[saag] Effects of Ubiquitous Encryption Draft: Caching in Mobile Networks

[Natasha Rooney <[e-mail]>]

Hi all!

First time post to this mailing list for me to please excuse any process mistakes! I have collected some information on caching in mobile networks (and on mobile) for the Ubiquitous Encryption draft. A lot of this information comes from academic studies and information that some mobile operators are willing to share. This is not my area of expertise so I am happy to hear any suggestion for changes. Also I would like to say that I support this draft not as a way to mitigate these issues but as one place which shows the effects of ubiquitous encryption for the IETF and the wider community. Many thanks and let me know if you have any questions!

Natasha

New suggested content below:

2.1.X.  Caching in Mobile Networks

Mobile networks operate a centralised architecture; traffic traverses through a small number of packet-gateways within the Core Network before reaching the internet[1]. These centralised architectures have lead mobile network operators to cache content. Forward caching is used in most cases [4].

Caching tends to occur in the Core Network. In LTE networks caching happens in the Packet Gateway (PGW) in the Evolved Packet Core (the evolution of the Core Network) [1]. Within 3G networks caching can again happen at the PGW and sometimes more specifically at the GI Interface which connects the GGSN (Gateway GPRS support node) and the PGW. Web caching can reduce download bandwidth consumption to around 25% [1] and have a cache hit ratio around 33%. Cache hit ratios naturally grow as the population increases.

Caching can happen at the Radio Access Network but is much less common; caching at this level is harder due to managing handover of users between base stations, although this technique may be suitable for some video use cases.

Caching in the mobile network both delivers content faster to users and create savings for mobile operators [5]. Caching at the RAN or on the handset would be preferred for latency saving [4], but cost savings and ease of deployment, use, and development of Core Network caches have lead to caching within the core network being more widely used.

2.1.X.1 Caching in Future Evolved Networks

Within the next few years a shift away from caching towards CDNs, interconnected CDNs and software defined networking is expected. This may offer further methods for moving content closer to the customer and over those bottlenecks in the network. In this case we may find the effects listed here to be less drastic and reliance on caching to decrease.

2.1.X.2 Caching Video

Video transcoding can often occur at the same time as content caching within the operator network. Some caching systems will request a video asset, discover the format and transcode this to a suitable mobile format and cache before delivering the content to the user [2]. Encrypting video content means both this caching and transcoding are no longer possible.

2.1.X.3 On-Device Caching

Transparent on-device caching caches data from browsers and apps on the device. This caching method can be configured to cache data specifically to a particular user, making content retrieval extremely fast by not needing to traverse any network [6]. Encrypted content cannot be cached by on-device cache solutions.

[1] http://www.cs.princeton.edu/~sihm/papers/monbot-mobisys13.pdf
[2] http://www.rcrwireless.com/20140522/wireless/video-optimization-cache-king-fixed-networks-mobile
[3] http://www-personal.umich.edu/~hjx/file/mobisys12_caching.pdf
[4] J. Erman, A. Gerber, M. Hajiaghayi, D. Pei, S. Sen, and O. Spatscheck. To Cache or not to Cache: The 3G case. IEEE Internet Computing, 2011., http://www-math.mit.edu/~hajiagha/InternetComputing.pdf
[5] http://pennysleuth.com/invest-in-cell-phone-infrastructure-for-growth-in-2010/
[6] http://www.mobolize.com/wp/wp-content/uploads/2015/01/Mobile-Endpoint-Optimization-Technical-WP.pdf

Thanks again!

Natasha


Natasha Rooney | Web Technologist | GSMA | [e-mail] | [phone] | @thisNatasha | Skype: [e-mail]
Tokyo, Japan


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