Internet DRAFT - draft-caulfield-cdni-rate-pacing
draft-caulfield-cdni-rate-pacing
Network Working Group M. Caulfield
Internet-Draft Cisco Systems
Intended status: Standards Track October 27, 2014
Expires: April 30, 2015
CDNI Rate Pacing
draft-caulfield-cdni-rate-pacing-02
Abstract
Rate pacing is a class of network traffic shaping which limits the
transmission rate of data over a network. This document defines CDNI
extensions for downstream CDNs to support rate pacing on behalf of
upstream CDNs.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 30, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. CDNI Interfaces Impact . . . . . . . . . . . . . . . . . . . 3
2.1. Footprint & Capabilities Interface . . . . . . . . . . . 3
2.2. Metadata Interface . . . . . . . . . . . . . . . . . . . 3
2.2.1. RatePacing Metadata . . . . . . . . . . . . . . . . . 4
2.3. Request Routing Redirection Interface . . . . . . . . . . 4
2.4. Logging Interface . . . . . . . . . . . . . . . . . . . . 5
2.5. Control Interface . . . . . . . . . . . . . . . . . . . . 5
3. Token Bucket Rate Pacing Algorithm and Parameters . . . 5
3.1. TokenBucketParams Object . . . . . . . . . . . . . . . . 6
3.2. Token Bucket Metadata Example . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
4.1. CDNI Rate Pacing Algorithms Registry . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
7. Normative References . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Rate pacing is a class of network traffic shaping which limits the
transmission rate of data over a network. In the context of a
Content Delivery Network (CDN), rate pacing provides an important
business advantage to a Content Service Provider (CSP) by ensuring
that a CDN which is delivering content on behalf of that CSP does not
deliver significantly more data than necessary to an end client.
For example, suppose an end client is watching some Constant Bit Rate
(CBR) video encoded at 1500 kbps. In the absence of rate pacing, the
CDN delivering this content may send it to the client at 3000 kbps.
If the client chooses to terminate the session before watching the
entire video, up to half the transmitted data is wasted. This waste
leads to unnecessary cost for the CSP and diminished useful capacity
for the CDN.
Rate pacing requires configuration on a per-content basis. In order
to enable rate pacing in a CDNI environment, the CDNI interfaces need
to be extended to optionally support this feature.
This document describes:
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1. CDNI interface extensions required for supporting rate pacing
2. a token bucket rate pacing algorithm for CDNs
2. CDNI Interfaces Impact
2.1. Footprint & Capabilities Interface
[I-D.ietf-cdni-footprint-capabilities-semantics] defines the CDNI
Footprint and Capabilities semantics. But at the time of writing, no
FCI syntax specification has been accepted as a working group
document.
[I-D.ietf-cdni-footprint-capabilities-semantics] states that:
"The CDNI FCI specification SHOULD define the registry (and the rules
for adding new entries to the registry) for the different capability
types. Each capability type MAY further have a list of valid values.
The individual CDNI interface specifications which define a given
capability SHOULD define any necessary registries (and the rules for
adding new entries to the registry) for the values advertised for a
given capability type."
This document defines a new capability type: "RatePacing" to be added
to the FCI capability types registry. The value of this capability
contains one or more rate pacing algorithm names from the Rate Pacing
algorithms registry (Section 4.1). For example, the value may be
"token-bucket/v1" to indicate that the advertising CDN supports the
token bucket algorithm described later in this document.
A CDN MAY advertise the "RatePacing" capability in the FCI if it
implements this specification. A CDN MUST advertise the "token-
bucket/v1" as a value in the list of algorithms if it advertises
"RatePacing" as a capability.
2.2. Metadata Interface
A new RatePacing metadata object is defined to represent the
configuration for rate pacing. The RatePacing object has MIME type
"application/cdni.RatePacing.v1". RatingPacing MAY appear within the
metadata list of either HostMetadata or PathMetadata (i.e. may have
either host-level scope or a path-level scope). The following
section defines the properties of the RatingPacing object.
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2.2.1. RatePacing Metadata
The presence of the RatePacing Metadata indicates that a dCDN MUST
comply with this specification in order to deliver a piece of
content. The metadata indicates the rate pacing algorithm name
required for delivering the content and the relevant parameters for
that algorithm.
Property: algo
Description: Rate pacing algorithm name from the Rate Pacing
Algorithms registry. Dictates the structure of the "params"
value. For example, "token-bucket/v1".
Type: String
Mandatory-to-Specify: Yes.
Property: params
Description: An object containing algorithm-specific properties
and values which are relevant to the rate pacing algorithm
specified by the "algo" property. Each algorithm dictates its
own parameters.
Type: Object
Mandatory-to-Specify: Yes.
2.3. Request Routing Redirection Interface
The RRI is not impacted by rate pacing. However, if the metadata for
a piece of content indicates that rate pacing is required by the
uCDN, then a request router should only redirect requests for that
content to CDNs which advertise "RatePacing" as a capability. The
request router should also limit its choice of dCDNs to those which
advertise the same rate pacing algorithm as is specified by the rate
pacing metadata. Note that this behavior is not specific to rate
pacing and is true of any CDNI feature.
For example, if the metadata for a piece of content includes a
GenericMetadata object of type "application/cdni.RatePacing.v1" and
the "algo" property in the value of that GenericMetadata is "token-
bucket/v1", then the request router of the uCDN should only redirect
requests for that piece of content to dCDNs which advertise a
capability type of "RatePacing" and a capability value of "token-
bucket/v1".
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2.4. Logging Interface
The rate at which a piece of content was delivered MAY be indicated
via the LI. The "sc-rate" field indicates the rate in bytes per
second as a decimal number. The bytes measured should correspond to
the sc-entity-bytes field.
sc-rate:
format: DEC
field value: the average rate in bytes per second at which a
response was delivered from Surrogate to client.
occurence: there MUST be zero or exactly one instances of this
field.
Note that existing fields defined by [I-D.ietf-cdni-logging] include
the bytes delivered and the time taken to service a request, which
could be used to estimate the delivery rate. However, the time taken
includes the acquisition latency which is not relevant to rate
pacing.
2.5. Control Interface
The CI is not impacted by rate pacing.
3. Token Bucket Rate Pacing Algorithm and Parameters
Token bucket is one example of a rate pacing algorithm. Token bucket
is described generically by [RFC1363].
The token bucket algorithm is characterized by two parameters:
1. Rate - the number of tokens added to the bucket per second
2. Size - the maximum number of tokens in the bucket
This document specifies the CDNI Token Bucket Rate Pacing algorithm.
It is based on the generic token bucket algorithm described above,
but applied to a CDNI context.
For the purpose of this document, each token represents one byte
transmitted as part of the body of an HTTP response from a Surrogate
in a dCDN. Tokens do not represent bytes which are part of HTTP
headers, the HTTP status line, TCP signaling, or any lower layer
protocol.
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The algorithm name "token-bucket/v1" is registered as a Rate Pacing
algorithm. This algorithm name MUST appear as the value of the
"RatePacing" capability. This name may also appear as the value of
the "algo" property in the "RatePacing" metadata object.
If a RatePacing metadata object's "algo" value is "token-bucket/v1"
then the metadata object's "params" MUST be an object of type
TokenBucketParams, described below.
3.1. TokenBucketParams Object
Property: rate
Description: Rate of tokens per second to be added to the
bucket as described by the token bucket algorithm. This value
MUST be a positive integer. Each token represents one byte.
Type: Integer
Mandatory-to-Specify: Yes.
Property: size
Description: Maximum number of tokens per bucket as described
by the token bucket algorithm. This value MUST be a positive
integer.
Type: Integer
Mandatory-to-Specify: Yes.
3.2. Token Bucket Metadata Example
{
"metadata": [
{
"generic-metadata-type": "application/cdni.RatePacing.v1",
"generic-metadata-value": {
"algo": "token-bucket/v1",
"params": {
"rate": 100000,
"size": 25000
}
}
}
]
}
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4. IANA Considerations
This document requests the following of IANA:
Addition of RatePacing in the CDNI Capability Registry defined in
TBD.
Addition of "RatePacing" to the standard partition of the CDNI
GenericMetadata Type Registry defined in [I-D.ietf-cdni-metadata]:
+-----------------------------+-------------+---------+------+------+
| Type name | Specificati | Version | MTE | STR |
| | on | | | |
+-----------------------------+-------------+---------+------+------+
| application/cdni.RatePacing | RFCthis | 1 | true | true |
| .v1 | | | | |
+-----------------------------+-------------+---------+------+------+
Addition of "sc-rate" in the CDNI Logging Field Names Registry
defined in [I-D.ietf-cdni-logging].
4.1. CDNI Rate Pacing Algorithms Registry
IANA is requested to create a new registry, CDNI Rate Pacing
Algorithms. The following table defines the initial values of the
registry:
+-----------------+---------------+
| Algorithm Name | Specification |
+-----------------+---------------+
| token-bucket/v1 | RFCthis |
+-----------------+---------------+
New rate pacing algorithm registrations MUST specify RatePacing
parameter objects as shown in Section 3.1 and MUST describe the
algorithm for rate pacing.
5. Security Considerations
A malicious CSP might attempt to use rate pacing to instruct a dCDN
to delivery some content at a very low rate thereby in order to
exhaust the resources of a dCDN by forcing connection state to be
maintained for longer than usual. The decision to enforce a rate is
left to the discretion of a dCDN. An implementation of rate pacing
should implement reasonable lower (and upper) bounds to avoid such
cases.
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6. Acknowledgements
The author would like to thank Francois Le Faucheur for his
contributions and feedback.
7. Normative References
[I-D.ietf-cdni-footprint-capabilities-semantics]
Seedorf, J., Peterson, J., Previdi, S., Brandenburg, R.,
and K. Ma, "CDNI Request Routing: Footprint and
Capabilities Semantics", draft-ietf-cdni-footprint-
capabilities-semantics-03 (work in progress), July 2014.
[I-D.ietf-cdni-logging]
Faucheur, F., Bertrand, G., Oprescu, I., and R.
Peterkofsky, "CDNI Logging Interface", draft-ietf-cdni-
logging-14 (work in progress), October 2014.
[I-D.ietf-cdni-metadata]
Niven-Jenkins, B., Murray, R., Caulfield, M., Leung, K.,
and K. Ma, "CDN Interconnection Metadata", draft-ietf-
cdni-metadata-07 (work in progress), July 2014.
[RFC1363] Partridge, C., "A Proposed Flow Specification", RFC 1363,
September 1992.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Author's Address
Matt Caulfield
Cisco Systems
1414 Massachusetts Ave
Boxborough, MA 01719
USA
Phone: +1 978 936 9307
Email: mcaulfie@cisco.com
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