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This type of behaviour is classified as a 'revenue leak' within carriers and is a known irritant in the wireless telecom industry. The nature of the irritant is

by otoburb 13y ago

This type of behaviour is classified as a 'revenue leak' within carriers and is a known irritant in the wireless telecom industry. The nature of the irritant is naturally completely dependent on your point of view (end-user vs. carrier). Deep Packet Inspection (DPI) has several purported benefits and use-cases, most entirely technical and usually driven by entailing cost-saving/traffic steering requirements, with a few key use-cases around which revenue generating business cases can be modeled. Distinguishing tethering from on-device traffic via DPI is one way of accomplishing this; there are other, potentially more cost-effective ways to accomplish the same behaviour as already noted in this thread elsewhere (e.g. user-agent detection). As per the OP, another detection method is to have the OEM add a special route/flag when tethering is detected. The nature of the flag takes various forms (which in this case resulted in a new sourceIP from a different subnet be assigned to the device). Anybody that operates a network (wireless or fixed) implements similar traffic steering/shaping/QoS techniques. Without them, one cannot optimally leverage their heavy network capital investments.

e28eta 13y ago
Isn't user agent detection a form of DPI? They're looking inside the packets being sent, instead of simply using the level 2 and 3 information to determine where and how to route the packets.
- otoburb 13y ago
  Yes, user-agent detection is a form of DPI. At least in the telecom space, DPI often refers to investigating layer-7 packet payloads versus only parsing the L7 HTTP headers as an example. Arguably, due to the nested encapsulation of the ISO model which we all loosely base our understanding of the various network and application protocols, one could technically claim that parsing an IP (or TCP) payload counts as DPI, but that's not how the term is generally marketed or used by vendors nor network engineering or operating teams. The wikipedia DPI entry[1] is vague; IMO perhaps deliberately. For the purpose of this discussion, perhaps it would help to distinguish between source IP filtering (as per the OP) and L7 DPI capability.
gabriel34 13y ago
I understand that the pressure to drive down costs ends up driving traffic shaping. Such pressure comes from customers , competition, shareholders and managers inside the organization. You sell me a product for a price; if I want a different product, the price will be different. BUT I should know and be able to choose what I buy. Don't lie to the customers. PS.: Plus Carriers operate in a heavily distorted market (in most places competition is not free, there is heavy governmental influence and the customer has no choice) so the whole "invisible hand" argument I opened with is debatable.

by otoburb 13y ago

e28eta 13y ago

Isn't user agent detection a form of DPI? They're looking inside the packets being sent, instead of simply using the level 2 and 3 information to determine where and how to route the packets.

otoburb 13y ago
Yes, user-agent detection is a form of DPI. At least in the telecom space, DPI often refers to investigating layer-7 packet payloads versus only parsing the L7 HTTP headers as an example. Arguably, due to the nested encapsulation of the ISO model which we all loosely base our understanding of the various network and application protocols, one could technically claim that parsing an IP (or TCP) payload counts as DPI, but that's not how the term is generally marketed or used by vendors nor network engineering or operating teams. The wikipedia DPI entry[1] is vague; IMO perhaps deliberately. For the purpose of this discussion, perhaps it would help to distinguish between source IP filtering (as per the OP) and L7 DPI capability.

gabriel34 13y ago

I understand that the pressure to drive down costs ends up driving traffic shaping. Such pressure comes from customers , competition, shareholders and managers inside the organization. You sell me a product for a price; if I want a different product, the price will be different. BUT I should know and be able to choose what I buy. Don't lie to the customers. PS.: Plus Carriers operate in a heavily distorted market (in most places competition is not free, there is heavy governmental influence and the customer has no choice) so the whole "invisible hand" argument I opened with is debatable.