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Gi Firewall for mobile subscribers


Let me clarify a few points:

1. I am in favor of end to end connectivity and IPv6 can help restore this.

2. In the fixed broadband portion of the network this is the case.
IPv6 is routed to the subscriber CPE.
Firewall on the CPE is turned on by default, but can be turned off by the user.

3. In the mobile portion life are a bit more complicated.
Unsolicited traffic from the internet towards an idle subscriber triggers a signaling process called paging.
Extra paging is expensive in terms of signaling resource utilization, as well as on device battery.


Sent from my iPhone

On 10 Apr 2019, at 22:52, Owen DeLong <owen at delong.com<mailto:owen at delong.com>> wrote:

We have an ongoing discussion about Gi firewall (adding a firewall between the subscribers and the internet, allowing only subscriber initiated connections), for the IPv6 traffic.

The firewall is doing very little security, the ruleset is very basic, allowing anything from subscribers to the internet and blocking all traffic from the internet towards the subscribers.
We have a few rules to limit the number of connections per subscriber (to a relatively high number) and that is it.

What would be the process for a subscriber who wishes to allow inbound connections?

If you are simply saying that as a customer of your ISP you simply can't allow inbound IPv6 connections at all, then you are becoming a very poor substitute for an ISP IMHO.

 One of the arguments in favor of having the firewall is that unsolicited traffic from the internet can "wake" idle mobile devices, and create signaling (paging) storms as well as drain user batteries.

There are lots of ways to configure alerts and reduce this problem space. If you want to provide a checkbox on the my.t-mobile page for the user to turn this firewall on or off on a per device basis, then sure, I could see that as viable. Even if it annoyingly defaults to on.

On the other hand, allowing only subscriber initiated traffic is mostly achievable using ACLs on the mobile core facing routers, or is it with the growing percentage of UDP traffic ?
Is it even desirable to allow only subscriber initiated traffic?

Case in point, I will occasionally end up tethering my laptop (mobile hot spot) and want certain authorized individuals to be able to VNC into it via that tethering connection.

There have been other times when I've had things on the other side of a tether that I wanted to ssh into.

There are also things like Particle IONs where it is desirable to be able to push firmware updates OTA. I realize that Particle is sadly lagging on IPv6 support, but it will, hopefully, one day become a valid use case as well.

BTW - I don't mention IPv4 traffic on the mobile network as it's all behind CGNAT which don't allow internet initiated connections.
Yes, but IPv6 is supposed to hope us recover from this travesty.

Anyway, we are very interested to know hear more opinions,  and especially to hear what are other mobile operators do.

As is tradition, most operators screw the customer in one way or another in this regard. Some haven't thought about screwing customers in this particular way in IPv6 yet and so IPv6 sometimes works as one would hope.


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