Overview:

A SIP trunk is a service offered by an ITSP (Internet Telephony Service Provider) to use Session Initiation Protocol (SIP) to set up communications between an enterprise PBX and the ITSP. A trunk may include multiple voice sessions (as many as the enterprise needs). While some see SIP as just voice, SIP Trunking it can also serve as the starting point for the entire breadth of real-time communications possible with the protocol, including Instant Messaging, presence applications, white-boarding and application sharing. The potential for a rapid ROI is a key driver of SIP trunk deployments. However, maximum return on investment can be achieved when you extend VoIP outside of the corporate LAN. In terms of infrastructure purchases, SIP trunks provide an immediate cost-savings. They eliminate the need to purchase costly BRIs, PRIs or PSTN gateways.

Audience:

Large Enterprises
Fixed Network Operators
Wireless Network Operators
Major Backbone Providers
Interconnect and Wholesale Solution Providers
ISPs (Internet Service Providers)
ITSPs (Internet Telephony Service Providers)
Cable Operators and MSO Companies
Hosted and Managed Service Providers

1-What is SIP Trunking?...........................................................................1

1.1. What is SIP Trunking?........................................................................................2

1.2. What is SIP protocol?.........................................................................................2

2-The Benefits of SIP Trunking.........................................................................4

2.1. Reducing Costs....................................................................................................6

2.2. Bandwidth Utilization.........................................................................................6

2.3. Flexibility to Add New Lines.............................................................................6

2.4. Least Cost Routing (LCR)....................................................................................6

3-SIP Trunking Infrastructure...................................................................8

3.1. The PBX Component............................................................................................9

3.1.1. The Traditional PBX.......................................................................9

3.1.2. The IP-PBX ................................................................................9

3.1.3. Benefits of IP-based PBXs over Legacy Systems...................................9

3.1.3.1. Connect Multi-vendor End Points............................................9

3.1.3.2. User Management ...............................................................10

3.1.3.3. Integration with other IP-based Applications..............................10

3.2. Enterprise Session Boarder Controller (E-SBC) ...............................................10

3.2.1. Firewall/NAT Traversal ..............................................................10

3.2.2. Mediation between PBX and Service Provider Equipment ........................11

3.2.3. Reliability and Survival Features ....................................................12

3.2.4. E-SBC Security features ................................................................12

3.3. The Service Provider Component.......................................................................13

3.3.1. Different types of SIP Trunking service providers.......................................13

3.3.2. PSTN Connectivity....................................................................................14

3.3.3. Local breakout............................................................................14

4-Interoperability.............................................................................................................15

4.1. SIP Standards .....................................................................................................16

4.2. SIP Trunking by means of SIPconnect ..........................................................16

4.3. Interoperability ...................................................................................................17

5-Security Consideration................................................................................................19

5.1. Threats................................................................................................................20

5.2. Importance of a Stable Platform.........................................................................20

5.3. SIP Signaling......................................................................................................20

5.4. Controlling Media..............................................................................................21

6-Quality of Service and Reliability..........................................................22

6.1. QoS - Different Service Provider Approaches...................................................23

6.1.1. Service Provider Controlling the Connection all the Way..........................23

6.1.2. Over-provisioning of Links...........................................................23

6.2. Prioritization of Voice Traffic............................................................................23

6.3. Call Admission Control......................................................................................24

6.4. Poor Voice Quality.............................................................................................24

6.5. MPLS (Multiprotocol Label Switching)............................................................24

6.6. Reliability of SIP trunk......................................................................................24

6.7. SIP Trunking may be more Reliable..................................................................25

6.7.1. Failover to Secondary SIP Trunking Provider ........................................25

6.7.2. Failover to Secondary Internet Service Provider ..................................25

6.7.3. Failover to Secondary Edge Equipment.............................................25

7-Choosing a SIP Trunking Provider............................................................................26

8-Current SIP Trunking Providers................................................................................28

9-SIP (VOIP) Communication Market..........................................................................29
 

Keywords: SIP Trunking, VoIP, Unified Communications, ITSP, SBC, SIPconnect, ISP