WSON Optical Interface Class
draft-martinelli-wson-interface-class-01

Abstract

Current work on wavelength switched optical network includes several considerations regarding the interface signal compatibility. In particular ingress and egress optical interfaces will require a check on several optical parameters to assess if the signal generated by the ingress interface can be compatible with the receiving interface. Current solution available encode all parameters in WSON protocol extensions while in this draft will propose an alternative method to keep into account the signal compatibility issue at protocol level.

Status of this Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on May 03, 2012.

Copyright Notice

Copyright (c) 2011 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
• 1.1. Requirements Language
• 2. Existing WSON Signal Compatibility protocol extension
• 3. Optical Interface Class
• 3.1. Concept and Procedures
• 3.2. Encoding
• 4. Optical Interface Class Semantic
• 5. Acknowledgements
• 6. IANA Considerations
• 7. Security Considerations
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Appendix A. Encoding example
• Authors' Addresses

1. Introduction

The current work on Wavelength Switched Optical Network (WSON) define the need of assessing the signal compatibility during the routing and wavelength assignment (RWA) process. In details, the [RFC6163] reports the ingress and egress interfaces and the regeneration points as places where the optical signal compatibility must be assured. Regarding how to evaluate, there are a list of parameters identified according to ITU specification [ITU-G.698.1] and [ITU-G.698.2]. In particular the following set of parameters has been chosen: signal bit rate, modulation format, forward error correction.

At the current state of art new high bit rates (40G/100G) are under development as well as new modulation formats and it is not clear if and when there will be a dominating technology. In a current realistic scenario DWDM optical networks manage different bit-rates as well as different modulation formats over the same link. So in general different signal characteristics will coexist at the same time.

To a further extent, the WSON activity will consider the case where the control plane has optical impairments awareness as detailed in [I-D.ietf-ccamp-wson-impairments]. The Control Plane function related to impairment awareness might require some additional interface parameters to assess the optical feasibility path. In such a case is likely further protocol extensions might be required just to add some parameters.

Scope of this draft is to propose an Optical Interface Class identifier as a solution for the WSON signal compatibility problem. To some extend the idea is have protocol extensions independent from optical technology evolution by keeping the semantic of optical characteristics separated from protocol scope. The final goal is a simplified but general representation rather than encoding saving.

1.1. Requirements Language

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].

2. Existing WSON Signal Compatibility protocol extension

Within the current WSON activity the signal compatibility encoding is defined within the [I-D.ietf-ccamp-rwa-wson-encode]. In details, the following list of parameters is considered:

• Modulation Format. Only NRZ currently defined.
• FEC, according to G.709 and G.975.
• Bit Rate.

Note that this list of parameters is defined by ITU and might be subject to change due to internal physics.

At the current status, the above encoding is going to be used within several WSON specific protocol extensions.

• OSPF [I-D.ietf-ccamp-wson-signal-compatibility-ospf] since the path computation function need to consider optical interface parameters during the RWA process.
• RSVP [I-D.ietf-ccamp-wson-signaling] since during the signaling phase there is the need to know optical ingress and egress interface properties (and eventually interfaces at regeneration point).
• In addition, PCEP extension might need similar parameters as envisaged here [I-D.lee-pce-wson-rwa-ext].

In case of any update from ITU standards regarding optical signals and interfaces all the above drafts making use of the same information needs an update.

3. Optical Interface Class

3.1. Concept and Procedures

The Optical Interface Class will be a unique number that identify all information related to optical characteristic's of a physical interface. Since current implementation of physical interfaces may support different optical caracteristics, a single interface may support multiple interface classes.

In term of RWA process the only operation required to assess the optical compatibility (interfaces or regeneration points) is to check if the two optical endpoint have the same Class value. Note that if a regeneration happens, the complete LSP may have more then two optical enpoints since regenerations shall satisfy the signal compatibility as well. The procedure of signal compatibility assessment become just a numbers comparison: if two Optical Interface Class are equals the signal compatibility constrain is satisfied. GMPLS protocols don't have to implement any logic related to signal compatibility while this would be teh case if the parameters are listed explicitly.

This procedure is easily generalized in case more than one class is available for each interface since it's sufficient to find two matching values between each segment of a WSON LSP.

   +---+    +----+   +----+     +-----+     +----+    +---+
   | I |----| N1 |---| N2 |-----| REG |-----| N3 |----| E |
   +---+    +----+   +----+     +-----+     +----+    +---+
     class1                class1    class2         class2
   |<----------------------------->|<-------------------->|
                            LSP
   |<---------------------------------------------------->|
                                             
            

In case the RWA process will result in a path that need a wavelength conversion each interface involved in the wavelength conversion must satisfy the Optical Interface Class constrain. As represented in Figure 1, two different Optical Interface Classes are required for the given LSPs.

By using the Optical Interface Class concept every protocol extensions supporting WSON does not need to care about DWDM signal details and does not need to consider technology specific evolution. If a new parameter values are standardized (e.g. new modulation formats become standard) the wson protocols and RWA don't need any extensions.

3.2. Encoding

The following Optical Interface Class must be be used in proper TLVs for different WSON protocol extensions.

In case an optical interface or a regeneration point will support multiple optical capabilities, a list of Interface Classes can be used. Note that the concept of list is already defined in [I-D.ietf-ccamp-rwa-wson-encode].

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|     Reserved                |    OI Code Points             |                                       
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              Optical Interface Class                          |                                       
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            

Where the first 32 bist of the encoding shall be used to indentify the sematic of the Optical Interface Class in the following way:

S

Standard bit set to 1 if use the code points to indentify ITU.T application codes.

OI Code Points

The following values are identified when the S bit is 0:

• 0: reserved
• 1: Enterprise Specific Optical Interface Class

When the S bit is set to 1:

• 0: reserved
• 1: [ITU-G.698.1] application code.
• 2: [ITU-G.698.2] application code.

The Optical Interface Class encoding is a number 64 bits wides. In case S=0 and OI code point is 1, the first 32 bits shall match the IANA enterprise number.

4. Optical Interface Class Semantic

The semantic of the Optical Interface Class must be defined outside the control plane but it must be unique for all control plane elements. In this way the same class value will have the same meaning on every network node. Within this hypothesis, we need to solve the problem on how to make any network element aware of the semantic behind the Optical Interface Class and make sure it can figure out the right value for its interfaces.

An example of semantic is the "Application Code" within [ITU-G.698.1] and [ITU-G.698.2]. The Application Code could be easily represented by a number represented by the Optical Interface Class. This number might be used as an index to access a table containing all the values associated with a specific interface using mechanisms like Directory Services. Note that each single interface parameter could be retrieved through a MIB. As an example, [draft-galimbe-kunze-g698-2-snmp-mib] gives another example on the Optical parameter specification includes the OII definition in compliance with [ITU-G.698.2] Chapter 5.3.

Every time a new optical interface is defined or introduced into the market, only a MIB update will be required but there will be no impact on WSON protocols.

Note also that the Control Plane may become aware of the Optical Interface Class semantic by a various of other ways like the network management system or manual provisioning.

As a matter of fact in current WSON technology, standard and proprietary information must co-exist. The introduction of the Optical Interface Class does not change or limit this possibility since the class identifier can be a means to access either public or vendor specific information. In term of protocol encoding however, this solution has the advantage to limit eventually proprietary information in a fixed size field.

5. Acknowledgements

6. IANA Considerations

Optical Interface code points needs to be assigned by IANA?

All drafts are required to have an IANA considerations section (see the update of RFC 2434 [I-D.narten-iana-considerations-rfc2434bis] for a guide). If the draft does not require IANA to do anything, the section contains an explicit statement that this is the case (as above). If there are no requirements for IANA, the section will be removed during conversion into an RFC by the RFC Editor.

7. Security Considerations

All drafts are required to have a security considerations section. See RFC 3552 [RFC3552] for a guide.

8. References

8.1. Normative References

8.2. Informative References

Appendix A. Encoding example

In this section we try to represent how the encoding will change considering the Optical Interface Class. The main result of the Optical interface class will be not encoding saving in term of bytes but a simplified protocol support for new optical technologies.

According to Section 5 of [I-D.ietf-ccamp-rwa-wson-encode] the encoding shall foresee a list of: Input Modulation Type, Input FEC Type, Input Client Signal Types. All the basic objects has a lenght dependent on values carried on. For example if the modulation format is a standard one, the related sub TLV will be 32 bits, if the modulation formart is a proprietary one the length is not known a priori.

Using the concept of interface class the same object will likely become as the one represented in Figure 3.

   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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                     RB Set Field                              |
:                                                               :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I|E|                      Reserved                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             Type/length for Interface Class list              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               Input Interface Class=1                         |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               Input Interface Class=2                         |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               Input Interface Class=3                         |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Processing Capabilities List Sub-Sub-TLV (opt)        |
:                                                               :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|             Type/length for Interface Class list              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               Output Interface Class=A                        |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               Output Interface Class=B                        |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                             
            

With the following notes:

• Current draft just defines the Optical interface class encoding as 3 words of 32 bits but, for usage within WSON protocol extentions a proper TLV header shall be defined. In this case we represent a list since the original example in [I-D.ietf-ccamp-rwa-wson-encode] use lists.
• Current example just represent input and output classes by numbers (1,2,3) and letters (A,B) since example only shows how encoding is simplified.
• Optical interface classes has a fixed size while basic encoding blocks of [I-D.ietf-ccamp-rwa-wson-encode] have sizes that varies depending on proprietary informations.

As in the example above, the concept of Optical interface class is not to save encoding bytes but to keep the optical semantic outside of GMPLS protocols.

Authors' Addresses