Callcentric Runaroud

[bboyd]

For the past couple of weeks our service provider (Callcentric) has been having "problems". Our inbound and outbound connections are cut off while they "research" into these attacks that are taking down the system. I was just curious to know what other people are doing while this complete mess gets sorted out. I really like callcentric compared to other providers but didn't know if someone has a redundant service they would recommend while primary services are down. If I could get just inbound to work while on redundant services that would be fine by me.

 

[rayfield]

I've been using Callcentric for my service at my office for almost 1 year, with no problems that I can remember. But this situation over the last couple of weeks has really caused me serious problems.

So, I set up an account with VoIPStreet. I set up outbound calling to go through them.

Then for inbound, I set up call forwarding in Callcentric's system, to forward all calls to my 'main' DID number (which, of course, is on Callcentrics system) to a DID number on VoIPStreet's system.

Doing this adds a couple of extra seconds, when someone dials my 'main' DID number, before they start to hear ringing. But, this is working well, so far. At this point, call forwarding has not been affected by the 'attacks' on Callcentric's servers.

As to VoIPStreet's service, I've used them off and on, for several months now, to 'test' their service. So far, the quality of service seems to be near, or even comparable to, Callcentric's service. I've also used Vitelity, but in my experience with them, their call quality isn't quite as good as Callcentric's (or VoIPStreet's). I may end up porting my 'main' number from Callcentric over to VoIPStreet and just using them. I've also got a couple of customers, who have been using Callcentric's service, that may end up being switched to VoIPStreet's service.

John Rayfield, Jr.

 

[bboyd]

I am glad to hear we are not the only ones having so much trouble. I have about had it with the anyways, no customer service, always a problem, and you can only get ahold of them thru that stupid ticket thing. But it is neither here nor there now. Do you have something on the setup connection between your 3cx server and your VoipStreet account? I can't find anything on a setup documentation like the other service providers.

 

[jpillow]

I've had the exact same problem, and the worst part is they will not even answer ticket nor give updates.

 

[DBOD]

I also had some troubles during the DDOS attack. I managed to keep inbound calls coming by going to the callcentric site and forwarding my DIDs to my PBX directly. It defaults to forward to the registered SIP but registration was failing frequently during the attack.

My concern about the forwarding though was I have a dynamic IP address. Fortunately it almost never changes. Actually I'm not sure it has ever changed. Now that CC is up and running again I have reverted back to the default condition.

My current settings are

SIP server callcentric.com port 5060
Outbound Proxy server srv.callcentric port 0

This has worked very well for the last two weeks. CC was pretty good about getting trouble tickets answered during the crisis.
Good luck.

 

[DBOD]

One more change I made during the crisis was to add another voip provider. I went with voip.ms and it was easy to configure them for outbound calls. I set them up to be an alternate provider in my outbound rules and it saved me a few times during CCs problems. I will keep them as a back up for now. I didn't need to purchase any DIDs. They let me put my main phone number on the caller id without any problem. Their site was easy to use. They may even be cheaper. One problem that I did have with voip.ms was my staff was complaining about DTMF issues like not hearing ringing or button tones. It is probably a configuration issue on my side though which when I finish putting out all my other fires I will investigate.

For now callcentric is more robust and my system is also.

 

[ao]

Call Centric Updates?

Does anyone have any useful information pertaining to Call Centric? My PBX can't register to their service, in addition to all of my customers phone systems. This is a disaster!

 

[jpillow]

Does anyone have any useful information pertaining to Call Centric? My PBX can't register to their service, in addition to all of my customers phone systems. This is a disaster!

Get a new provider thats what seems to be the concensus

 

[DBOD]

Stop using DNS A records. Move over to the DNS SRV records. You can force 3CX to look for SRV records by specifying port 0 in the Outbound Proxy server.

I have been DID forwarding all incoming calls directly to my SIP URL. You can change that setting on Callcentrics website. It works well if you have a static IP or even a dynamic IP like mine that never changes. By default Callcentric forwards incoming calls to the registered SIP. If you aren't registered they don't know where to send it. By forwarding incoming call to a SIP URL you get around the registration problem. Forwarding to sip url only works if you have your sip ports open (range 5060-5080 and 10123). It may not be opened if you are not registered. Check your router and PBX firewalls. Also if you use inbound firewalls that explicitly allow UDP RTP traffic from callcentric, remember they now have 20 IPs that you must allow unless you are fortunate enough to have a router that allows you to specify a range of IPS. Mine unfortunately makes me manually enter them. Callcentric only uses 20 now (up from 12 a few weeks ago) but their address range covers 255 addresses that they can use at any time.

For outbound calls you need to use Outbound Proxy server callcentric.com port 0 (current recommendation) or even srv.callcentric.com port 0 (older recommendation from callcentric). This actually works quite well. This also presumes your DNS is correctly reporting SRV records. Many DNS servers are reporting truncated responses or have other issues because Callcentric is reporting so many servers that is exceeds the size limitations of UDP. If you use a good DNS server and get a truncated response, your host should use TCP to get the full list of Callcentric SRV servers. The answer to the query should in 40 servers. alpha1 thru alpha20.callcentric.com with ports 5080 and ports 10123. Callcentric lists two DNS servers that they tested and respond correctly. You can use any DNS server that you wish. I have AT&T U-verse. Their two DNS servers work correctly. However the U-verse modem operates as a DHCP server and wants the LAN to use it (192.168.1.254) as the DNS server. You would think that it would turn around and use the two At&t DNS servers and work correctly. It does not. So explicitly specify which DNS servers I want to use on my Windows 7 PBX. On Windows 7 you must check the "validate settings on exit" box to get the new DNS settings to be effective. And then you must also restart all 3CX services if you want it to use the new DNS setting. Might be easier to reboot.

Now I haven't tried this yet but I think the SIP server is also going to work better with callcentric.com port 0. Get your DNS straignt first. And get Wireshark so you can see what is going on.

Goodluck.

 

[DBOD]

For the last month I have been running my 3CX system with both the sip server and outbound proxy server set to callcentric.com port 0. Specifying Port 0 seems to force it to use SRV records.Last nights registration problems made me look at what is happening a little closer. I tried a few different configurations and this is what is happening using Wireshark.

SIP and Outbound Proxy servers set to callcentric.com port 0

3CX pulls the SRV EDNS records correctly. 40 different answers to the UDP/TCP query with ports 5080 and 10123 on 20 servers in a different order each time but with the same priority set. 3Cx then selects alpha1.callcentric.com EVERY time and pulls the A record to get the ip address. It then proceeds to register with callcentric.com on one of the SRV ports.

SIP and Outbound Proxy servers set to callcentric.com port 5080 or 10123 or 5060
3CX only pulls the DNS A records. It gets 20 different answers to the UDP query in a different order each time. 3CX then selects the first server in the list for registration on port 5080 or 10123 or 5060 depending on the one you specified.
Now I don't know all of the details of how a DDOS attack works or how to mitigate one. But I can understand why having more servers and more ports helps callcentric and ergo the customers. But I have a few questions.

Are both CC and 3CX behaving correctly when it comes to using the DNS SRV records? Why does CC return them always with the same priority in the small sample sets that I have seen? Why does 3CX use the first one in the list for A records but always pull alpha1.callcentric.com from the SRV records. If 3CX always uses alpha1.callcentric.com, does that undermine callcentric's attempts to load balance and DDOS attack mitigate? Does it also make 3CX users on CC more vulnerable to degraded or no service? Would it be better to just specify port 5080 or 10123 and use the A records so we get assigned servers more randomly? If registration results in a new server assignment every 60 seconds, can 3CX/Callcentric play nice in the middle of a call?
I have seen a few BYE sip messages return a transaction leg not valid error. I have wondered if that was from server reassignment in the middle of a call. I also wondered when that call gets terminated finally. Anyone with thoughts? Thanks.