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Technical Guide

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Product

SIP Trunking

SIP trunks  are typically configured as a direct logical connection between the Colt SIP Trunking platform and the customers’ IP PBX  (or SBC). The service does not provide a registration capability (with respective challenge authentication), but trunks are established using IP addresses to exchange  SIP Signalling messages between the customers IP PBX (or SBC) and the Colt Session Border Controller (SBC).

A Trunk is defined as a logical entity used for VoIP signalling and media control, defined between a unique pair of IP addresses on the Colt Session Border Controller (SBC) and the Customers  IP-PBX (or SBC) Equipment. A Trunk Group is a logical entity that defines the grouping between one or more trunks, belonging to the same customer, that share the same DDI telephone number ranges and other parameters such as call admission control and other features.

Number Hosting

Number Hosting stands for wholesale SIP Trunking, enabling you as a Colt customer to offer SIP Trunking capabilities to your customers – our end users. You decide about the offered features and can add phone numbers to your trunks according to your needs.

Voice Line (v)

Colt’s ISDN services combine the traditional TDM Voice service with the advantages of SIP trunking.

Voice Line (v) is an enhanced ISDN service over SIP. Colt deliver full inbound and outbound services with ISDN Primary Rate Interface (PRI/ISDN30)) across Colt’s VoIP platform. the IP network. The service provides a range of TDM interfaces that can be connected to the your (TDM based or hybrid) PBX, allowing you to continue with ISDN telephony. Depending on the access type, we can present up to 10 PRIs (300 voice channels). For outbound traffic you route ISDN/TDM traffic to the on-premise Colt managed Voice Gateway which will convert the traffic to VoIP, and will route calls to the Colt VoIP network and to the PSTN. For inbound traffic the reverse happens.

Voice Line (v) over Internet

Here are the prerequisites for ISDN over Internet service

Mandatory conditions your connectivity should be compliant with:

- In case a capacity of more than 2 PRIs is required, a bespoke solution with POC is due.

- In case of convergence, the minimum bandwidth capacity is the double of IP bandwidth required for voice traffic, otherwise the minimum requirement is the IP bandwidth required for Voice.

- Your broadband router should support QOS, COS and IPSec passthru. Unless static routing is chosen, one DHCP enabled LAN port must be available for Colt s Voice Gateway per max. 2 PRIs.

- In case of Firewall, to allow the traffic to pass through, the customer will have to  whitelist IP Addresses of the Colt target routers  212.36.166.254 & 213.41.124.30.

- UDP ports 500 & 4500 should be enabled to all the IPSec protocol to build the encrypted tunnel from the customer's router to the Colt target routers.

- Colt cannot manage your router. In case of issues with the internet connectivity, your must handle the communications and resolution with the ISP (Internet Service Provider). The ISP must allow traffic to pass through.

Summary

Trunk Group ID

A trunk group gathers multiple trunks, if applicable. Even in case of a single trunk, Colt allocates it to a Trunk Group, which is higher up in the hierarchy.

Colt also assigns a Voice Line (v) service to a Trunk Group, even if this is an ISDN Service supporting your TDM PBX. A trunk group consolidates the phone numbers (DDIs) across multiple trunks or PRIs. For Voice Line (v), this allows Colt to do complex incoming call distribution in case of a solution covering more than 1 site or PRIs.

Voice Service Country

This is the country to which the phone number ranges belong.

CLI Billing

If ‘CLI Billing’ is set to ‘Yes’, we can bill calls from your number ranges on different BCNs, hence separate invoices are generated. This complexity is usually not required and plain Trunk based billing is applied, which still allows you to analyse your usage. The functionality only applies to the SIP Trunking product.

Trunk Group

A Trunk Group is a group of trunks that share the same DDI number ranges and typically used for resiliency.

Encryption

SIP Trunking provides both SIP signalling and audio encryption. Encrypting the signalling through SIP TLS (Transport Layer Security) only can be ordered, but for complete security, customers can secure the audio stream with SRTP(SecureReal-TimeProtocol)media encryption.

If you have not chosen for any encryption, you can ignore this part.

In case you have chosen for Encryption, you need to fill out the details and attach your certificate in order to proceed with the delivery. Please contact the Order Owner in case you are having trouble with the exchange of certificates.

Signalling Transport Protocol & Signalling Port

This applies only to SIP Trunking and Number Hosting.

The following SIP transport types are supported:

  • SIP-TCP (Port 5060)*
  • SIP-UDP (Port 5060)*
  • SIP-TLS (Port 5061)

Colt can support any signalling port towards customer SIP equipment. The TCP/UDP port is fixed on in the Colt Voice Network but can be customised for requests sent towards the customer. Please notify us using the notes if required.

*Colt can support other than 5060 as signalling port for receiving SIP signalling, however this will be bespoke configuration. If required, please engage your Account Executive.

The maximum SIP PDU size is 6 K bytes.

Routing Sequence

This applies only to SIP Trunking and Number Hosting, in case of multiple trunks.

Outgoing Call Distribution (Customer to Colt)

For outgoing calls, resilient trunks operate in active/active configuration. Calls can be sent to any trunk. You decide the outgoing call distribution.

Incoming Call Distribution (Colt to Customer)

incoming call distribution

For incoming calls, resilient trunks can operate as follows

  • Active/Standby - In this method a sequential route selection is used. Calls will first be attempted on the primary or active trunk. In the event of primary trunk is unreachable (no response to SIP Invite or TCP timer expiry) or the number of calls exceeds the call limit set, calls will be attempted on the next available secondary(or standby) trunk.
  • Load share - In this method round-robin route selection is used routing call which results in 50:50 load-share across available trunks. Therefore it is also called as load sharing. Whenever trunk exceeds call limit set or unreachable will be put off from selection till it restored to normal.
  • Proportion- In this method calls can be routed with % of calls. E.g one trunk with 60% of calls and second one with 40%. Out of 10 calls 6 calls are routed through first trunk, whereas 4 calls with second trunk.

Codecs

The following audio codecs are supported for SIP Trunking. Not all codecs are enabled by default. The far right column describes whether it’s possible to transcode to other codecs e.g. G.729a to G.711 if there is a codec mismatch.

  • 729ª                                                 (enabled by default unless ordered differently)
  • 711alaw - Out of Band DTMF (RFC4733) (enabled by default unless ordered differently)
  • 726 (32Kbps)                                                 (enabled by default unless ordered differently)
  • 722
  • 722.1
  • 711ulaw - Out of Band DTMF (RFC4733)
  • iLBC (end to end IP only,2Kbps, iLBC can fallback to lower bit rate 13.33Kbps/30ms depending on mode parameter in offer/answer)

 

  • All codecs support T.38 (fax)
  • Sample size: 20ms
  • Silence suppression and comfort noise based on RFC3389 (for codecs that do not support discontinuous transmission) are not enabled by default. Note that Colt gateways may insert comfort noise towards the PSTN in case of discontinuous transmission.
  • In order to insure 100% successful IP to IP calls, we strongly advice customers to support G711Alaw 20ms codec as a fall-back. If you cannot support the G711Alaw codec then Colt can provide a transcoding capability, however this is a chargeable feature. If neither of above requirements are met, you take the risk of having IP to IP calls failed when our end-supplier supports G711 alaw 20 ms only.
  • Overall, Colt supports transcoding for the above mentioned codecs, but this is an orderable feature and disabled per default. If required, please request a modification via your Account Executive.
  • RTCP is disabled by default but can be enabled on request.
  • RTCP-XR is not supported.
  • Video codecs are not supported.

CLI Presentation

The CLI Presentation defines the number presented to the caller when the calling party screening fails, also when calling emergency services.

CLIP Screening & CLIR per Call (Number Ranges)

This is the default option. The CLI is screened against configured ranges and the default CLI is inserted if screening fails.

If the numbers sent through by the PBX are within the known ranges with Colt, this number will be shown, otherwise, the Default CLI will be shown.

CLIR : ‘CLI-Restricted’

It prevents CLI presentation to destination parties.

The called party will not see who is calling.

CLIP No Screening

This option ensures that provided CLI is not screened by COLT and is sent to the 3rd Party. (The network CLI is still provided and screened by COLT.)

Whatever number is sent through by the Customer’s PBX will be shown to the called party.

Presentation Number

It is a restricted CLIP No Screening option. The CLI is screened against an authorized Number Range. If screening fails, the Default CLI is sent.

 

CLI Presentation is regulated, in particular for ‘CLIP – No Screening’ and ‘Presentation Number’. This means, the options are not allowed in all countries, and for those countries where they are allowed, we (operators and users) must follow the regulation.

CLI Regulatory Requirements regarding CLI Presentation 'Presentation Number' and 'CLIP - No Screening" can be found here.

 

Tip: If you have many different ranges, or parts of ranges wherefore you require a specific presentation number, please provide further details in an excel file, attach them and inform us in the notes, unless you have provided all information in the order form already.

Egress Number Format

Egress Number Format is the format used for CLIs (phone numbers) of Incoming calls from your perspective.

If the Egress Number Format Colt configures does not match with your PBX, incoming calls will fail.

 

SIP Trunking options

  • E.164 (International with leading +)
  • All International with +
  • International without +
  • International with leading 00
  • National
  • National with leading 0
  • Extension digits

If not provided, default settings are International with leading +.

If the number format for your outgoing calls is not supported, only the Default CLI (Customer Default Number) will appear in the CDRs, and not the DDIs with the extension of the actual caller.

 

Voice Line (v) options

  • National (NSN, TON=NAT)
  • National (0 NSN, TON=UNK)
  • International (CCNSN, TON=INT)
  • International (00CCNSN, TON= INK)
  • Extension Digits (TON=UNK)
  • Subscriber (SUB, TON= SUB)

If not provided, default settings are NSN (TON=NAT).

'TON'=Type of Number

'NSN' = National Significant Number. It is the number of digits after the leading 0 trunk code or +cc international prefix.

 

When the Egress Number Format is set to ‘Extension Digits’, we require the number of extension digits from you, otherwise this is not applicable.

Customer Default Number (Default CLI)

For each Trunk, Colt defines a Default CLI.

When is the Default CLI used ?

  • If the number format for your outgoing calls is not supported, only the Default CLI (Customer Default Number) will appear in the CDRs, and not the DDIs with the extension of the actual caller.
  • In case the CLI Presentation is CLIP No Screening and you are presenting numbers which are not allowed, the Default CLI (Customer Default Number) will apply.

Trunks

A Trunk is a logical entity used for VoIP signalling and media, defined between a unique pair of IP addresses on the Colt SBC (VoIP Network) and Customer IP-PBX Equipment.

For Number Hosting, Colt supports shared CAC (Call Admission Control). If required, please specify this in the notes.

For Number Hosting, Colt supports multiple origin/ termination IP addresses for a single trunk. If required, please specify this in the notes.

Trunk Site Alias

Please add any identifier for the site to which the trunk is to be allocated (IP-PBX).

Proportion

See ‘Routing Sequence’ under ‘Trunk Group’

IP Addresses

See also POP and / or Trunk Resiliency under Features

 

Originating and Terminating IP Address

The Originating and Terminating Addresses are usually the same ones, unless NAT applies for instance in case of (Colt/3rd party) internet access with a firewall.

The IP Addresses can be existing if it is an addition of a trunk to an existing trunk group.

For deliveries over an Internet access (Colt or 3rd party), mind if NAT is required.

  • If your PBC has a public address – no NAT is applicable. Your (IP-PBX / SBC) Originating IPv4 Address Range is the Media Concentrator Public IP Address.
  • If your PBX is behind a router using NAT and Port Forwarding, NAT is applicable. Your Originating IPv4 Address Range is the WAN Side Public IP Address of the NAT Device. If your termination address is a private address, an additional public address must be given. If the termination address is already a public address for the NAT device, the terminating and public address can be the same.

 

Host Equipment Address

This only applies to SIP Trunking and Number Hosting over IP VPN.

For deliveries over a Colt IP VPN, Colt requests a customer's /27 per POP to avoid IP Address collisions and which suffices for 25 trunks. This is usually a private address. Private or Public, the Address (range) cannot be in use.

In case of an additional trunk to an existing network, the /27 must be in the same subnet as the original one.

 

 

Recommendation if you don't know which IP Addresses to provide

For a trunk over a new Colt IP VPN connection, we can work with the following Private IP Addresses:

IPPBX IP 1 = 10.0.0.2/29 (IPVPN plus – LAN PORT = 10.0.0.1/29)

IPPBX IP 2 = 10.0.10.2/29 (IPVPN plus – LAN PORT = 10.0.10.1/29)

COLT SBC (Primary) = 192.168.0.0/27

COLT SBC (Resilient) = 192.168.0.32/27

If no resilience, ignore the secondary addresses.

For a trunk over an new Internet access without NAT, do as follows:

IPPBX IP = Assign the last IP provided by the new IP Access

For a trunk over a new Internet access with NAT (in case of a firewall for instance), we will require your NAT IP address details.

 

 

 

 

More details regarding IP Addresses can be found here below.

Connectivity to customers with IP VPN makes use of the MPLS enabled access switches in Colt VoIP POPs. The Customer IP VPN is terminated on the access switch and presented on a dedicated VLAN interface towards the SBC. A Host Equipment Subnet is configured between the SBC and the access switch which hosts the SIP signalling and media addresses that the customer uses to connect to the VoIP POP from their VPN.

VoIP PoP config for IPVPN

VoIP POP Configuration for IP-VPN

The Host Equipment Subnet is allocated a /27 IP Address range from the customers address space. This is typically an RFC1918 private address range that is routable from the customer a network. The subnet should* be a /27 due to a design constraint on the Colt SBC**.

If multiple trunks are required on the same SBC e.g. for resiliency or multi-country support, up to 26 trunks can be setup with separate SIP signalling IP addresses on the SBC sharing the same customer signalling IP address.

For each additional POP, or if more than 26 signalling IP addresses are required on the same POP, a separate /27 subnet is required.

SBC Host Equipment Subnet IP Address Allocation e.g. 10.0.0.0/27
First Useable IP SBC NEXT HOP .1
Second Useable IP RESERVED .2
Third Useable IP RESERVED .3
Fourth Useable IP SBC MEDIA / INTERFACE ADDRESS .4
Last Non Broadcast IP N 1st SBC SIP SIGNALLING ADDRESS .30
N-n nth SBC SIP SIGNALLING ADDRESS (1  ≤ n ≤ 26) .(31-n)

 

*The one exception is where public IP addresses are used in which case there are no restrictions on the subnet mask

**The design constraint requires that all (potentially) overlapping subnets (across different customers on the SBC) must use the same subnet mask. The subnet size has been standardised to /27 for this purpose.

  • eBGP is standard configuration with IP-VPN. BFD with BGP is a bespoke solution.
Last Non Broadcast IP N 1st SBC SIP SIGNALLING ADDRESS .30
N-n nth SBC SIP SIGNALLING ADDRESS (1  ≤ n ≤ 26) .(31-n)

Call Admission Control (CAC)

We strongly advise to use the following default settings:

In Call Limit for Trunk, max. inbound calls, max number of simultaneous calls, out call limit for trunk, overall call limit for trunk: Same as number of ordered channels

Inbound – Outbound split: NO

Type of CAC: Both ways CAC with individual Trunk CAC

If you do have special needs, you can update the settings accordingly on the portal, but please write some additional information in the notes as well.

 

Call Admission Control (CAC) defines the maximum call rate and maximum number of concurrent calls that can be supported on a trunk.

A default call-limit of 200 concurrent calls is applied to all trunks unless otherwise specified. There is also a default call rate limit (CRL) of 10 call attempts per sec (CAPS) applied to all trunks. Both limits can be increased on request. Our maximum is 30 calls per sec.

When the call limit or CRL is exceeded on a trunk, the Colt SBC returns a Q.850 release cause 34  or SIP 503 service unavailable error response. When the call limit is exceeded and resilient trunks are available, calls may overflow onto the other trunks.

The call rate limiting uses a token bucket policer which allows the call rate to temporarily burst above the defined limit. Only the calls that exceed the limit are dropped and there is no temporary lockout.

Note: CAPS will be set to lower limit, if call duration is very short. Discuss with local Solution Architect for more information.

 

Technical Details

Shelf ID

Colt requires to know where exactly (on which shelf of the cabinet) to install the Voice Gateway, so that you can easily connect your PBX to it. If there is no specific shelf, you can set it to N/A or 1.

Topology

A Voice Line (v) solution can cover a single or multiple sites. For two (virtual) sites, we can apply Dual Homing. It is a type of voice resiliency which can be applied in case of two (virtual) sites, each equipped with the same number of PRIs. The call distribution will be mirrored and the trunks will be managed on different Colt POPs.

Max Channels (PRI)

This is 30 per default.

CRC4

The CRC4  is your PBX setting used for error checking. Per default, Colt applies 'On' (Framing 'MF').

However, it is very important you verify this on your PBX. In case colt’s setting does not matches with your, the connection between your PBX and the Colt Voice Gateway (L2) will be disabled. Calling would not be possible !

CLI Presentation

The CLI Presentation defines the number presented to the caller when the calling party screening fails, also when calling emergency services.

CLIP Screening & CLIR per Call (Number Ranges)

This is the default option. The CLI is screened against configured ranges and the default CLI is inserted if screening fails.

If the numbers sent through by the PBX are within the known ranges with Colt, this number will be shown, otherwise, the Default CLI will be shown.

CLIP Default (Main) Number

The Default CLI is permanently inserted regardless of what CLI the customer sends.

This is usually the number of the Reception of the Customer, where the called party will call back to.

CLIR : ‘CLI-Restricted’

It prevents CLI presentation to destination parties.

The called party will not see who is calling.

CLIP No Screening

This option ensures that provided CLI is not screened by COLT and is sent to the 3rd Party. (The network CLI is still provided and screened by COLT.)

Whatever number is sent through by the Customer’s PBX will be shown to the called party.

Presentation Number

It is a restricted CLIP No Screening option. The CLI is screened against an authorized Number Range. If screening fails, the Default CLI is sent.

 

CLI Presentation is regulated, in particular for ‘CLIP – No Screening’ and ‘Presentation Number’. This means, the options are not allowed in all countries, and for those countries where they are allowed, we (operators and users) must follow the regulation.

CLI Regulatory Requirements regarding CLI Presentation 'Presentation Number' and 'CLIP - No Screening" can be found here.

 

Tip: If you have many different ranges, or parts of ranges wherefore you require a specific presentation number, please provide further details in an excel file, attach them and inform us in the notes, unless you have provided all information in the order form already.

Egress Number Format

Egress Number Format is the format used for CLIs (phone numbers) of Incoming calls from your perspective.

If the Egress Number Format Colt configures does not match with your PBX, incoming calls will fail.

 

Voice Line (v) options

  • National (NSN, TON=NAT)
  • National (0 NSN, TON=UNK)
  • International (CCNSN, TON=INT)
  • International (00CCNSN, TON= INK)
  • Extension Digits (TON=UNK)
  • Subscriber (SUB, TON= SUB)

If not provided, default settings are NSN (TON=NAT).

'TON'=Type of Number

'NSN' = National Significant Number. It is the number of digits after the leading 0 trunk code or +cc international prefix.

 

SIP Trunking options

  • E.164 (International with leading +)
  • All International with +
  • International without +
  • International with leading 00
  • National with leading 0
  • Extension digits

If not provided, default settings are International with leading +.

If the number format for your outgoing calls is not supported, only the Default CLI (Customer Default Number) will appear in the CDRs, and not the DDIs with the extension of the actual caller.

 

When the Egress Number Format is set to ‘Extension Digits’, we require the number of extension digits from you, otherwise this is not applicable.

Customer Default Number (Default CLI)

For each Trunk, Colt defines a Default CLI. It is recommended to set this to your main number, for instance the number of the reception, as this is the number which will be presented in case there is something wrong with the number format or CLI Presentation.

The same applies for a Voice Line (v) PRI or set of PRIs.

When is the Default CLI used ?

  • If the number format for your outgoing calls is not supported, only the Default CLI (Customer Default Number) will appear in the CDRs, and not the DDIs with the extension of the actual caller.
  • In case the CLI Presentation is CLIP No Screening and you are presenting numbers which are not allowed, the Default CLI (Customer Default Number) will apply.

Routing Type

For a Voice Line (v) service delivered over your existing internet access supplied by another ISP (Internet Service Provider) than Colt, we need to know if you like DHCP (dynamic) or static routing.

In the case of static routing, we require your IP address details for the routing.

  • Routers Fixed IP Interface Address for Colts device (Dedicated Private or Public address)
  • Routers Fixed IP Interface Address for gateways traffic (Dedicated Private or Public address, same subnet)
  • Subnet Mask for the above ( /xx)

Please read the prerequisites for a Voice Line (v) service over Internet under the topic ‘Product’.

Port Group

The Port Group concept only applies to the Voice Line (v) product and is required to define the Incoming Call Distribution. It applies per number range and specifies to which PRIs/BRIs the incoming traffic is routed.

A Port Group groups DDIs for which incoming calls need to be delivered to the same ports: DDIs following the same routing for incoming calls belong to the same port group.

It is not applicable if the port (interface) is only used for outbound traffic

For incoming calls, DDIs are to be allocated to the port (interfaces, BRIs, PRIs) as configured on the customer's PBXs. A DDI can be allocated to different ports.

You can add or remove port groups on the portal and allocate

  • the relevant DDIs
  • the relevant port (PRIs interfaces)

Do this consciously and slowly and allow some time for the portal to synch with our order handling system !

Telephone Numbers (DDIs, CLIs)

Numbering Plan - Portability

Regarding the activation of the numbers which require port in, please note that Porting In from the donating operator to Colt will be scheduled and executed AFTER the completion (and start of the invoicing) on the voice service.

In case you order no Colt DDIs and only wish to port in numbers from another operator, Colt will temporary provide test numbers to enable testing and the completion of the order, prior to the porting.

Where customers wish to retain existing telephone numbers, they make use of Colts Number Portability Service. Local in-country Letter of Authorisations (Porting forms) must be completed and signed to comply with local regulations.

In order to enable a flawless porting, it is highly recommended that the customer provides Colt with the number ranges, the correct grouping of the number ranges and the relevant legal addresses and owners of the DDIs which need to be ported. This information can be obtained by the customer from their current provider. Number ranges are usually to be ported as a complete range. Most operators will not allow ranges to be split over different operators. In principle, Colt cannot obtain these details from the donor operator.

Numbering Plan – Reservation of New Colt Numbers

Please mind that in case you have reserved new colt numbers for your configuration, the reservation is only valid for three months as of the reservation date. If not activated within 3 months, the numbers will be set free again and can be reserved for other customers.

Number Ranges

A range consists out of a single number or (muliplications of) 10,100 or 1000 consecutive DDS.

Apply per service

Number Ranges are configured per service (site, trunk) to support customer's outgoing traffic

LAC - Local Area Code (Also known as 'prefix')

In case of a hybrid PBX, it is possible to have number ranges with different LACs on the same service.

Usually with leading zero

Range Start

The last digit of the first DDI of a range is always 0 unless it's a single number

Range End

The last digit of the last DDI of a range is always 9.

Not applicable if single number

Default CLI

Defines nr. presented to the caller when the calling party screening fails, also when calling emergency services

To allow for a good working service and complete CDRs, the Voice Service Details settings should match with the configuration of the customer's PBX. If the wrong or NO CLI is set up (customer A-number) in the customer's PBX, calls to the emergency services will use the Default CLI, hence the emergency services in the wrong area may be called. To avoid this, the PBX must enable the customers' CLIs to be sent to Colt. If no Default CLI is given by the customer, Colt will set any number of the given ranges as default.

Main Number

Applies per number range

Appears in the CDRs (unless a reseller profile is applied)

Displayed to the called party depending on chosen CLI Presentation

If no Main CLI is given by the customer, Colt will set any number of the given ranges as main number.

Number Range type

Applies per number range

Defines if Colt should apply and activate new DDIs, port in DDIs or migrate DDIs from another Colt service to the new service

Emergency Address

Applies per number range

Colt has a legal obligation to register customer's DDIs with physical address of the users to the authorities. It is possible that in case of a hybrid PBX or in case of an installation at a datacenter, this address does not match with the actuall address of the users. If so, the correct address should be given to pass the address to the emergency services (ambulance, police) when needed. As the processes are automated, accuracy is important.

Features

Depending on the features you have ordered, you can specify the details under this section.

Voice Resiliency (Inbound) – Call Diversion

  • Partial Number Replacement
    • Automated diversion of incoming calls to pre-configured ranges in case of failure
    • We will require the destination numbers (ranges) to route to in case the functionality is triggered.
  • Inbound Call Rerouting
    • Automated diversion of incoming calls to pre-configured single number in case of failure.
    • We will require the destination number to route to in case the functionality is triggered.
  • Disaster Recovery
    • Diversion upon request of incoming calls to pre-configured ranges
    • We will require the destination numbers (ranges) to route to in case the functionality is invoked by you. We will preconfigure the routing.
    • To invoke the service, or to test it, you will need to call our Support Desk.

Tip for Partial Number Replacement: If you have many different ranges, or parts of ranges wherefore you require different destination numbers, please provide further details in an excel file, attach them and inform us in the notes, unless you have provided all information in the order form already.

Tip for Disaster Recovery: Please use the template to provide us with your details.

Call Barring

In case you don’t want to have your users to certain (groups of) destinations (defined per local area code), we can have those blocked. You can only choose one set of destinations to be barred. Please select the profile you wish to disable.

Transcoding

If not filled out yet, just add the number of channels (per trunk). If you require this to be less than the number of channels, a bespoke set up is required and you need to engage with your Account Executive to arrange validate and order this.

Transcoding is an optional feature and is disabled by default. It allows customers to connect equipment that supports only a limited set of codecs. Transcoding involves translating the media stream from one encoding format on ingress, to another encoding format on egress and vice versa. Transcoding ensures that calls can be established even when there is no common end-to-end codec.

  • In general, transcoding will only be required where the customer has endpoints that do not support G.711alaw (either 1st choice codec or as a fall back)
  • It only applies to IP-to-IP call flows (see exceptions below)
  • When transcoding is enabled, it is applied selectively, on a call-by-call basis.
  • Transcoding only occurs as a last resort when the network and endpoints cannot agree a common codec end- to-end. Usually, this occurs regardless of codec priorities configured in the network and on the endpoints (see exceptions below)
  • Transcoding consumes additional DSP resources on the SBC and is only configured when explicitly required

When the codec list on a trunk is customised (codecs removed or added) selective transcoding is enabled by default for all all codecs apart from G.711alaw.This is done to ensure interoperability with other endpoints in the Colt network.

Transcoding for Fax

For customers that support fax passthrough and not T.38 transcoding will not be configured since it most cases fallback from T.38 to G.711 will work. Transcoding can be enabled manually if a fault is raised.

Transcoding for DTMF and sample size

In some cases a mismatch of DTMF or sample size encoding may cause a less preferred codec to be selected or a call to fail. In this case, manually configuring ‘Different DTMF Relay’ or ‘Different Packet Size’

Trunk and / or POP Resiliency

Overview
trunk resiliency
Trunk Topologies

The options below describe how multiple SIP trunks can be connected to the same VoIP Access service e.g. for resiliency or multiple country trunks. For a given access network, the combination of the customer IP-PBX IP and SBC IP must be unique for each trunk.

Single POP Topologies

Multiple trunks on the same POP may be used to connect equipment or sites with separate DDIs, for multi-country support where a separate trunk is required for each country, or for expansion if the limit main numbers is exceeded on a trunk. It may also be used for load sharing or resilient configurations  where hierarchical call admission control is required (only supported on single SBC).

If multiple trunks are configured on the same POP and share the same access network, by default, all trunks share the same SBC IP address. In this case a separate IP-PBX IP address is required for each trunk. This is the default configuration for multiple trunks on same POP.

Multiple trunks

Multiple Trunks - Single POP & Separate IP-PBX IP per Trunk

trunk resiliency 2

Alternatively, if a single IP-PBX IP is shared for all trunks, a separate SBC IP must be used for each trunk as shown in the figure below. For this option This option is only supported for customers with a IP-VPN or Ethernet connection and a maximum of 26 trunks can be configured per SBC subnet.

multiple trunks single POP

Multiple Trunks - Single POP & Single IP-PBX IP

pop resiliency

Multi POP Topologies

Multi-POP topologies are typically used for trunks in a resilient configuration since they protect against the failure of a single POP or SBC. The examples below show how groups of resilient trunks can be built across separate POPs. These examples assume separate SBC IP address are setup on the same POP to handle multiple trunks to the same IP-PBX IP (see above).

dual pop

Multiple Trunks - Dual POP, Single IP-PBX

separate IPPBX

Multiple Trunks - Dual POP, Separate IP-PBX

trunk and pop resiliency
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Multiple Trunks -  Dual POP, Separate IP-PBX (Meshed)

resiliency 2

Trunk Resiliency

Trunk resiliency secures communication against any failure between your IP-PBX and Colt SBC. Resilient trunks can also be used for load sharing across multiple SIP peers. One primary trunk can have maximum up to 26 secondary or resilient trunks.

Any of the trunk topologies described in the previous section can be used to provide resiliency or load sharing. For geographic redundancy, secondary trunks can be built on a separate SBC and POP.

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