The Signalling Storm is coming, its not the question of 'if' but when. This was the unanimous message from the Signaling Focus Day of the 8th LTE World Summit 2012. Several high profile outages have been associated to the Signalling storm, NTT Docomo and Verizon being the main one. Luckily the Telenor outage was due to software issues.
The problem is divided into two parts, the Access network part where the Air Interface is the bottleneck and the core network part which can easily be swamped by the overwhelming amount of Signalling due to more intelligent billing system and always on devices with background applications generating much more amount of traffic as would have on an older system. Lets look at them in turn.
Core Network Signalling Storm:
As I reported earlier, Diameter has been highlighted as a way of salvation for the operators with dozens of use cases but due to its immaturity has caused outages and have given it a bad name. As Connected Planet mentions, "According to one signaling expert, launching the iPhone’s browser, for example, instantly sets off about fifteen individual network signaling requests. Beyond that, 4G network software elements supporting increasingly sophisticated mobile service scenarios “talk” to each other at rates that traditional TDM/SS7-based networks never had to deal with." Hopefully a stable implementation of Diameter protocol will help not only solve the signalling storm but will help generate new models for charging and revenue generation.
A presentation by Ed Gubbins of Current Analysis, comparing the big vendors of Diameter Signalling is available here.
Access Network Signalling Storm:
My thinking is that the Core Network Signalling problem will become an issue some years down the road whereas the Access Network Signalling problem will be seen sooner rather than later. In fact for 3G/HSPA the problem is becoming more visible as the market has matured and more and more users are moving towards using smartphones, Since LTE rollouts are in its infancy (in most markets) the problem is still some way away.
One of the reasons for Signalling storm is the incorrect APN name. I reported earlier about Telefonica's approach to solve this problem by using 'Parking APN', see here.
Also embedded below are couple of presentations from the Signalling Focus day that talk about the problem from Access Network point of view
Other Interesting Reading Material
Finally there is an excellent whitepaper from Heavy Reading titled "The Evolution of the Signalling Challenge in 3G & 4G networks", available here to download.
Another excellent article summarising the problem is from Huawei magazine available here.
2 comments:
Hmm. A lot of marketing, smoke and mirrors.
Yes it is a problem that signalling is increasing a lot due to smartphones, BUT:
Cell/URA_PCH has been available for 5-6 years and finally implemented.
3GPP Fast Dormancy once implemented on terminals, will help greatly not to mention CPC, FDPCH, SRB on HSPA, High speed FACH et al. It's a matter of terminals that don't support the newer more advanced features. The network can only wait until the terminal vendors (and some late network vendors) come and implement the features.
Huawei's concept of using two-tunnel for smartphones is not very smart since it increases user plane latencies by going through an SGSN on the very devices it should be minimised on. Seems more of an hack to work around their own deficiencies.
APN parking or Smart APN has been available for several years on some vendors' SGSNs. In those cases if the DNS lookup for the APN fails, it takes the user's profile's APN or the SGSNs default APN (in that order) and tries again. No storms due to misconfigured APNs.
Some of the stuff in the slidesets is brilliant marketing, but ptoblems already solvable with current solutions.
LTE Signaling
Tuesday, July 10, 2012 There is a Signaling storm coming are you ready?
LTE Signaling Blog, here let us share ideas to protect the operators from the typhoon brewing off the coast of this arena…..
http://diametriq.blogspot.com/2012/07/there-is-signaling-storm-coming-are-you.html?spref=tw
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