Generalized Interface Switching Capability Descriptor - Switching Capability Specific Information
draft-ietf-teas-gmpls-scsi-03

Abstract

This document defines a generic information structure for information carried in routing protocol Interface Switching Capability Descriptor (ISCD) Switching Capability Specific Information (SCSI) fields. This "Generalized SCSI" can be used with routing protocols that define GMPLS ISCDs, and any specific technology. This document does not modify any existing technology specific formats and is defined for use in conjunction with new GMPLS Switching Capability types. The context for this document is Generalized MPLS, and the reader is expected to be familiar with the GMPLS architecture and associate protocol standards.

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Table of Contents

• 1. Introduction
• 2. Terminology
• 3. Generalized SCSI Formats
• 4. Procedures
• 5. Security Considerations
• 6. IANA Considerations
• 7. Acknowledgments
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Authors' Addresses

1. Introduction

The context for this document is Generalized MPLS, and the reader is expected to be familiar with the GMPLS architecture, associate terminology and protocol standards. Notably, but not limited to, [RFC3945], [RFC4202], [RFC4203] and [RFC5307].

The Interface Switching Capability Descriptor (ISCD) [RFC4202] allows routing protocols such as OSPF and ISIS to carry technology specific information in the the Switching Capability-specific information (SCSI) field, see [RFC4203] and [RFC5307]. The format of an SCSI field is dictated by the specific technology being represented as indicated by the ISCD Switching Capability (SC) type field. Existing Switching Capabilities are managed by IANA in the Switching Types registry and the related "IANA-GMPLS-TC-MIB" definitions.

[RFC7138] introduced a "sub-TLV" structure to its technology specific SCSI field. The Sub-Type-Length-Value (TLV) based approach allows for greater flexibility in the structure, ordering, and ability to support extensions of the SC (technology) specific format. This Sub-TLV approach is also used in [RFC7688].

This document generalizes this approach and defines a new generalized SCSI field format for use by future specific technologies and Switching Capability types. The generalized SCSI carries SCSI-TLVs that may be defined within the scope of a specific technology, or shared across multiple technologies (e.g., [I-D.ietf-ccamp-ospf-availability-extension]). This document also establishes a registry for SCSI-TLV definitions that may be shared across multiple technologies.

2. Terminology

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 interpreted as described in [RFC2119].

The reader is expected to be familiar with GMPLS terminology, e.g. as found in [RFC3945], as well as the terminology used in [RFC4202], [RFC4203] and [RFC5307].

3. Generalized SCSI Formats

The Generalized SCSI is composed of zero or more variable length type-length-value fields which are each called a SCSI-TLV. There are no specific size restrictions on these SCSI-TLV. Size and other formatting restrictions may be imposed by the routing protocol ISCD field, refer to [RFC4203] and [RFC5307].

The SCSI-TLV format is:

            
    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              |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ...                           Value                           ...
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            
          

Figure 1: TLV format

Type (2 octets):

This field indicates the type and structure of the information contained in the Value field.

Length (2 octets):

This field MUST be set to the size, in octets (bytes), of the Value field. The value of the field MUST be zero or divisible by 4. Note that this implies that the Value field can be omitted or contain padding.

Value (variable):

A variable length field, formatted according to the definition indicated by value of the Type field. This field can be omitted for certain types.

4. Procedures

The ISCD can include a Generalized SCSI when advertising technologies whose Switching Capability definition references this document. The corollary of this is that the Generalized SCSI MUST NOT be used for ISCDs of technologies whose Switching Capability definition do not reference this document.

The Generalized SCSI MAY contain a sequence of zero or more SCSI-TLVs. Sub-TLV parsing (format) errors, such as an underrun or overrun, MUST be treated as a malformed ISCD. SCSI-TLVs MUST be processed in the order received and, if re-originated, ordering MUST be preserved. Unknown SCSI-TLVs MUST be ignored and transparently processed, i.e., re-originated when appropriate. Processing related to multiple SCSI-TLVs of the same type may be further refined based on the definition on the type.

5. Security Considerations

This document does not introduce any security issue beyond those discussed in [RFC4203] and [RFC5307]. As discussed there, the information carried in ISCDs are not used for SPF computation or normal routing and the extensions here defined do not have direct effect on IP routing. Tampering with GMPLS TE LSAs may have an effect on the underlying transport network. Mechanisms such as [RFC2154] and [RFC5304] to protect the transmission of this information are suggested.

6. IANA Considerations

This document defines a new SCSI-TLV that is carried in the SCSI field of the ISCDs defined in [RFC4203] and [RFC5307]. The SCSI-TLV includes a 16-bit type identifier (the Type field). The same Type field values are applicable to the new SCSI-TLV.

IANA is requested to create and maintain a new registry, the "Generalized SCSI (Switching Capability Specific Information) TLVs Types" registry under either the the "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Parameters" registry or a new "Generalized Multi-Protocol Label Switching (GMPLS) Routing Parameters" registry, at their desecration.

The definition of the new registry is as follows:

            
    Value       SCSI-TLV                Switching Type   Reference
    ---------   ----------------------- --------------   ---------
    0           Reserved                                 [This ID]
    1-65535     Unassigned              (value list)     [This ID]
        
          

The registry should be established with registration policies of "Specification Required", see [RFC5226].

REMOVE THIS AFTER PUBLICATION: The designated expert will be appointed by the Routing AD. It is suggested to appoint any current TEAS WG chair.

7. Acknowledgments

The authors would like to thank Adrian Farrel and Julien Meuric for the careful review and suggestions. Thomas Heide Clausen provided useful comments as part of the Routing Directorate review.

8. References

8.1. Normative References

8.2. Informative References

Authors' Addresses