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.

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Copyright Notice

Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

• 1. Introduction
• 2. Terminology
• 3. Deployment Considerations in an ISP
• 4. Routing and Caching Control
• 5. ICN for ISP Example
• 6. Security Considerations
• 7. References
• 7.1. Normative References
• 7.2. Informative References
• Authors' Addresses

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 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.

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 |
    +-------+

 +-----------+                +------------+              +---------+
 |  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

7.2. Informative References

Authors' Addresses