3G Router for VOIP

[Broadcom]

Peon, did you ever get to the bottom of this?

I'm also using 3G with an IP phone, and have discovered that incoming call issues can be related to what mode the 3G router is in. In idle mode (WCDMA) if the signal is poor, the invite packets aren't responded to quick enough and the call goes to voicemail, even thought the phone sometimes rings. When the router switches to HSPA, the latency is good and all works as it should.
Really, the invites should have a longer timeout, I understand up to 32 seconds, but that's not what I'm experiencing.

[Peon]

Broadcom, the Atcom phones have worked over the YeaLink phones. I adjusted payload length from 20ms to 30ms. This seemed to work better. I have been using only 1 phone. Shortly I will add another 3 and report the results.

[gmza]

It seems that Vodacom has made another change that has blocked VoIP. All existing users that were working fine for months suddenly stopped working all at the same time. I give up with VC; I'm now just advising people to cancel their Vodacom 3G and go with any of the others (MTN/CellC/8ta).

VC are so anti-competitive in so many different manners, that this is hardly a surprise. Blocking VoIP over their 3G is the tip of the iceberg.

[Peon]

I concur, VodaCom I as a client am calling you out. You are blocking my VoIP. As I write this I have 1 of the trouble phones on my table running over adsl. Its flawless. We will not pay a single cent until you fix this.

How can you advertise being a pro South African company yet engage is childish practices, not even uncompetitive, childish.

Now the problem has widened and includes SMTP traffic. No SMTP traffic works.

I must also confess that you Advanced Data Support was lacking. Advanced Data Support could not give me a definitive answer.

Not a single cent until you send a team out to us.

[WireFree]

It seems that Vodacom has made another change that has blocked VoIP. All existing users that were working fine for months suddenly stopped working all at the same time. I give up with VC; I'm now just advising people to cancel their Vodacom 3G and go with any of the others (MTN/CellC/8ta).

VC are so anti-competitive in so many different manners, that this is hardly a surprise. Blocking VoIP over their 3G is the tip of the iceberg.

Hi gmza and Peon,

I've done some of my own investigations this evening. I used a Cell C SIM and a Vodacom SIM with a SIP client on my laptop and a SIP server on the Internet.

1) I've noticed that Vodacom is now assigning private IP addresses to me. Previously I used to be assigned a public IP address. Since I am assigned a private IP address there is a NAT router before the Internet with a SIP ALG.
2) Cell C assigns a public IP address. A SIP trace on my laptop and a SIP trace on my Internet server shows that the SIP messages are identical. So there is no modification are broken SIP ALG on their firewall.
3) On Vodacom however, the SIP ALG is modifying the SIP messages as well. The REGISTER message from my laptop is modified to include the public IP address and "102 REGISTER" becomes a "106 REGISTER". The response from my server also never reaches my laptop.

I suspect that they've installed a NAT router with a broken SIP ALG. It may not be a deliberate attempt to block SIP, or else there is no point in them sending the SIP REGISTER message to the SIP server on the Internet. Anyway, the SIP traffic on Vodacom is probably small compared to Skype, which isn't easy to block.

Peon, I suspect the same broken NAT router is affecting your SMTP traffic.

WireFree

[gmza]

Hi WireFree

In the original tests we did, registrations worked fine. The signalling was broken during call initiation (response to INVITE packet). But that being said, something changed more recently that has broken registrations as well.

Keep in mind that there is a regular APN and an unrestricted one. The unrestricted is supposed to use public IPs and not be subject to NAT, ALGs, etc. Operative word being "supposed."

But I hear what you're saying and, if that is the case, then simply moving the SIP signalling to a port other than 5060 should do the trick, so I've created a secondary port on the server side.

I don't have my Vodacom test SIM with me at the moment (it's at the office), but I'll PM Peon the new UDP port to try.

Thanks for the suggestion.

[WireFree]

But I hear what you're saying and, if that is the case, then simply moving the SIP signalling to a port other than 5060 should do the trick, so I've created a secondary port on the server side.

Let me know how it goes. With SIP on a different port the signalling should be fine but the RTP ports may not open up on the firewall. The ALG on 5060 is responsible for opening the ports for RTP. On the unrestricted APN you should not have a problem. The only risk with the unrestricted APN, is that anyone on the public Internet can send arbitrary traffic to your IP address and you get billed for it.

WireFree

[gmza]

Let me know how it goes. With SIP on a different port the signalling should be fine but the RTP ports may not open up on the firewall. The ALG on 5060 is responsible for opening the ports for RTP. On the unrestricted APN you should not have a problem. The only risk with the unrestricted APN, is that anyone on the public Internet can send arbitrary traffic to your IP address and you get billed for it.

WireFree

My side is NAT friendly, so it automatically discovers when there is NAT at play and responds with the RTP to the actual (public) IP address that the SIP originates from, not to the signalled (private) IP address that the SIP signalling refers to. For this reason there is no need for an ALG.

Initial feedback is that it appears to work fine when not using port 5060, so I think you're right: it's a broken ALG. It's just strange because one of the sites affected is supposed to be on the public APN...

I'll test fully during the week when I have access to the VC SIM. Then I can also set up Wireshark on both ends and see that no packets are being dropped or meddled with!

None of this explains, however, why other non-standard ports are being blocked. E.g. Last time I tried (admittedly months ago), ViBE routers that talked happily over ADSL wouldn't play nicely over VC 3G. That's not on port 5060.

[TSpeed]

hi gmza, Sip connected through Vodacom 3g with my E71, can make and receive calls, don't think it is a port 5060 issue , maybe something else like firewall or nat

[WireFree]

hi gmza, Sip connected through Vodacom 3g with my E71, can make and receive calls, don't think it is a port 5060 issue , maybe something else like firewall or nat

Hi TSpeed,

In which town/city are you located?

WireFree

[TSpeed]

WireFree, i am in Pretoria, sinoville , make use of my own sip server. I do offer free sip accounts at http://www.rapidaccess.co.za/Services.html You can create a free account, or download our Sip client which will auto
create the account. Just make sure you run the application as Administrator as i write information into the registry.

[WireFree]

WireFree, i am in Pretoria, sinoville , make use of my own sip server. I do offer free sip accounts at http://www.rapidaccess.co.za/Services.html You can create a free account, or download our Sip client which will auto
create the account. Just make sure you run the application as Administrator as i write information into the registry.

I've registered on your website.
On my office LAN I get "Got 404 Not found on SIP register". Anyway, this suggests that I received a response from your SIP server for a REGISTER.

On Vodacom, I get no response back!

I assume your phone works in Pretoria because you are probably breaking out on a different NAT router/firewall.

WireFree

[TSpeed]

WireFree, i suspect you used your username to log in and not your user id <314> therefore the 404 message, remember password is case sensitive, must be exactly the same as when account was created, anyhow i think your problem lies with VC APN, you have to apply for unrestricted APN at Vodacom.

[WireFree]

you have to apply for unrestricted APN at Vodacom.

As I mentioned earlier the risk with the unrestricted APN is that anyone on the public Internet can send arbitrary traffic to your IP address and you get billed for it. Someone on the Internet can just send packets continuously to the IP range assigned to the unrestricted APN and either cause you to get a HUGE bill on your contract SIM at the end of the month or deplete the data bundle/airtime on your pre-paid SIM (a form of DoS). Even if you don't respond to strange out of the blue packets from the Internet, Vodacom still bills you for it.

The unrestricted APN would work best on an uncapped billing model, or speed based billing model.

[TSpeed]

Unless you are updating DNS and making your IP address public, i doubt that you will ever get a DoS attack. a DoS attack normally
targets installations running a type of service like WEB Hosting or Voip service. So i would say it is rather safe to apply for unrestricted APN of you only running a VOIP client.