Internet DRAFT - draft-jhs-forces-protoextenstion
draft-jhs-forces-protoextenstion
Internet Engineering Task Force J. Hadi Salim
Internet-Draft Mojatatu Networks
Intended status: Informational January 5, 2014
Expires: July 9, 2014
ForCES Protocol Extensions
draft-jhs-forces-protoextenstion-02
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.
Status of This Memo
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Table of Contents
1. Terminology and Conventions . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Problem Overview . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Table Ranges . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Error codes . . . . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Update Proposal . . . . . . . . . . . . . . . . . . 5
4.1. Table Ranges . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Error Codes . . . . . . . . . . . . . . . . . . . . . . . 6
4.2.1. New Codes . . . . . . . . . . . . . . . . . . . . . . 7
4.2.2. Vendor Codes . . . . . . . . . . . . . . . . . . . . 7
4.2.3. Extended Result TLV . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
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.
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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,
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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.
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. 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 (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:
o Dump the whole table and filter for the needed 2000 table rows.
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o Send upto 10000 ForCES PL requests with monotonically incrementing
indices and stop when the needed 2000 entries are retrieved.
o 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.
OPER = GET
PATH-DATA:
flags = F_SELTABRANGE, IDCount = 2, IDs = {1,6}
TABLERANGE-TLV content = {11,23}
Figure 1: ForCES table range request
Figure 1 illustrates a GET request for a range of rows 11 to 23 of a
table with component path of "1/6".
Path flag of F_SELTABRANGE (0x2 i.e bit 1, where bit 0 is F_SELKEY as
defined in RFC 5810) is set to indicate the presence of the Table-
range TLV. The pathflag bit F_SELTABRANGE can only be used in a GET
or DEL and is mutually exclusive with F_SELKEY. The FE MUST enforce
those constraints and reject a request with an error code of
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E_INVALID_TFLAGS with a description of what the problem is (refer to
Section 4.2).
The Table-range TLV contents constitute:
o A 32 bit start index. An index of 0 implies the beggining of the
table row.
o A 32 bit end index. A value of 0xFFFFFFFFFFFFFFFF implies the
last entry. XXX: Do we need to define the "end wildcard"?
The response for a table range query will either be:
o The requested table data returned (when at least one referenced
row is available); in such a case, a response with a path pointing
to the table and whose data content contain the row(s) will be
sent to the CE. The data content MUST be encapsulated in
sparsedata TLV. The sparse data TLV content will have the "I" (in
ILV) for each table row indicating the table indices.
o An Extended result TLV when:
* Response is to a range delete request. The Result will either
be:
+ A success if any of the requested for rows is deleted
+ A proper error code if none of the requested for rows cannot
be deleted
* data is absent where the result code of E_EMPTY with an
optional content string describing the nature of the error
(refer to Section 4.2).
* When both a path key and path table range are reflected on the
the pathflags, an error code of E_INVALID_TFLAGS with an
optional content string describing the nature of the error
(refer to Section 4.2).
* other standard ForCES errors (such as ACL constraints trying to
retrieve contents of an unreadable table), accessing unknown
components etc.
4.2. Error Codes
We propose several things:
1. A new set of error codes.
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2. Allocating currently reserved codes for vendor use.
3. A new TLV, EXTENDED-RESULT-TLV (0x118) that will carry a code
(which will be a superset of what is currently specified in RFC
5812) but also an optional cause content. This is illustrated in
Figure 2.
4.2.1. New Codes
Extended-Result TLV Result Value is 32 bits and is a superset of RFC
5810 Result TLV Result Value. The new version code space is 32 bits
as opposed to the RFC 5810 code size of 8 bits.
+-------------+--------------------+--------------------------------+
| Code | Mnemonic | Details |
+-------------+--------------------+--------------------------------+
| 0x100 | E_EMPTY | Table is empty |
| 0x101 | E_INVALID_TFLAGS | Invalid table flags |
| 0x102 | E_INVALID_OP | Requested operation is invalid |
| 0x103 | E_CONGEST_NT | Node Congestion notification |
+-------------+--------------------+--------------------------------+
Table 1: New codes
4.2.2. Vendor Codes
Codes 0x18-0xFE are reserved for use as vendor codes. Since these
are freely available it is expected that the FE and CE side will both
understand the semantics of any used codes.
4.2.3. Extended Result TLV
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 = EXTENDED-RESULT-TLV | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Cause content |
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Extended Result TLV
o Like all other ForCES TLVs, the Extended Result TLV is expected to
be 32 bit aligned.
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o The Result Value derives and extends from the same current
namespace as specified in RFC 5810, section 7.1.7. The main
difference is that we now have 32 bit result value (as opposed to
the old 8 bit).
o The optional result content is defined to further disambiguate the
result value. It is expected Utf-8 values to be used. However,
vendor specific error codes may choose to specify different
contents. Additionally, future codes may specify cause contents
to be of types other than string..
o It is recommended that the maximum size of the cause string should
not exceed 32 bytes. We do not propose the cause string be
standardized.
XXX: Backward compatibility may require that we add a FEPO capability
to advertise ability to do extended results so that the CE is able to
interpret the results and a FEPO compatibility flag to define what
TLV setting would be used. Alternatively, the backward compatibility
can be made a configuration option (which helps reduce clutter on
FEPO LFB given that it is expected that in the future it makes sense
for implementations to support only extended Result TLVs).
5. IANA Considerations
This document registers two new top Level TLVs and two new path
flags.
The following new TLVs are defined:
o Table-range TLV (type ID 0x117)
o EXTENDED-RESULT-TLV (type ID 0x118)
The following new path flags are defined:
o F_SELTABRANGE (value 0x2 i.e bit 1)
The Defined Result Values are changed:
o codes 0x18-0xFE are reserved for vendor use.
o codes 0x100-102 are defined by this document.
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6. Security Considerations
TBD
7. References
7.1. Normative References
[RFC3746] Yang, L., Dantu, R., Anderson, T., and R. Gopal,
"Forwarding and Control Element Separation (ForCES)
Framework", RFC 3746, April 2004.
[RFC5810] Doria, A., Hadi Salim, J., Haas, R., Khosravi, H., Wang,
W., Dong, L., Gopal, R., and J. Halpern, "Forwarding and
Control Element Separation (ForCES) Protocol
Specification", RFC 5810, March 2010.
[RFC5811] Hadi Salim, J. and K. Ogawa, "SCTP-Based Transport Mapping
Layer (TML) for the Forwarding and Control Element
Separation (ForCES) Protocol", RFC 5811, March 2010.
[RFC5812] Halpern, J. and J. Hadi Salim, "Forwarding and Control
Element Separation (ForCES) Forwarding Element Model", RFC
5812, March 2010.
7.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Author's Address
Jamal Hadi Salim
Mojatatu Networks
Suite 400, 303 Moodie Dr.
Ottawa, Ontario K2H 9R4
Canada
Email: hadi@mojatatu.com
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