RFC 9376
Applicability of GMPLS for beyond 100 Gbit/s Optical Transport Network
RFC 9376: Applicability of GMPLS for beyond 100 Gbit/s Optical Transport Network 🦋
Who wrote it: Q. Wang (ed.) from ZTE Corporation, R. Valiveti (ed.) from Infinera Corp, H. Zheng (ed.) from Huawei, H. van Helvoort from Hai Gaoming BV, and S. Belotti from Nokia. 💅
The vibe: Informational, published March 2023, ISSN 2070-1721. ✨
Obsoletes and updates: The header has no "Obsoletes" or "Updates" lines, so this doc doesn't replace or change any earlier RFC. 🫶
Abstract
okay so this doc looks at whether the GMPLS routing and signaling stuff we already have can set up Optical Data Unit-k (ODUk) Label Switched Paths (LSPs) over Optical Data Unit-Cn (ODUCn) links 🔥. The ODUCn links are defined in the 2020 version of ITU-T Recommendation G.709, so it's all about that version bestie 🌈.
Status of This Memo
ngl this one is NOT a standards track spec 🙈. It's just published for info. 🎀
This is an IETF product, so it represents what the IETF community agreed on. It got public review and the IESG approved it for publication. Not every IESG-approved doc is a candidate for any level of Internet Standard, though, so check out Section 2 of RFC 7841 if you're curious 🧐.
If you want the current status, any errata, or a way to send feedback, head to https://www.rfc-editor.org/info/rfc9376 💜.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. ©️✨
This doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as they stood on the publication date. Read those carefully, bestie, because they explain your rights and restrictions with respect to this doc. 📜 Any Code Components pulled out of this doc need Revised BSD License text, as described in Section 4.e of the Trust Legal Provisions, and they come without warranty as the Revised BSD License says 🌸.
Table of Contents
1. Introduction
2. OTN Terminology Used in This Document
3. Overview of OTUCn/ODUCn in G.709
3.1. OTUCn
3.1.1. OTUCn-M
3.2. ODUCn
3.3. Tributary Slot Granularity
3.4. Structure of OPUCn MSI with Payload Type 0x22
3.5. Client Signal Mappings
4. GMPLS Implications and Applicability
4.1. TE Link Representation
4.2. GMPLS Signaling
4.3. GMPLS Routing
5. IANA Considerations
6. Security Considerations
7. References
7.1. Normative References
7.2. Informative References
Appendix A. Possible Future Work
Contributors
Authors' Addresses1. Introduction ✨
so the current GMPLS routing [RFC7138] and signaling [RFC7139] extensions can handle Optical Transport Network (OTN) signals and capabilities from the 2012 version of ITU-T Recommendation G.709 [ITU-T_G709_2012] 💖.
Then in 2016 a new G.709 version dropped: [ITU-T_G709_2016] 🍓. It brought in higher-rate Optical Transport Unit (OTU) and Optical Data Unit (ODU) signals called "OTUCn" and "ODUCn", with a nominal rate of n*100 Gbit/s 🚀. According to [ITU-T_G709_2016], OTUCn and ODUCn only do the digital section-layer job, and ODUCn only supports ODUk clients 🎀. This doc is focused on using the GMPLS stuff we already have to set up ODUk (e.g., ODUflex) LSPs over ODUCn links, no matter how those links were set up 💅.
Because [ITU-T_G709_2020] doesn't add any new features to OTUCn and ODUCn compared to [ITU-T_G709_2016], the doc first gives an overview of OTUCn and ODUCn signals in [ITU-T_G709_2020]. After that it checks how the current GMPLS routing and signaling can be used to set up ODUk (e.g., ODUflex) LSPs over ODUCn links 🦋.
This doc assumes you already know OTN, GMPLS, and how GMPLS gets applied in OTN 🧚. So it doesn't give any background on OTN links with capacities of 100 Gbit/s or less. You can find that in docs like [RFC7062] and [RFC7096] 📚. What it does do is give an overview of the data plane primitives that enable links with capacities greater than 100 Gbit/s, and look at the extensions the current GMPLS routing and signaling would need to support the evolution of OTN 🌈.
2. OTN Terminology Used in This Document 🎀
Here are the key terms, bestie 💜:
- FlexO: Flexible OTN information structure. It usually has a specific bitrate and frame format made of overhead and payload, used together to carry an OTUCn signal 🌸.
- LSP: Label Switched Path 🦋.
- MSI: Multiplex Structure Indicator. This tells you how the tributary slots in an OPU payload area are grouped to carry a client signal that's multiplexed into an OPU 🧚. The individual clients multiplexed into that payload area are told apart by the Tributary Port Number (TPN) ✨.
- ODU: Optical Data Unit. An ODU has the frame structure and overhead defined in Figure 12-1 of [ITU-T_G709_2020] 💅. There are two ways to form an ODU: a) by encapsulating a single non-OTN client, like SONET/SDH (Synchronous Optical Network / Synchronous Digital Hierarchy) or Ethernet, or b) by multiplexing lower-rate ODUs 🍓. Generally the ODU layer is the path layer in OTN. The one exception is the ODUCn signal (defined below), which is a section-layer signal 🙈. When you sort ODUs by bitrate, there are two types: fixed rate and flexible rate. Flexible-rate ODUs, called "ODUflex", have a rate that's 239/238 times the bitrate of the client signal they encapsulate 🔥.
- ODUC: Optical Data Unit-C. This signal has a bandwidth of about 100 Gbit/s and a slightly higher bitrate than the fixed rate ODU4 signal 💖. It uses the format from Figure 12-1 of [ITU-T_G709_2020]. It's the building block for the higher-rate ODUCn signal (defined below) 👑.
- ODUCn: Optical Data Unit-Cn, where Cn means a bitrate of about
n*100Gbit/s 🌈. Its frame structure is made of "n" interleaved frame and multiframe synchronous instances of the ODUC signal, and each one uses the format in Figure 12-1 of [ITU-T_G709_2020] ✨. - ODUflex: Optical Data Unit - flexible rate. An ODUflex has the same frame structure as a "generic" ODU, but its rate is a fixed multiple of the bitrate of the client signal it encapsulates 🦋. [ITU-T_G709_2020] defines specific ODUflex containers needed to carry specific clients, like 50GE, 200GE, 400GE, and so on 🎀.
- ODUk: Optical Data Unit-k, where k is one of {0, 1, 2, 2e, 3, 4} 💅. The term "ODUk" means an ODU whose bitrate is fully specified by the index k. For k = {0, 1, 2, 2e, 3, 4}, the ODUk bitrates are approximately 1.25 Gbit/s, 2.5 Gbit/s, 10 Gbit/s, 10.3 Gbit/s, 40 Gbit/s, and 100 Gbit/s, in that order 🔥.
- OPUC: Optical Payload Unit-C. This signal has a payload of about 100 Gbit/s 🌸. It's the payload area of the ODUC signal 🧚.
- OPUCn: Optical Payload Unit-Cn, where Cn means the bitrate is about
n*100Gbit/s 💜. It's the payload area of the ODUCn signal 🍓. - OTN: Optical Transport Network 🦋.
- OTUC: Optical Transport Unit-C. This signal has a bandwidth of about 100 Gbit/s 🌈. It's the building block for the OTUCn signal (defined below), which has a bandwidth of about
n*100Gbit/s ✨. - OTUCn: Fully standardized Optical Transport Unit-Cn 💖. This frame structure comes from extending the ODUCn signal with OTU layer overhead. You can see its structure in Figure 11-4 of [ITU-T_G709_2020] 🎀. Note that ITU-T defines "fully standardized" in Section 6.1.1 of [ITU-T_G709_2020] 📚.
- OTUCn-M: This is an extension of the OTUCn signal described above 🙈. It has the same amount of overhead as OTUCn but a smaller payload area 🔥. Specifically, its payload area consists of M tributary slots (each 5 Gbit/s), where M is less than
20*n, which is the number of tributary slots in the OTUCn signal 👑. - PSI: Payload Structure Indicator. This is a 256-byte signal that describes how the OPU signal is put together 💅. This field is a concatenation of the payload type (PT) and the Multiplex Structure Indicator (MSI) defined above 🌸.
- TPN: Tributary Port Number. It shows the port number of the client signal carried in one specific tributary slot 🧚.
For more detail on some of these terms, check out [ITU-T_G709_2020] 💜.
3. Overview of OTUCn/ODUCn in G.709 🌈
This section gives an overview of the OTUCn/ODUCn signals defined in [ITU-T_G709_2020] 🦋. The text here is purely descriptive and not normative ✨. For the full description of OTUCn/ODUCn signals, go to [ITU-T_G709_2020] 💅. If this text ever disagrees with [ITU-T_G709_2020], that other document wins 👑.
3.1. OTUCn ✨
okay so bestie, [ITU-T_G709_2020] has a whole plan for client signals faster than 100 Gbit/s 🚀 Instead of tying the OTU signal's rate to the client rate, it goes with a general, scalable approach that decouples the two. The new OTU signal is called "OTUCn", and it's defined to run at (approximately) n*100 Gbit/s. Here are the key characteristics, no cap:
- The OTUCn signal contains one ODUCn. The OTUCn and ODUCn signals perform digital section-layer roles only (see Section 6.1.1 of [ITU-T_G709_2020]) 💅
- The OTUCn signals are formed by interleaving n synchronous OTUC signals (which are labeled 1, 2, ..., n) 🎀
- Each of the OTUC instances has the same overhead as the standard OTUk signal in [ITU-T_G709_2020]. Note that the OTUC signal doesn't include the Forward Error Correction (FEC) columns illustrated in Figure 11-1 of [ITU-T_G709_2020]. The OTUC signal includes an ODUC. 🦋
- The OTUC signal has a slightly higher rate compared to the OTU4 signal (without FEC). This is to ensure that the OPUC payload area can carry an ODU4 signal. 🌸
- The combined signal OTUCn has n instances of OTUC overhead and n instances of ODUC overhead. 👑
The OTUCn, ODUCn, and OPUCn signal structures are presented in a (physical) interface-independent manner, using n OTUC, ODUC, and OPUC instances that are marked #1 to #n. Very clean 🧚
OTUCn interfaces can be categorized based on the type of peer network element:
- inter-domain interfaces: These are used for connecting OTN edge nodes to (a) client equipment (e.g., routers) or (b) hand-off points from other OTN. [ITU-T_G709.1] (ITU-T Recommendation G709.1) specifies a flexible interoperable short-reach OTN interface over which an OTUCn (n >=1) is transferred, using bonded Flexible OTN information structure (FlexO) interfaces, which belong to a FlexO group. 🌈
- intra-domain interfaces: Here the OTUCn is transported using a proprietary (vendor-specific) encapsulation, FEC, etc. It is also possible to transport OTUCn for intra-domain links using FlexO. 🔥
3.1.1. OTUCn-M
okay this one is lowkey clever 🙈 The standard OTUCn signal has the same rate as the ODUCn signal. That means the OTUCn can only ride over wavelength groups with a total capacity that's a multiple of (approximately) 100 Gbit/s. But modern optical interfaces support a whole variety of bitrates per wavelength, depending on the reach requirements for the optical path, so that's a problem 😭
So if the total rate of the ODUk LSPs planned for an ODUCn link is smaller than n*100 Gbit/s, you can "crunch" the OTUCn, and the unused tributary slots are simply not transmitted. [ITU-T_G709_2020] supports this reduced-rate version, called "OTUCn-M". The OTUCn-M signal is derived from the OTUCn signal by keeping all the n instances of overhead (one per OTUC instance), but with only M (M is less than 20*n) OPUCn tributary slots available to carry ODUk LSPs. It's giving efficiency ✨
3.2. ODUCn
The ODUCn signal defined in [ITU-T_G709_2020] can be viewed as being formed by the appropriate interleaving of content from n ODUC signal instances. The ODUC frames have the same structure as a standard ODU in the sense that they have the same overhead and payload areas, but they run at a higher rate, since their payload area can embed an ODU4 signal. Same vibes, bigger body 💖
The ODUCn is a multiplex section ODU signal and is mapped into an OTUCn signal, which provides the regenerator section layer. In some scenarios, the ODUCn and OTUCn signals will be coterminated, i.e., they will have identical source/sink locations (see Figure 1). In Figure 1, the term "OTN Switch" has the same meaning as that used in Section 3 of [RFC7138].
Then there's regeneration 🦋 [ITU-T_G709_2020] allows the ODUCn signal to pass through one or more digital regenerator nodes (shown as nodes B and C in Figure 2). These terminate the OTUCn layer but pass the regenerated (but otherwise untouched) ODUCn towards a different OTUCn interface, where a fresh OTUCn layer is initiated. This process is termed "ODUCn regeneration" in Section 7.1 of [ITU-T_G872]. In this example, the ODUCn is carried by three OTUCn segments.
Specifically, the OPUCn signal flows through these regenerators unchanged. That means the set of client signals, their TPNs, and tributary-slot allocations all stay exactly the same 🫶
+--------+ +--------+
| +-----------+ |
| OTN |-----------| OTN |
| Switch +-----------+ Switch |
| A | | B |
| +-----------+ |
+--------+ +--------+
<--------ODUCn------->
<-------OTUCn------>
Figure 1: ODUCn Signal +---------+ +--------+ +--------+ +--------+
| +--------+ | | +----------+ |
| OTN |--------| OTN | | OTN |----------| OTN |
| Switch +--------+ Regen +--------+ Regen +----------+ Switch |
| A | | B | | C | | D |
| +--------+ | | +----------+ |
+---------+ +--------+ +--------+ +--------+
<-------------------------ODUCn-------------------------->
<---------------><-----------------><------------------>
OTUCn OTUCn OTUCn
Figure 2: ODUCn Signal - Multi-Hop3.3. Tributary Slot Granularity
Quick history bit 📜 [ITU-T_G709_2012] introduced support for 1.25 Gbit/s granular tributary slots in OPU2, OPU3, and OPU4 signals. Then [ITU-T_G709_2020] defined the OPUC with a 5 Gbit/s tributary slot granularity. This means the ODUCn signal has 20*n tributary slots (of 5 Gbit/s capacity each). The range of tributary port number (TPN) is 10*n instead of 20*n, which restricts the maximum client signals that could be carried over one single ODUC1. Little plot twist there 👀
3.4. Structure of OPUCn MSI with Payload Type 0x22
As mentioned above, the OPUCn signal has 20*n tributary slots (TSs), each 5 Gbit/s. The OPUCn MSI field has a fixed length of 40*n bytes and indicates the availability and occupation of each TS. Two bytes are used for each of the 20*n tributary slots, and each such information structure has the following format (see Section 20.4.1 of [ITU-T_G709_2020]):
- The TS availability bit indicates if the tributary slot is available or unavailable. ✅
- The TS occupation bit indicates if the tributary slot is allocated or unallocated. 📦
- The tributary port number (14 bits) indicates the port number of the client signal being carried in this specific TS. A flexible assignment of tributary port to tributary slots is possible. Numbering of tributary ports is from 1 to 10*n. 🧩
The concatenation of the OPUCn payload type (PT) and the MSI field is carried over the overhead byte designated as PSI in Figure 15-6 of [ITU-T_G709_2020]. 🎀
3.5. Client Signal Mappings
Here's how the ITU-T maps non-OTN client signals into the right ODU containers 💅
- All client signals are mapped into an ODUj or ODUk (e.g., ODUflex) as specified in Section 17 of [ITU-T_G709_2020].
- The terms "ODUj" and "ODUk" are used in a multiplexing scenario, with ODUj being a low-order ODU that is multiplexed into ODUk, a high-order ODU. As Figure 3 illustrates, the ODUCn is also a high-order ODU into which other ODUs can be multiplexed. The ODUCn itself cannot be multiplexed into any higher-rate ODU signal; it is defined to be a section-level signal. 🌸
- ODUflex signals are low-order signals only. If the ODUflex entities have rates of 100 Gbit/s or less, they can be transported over either an ODUk (k=1..4) or an ODUCn. For ODUflex connections with rates greater than 100 Gbit/s, ODUCn is required. 🦋
- ODU Virtual Concatenation (VCAT) has been deprecated. This simplifies the network and the supporting hardware, since multiple different mappings for the same client are no longer necessary. Note that legacy implementations that transported sub-100 Gbit/s clients using ODU VCAT shall continue to be supported. Old friends still get a seat at the table 🫶
| | | | | |
| | | | | |
| | | | | |
+---+---+---+----+ | | |
| OPUj | | | |
+----------------+ | | |
| ODUj | | | |
+----------------+----------------------+---+---+----------+
| |
| OPUk |
+----------------------------------------------------------+
| |
| ODUk k in {0,1,2,2e,3,4,flex}|
+-------------------------+-----+--------------------------+
| | | |
| OTUk, OTUk-SC, OTUk-V | | OPUCn |
+-------------------------+ +--------------------------+
| |
| ODUCn |
+--------------------------+
| |
| OTUCn |
+--------------------------+
Figure 3: Digital Structure of OTN Interfaces (from Figure 6-1 of
[ITU-T_G709_2020])4. GMPLS Implications and Applicability ✨
4.1. TE Link Representation
Okay bestie, so 💖 Section 3 of [RFC7138] already explains how to represent G.709 OTUk/ODUk as TE links in GMPLS, and OTUCn links can be represented the exact same way 🦋 Figure 4 shows a one-hop OTUCn TE link, which is the simplest version of this.
+----------+ +---------+
| OTN | | OTN |
| Switch +-------------------+ Switch |
| A | | B |
+----------+ +---------+
|<---------OTUCn Link---------->|
|<---------TE Link------------->|
Figure 4: One-Hop OTUCn TE LinkIt also gets spicy 🌶️ You can make a TE link that spans more than one hop by creating forward adjacencies (FAs) between nodes that aren't next to each other (see Figure 5). In Figure 5, nodes B and C are doing the ODUCn regeneration function described in Section 7.1 of [ITU-T_G872], and they are not electrically switching the ODUCn signal from one interface to another. Same as the one-hop case, multi-hop TE links advertise the ODU switching capability ✨
+--------+ +--------+ +--------+ +---------+
| OTN | | OTN | | OTN | | OTN |
| Switch |<------->| Regen |<-------->| Regen |<------->| Switch |
| A | OTUCn | B | OTUCn | C | OTUCn | D |
+--------+ Link +--------+ Link +--------+ Link +---------+
|<-------------------- ODUCn Link -------------------->|
|<---------------------- TE Link --------------------->|
Figure 5: Multi-Hop ODUCn TE LinkThe two endpoints of a TE link get configured with the supported resource information, which may include whether the TE link is supported by an ODUCn, ODUk, or OTUk 🧚 They also get the link attribute information, like the slot granularity and the list of available tributary slots 💅
4.2. GMPLS Signaling
Once the ODUCn TE link is configured, the GMPLS mechanisms defined in [RFC7139] can be reused to set up ODUk/ODUflex LSPs with no changes 🔥 The resource on the ODUCn link that the ODUk/ODUflex client signal can see is a set of 5 Gbit/s slots, so the label defined in [RFC7139] can handle setting up an ODUk/ODUflex client signal over an ODUCn link. It's giving efficient reuse 😭
In [RFC7139], the OTN-TDM GENERALIZED_LABEL object shows how the lower-order (LO) ODUj signal is multiplexed into the higher-order (HO) ODUk link. Same vibe here: the OTN-TDM GENERALIZED_LABEL object is used to show how the ODUk signal is multiplexed into the ODUCn link. The ODUk signal type is indicated by Traffic Parameters. The IF_ID RSVP_HOP object points to the interface associated with the TE link, so the two nodes at the ends of the TE link know (through internal/local configuration) the attributes of the ODUCn TE Link 👑
The TPN defined in [ITU-T_G709_2020] (where it is referred to as "tributary port #") for an ODUCn link has 14 bits, but this field in [RFC7139] only has 12 bits. So some extension work will eventually be needed 🎀
Heads up: a 12-bit TPN field can support ODUCn links with up to n=400 (i.e., 40 Tbit/s links), so this need is not urgent 💜
Figure 6 illustrates the label format defined in [RFC7139] for multiplexing ODU4 onto ODUC10. One ODUC10 has 200 slots (each 5 Gbit/s), and twenty of them are allocated to the ODU4. With this label encoding, only 20 out of the 200 bits in the mask are non-zero, which is very inefficient 🙈 The inefficiency grows for larger values of "n", so an optimized label format may be desirable.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TPN = 3 | Reserved | Length = 200 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0| Padding Bits(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Label Format4.3. GMPLS Routing
For routing, it's deemed that no extension to the current mechanisms defined in [RFC7138] is needed 🌸
The ODUCn link is the lowest layer of the ODU multiplexing hierarchy that involves multiple ODU layers. It's assumed to already be configured when GMPLS is used to set up ODUk over ODUCn. So the resources that need to be advertised are the ones exposed by this ODUCn link and the ODUk multiplexing hierarchy on it 🦋 The 5 Gbit/s OPUCn time slots do not need to be advertised, but the 1.25 Gbit/s and 2.5 Gbit/s OPUk time slots do need to be advertised, using the mechanisms already defined in [RFC7138].
Since there's a 1:1 correspondence between the ODUCn and the OTUCn signal, there's no need to explicitly define a new value for the ODUCn signal type in the OSPF-TE routing protocol. Iconic simplicity 👑
5. IANA Considerations 📋
This document has no IANA actions. Nothing to register, nothing to update, we're just vibing 🫶
6. Security Considerations 🚨
Okay, this part is seriously important, so let's go 💀 This document analyzes the applicability of the protocol extensions in [RFC7138] and [RFC7139] for use in the 2020 version of ITU-T Recommendation G.709 [ITU-T_G709_2020], and it finds that no new extensions are needed. Therefore, this document introduces no new security considerations to the existing signaling and routing protocols beyond the ones already described in [RFC7138] and [RFC7139]. Please refer to [RFC7138] and [RFC7139] for further details of the specific security measures. Additionally, [RFC5920] addresses the security aspects that are relevant in the context of GMPLS. Read those docs, bestie, they've got the receipts 🔐
7. References
7.1. Normative References
[ITU-T_G709_2020]
ITU-T, "Interfaces for the optical transport network",
ITU-T Recommendation G.709, June 2020.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.
[RFC7138] Ceccarelli, D., Ed., Zhang, F., Belotti, S., Rao, R., and
J. Drake, "Traffic Engineering Extensions to OSPF for
GMPLS Control of Evolving G.709 Optical Transport
Networks", RFC 7138, DOI 10.17487/RFC7138, March 2014,
<https://www.rfc-editor.org/info/rfc7138>.
[RFC7139] Zhang, F., Ed., Zhang, G., Belotti, S., Ceccarelli, D.,
and K. Pithewan, "GMPLS Signaling Extensions for Control
of Evolving G.709 Optical Transport Networks", RFC 7139,
DOI 10.17487/RFC7139, March 2014,
<https://www.rfc-editor.org/info/rfc7139>.7.2. Informative References
[ITU-T_G709.1]
ITU-T, "Flexible OTN short-reach interfaces", ITU-T
Recommendation G.709.1, June 2018.
[ITU-T_G709_2012]
ITU-T, "Interfaces for the optical transport network",
ITU-T Recommendation G.709, February 2012.
[ITU-T_G709_2016]
ITU-T, "Interfaces for the optical transport network",
ITU-T Recommendation G.709, June 2016.
[ITU-T_G872]
ITU-T, "Architecture of optical transport networks", ITU-T
Recommendation G.872, December 2019.
[RFC7062] Zhang, F., Ed., Li, D., Li, H., Belotti, S., and D.
Ceccarelli, "Framework for GMPLS and PCE Control of G.709
Optical Transport Networks", RFC 7062,
DOI 10.17487/RFC7062, November 2013,
<https://www.rfc-editor.org/info/rfc7062>.
[RFC7096] Belotti, S., Ed., Grandi, P., Ceccarelli, D., Ed.,
Caviglia, D., Zhang, F., and D. Li, "Evaluation of
Existing GMPLS Encoding against G.709v3 Optical Transport
Networks (OTNs)", RFC 7096, DOI 10.17487/RFC7096, January
2014, <https://www.rfc-editor.org/info/rfc7096>.Appendix A. Possible Future Work 🔮
As noted in Section 4.2, the GMPLS TPN field defined in Section 6.1 of [RFC7139] is only 12 bits, whereas an ODUCn link could require up to 14 bits. The need isn't urgent, but future work could extend the TPN field in GMPLS to use the Reserved bits immediately adjacent to it 🌈 This would need to be done in a backward-compatible way.
Section 4.2 also notes that the current encoding of GMPLS labels can be inefficient for larger values of n in ODUCn. Future work might look at a more compact, yet generalized, label encoding to address this issue, should it be felt (after analysis of the operational aspects) that the current encoding is causing problems. Introducing a new label encoding would need to use a new pairing of LSP encoding type and Generalized Payload Identifier (G-PID) to make sure it interoperates correctly ✨
Contributors 🫶
Iftekhar Hussain
Infinera Corp
Sunnyvale, CA
United States of America
Email: IHussain@infinera.com
Daniele Ceccarelli
Ericsson
Email: daniele.ceccarelli@ericsson.com
Rajan Rao
Infinera Corp
Sunnyvale,
United States of America
Email: rrao@infinera.com
Fatai Zhang
Huawei
Email: zhangfatai@huawei.com
Italo Busi
Huawei
Email: italo.busi@huawei.com
Dieter Beller
Nokia
Email: Dieter.Beller@nokia.com
Yuanbin Zhang
ZTE
Beijing
Email: zhang.yuanbin@zte.com.cn
Zafar Ali
Cisco Systems
Email: zali@cisco.com
Daniel King
Email: d.king@lancaster.ac.uk
Manoj Kumar
Cisco Systems
Email: manojk2@cisco.com
Antonello Bonfanti
Cisco Systems
Email: abonfant@cisco.com
Yuji Tochio
Fujitsu
Email: tochio@fujitsu.comAuthors' Addresses 💌
Qilei Wang (editor)
ZTE Corporation
Nanjing
China
Email: wang.qilei@zte.com.cn
Radha Valiveti (editor)
Infinera Corp
Sunnyvale, CA
United States of America
Email: rvaliveti@infinera.com
Haomian Zheng (editor)
Huawei
China
Email: zhenghaomian@huawei.com
Huub van Helvoort
Hai Gaoming BV
Almere
Netherlands
Email: huubatwork@gmail.com
Sergio Belotti
Nokia
Email: sergio.belotti@nokia.com📦 where this page comes from
- ietf: rfc9376 2023-03
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms