Internet DRAFT - draft-liu-cdni-cost
draft-liu-cdni-cost
CDNI H. Liu
Internet-Draft Yale University
Intended status: Informational Oct 22, 2011
Expires: April 24, 2012
A Cost Perspective on Using Multiple CDNs
draft-liu-cdni-cost-00
Abstract
This document describes several potential price and charge issues in
CDN interconnection. It discusses some optional charge models when
CDNs are interconnected and presents a need from Content Service
Providers (CSP) or CDNs to optimize their cost locally and guarantee
their performance. It finally shows how can CDNI frameworks and
protocols support price, charge and policy information exchanging.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1.1. Content Customer (CC) . . . . . . . . . . . . . . . . . 3
1.1.2. Content Service Provider (CSP) . . . . . . . . . . . . 3
1.1.3. Upstream CDN (U-CDN) . . . . . . . . . . . . . . . . . 3
1.1.4. Downstream CDN (D-CDN) . . . . . . . . . . . . . . . . 3
1.1.5. Relay CDN (R-CDN) . . . . . . . . . . . . . . . . . . . 3
2. Charge Models in CDNI . . . . . . . . . . . . . . . . . . . . . 3
2.1. CDNI Network . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Recursive Charge Model . . . . . . . . . . . . . . . . . . 4
2.3. Interative Charge Model . . . . . . . . . . . . . . . . . . 5
3. Local Optimization . . . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Considerations . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
The cost optimization perspective so far has not been considered in
inter-connecting multiple Content Delivery Networks (CDNs).
Specifically, a Content Service Provider (CSP) with multiple CDNs may
consider cost or conduct cost optimization, in addition to
performance, when deciding how to direct a request when it has
multiple candidate CDNs.
This draft discussses some potential charge/price models in CDNI and
shows that CSPs and CDNs can optimize their benefit locally, based on
charge and performance information. It also shows how to integrate
the model into CDNI's protocol and architecture design.
1.1. Concepts
1.1.1. Content Customer (CC)
A content customer downloads and consume content from Internet.
1.1.2. Content Service Provider (CSP)
A content service provider leverages CDNs to delivery their content
to content customers over Internet.
1.1.3. Upstream CDN (U-CDN)
Upstream CDNs are directly connected with CSPs. CSPs have commercial
contract with upstream CDNs and can upload content objects into them.
Upstream CDNs charge their CSPs according to the storage, number of
requests and traffic usage.
1.1.4. Downstream CDN (D-CDN)
Downstream CDNs serve content customers directly. The content
requests will be finally redirected to downstream CDNs.
1.1.5. Relay CDN (R-CDN)
If a CDN is on the path of content delivery, but is neither an
upstream CDN nor a downstream CDN, it is a relay CDN.
2. Charge Models in CDNI
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2.1. CDNI Network
Figure 1 shows a simple case when CDNs are interconnected. CSP rents
two upstream CDNs, U-CDN-1 and U-CDN-2. To delivery content to CC-2,
CSP-1 can choose either U-CDN-1 or U-CDN-2 to carry the task.
Typically, the costs and performances of U-CDN-1 and U-CDN-2 are
different. CSP needs the price and performance information for the
decision. Next we present two potential and simple charge models in
CDNI.
+-------+
| CSP-1 |-----------------------
+-------+ |
| |
,---------. ,---------.
,-' `-. ,-' `-.
( U-CDN-1 ) ( U-CDN-2 )
`-. ,-' `-. ,-'
`---------' `---------'
| /
,---------. /
,-' `-. /
( R-CDN-1 ) /
`-. ,-' /
/ `---------' \ /
/ \ /
,---------. ,---------. /
,-' `-. ,-' `-.
( D-CDN-1 ) ( D-CDN-2 )
`-. ,-' `-. ,-'
`---------' `---------'
| |
+-------+ +-------+
| CC-1 | | CC-2 |
+-------+ +-------+
A Simple Case of CDN Interconnection
Figure 1
2.2. Recursive Charge Model
In this model, CSP-1 does not know about how U-CDN-1 and U-CDN-2 will
handle the content delivery tasks. It only redirects the requests
from CCs to U-CDN-1 or U-CDN-2, and the upstreaming CDNs will
response or redirect the requests. For CSP-1, it only knows about
the price and the performance to select U-CDN-1 or U-CDN-2. U-CDN-1
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will make contracts with R-CDN-1 and so does U-CDN-2 with D-CDN-2.
2.3. Interative Charge Model
In this model, CSP-1 has the knowledge about the details of the
content delivery paths. Interatively, U-CDN-1 tells CSP-1 about the
price to R-CDN-1, R-CDN-1 tells CSP-1 about the prices of D-CDN-1 and
D-CDN-2. When CSP-1 knows about all the options to delivery the
content, it can choose an optimal one which can maximize its
benefits.
3. Local Optimization
With the price and performance information provided by CDNs, CSPs can
locally perform an optimization. If its target is to minimize its
CDN cost, it needs to consider the storage and traffic costs of all
the options. It can smartly put populary content into CDNs whose
traffic prices are cheaper and put cold content into CDNs whose
storage prices are cheaper. If its targets is to get best delivery
performance, it can choose the best delivery path according to the
performance feedback information.
4. Protocol Considerations
Given that CDN charge or price infomation is various with time and
essential to CPs and CDNs, it is best to be considered in CDNI
protocol design. The messages carrying this information can be
exchanged among CPs and CDNs. The CDN performance information can be
sent by CDNs themselves or CCs to CSPs. To select a U-CDN or a
content delivery path, a CSP can leverage the request redirection
mechanism.
5. Security Considerations
This document does not contain any security considerations.
6. IANA Considerations
This document does not have any IANA considerations.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", BCP 14, RFC 2119, March 1997.
Author's Address
Hongqiang Liu
Yale University
Email: hongqiang.liu@yale.edu
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