ICN Research Group L. Li
Internet-Draft X. Xu
Intended status: Informational J. Wang
Expires: January 10, 2013 Z. Hao
ZTE Corporation
July 9, 2012
Information-Centric Network in an ISP
draft-li-icnrg-icn-isp-00
Abstract
ICN (Information-Centric Network) may be deployed over different
underlying networks, e.g. ad hoc networks, DTN and ISP's networks.
This document discusses deploying ICN in ISP's existing networks and
ICN design for ISP.
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 for ISP Example . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
ICN (Information-Centric Network) may be deployed over different
underlying networks, e.g. ad hoc networks, DTN and ISP's networks.
This document discusses deploying ICN in ISP's existing networks and
ICN design for ISP.
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, self-generation and centralized generation. In the self-
generation way, content routers run a routing protocol to exchange
topology data inside an AS or among ASes. Then each content router
runs a routing algorithm locally to generate a routing table.
Alternatively, inside an AS, content routing tables can be generated
by the centralized way. In this way, one or more controllers collect
topology data, and generate routing tables for 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 for ISP Example
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 above figure 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. Content request routing in the example is shown in the
figure below.
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+-----------+ +------------+ +---------+
| content | | content | | content |
| consumer | | router 1 | | router 2|
+----+------+ +-----+------+ +----+----+
| | |
| | |
.----------------. | |
|1.obtain content| | |
| name | | |
`----------------' | |
| | |
| | |
| 2.Send content request | |
|---------------------------->| |
| encapsuled in IP packet | |
| | |
| .-----------------. |
| | 3.look up cache | |
| | and PIT table | |
| `-----------------' |
| | |
| | |
| .-----------------. |
| | 4.look up | |
| | routing table | |
| `-----------------' |
| | |
| | |
| | |
| | 5. Send content request |
| |------------------------->|
| | encapsuled in IP packet |
| | |
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.
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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., Cue, P., 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
RD Building 1,Zijinghua Road No.68
Yuhuatai District,Nanjing 210012
P.R.China
Email: li.lichun1@zte.com.cn
Xin Xu
ZTE Corporation
RD Building 1,Zijinghua Road No.68
Yuhuatai District,Nanjing 210012
P.R.China
Email: xu.xin18@zte.com.cn
Jun Wang
ZTE Corporation
RD Building 1,Zijinghua Road No.68
Yuhuatai District,Nanjing 210012
P.R.China
Email: wang.jun17@zte.com.cn
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Zhenwu Hao
ZTE Corporation
RD Building 1,Zijinghua Road No.68
Yuhuatai District,Nanjing 210012,
P.R.China
Email: hao.zhenwu@zte.com.cn
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