "centralized SA," since a single entity does the spectrum (frequency slot) assignment before the signaling procedure even starts 👑

with centralized SA, the assigned frequency slot goes into the RSVP-TE Path message during signaling 📨 with routing and distributed SA, only the requested slot width of the flexi-grid LSP goes in the Path message, so the network elements involved can pick the frequency slot themselves 🧚

if the capability to switch or convert the whole optical spectrum allocated to an optical spectrum LSP isn't available at nodes along the LSP's path, then the LSP is subject to the Optical "Spectrum Continuity Constraint," as described in [RFC7698] 🙈

the rest of this section lists the extra routing-protocol extensions for a flexi-grid network 💅

3.1. Available Frequency Ranges 🌈

for flexi-grids, the central frequency steps up from 193.1 THz with 6.25 GHz granularity 🍓 how the central frequency and the slot width of a frequency slot get calculated is defined in [G.694.1], using a nominal central frequency n and a slot width m 🔥

on a DWDM link, allocated or in-use frequency slots don't overlap each other 🫶 but the border frequencies of two frequency slots can be the same frequency, meaning the upper bound of one frequency slot and the lower bound of the directly adjacent one are equal 💜

                     Frequency Slot 1   Frequency Slot 2
                       +-----------+-----------------------+
                       |           |                       |
  -9 -8 -7 -6 -5 -4 -3 -2 -1 0  1  2  3  4  5  6  7  8  9 10  11
...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--...
                       ------------ ------------------------
                             ^                 ^
                Central F = 193.1 THz   Central F = 193.1375 THz
                 Slot width = 25 GHz    Slot width = 50 GHz

              Figure 1: Two Frequency Slots on a Link

Figure 1 shows two frequency slots that sit right next to each other on a link 🎀 the highest frequency of slot 1, which is n=2, is also the lowest frequency of slot 2 🌸 so in this example, the frequency range from n=-2 to n=10 is unavailable to other flexi-grid LSPs 🚫 available central frequencies are advertised for m=1, which means that for an available central frequency n, the frequency slot from central frequency n-1 to central frequency n+1 is available ✨

so, to make it super clear which frequency slots are usable for LSP establishment and which aren't, the routing protocol advertises the availability of frequency slots for flexi-grid DWDM links 💖 a set of non-overlapping available frequency ranges gets disseminated, so resource management on flexi-grid DWDM links and the RSA procedures (described in Section 4.8 of [RFC7698]) can work efficiently 🧚

3.2. Application Compliance Considerations 💅

as [G.694.1] describes, devices or applications that use flexi-grid might not be able to support every possible slot width or position (central frequency) 🦋 in other words, applications or implementations can be defined where only a subset of the possible slot widths and positions are required to be supported 🌷

for example, an application could be defined where the nominal central frequency granularity is 12.5 GHz (it only requires even values of n), and that same application only requires slot widths that are a multiple of 25 GHz (it only requires even values of m) 🍓

so, to support all possible applications and implementations, the following information SHOULD be advertised for a flexi-grid DWDM link 🫶

  • Channel Spacing (C.S.): as defined in [RFC7699] for flexi-grid, set to 5 to denote 6.25 GHz 💜
  • Central frequency granularity: a multiplier of C.S. 🌸
  • Slot width granularity: a multiplier of 2*C.S. ✨
  • Slot width range: two multipliers of the slot width granularity, each indicating the minimal and maximal slot width supported by a port, respectively 🔥

the combination of slot width range and slot width granularity can be used to work out the set of slot widths supported by a port 👑

okay bestie, let's compare fixed-grid DWDM links 🎀 on a fixed-grid link, every wavelength gets its own predefined central frequency, kind of like assigned seats at a concert 🎟️ The usable frequency range is basically implied by the channel spacing. Every wavelength on the link can be labelled with an identifier that mostly tells you its central frequency, using the label defined in [RFC6205]. And whether each wavelength is available or not can be advertised through a routing protocol 💌

Figure 2 shows a link with a fixed grid and 50 GHz channel spacing 💅 The central frequencies are predefined by the values of "n", and each wavelength takes up a fixed 50 GHz range as described in [G.694.1].

     W(-2)  |    W(-1)  |    W(0)   |    W(1)   |     W(2)  |
...---------+-----------+-----------+-----------+-----------+----...
      |   50 GHz  |  50 GHz   |  50 GHz   |   50 GHz  |

    n=-2        n=-1        n=0         n=1         n=2
...---+-----------+-----------+-----------+-----------+----------...
                              ^
                 Central F = 193.1 THz

             Figure 2: A Link Supports Fixed Wavelengths
                     with 50 GHz Channel Spacing

Unlike fixed-grid DWDM links, on a flexi-grid DWDM link the slot width of the frequency slot is flexible, as described in Section 3.1 🦋 That means the value of m in the following formula from [G.694.1] is uncertain until a frequency slot is actually allocated for a flexi-grid LSP 🌈

Slot Width (in GHz) = 12.5GHz * m

So for flexi-grid, the available frequency slots (or ranges) get advertised for the link instead of the specific "wavelength" points that are enough for a fixed-grid link. This advertisement is also represented by the combo of central frequency granularity and slot width granularity 🧚

4. Extensions 🎀

the network-connectivity topology made from the links and/or nodes, plus the node capabilities, is the same as for WSON, as described in [RFC7698] 🌸 These can be advertised by the GMPLS routing protocols using Opaque Link State Advertisements (LSAs) [RFC3630] in the case of OSPF-TE [RFC4203] (refer to Section 6.2 of [RFC6163]). For flexi-grid, the available frequency ranges get advertised for the link instead of the specific "wavelengths." This section defines the GMPLS OSPF-TE extensions that support advertising those available frequency ranges for flexi-grid DWDM links 👑

4.1. Interface Switching Capability Descriptor (ISCD) Extensions for Flexi-Grid

this section defines a new value for the Switching Capability field of the ISCD: 152, with the type name Flexi-Grid-LSC 💖

            Value              Name
            -----              --------------
            152                Flexi-Grid-LSC

Switching Capability and Encoding values MUST be used as follows: ✨

            Switching Capability = Flexi-Grid-LSC

            Encoding Type = lambda (as defined in [RFC3471])

When the Switching Capability and Encoding fields are set to the values above, the ISCD is interpreted as in [RFC4203], with the optional inclusion of one or more Switching Capability Specific Information (SCSI) sub-TLVs 🫶

As the "Max LSP Bandwidth at priority x" (x from 0 to 7) fields in the generic part of the ISCD [RFC4203] aren't meaningful for flexi-grid DWDM links 🙈, the values of these fields MUST be set to zero and MUST be ignored. The SCSI defined below gives the matching info for flexi-grid DWDM links instead 💜

4.1.1. Switching Capability Specific Information (SCSI)

[RFC8258] defines a Generalized SCSI for the ISCD. This document defines the Frequency Availability Bitmap as a new type of Generalized SCSI TLV 🦋 The technology-specific part of the flexi-grid ISCD includes the available frequency-spectrum resource, plus the info on max slot widths per priority. The format of this flexi-grid SCSI, the Frequency Availability Bitmap sub-TLV, looks like this 🍓

     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  = 11           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Priority    |                   Reserved                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~ Max Slot Width at Priority k  |   Unreserved Padding          ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | C.S.  |       Starting n              | No. of Effective Bits |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Bitmap                  ...                             ~
    ~      ...                              |  padding bits         ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type (16 bits): the type of this sub-TLV (11) 🌷

Length (16 bits): the length of the value field of this sub-TLV, in octets 📏

Priority (8 bits): a bitmap that shows which priorities are being advertised. The bitmap is in ascending order: the leftmost bit is priority level 0 (i.e., the highest), and the rightmost bit is priority level 7 (i.e., the lowest). A bit is set (1) for each priority represented in the sub-TLV, and clear (0) for each priority not represented. At least one priority level MUST be advertised. If only one priority level is advertised, it MUST be at priority level 0. 🔥

Reserved: the Reserved field MUST be set to zero on transmission and MUST be ignored on receipt 🙈

Max Slot Width at Priority k (16 bits): this field shows the maximal frequency slot width supported at a particular priority level, up to 8. It's set to the max frequency slot width supported, in the unit of 2*C.S., for that priority level. One field MUST be present for each bit set in the Priority field, and each present field is ordered to match the Priority field. Fields MUST be present for the priority levels indicated in the Priority field 💅

Unreserved Padding (16 bits): this padding keeps Max Slot Width at Priority k 32-bit aligned 🧁 When k is an odd number, the Unreserved Padding field MUST be included. When k is an even number, the Unreserved Padding field MUST be omitted. This field MUST be set to 0 and MUST be ignored on receipt.

C.S. (4 bits): as defined in [RFC7699]; it's currently set to 5 🌈

Starting n (16 bits): as defined in [RFC7699]. This value marks the starting point of the nominal central frequency of the frequency availability bitmap sub-TLV ✨

No. of Effective Bits (12 bits): the number of effective bits in the Bitmap field 🦋

Bitmap (variable): this shows whether a basic frequency slot is available for flexi-grid LSP setup. A basic frequency slot is characterized by a nominal central frequency and a fixed m value of 1 🍓 The first nominal central frequency is the value of starting n, and the subsequent nominal central frequencies are implied by the position in the bitmap. Setting a bit to 1 means the corresponding central frequency is available for a flexi-grid LSP with m=1, and setting it to 0 means that central frequency is unavailable. Also, a centralized SA process will need to extend this to high values of m by checking a sufficiently large number of consecutive basic frequency slots that are available 🧠

padding bits (variable): padded after the Bitmap to make it a multiple of four bytes, if necessary. Padding bits MUST be set to 0 and MUST be ignored on receipt. 🫧

An example is provided in Section 4.1.2. 🎀

Okay so picking up right where we left off 💖

4.1.2. An SCSI Example ✨

Figure 3 shows an example of the available frequency spectrum resource of a flexi-grid DWDM link 🌈

   -9 -8 -7 -6 -5 -4 -3 -2 -1 0  1  2  3  4  5  6  7  8  9 10  11
...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--...
                        |--Available Frequency Range--|

               Figure 3: Flexi-Grid DWDM Link Example

The + is the allowed nominal central frequency, and the -- is a central frequency granularity of 6.25 GHz, which is currently standardized in [G.694.1] 🫶 The number on top of the line is the "n" in the frequency calculation formula (193.1 + n * 0.00625). So when n equals zero, the nominal central frequency is 193.1 THz 💅

Okay, so in this example the lowest nominal central frequency supported is n=-9, and the highest is n=11. Quick heads up, though: those can't be used as a nominal central frequency for setting up an LSP 🙈 They're just a way to express the supported frequency range. Using the encoding from Section 4.1.1, the relevant fields to express the frequency resource availability can be filled in like this:

 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  = 11           |           Length              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Priority    |                   Reserved                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Max Slot Width at Priority k  |   Unreserved Padding          ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   5   |       Starting n (-9)         | No. of Effec. Bits(21)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0|0|0|0|0|0|0|1|1|1|1|1|1|1|1|1|0|0|0|0|  padding bits (0s)  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

In the example above, the starting n gets picked as the lowest nominal central frequency, which is -9 💜 Looking at the bitmap, n=-1 to 7 can be used to set up LSPs 🦋 Other starting n values can totally be chosen to represent the bitmap too! For instance, the first available nominal central frequency (a.k.a. the first available basic frequency slot) can be picked, and then the SCSI gets expressed like this 🧚

 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  = 11           |           Length              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Priority    |                   Reserved                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Max Slot Width at Priority k  |   Unreserved Padding          ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   5   |       Starting n (-1)         | No. of Effec. Bits(9)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|1|1|1|1|1|1|1|1|            padding bits (0s)                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

This encoding says that, apart from the advertised available nominal central frequencies, the other nominal central frequencies within the whole frequency range supported by the link are not available for flexi-grid LSP setup 🙅‍♀️

If an LSP with slot width m equal to 1 gets set up using this link, say using n=-1, then the SCSI information gets updated to look like this 🔥

 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  = 11           |           Length              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Priority    |                   Reserved                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Max Slot Width at Priority k  |   Unreserved Padding          ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   5   |       Starting n (-1)         | No. of Effec. Bits(9)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0|1|1|1|1|1|1|1|            padding bits (0s)                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.2. Extensions to the Port Label Restrictions Field 🎀

Okay bestie, this part is giving main character energy 👑 As described in Section 3.2, a port that supports flexi-grid might only support a restricted subset of the full flexible grid. The Port Label Restrictions field is defined in [RFC7579]. It can be used to describe the label restrictions on a port, and it is carried in the top-level Link TLV as specified in [RFC7580]. A new restriction type, the flexi-grid Restriction Type, is defined here to specify the restrictions on a port to support flexi-grid 🦋

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MatrixID      | RstType = 5   | Switching Cap |   Encoding    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  C.S. |     C.F.G     |    S.W.G      |     Reserved          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Min Slot Width           |        Reserved               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Here's the field breakdown, bestie 🫶

  • MatrixID (8 bits): As defined in [RFC7579].
  • RstType (Restriction Type, 8 bits): Takes the value of 5 to indicate the restrictions on a port to support flexi-grid.
  • Switching Cap (Switching Capability, 8 bits): As defined in [RFC7579], it MUST be consistent with the one specified in ISCD as described in Section 4.1.
  • Encoding (8 bits): As defined in [RFC7579], it MUST be consistent with the one specified in ISCD as described in Section 4.1.
  • C.S. (4 bits): As defined in [RFC7699]. For flexi-grid, it is 5 to denote 6.25 GHz.
  • C.F.G (Central Frequency Granularity, 8 bits): A positive integer. Its value indicates the multiple of C.S., in terms of central frequency granularity.
  • S.W.G (Slot Width Granularity, 8 bits): A positive integer. Its value indicates the multiple of 2*C.S., in terms of slot width granularity.
  • Min Slot Width (16 bits): A positive integer. Its value indicates the multiple of 2*C.S. (in GHz), in terms of the supported minimal slot width.
  • Reserved: The Reserved field MUST be set to zero on transmission and SHOULD be ignored on receipt.

5. IANA Considerations 🌸

5.1. New ISCD Switching Type 💜

IANA has made the following assignment in the "Switching Types" sub-registry of the "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Parameters" registry located at https://www.iana.org/assignments/gmpls-sig-parameters:

      Value      Name                Reference
      -------    ----------------    ----------
      152        Flexi-Grid-LSC      RFC 8363

5.2. New SCSI Type 🍓

This document defines a new generalized SCSI sub-TLV that is carried in the Interface Switching Capability Descriptors [RFC4203] when the Switching Type is set to Flexi-Grid-LSC.

IANA has made the following assignment in the "Generalized SCSI (Switching Capability Specific Information) TLV Types" sub-registry [RFC8258] of the "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Parameters" registry located at https://www.iana.org/assignments/gmpls-sig-parameters:

Value  SCSI-TLV                        Switching Type   Reference
-----  -----------------------------   --------------   ---------
 11    Frequency Availability Bitmap   152              RFC 8363

6. Security Considerations 🚨

Okay, this one is SERIOUS bestie, so pay attention 😭

This document extends [RFC4203] and [RFC7580] to carry flexi-grid-specific information in OSPF Opaque LSAs. This document does not introduce any further security issues other than those discussed in [RFC3630] and [RFC4203]. To be more specific, the security mechanisms described in [RFC2328], which apply to Opaque LSAs carried in OSPF, still apply. An analysis of the OSPF security is provided in [RFC6863] and applies to the extensions to OSPF in this document as well 🔐

7. References 📚

7.1. Normative References 💖

[G.694.1]  International Telecommunication Union, "Spectral grids for
           WDM applications: DWDM frequency grid", ITU-T
           Recommendation G.694.1, February 2012,
           <https://www.itu.int/rec/T-REC-G.694.1/en>.

[RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119,
           DOI 10.17487/RFC2119, March 1997,
           <https://www.rfc-editor.org/info/rfc2119>.

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

[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,
           <https://www.rfc-editor.org/info/rfc4203>.

[RFC6205]  Otani, T., Ed. and D. Li, Ed., "Generalized Labels for
           Lambda-Switch-Capable (LSC) Label Switching Routers",
           RFC 6205, DOI 10.17487/RFC6205, March 2011,
           <https://www.rfc-editor.org/info/rfc6205>.

[RFC7579]  Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and
           J. Han, "General Network Element Constraint Encoding for
           GMPLS-Controlled Networks", RFC 7579,
           DOI 10.17487/RFC7579, June 2015,
           <https://www.rfc-editor.org/info/rfc7579>.

[RFC7580]  Zhang, F., Lee, Y., Han, J., Bernstein, G., and Y. Xu,
           "OSPF-TE Extensions for General Network Element
           Constraints", RFC 7580, DOI 10.17487/RFC7580, June 2015,
           <https://www.rfc-editor.org/info/rfc7580>.

[RFC7699]  Farrel, A., King, D., Li, Y., and F. Zhang, "Generalized
           Labels for the Flexi-Grid in Lambda Switch Capable (LSC)
           Label Switching Routers", RFC 7699, DOI 10.17487/RFC7699,
           November 2015, <https://www.rfc-editor.org/info/rfc7699>.

[RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
           2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
           May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8258]  Ceccarelli, D. and L. Berger, "Generalized SCSI: A Generic
           Structure for Interface Switching Capability Descriptor
           (ISCD) Switching Capability Specific Information (SCSI)",
           RFC 8258, DOI 10.17487/RFC8258, October 2017,
           <https://www.rfc-editor.org/info/rfc8258>.

7.2. Informative References 📚

Acknowledgments 🎀

This work was supported in part by the FP-7 IDEALIST project under grant agreement number 317999. 💖

This work was supported in part by NSFC Project 61201260. 🫶

Contributors 🌸

These legends helped make this happen! 💜

Adrian Farrel
Juniper Networks

Email: afarrel@juniper.net


Fatai Zhang
Huawei Technologies

Email: zhangfatai@huawei.com


Lei Wang
Beijing University of Posts and Telecommunications

Email: wang.lei@bupt.edu.cn


Guoying Zhang
China Academy of Information and Communication Technology

Email: zhangguoying@ritt.cn

Authors' Addresses 🦋

Here's where you can find the authors. Slide into their inboxes respectfully! 🧚

Xian Zhang
Huawei Technologies

Email: zhang.xian@huawei.com


Haomian Zheng
Huawei Technologies

Email: zhenghaomian@huawei.com


Ramon Casellas, Ph.D.
CTTC
Spain

Phone: +34 936452916
Email: ramon.casellas@cttc.es


Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
Emilio Vargas 6
Madrid, 28045
Spain

Phone: +34 913374013
Email: oscar.gonzalezdedios@telefonica.com


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

Email: daniele.ceccarelli@ericsson.com
📦 where this page comes from