ICN Research Group L. Li
Internet-Draft X. Xu
Intended status: Informational J. Wang
Expires: April 23, 2013 Z. Hao
ZTE Corporation
October 20, 2012
Information-Centric Network in an ISP
draft-li-icnrg-icn-isp-01
Abstract
Information-Centric Network (ICN) may be deployed over different
underlying networks, e.g. ad hoc networks, DTN and ISP's networks.
This document discusses deploying ICN in an ISP's existing networks
and ICN design for ISPs.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Deployment Considerations in an ISP . . . . . . . . . . . . . . 3
4. Routing and Caching Control . . . . . . . . . . . . . . . . . . 4
5. ICN with a Centralized Controller . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
Information-Centric Network (ICN) may be deployed over different
underlying networks, e.g. ad hoc networks, DTN and ISP's networks.
This document discusses deploying ICN in an ISP's existing networks
and ICN design for ISPs.
2. Terminology
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].
3. Deployment Considerations in an ISP
Information-centric networks can be deployed on top of layer-3 or
layer-2 networks. It should be preferable for ISPs to deploy ICN as
an overlay network on top of layer-3 networks, for the following
considerations: firstly, in the case of incremental deployment,
packets between newly deployed content routers have to go through
ordinary routers which do not understand ICN protocols; secondly,
content routers should be preferably deployed in areas with
requirements of reducing cost or improving Quality of Service (QoS),
and there is no necessity of deployment in areas where QoS
requirements can be fulfilled, and link cost is lower.
Content routers may be deployed at the edges of networks close to
content consumers, for the following considerations: firstly, early
cache hit at network edges means better QoS and more link cost
savings; secondly, deploying caches at network edges can mitigate the
impact of unstable wireless link in the case of mobile access users;
thirdly, it is easier to handle the requests since traffic is light
at network edges, and cache hits at network edges reduce the load at
content routers in core network which forwarding high volume traffic.
Content routers with huge cache spaces may be deployed in core
networks to achieve high cache hit rates. Research on cache, e.g.
[web_caching] and [cooperative_caching], shows that both cache size
and serving user number affect cache hit rate. Though early cache
hit is better, cache hit rate at network edge is limited. An edge
content router's cache hit rate is limited by its cache size and
serving user number. Firstly, in order to reach a high cache hit
rate, huge cache space is needed. But it's costly to deploy huge
cache spaces in large number of edge content routers. Secondly,
fewer users are served by an edge content router. As a result, a
large proportion of content requests are for one-time access
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contents, and hit rate is limited at network edges.
It is not necessary to deploy a deep hierarchy of content routers in
an ISP. On one hand, it is easier to deploy fewer content routers in
current network. On the other hand, it is preferable that the cache
space of a content router is much bigger that the one in a lower
tier, which means the number of tiers is small. Because of the Zipf-
like distribution of content requests, the cache size must grow
exponentially when the tier grows. Otherwise, cache hit rate of each
non-bottom tier is very low.
4. Routing and Caching Control
There are two ways to collect topology data and generate routing
table, namely, self-generation and centralized generation. In the
self-generation way, content routers run routing protocols to
exchange topology data inside an AS or among ASes. Then each content
router runs a routing algorithm locally to generate a routing table
independently. Alternatively, inside an AS, content routing tables
can be generated in a centralized way. In this way, one or more
controllers collect topology data, and generate routing tables for
all the content routers. Then the controller(s) sends route entries
to content routers.
There are also two ways to control caching. A content router can
decide to cache a content or not on its own by running a cache
replacement algorithm like LRU or LFU. However, an ISP may also want
to use centralized controller(s) to enforce some cache policies.
An ISP may utilize centralized controller(s) to enforce routing and
cache policy under following considerations. First, to meet QoS
requirement, an ISP may decide routing path and cache resource
assignment based on factors like content type, content download
frequency and distance to content source. Second, to reduce link
cost, an ISP may assign more cache resource for the contents passing
through costly links by controlling routing path and/or cache
priority. Third, to balance link load and cache load, an ISP may
optimize routes based on load status. Fourth, an ISP may provide
better services to paid users or content providers by controlling
routing path and/or cache priority.
To control routing and caching, an ICN controller may need to collect
not only topology data and traffic data, but also content data like
content type and content download frequency.
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5. ICN with a Centralized Controller
The figure below shows an example of ICN in an ISP. In this example,
there are two tiers of content routers, a tier of edge content
routers with small cache spaces and a tier of centric content routers
with huge cache spaces. To store massive contents, the centric
content routers use cache clusters. The ICN network is an overlay
network deployed over IP network. An ICN controller is responsible
for generating routing tables and sending route entries to content
routers.
O----------O O----------O
| content | | content |
| source |\ | source |
| node | \ | node |
O-+--------O \ O---+------O
/ \ |
/ \ |
/--------+--\ \ |
| | \,---------. ,----+----.
|controller |------------> ,' centric `. ,' edge `.
| | ( content ) ( content )
\-----------/ .'. router ,' `. router ,'
| `----+----' \ _..-'---+-----'
| .' | `. _.-' .' |
| .' | _..-\ .' |
| .' |__.-' \ .' |
| .' _.-| `..' |
| .' _.--' | .-'\ |
| .' __. | .' \ |
V .' _.-' | .' `. |
,---------. _.--' ,---+----.: \,---+-----.
,' edge `. ,' edge `. ,' edge `.
( content ) ( content ) ( content )
`. router ,' `. router ,' `. router ,'
`---+-----' `---------' `---------'
|
|
+--+----+
|content|
|client |
+-------+
The figure below depicts the roll of a centralized controller in the
ICN. Content routing tables of the routers and caching policy of the
centric content router (CCR) are all generated by the controller
according to its analysis of collected information, and ISP policies
can be enforced. When a content router starts up, it discovers the
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controller in the domain, registers at the controller, and obtains
its initial content routing table which is updated by the controller
afterward.
+--------+ +-------+ +-------+ +----------+ +-------+
| | | edge | |centric| | | | |
|content | |content| |content| | | |content|
|consumer| | router| | router| |controller| |source |
| | | (ECR) | | (CCR) | | | | |
+---+----+ +---+---+ +---+---+ +----+-----| +---+---+
| | | | |
1. content request:| | | |
icn://a.com/b/1.avi| | | |
|-------------->| | | |
| | | | |
| .---------------. | | |
| | 2. cache miss,| | | |
| |look up content| | | |
| | routing table | | | |
| `---------------' | | |
| | | | |
| | 3. forward content request |
| |------------------------------------------->|
| | | | |
| | 4. content response |
| |<-------------------------------------------|
| | | | |
| .---------------. | | |
| | 5. store the | | | |
| | content to | | | |
| | local cache | | | |
| `---------------' | | |
| | | | |
6. content response| | | |
|<--------------| | | |
~ ~ ~ ~ ~
| | 7. report request summary | |
| |---------------------------->| |
| | | | |
| | | .----------------. |
| | | | 8. analyse the | |
| | | |recv'd summaries| |
| | | `----------------' |
| | | | |
| | 9. instruction: | |
| | cache icn://a.com/b/* | |
| | |<-------------| |
| | | | |
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| | 10. routing table update: | |
| | icn://a.com/b/* -> CCR | |
| |<----------------------------| |
~ ~ ~ ~ ~
11. content request:| | | |
icn://a.com/b/2.avi| | | |
|-------------->| | | |
| | | | |
| 12. forward content req | | |
| |------------->| | |
| | | | |
| | .-----------------. | |
| | | 13. cache miss? | | |
| | |fetch the content| | |
| | | from source | | |
| | `-----------------' | |
| | | | |
| 14. content response| | |
| |<-------------| | |
| | | | |
15. content response| | | |
|<--------------| | | |
| | | | |
As shown by steps 1 to 6, upon receiving the content consumer's first
request to a video content in icn://a.com/b/, the edge content router
looks up the routing table, and forwards the request to the content
source. Upon receiving the response, it decides independently to
cache the content for a later use, according to a local cache
replacement algorithm.
As shown by steps 7 to 10, the controller collects request statistic
and generate routing tables and CCR caching policy in a centralized
way. Each content router generates a summary of requests it recently
received by some sampling techniques, and sends the summary to the
controller periodically. The controller generates content routing
table according to analysis of the summaries and the ISP's policies,
and sends the routing table updates to the routers. The controller
may decide that the centric content router stores entire or parts of
a content source site with higher request frequency. The centric
content router may prefetch the contents from the source site. The
edge content routers update their routing tables accordingly. A
routing table item in an aggregated form (in this example,
icn://a.com/b/*) will direct the requests to the centric content
router.
As shown by steps 11 to 15, upon receiving the content consumer's
second request to a video content in icn://a.com/b/, the edge content
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router forwards the request to the centric content routers.
6. Security Considerations
TBD
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[cooperative_caching]
Wolman, A., Voelker, G., Sharma, N., Cardwell, N., Karlin,
A., and H. Levy, "On the Scale and Performance of
Cooperative Web Proxy Caching", ACM Symposium on
Operating Systems Principles, 1999.
[web_caching]
Breslau, L., Cao, P., Fan, L., Phillips, G., and S.
Shenker, "Web Caching and Zipf-like Distributions:
Evidence and Implications", INFOCOM, 1999.
Authors' Addresses
Lichun Li
ZTE Corporation
Zijinghua Road 68
Yuhuatai District, Nanjing 210012
P. R. China
Email: li.lichun1@zte.com.cn
Xin Xu
ZTE Corporation
Zijinghua Road 68
Yuhuatai District, Nanjing 210012
P. R. China
Email: xu.xin18@zte.com.cn
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Jun Wang
ZTE Corporation
Zijinghua Road 68
Yuhuatai District, Nanjing 210012
P. R. China
Email: wang.jun17@zte.com.cn
Zhenwu Hao
ZTE Corporation
Zijinghua Road 68
Yuhuatai District, Nanjing 210012
P. R. China
Email: hao.zhenwu@zte.com.cn
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