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Comparison of SIP Tie vs SIP Trunk vs LSG vs LAG (PSTN)
8x8 Support

Comparison of SIP Tie vs SIP Trunk vs LSG vs LAG (PSTN)


Question: What are the differences between 8x8 Gateways?

The following describes the differences between 8x8 SIP Trunks, SIP Ties and Gateways, including a brief description of function and application.

Please note: Contact your Account Executive who can assist and answer questions on all of the options described here.

Applies To

  • Legacy SIP Trunk
  • VO SIP Tie
  • CC Carrier to VO SIP Tie
  • LSG (Local Survivable Gateway)
  • LAG/PSTN (Local Access Gateway)


Acronym Description
PSTN Public Switched Telephone Network
LAG Local Access gateway
LSG Local Survivability Gateway
VO Virtual Office
CC Call Center
SIP Session Initiated Protocol
PBX Private Branch Exchange
iPBX Internet Protocol Branch Exchange
IPSec IP Secure
8x8 has multiple options that are typically referred to as Gateways.  The term gateway is a misnomer when it comes to referencing the type of offering, it is used here as a generic label.  The Descriptions below will correctly label some as In/Out adapters and others as Gateways.


Legacy SIP Trunk

  • 8x8 Legacy SIP Trunks provide PSTN (Public Switched Telephone Network) carrier level call termination.
  • Customer supplied stand alone PBX such as Asterisk, Avaya, or Mitel
  • Third Party IVR, eIVR that requires a PSTN Service

VO SIP Tie (In/Out Adapter)

  • 8x8 SIP Tie trunks provide a direct call path "extension to extension" only between an 8x8 iPBX to a customers legacy PBX.
  • New customers moving from a legacy premise PBX such as Mitel or Avaya to 8x8 XCaaS that require extension to extension dialing between both systems.
  • Customers that require extension to extension dialing between 8x8 XcaaS and legacy IVR, eIVR connections.

VO SIP Tie with IPSec (In/Out Adapter)

  • An IPSec (IP Secure) tunnel is a secure connection between 8x8 XcaaS and a customers edge firewall in conjunction with a VO SIP Tie.
  • When secure call traffic is needed such as Banking or Medical.

CC Carrier

  • CC Carrier connects Call Center dialing through VO SIP Tie to a customers legacy PBX or IVR / eIVR.
  • Call Center deployments to a legacy PBX or other iPBX.

LSG (Local Survivable Gateway)

  • 8x8 solution stand alone appliance that allows in and out bound traffic if connection to 8x8 is lost.
    • Note: A customer provided PSTN circuit such as Analog, PRI/T1 or SIP Trunk is required.
  • Allows for Emergency and in or outbound call traffic to continue from a internet outage disrupting 8x8 services.

LAG/PSTN (local Access Gateway)

  • Local PSTN  by Country or region where PSTN termination is not permitted by Country or Regional laws (see Calling Countries for X-Series here)
  • Some countries and regions do not allow for PSTN termination only by said country providers.
  • When a third party IVR / eIVR or legacy PBX requires in country dialing.
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