For our readers in Uruguay, we are telling you about the implementation of ANTEL's SIP Trunk, hoping that it will be useful when contracting the service.
ANTEL has migrated its telephony core to IP, but until now it has maintained last-mile connectivity through traditional means, analog and digital lines (PRI, R2, BRI) using Media Gateways that perform media conversion.
This new service will allow for fully IP communication from end to end, from the signaling servers to the customer site without the need to insert equipment into the call path to convert the different media (IP-analog, IP-TDM or IP-GSM/3G).
Implementation in ANTEL
ANTEL's SIP Trunk service can be provided by any access medium available at the customer's site, whether dedicated fiber, FTTH or copper.
Since the maximum number of simultaneous calls that the Trunk can support depends on the access medium, this is an important factor to take into account when contracting the service.
Customers will be able to make and receive calls from or to any other ANTEL or third-party landline or mobile phone, national or international.
When contracting this service, the client will be able to choose between various plans for the number of simultaneous calls and number of telephone numbers.
It will be possible to migrate numbers that are in use by the client to the contracted Trunk. For the migration, in a first stage, the client must install a Trunk with new numbers and in a second stage, the numbers that need to be migrated are added.
The ANTEL MPLS network is used as transport to reach the NGN network.
Because the calls are not transported over the Internet high security and quality of service can be guaranteed.
Throughout the ANTEL network, calls are prioritized over other data.
In any case, if the client will interconnect the service with other networks, it is recommended that they install edge equipment (Firewall, E-SBC) between the PBX and the service connection.
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SIP Trunk Configuration
The service will be provided to the customer through an RJ45 port.
The Client must configure the following data in their IP PBX, which ANTEL will provide:
ANTEL SIP Server IP: IP to which the client should send SIP packets.
Client IP: IP from which the client should send SIP messages. It must be configured in PBX or Edge Equipment.
Default Gateway: IP that must be configured as Default Gateway to route packets to the Antel network.
Mask: Mask that the client must configure for the subnet where the “Client IP” is included
Telephone numbers: Numbers that the Client can use in the Trunk. It is important that the Client's outgoing calls have the CID configured with these numbers. Otherwise, the call will be rejected or will go out with the number included by default in the service.
Simultaneous calls: Number of simultaneous channels that the client can use.
The client must also configure the following parameters:
Source and destination SIP port: 5060
Supported codecs: G.711, T.38
Supported DTMF protocols: INBAND, RFC 2833
Session Expire (RFC4028): 600
NOTE: ANTEL trunk does not use SIP registration (no username and password are used). Antel sends the “OPTION” message as a heartbeat and the client equipment must automatically respond to this heartbeat with the message “200 OK” as shown in the following Wireshark capture example:
SIP Trunk Security Aspects
The client's IP PBX connects to the Public Telephone Network through an Antel Private Network, which guarantees the security and quality of the service.
It is important for the client to take care of their internal networks so as not to have security problems in their IP PBX just as they would do with a server.
Some recommended security measures are: using VLANs to separate the client's internal networks; properly configuring the Firewall or E-SBC to prevent Internet traffic from the Client on the IP PBX, gateways and IP phones; limiting TCP and UDP ports that can access the IP PBX.
Possible topologies:
Because SIP packets have an IP in the payload in addition to the network IP, this can cause difficulties if you want to do NAT. If the router is not able to interpret SIP, it will only change the network IP and will not be able to change the SIP IP within the payload.
Topology 1 – E-SBC:
If the client has an E-SBC, it will be in charge of the SIP communication with the ANTEL server. The PBX will have a Private IP address defined by the client both in the network layer and in the payload (SIP). When the packet arrives from the PBX to the E-SBC, the IPs are translated to the Trunk IPs provided by ANTEL. Since the E-SBC interprets the SIP packets, it is able to translate the IP of the payload.
The E-SBC will function as a telephony firewall, providing security, controlling and recording all SIP communications. This topology is recommended when the Trunk network needs to be interconnected with other networks.
Topology 2 Firewall:
In this topology, the client connects a firewall between the PBX and the ANTEL network, but the SIP communication will be between the PBX and the ANTEL server. The PBX will have a private IP address defined by the client in the network layer, but in the payload (SIP) the PBX must already incorporate the address provided by ANTEL because the firewall cannot translate this IP (most firewalls are not designed for telephony).
In a standard Firewall, a common error occurs when the packet arrives from the PBX to the Firewall, the Network IP is translated to the IP provided by ANTEL but the payload IP is not updated.
The firewall provides security, but it also needs to be configured correctly so that it does not block ports for call data packets.
Topology 3 Without Equipment:
In this topology, the client connects the PBX directly via UTP cable to the ANTEL equipment. The configuration is the simplest. The Trunk IPs provided by ANTEL are configured in the PBX both in the network layer and in the payload (SIP). It is recommended to use this “equipmentless” topology when the client does not need to interconnect the Trunk network with other networks.
Note: It is not recommended to connect the Trunk to a switch shared with other devices, either for security reasons or due to limitations in the ANTEL Modem MAC table. In this case, it is recommended to use VLANs or one of the previous topologies.
SIP Trunk Functional Testing
To check the operation of the SIP Trunk, it is recommended to perform the following tests:
Connectivity Tests:
Ping Default Gateway IP
Ping 190.64.60.4 and 190.64.60.20
Note: The SIP server IP does not respond to ping for security reasons, so the IPs 190.64.60.4 and 190.64.60.20 are used to test connectivity.
Trunk Tests:
– Outgoing and incoming calls: local, domestic, cell phones (ANTEL and other companies), international
– Make and answer multiple calls at the same time
– Make a call lasting more than 10 minutes
– Fax Operation
– Codec G.711
– DTMF
SIP Header Format:
As an example, here's what the SIP protocol INVITE should look like for a particular outgoing call:
Destination number to call: yxxxxxxx
ANTEL Server IP: 190.64.60.10
Client IP: wwww
Customer phone number: zvvvvvvv
INVITE yes: yxxxxxxx @190.64.60.10:5060 SIP/2.0
Via: SIP/2.0/UDP wwww:5060;
Contact: zvvvvvvv @ wwww:5060>
To: yxxxxxxx @190.64.60.10:5060>
From: « zvvvvvvv « zvvvvvvv @ wwww:5060>;tag=620f0b37
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REGISTER, SUBSCRIBE, NOTIFY, REFER, INFO, MESSAGE
Remote-Party-ID: « zvvvvvvv « zvvvvvvv @ wwww:5060>;party=calling
SIP Trunk Maintenance and Complaints
To claim the service the client can call 0800-2599 where you will have 24/7 technical support. The customer must file a claim with the Trunk service number.
It is important that the customer write down this number at the time of service installation in order to be able to make service claims quickly.
Note: Do not confuse the Trunk service number with its telephone numbers. The service number consists of the letter P and 5 numbers. Example: P12345
If the service must work in the event of a power outage, we recommend that the customer add a power backup to their IP PBX and the Modem that connects to the ANTEL network.
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In search of advice to hire a SIP Trunk for your company?
Talk to an expert.
In SimpleTECH We can help you, we have the specialized knowledge necessary for the change process to develop completely smoothly and without problems, please contact us.
We are the only Spanish-speaking 3CX Platinum and Support Partner in Latin America.
By: The team of SimpleTECH©
Montevideo, Uruguay
Sources:
Antel Uruguay www.antel.com.uy
