ForCES Protocol Extensions
draft-ietf-forces-protoextension-01

Abstract

Experience in implementing and deploying ForCES architecture has demonstrated need for a few small extensions both to ease programmability and to improve wire efficiency of some transactions. This document describes extensions to the ForCES Protocol Specification[RFC 5810] semantics to achieve that end goal.

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Table of Contents

• 1. Terminology and Conventions
• 1.1. Requirements Language
• 1.2. Definitions
• 2. Introduction
• 3. Problem Overview
• 3.1. Table Ranges
• 3.2. Error codes
• 4. Protocol Update Proposal
• 4.1. Table Ranges
• 4.2. Error Codes
• 4.2.1. New Codes
• 4.2.2. Vendor Codes
• 4.2.3. Extended Result TLV
• 4.3. Large Object Dumping
• 5. Acknowledgements
• 6. IANA Considerations
• 7. Security Considerations
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Author's Address

1. Terminology and Conventions

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 [RFC2119].

1.2. Definitions

This document reiterates the terminology defined by the ForCES architecture in various documents for the sake of clarity.

FE Model - The FE model is designed to model the logical processing functions of an FE. The FE model proposed in this document includes three components; the LFB modeling of individual Logical Functional Block (LFB model), the logical interconnection between LFBs (LFB topology), and the FE-level attributes, including FE capabilities. The FE model provides the basis to define the information elements exchanged between the CE and the FE in the ForCES protocol [RFC5810].

LFB (Logical Functional Block) Class (or type) - A template that represents a fine-grained, logically separable aspect of FE processing. Most LFBs relate to packet processing in the data path. LFB classes are the basic building blocks of the FE model.

LFB Instance - As a packet flows through an FE along a data path, it flows through one or multiple LFB instances, where each LFB is an instance of a specific LFB class. Multiple instances of the same LFB class can be present in an FE's data path. Note that we often refer to LFBs without distinguishing between an LFB class and LFB instance when we believe the implied reference is obvious for the given context.

LFB Model - The LFB model describes the content and structures in an LFB, plus the associated data definition. XML is used to provide a formal definition of the necessary structures for the modeling. Four types of information are defined in the LFB model. The core part of the LFB model is the LFB class definitions; the other three types of information define constructs associated with and used by the class definition. These are reusable data types, supported frame (packet) formats, and metadata.

LFB Metadata - Metadata is used to communicate per-packet state from one LFB to another, but is not sent across the network. The FE model defines how such metadata is identified, produced, and consumed by the LFBs, but not how the per-packet state is implemented within actual hardware. Metadata is sent between the FE and the CE on redirect packets.

ForCES Component - A ForCES Component is a well-defined, uniquely identifiable and addressable ForCES model building block. A component has a 32-bit ID, name, type, and an optional synopsis description. These are often referred to simply as components.

LFB Component - An LFB component is a ForCES component that defines the Operational parameters of the LFBs that must be visible to the CEs.

ForCES Protocol - Protocol that runs in the Fp reference points in the ForCES Framework [RFC3746].

ForCES Protocol Layer (ForCES PL) - A layer in the ForCES protocol architecture that defines the ForCES protocol messages, the protocol state transfer scheme, and the ForCES protocol architecture itself as defined in the ForCES Protocol Specification [RFC5810].

ForCES Protocol Transport Mapping Layer (ForCES TML) - A layer in ForCES protocol architecture that uses the capabilities of existing transport protocols to specifically address protocol message transportation issues, such as how the protocol messages are mapped to different transport media (like TCP, IP, ATM, Ethernet, etc.), and how to achieve and implement reliability, ordering, etc. the ForCES SCTP TML [RFC5811] describes a TML that is mandated for ForCES.

2. Introduction

Experience in implementing and deploying ForCES architecture has demonstrated need for a few small extensions both to ease programmability and to improve wire efficiency of some transactions. This document describes a few extensions to the ForCES Protocol Specification [RFC5810] semantics to achieve that end goal.

This document describes and justifies the need for 2 small extensions which are backward compatible. The document also clarifies on top of [RFC5810] how dumping of large components is achieved.

1. A table range operation to allow a controller or control application to request an arbitrary range of table rows.
2. Improved Error codes returned to the controller (or control application) to improve granularity of existing defined error codes.
3. FE response to a GET request (example to a large table) may not fit in one PL message, for example due to limited TLV space.

3. Problem Overview

In this section we present sample use cases to illustrate the challenge being addressed.

3.1. Table Ranges

Consider, for the sake of illustration, an FE table with 1 million reasonably sized table rows which are sparsely populated. Assume, again for the sake of illustration, that there are 2000 table rows sparsely populated between the row indices 23-10023.

ForCES GET and DEL requests sent from a controller (or control app) are prepended with a path to a component and sent to the FE. In the case of indexed tables, the component path can either be to a table or a table row index. The approaches for retrieving or deleting a sizeable number of table rows is at the programmatically level (from an application point of view) unfriendly, tedious, and abusive of both compute and bandwidth resources.

As an example, a control application attempting to retrieve the first 2000 table rows appearing between row indices 23 and 10023 can achieve its goal in one of:

• Dump the whole table and filter for the needed 2000 table rows.
• Send upto 10000 ForCES PL requests with monotonically incrementing indices and stop when the needed 2000 entries are retrieved.
• If the application had knowledge of which table rows existed (not unreasonable given the controller is supposed to be aware of state within an NE), then the application could take advantage of ForCES batching to send fewer large messages (each with different path entries for a total of two thousand).

As argued, while the above options exist - all are tedious.

3.2. Error codes

[RFC5810] has defined a generic set of error codes that are to be returned to the CE from an FE. Deployment experience has shown that it would be useful to have more fine grained error codes. As an example, the error code E_NOT_SUPPORTED could be mapped to many FE error source possibilities that need to be then interpreted by the caller based on some understanding of the nature of the sent request. This makes debugging more time consuming.

4. Protocol Update Proposal

This section describes proposals to update the protocol for issues discussed in Section 3

4.1. Table Ranges

We propose to add a Table-range TLV (type ID 0x117) that will be associated with the PATH-DATA TLV in the same manner the KEYINFO-TLV is.

   +---------------------+---------------------+
   |  Type (0x117)       |       Length        |
   +---------------------+---------------------+
   |                Start Index                |
   +-------------------------------------------+
   |                 End Index                 |
   +-------------------------------------------+
    

   OPER = GET
          PATH-DATA:
            flags = F_SELTABRANGE,  IDCount = 2, IDs = {1,6}
            TABLERANGE-TLV content = {11,23}
    

     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 = EXTENDEDRESULT-TLV   |              Length           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Result Value                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Optional Cause content                     |
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+