• facebook
  • google
  • linkedin
  • twitter

Business Voice SolutionsBusiness Voice Solutions


Need Help?


Enterprise Session Border Controllers


This page provides a summary of the InnoMedia Enterprise Session Border Controller (ESBC) product family.  The following subjects are covered:

The InnoMedia ESBC serving various Business Voice Service markets

The delivery of SIP-based VoIP services to Enterprise Voice customers has evolved considerably over recent years.  As shown below, the traditional method for deploying VoIP lines into SME customers relied upon placing a multi-line EMTA or ATA at the enterprise which then either (a) delivered direct lines through FXS ports to individual analog phones or fax machines/credit card readers or (b) connected to a legacy key system which then supplied connectivity to the phones within the enterprise.

Delivery of direct-line VoIP services to SME customers using multi-line ATA


Delivery of direct-line VoIP services to SME customers with key system using multi-line ATA

Business Solutions Key_phone

The above model, while workable, is not terribly scalable, nor does it accommodate newer modes of SIP connectivity required by operators such as Hosted deployments or SIP Trunking delivery.  With the introduction of an Enterprise Session Border Controller (ESBC) or Enterprise SIP Gateway (ESG), an ESBC with a PRI-based southbound interface can allow the operator to provide SIP-based voice services to an enterprise with a PRI-based PBX system.  An ESBC operating in SIP ALG mode can interface directly with IP phones on the Enterprise LAN in a Hosted PBX scenario.  For the SIP Trunking case, the ESBC operates in B2BUA mode and connects to the Enterprise IP-PBX.

The InnoMedia ESBC product family is particularly well placed to allow operators the choice of deploying Business Voice Services to their enterprise customers as all ESBC models are capable of operating in both SIP ALG and B2BUA modes for Hosted PBX and SIP Trunking applications respectively.  In addition, certain models with a PRI-based LAN interface are also available for delivering PRI-based services to enterprise customers.

Delivery of SIP-based VoIP services to TDM-PBX customers with SIP-PRI ESBC


Delivery of Hosted Services using ESBC with SIP ALG

ESBC with SIP ALG for Hosted Services

Delivery of SIP Trunking Services using ESBC with B2BUA

ESBC with B2BUA for SIP Trunking

The InnoMedia ESBC Function and Feature Highlights

SIP Incompatibilities and Normalization

One of the fundamental problems experienced by operators wishing to deploy voice services to enterprise customers that have existing SIP-based IP-PBX’s is that of SIP incompatibilities and interoperability issues between the operator’s SIP servers and the enterprise’s SIP-PBX.  This problem is exacerbated by the fact that the SIP protocol is quite ‘loose’ due to standards proliferation with multiple RFC’s often providing similar features.  In addition, different features are sometimes supported on different devices and individual implementation differences can also cause problems.

For the operator, they have a number of choices to deal with this problem.  They can restrict rollout to only those customers with ‘approved’ enterprise equipment – but this of course limits their addressable customer base.  Another choice is to tailor key elements in their network such as a core SBC to interoperate with dozens of different makes and models of PBX’s.  This can be very cumbersome and costly both in terms of manpower and time.

The InnoMedia ESBC addresses the problem of SIP incompatibility through a variety of different methods:

  1. By providing SIP-PBX and Trunk SIP profiles which allow the operator to simply select the appropriate choices on the LAN and WAN sides of the device and the ESBC is then responsible for providing SIP interoperability between both sides.
  2. In addition, the characteristics of each of these profiles can be edited via the GUI to tweak parameters in order to provide the operator with greater granularity in ensuring interoperability, or to modify operational behaviour.  These parameters include registration modes, SIP timers, SIP header usage and formats, security features etc.
  3. SIP Error Response codes can be mapped both in the LAN → WAN and WAN → LAN directions
  4. To provide even finer control of SIP messages traversing through the device and to allow in-field modification without changing the ESBC firmware image, the InnoMedia ESBC allows the user to create SIP Header Manipulation Rules (SHMR).

SIP Incompatibility and Normalization

Problem Statement

  • SIP protocol quite ‘loose’ due to:
    • Standards proliferation
    • Different features supported in devices
    • Implementation differences
  • Leads to incompatibilities between:
    • Enterprise equipment (IP-PBX & IP phones)
    • Service Provider core network equipment (SIP Softswitch/Application Server/Core SBC)
  • Service Provider can either:
    • Restrict rollout to only support customers with ‘approved’ enterprise equipment  → Restricts revenue potential
    • Tailor core network to interoperate with dozens of different models of PBX’s & IP Phones → Very cumbersome and costly



  • Introduce ESBC to ‘translate’ between SIP used in operator’s core and in enterprise → Signaling normalization

Profile-Based SIP Normalization

Profile selections for SIP Normalization between:

  • WAN interface (towards the service provider network) and
  • LAN interface (towards IP PBX/IP Phones)

Two sets of Profiles

  • WAN: SIP Trunk profiles and LAN: UA/SIP-PBX profiles
  • Easy selection/installation by System Integrators
  • Allows coexistence of IP-PBX/IP Phones with different profiles

Profile Based SIP Normalization

An example of the Trunk SIP Profile setting GUI page is given below.

ESBC Trunk SIP Profile

An example of an IPPBX profile is shown below.IPPBX Profile Example

SIP Header Manipulation Rules (SHMR)

The InnoMedia ESBC allows the user to create SIP Header Manipulation Rules (SHMR) which give finer control of SIP messages traversing through the device as well as in-field header manipulation without building a new ESBC firmware image.  
  • SHMR consists of a sophisticated scripting language which can modify SIP message contents both at LAN/WAN ingress and egress in the following directions:
    • ESBC WAN interface, inbound
    • ESBC WAN interface, outbound
    • ESBC LAN interface (NAT-Voice port), inbound
    • ESBC LAN interface (NAT-Voice port), outbound
  • Can modify SIP headers, parameters and SDP contents
  • Regular expressions allow sophisticated matching rules
  • Multi-level programmability enables functions to reference each other and pass parameters between them

For details about InnoMedia SHMR, please see InnoMedia SHMR Application Note.

Enterprise Firewall/NAT Traversal

Another issue alleviated by the InnoMedia ESBC is that of Enterprise Firewall/NAT Traversal.  Any Firewall/NAT deployed in the enterprise can be ‘unfriendly’ to SIP traffic and may lead to SIP traffic being blocked.  Enterprises can also be reluctant to allow any changes to their existing Firewall setup. 

With the InnoMedia ESBC in place, however, authorized SIP traffic can go through the dedicated SIP Firewall within the ESBC directly to SIP devices in the enterprise without any interference to the Enterprise Firewall.  On the other hand, a dedicated LAN port on the ESBC can operate as a Transparent Bridge port to send data traffic directly to the Enterprise Firewall as before.

Enterprise Firewall/NAT traversalpng
Problem Statement

  • Enterprise Firewall/NAT ‘unfriendly’ to SIP traffic
    • This can lead to SIP traffic being blocked
  • Enterprises are also reluctant to allow interference to their existing Firewall


  • Authorized SIP traffic goes through SIP Firewall within ESBC -> No interference with Enterprise Firewall
  • Transparent Bridge Port within ESBC sends data traffic directly to Enterprise Firewall as before

QoS Management

A critical issue that often affects SIP Trunking and Hosted PBX Voice deployments is QoS Management.  There is typically a lack of QoS on the access link between the operator’s core network and the edge of the enterprise, which can lead to voice quality problems as well as possibly cause call drops.

The InnoMedia ESBC offers two solutions to this problem.  In the case of a Cable HFC deployment, an ESBC model with an embedded cable modem (CM) can be chosen which will intelligently set up UGS service flows for SIP trunk traffic as needed.  This guaranteed QoS mechanism can be used in a PacketCable Multimedia (PCMM) framework with Policy Servers.  However, for those operators who do not have (or do not wish to use) PCMM, the InnoMedia ESBC can autonomously set up service flows without the need for a Policy Server using InnoMedia’s Smart-DQoS™ mechanism.  In this way, up to 24 UGS service flows can be accommodated for a DOCSIS 3.0 WAN connection.

For those operators wishing to use an Ethernet-based WAN connection to the ESBC, InnoMedia also offers TOS/DSCP packet handling and VLAN support.

QoS ManagementProblem Statement 

  • Lack of QoS on access link between operator’s core and edge of enterprise can cause:
    • Voice quality problems
    • Call drops


  • Cable:
    • Smart-DQoS™ intelligently sets up UGS service flows for SIP trunk traffic
    • Integrated Cable Modem allows guaranteed QoS for voice traffic
      • Works even without PCMM & Policy Servers or
      • Provides cost savings with PCMM
    • Up to 24 UGS service flows for DOCSIS 3.0
    • Even higher capacity with Smart-MGPI™ which enables multiple sub-flows in each SF
  • Ethernet:
    • TOS/DSCP, VLAN support

Performance Monitoring

Where the decentralized ESBC sitting at the demarcation point between the operator’s access network and the enterprise LAN can offer a key advantage over a centralized SBC deployed in the operator’s core network is in the area of performance monitoring.  For services with guaranteed SLA’s, the operator requires some degree of performance monitoring both in terms of voice quality and call statistics for each call placed to/from the enterprise.  However, with the centralized SBC, it is not possible to differentiate quality problems that arise on the access side of the operator’s own network versus those that originate in the enterprise LAN.

The InnoMedia ESBC offers a comprehensive set of tools to overcome this problem.  From its viewpoint at the edge between the operator’s network and the enterprise network, it can assess the quality on both sides and quickly and effectively provide feedback on any problems that may arise.  To do this, it provides both LAN and WAN VoIP performance metrics such as jitter, packet loss, delay, R-Factor and MOS as well as a SIP Endpoint Test Agent (SETA) capability.

Performance MonitoringProblem Statement

  • For services with guaranteed SLA’s, Operator needs performance monitoring for high quality SIP Trunk/Hosted solutions
  • Need to be able to assess voice quality and call statistics both on:
    • Link from operator’s core to enterprise demarc point
    • Link downstream from demarc point within enterprise


  • ESBC provides:
    • Both LAN & WAN VoIP Performance Metrics including MOS scores, R-factor
    • SIP Endpoint Test Agent

Call Monitoring and History

Call Monitoring

VoIP Call Quality Telemetry

VoIP Telemetry

SIP End-Point Test Agent and SIP-PRI Trace

The InnoMedia ESBC contains a test client, or SIP Endpoint Test Agent (SETA) that meets the SETA requirements of the CableLabs Enterprise SIP Gateway (ESG) specification.  This test client can be used by the network operator in one of two distinct ways:

  1. Test Client Originating Calls.  The test client can initiate test calls to a remote party telephone number.  Once the call is set up, a speech file is sent to the remote number for a period of time and the call quality is monitored to accumulate QoS statistics both during the call and for the call as a whole.
  2. Test Agent Terminating Calls.  The test agent can also be placed into loopback mode so that an external server such as the InnoMedia EMS can utilize it in performing call quality measurements.  The Voice Quality Monitoring (VQM) function on the EMS can deliver a speech file to the device and back and, in comparing the outgoing and received files, can generate an instantaneous MOS score by performing a PESQ-based analysis.

For case 1. above where the test client originates the test calls, the calls can either be initiated manually, or be pre-configured to occur on a regular basis (daily, weekly, monthly) and then build up a picture of the variation of test call quality over time.   The figure below shows a typical test call in progress (manually initiated by the test agent) as well as the results of the last such test call shown on the device’s web GUI.

SETA Operation

SETA Ladder Diagram

Media Transcoding

Another area in which the InnoMedia ESBC can simplify the task for the operator in deploying SIP Trunking services is through the use of sophisticated media handling such as transcoding. In many deployments, issues often arise due to incompatibilities between the media handling capabilities of the IP-PBX used in the enterprise and those media capabilities the operator wishes to offer in the access/core part of their network. For instance, there may be differences caused by the use of in-band DTMF versus RFC 2833 to transport DTMF signals, or G.711 In-band versus T.38 to transmit fax in different parts of the network. In addition, the enterprise IP-PBX may be capable of only offering certain speech codecs which differ from those used in the operator’s network.

To get around these problems, certain models within the ESBC product family (specifically, ESBC9378 and ESBC9578) offer media transcoding as an option. With this support, the following transcoding alternatives are possible between the WAN and LAN interfaces of the ESBC:

• Codec Transcoding to/from any of G.711, G.729, G.726
• DTMF Transcoding between RFC2833 and G.711 In-band
• Fax Transcoding between T.38 and G.711 In-band


  • InnoMedia ESBC 9378/9578 solves problem of incompatible media capabilities between:
    • SIP endpoint in Enterprise Network
    • SIP endpoint in Operator’s Core Network
  • Media Capabilities comprised of:
    • Codec Transcoding to/from any of G.711, G.729, G.726
    • DTMF Transcoding between RFC2833 and G.711 In-band
    • Fax Transcoding between T.38 and G.711 In-band


InnoMedia’s ESBC products are highly interoperable, and are SIPConnect 1.1 compliant and IMS ready.  Additionally, the ESBC products support major CableLabs ESG requirements.

The InnoMedia ESBC meets the vast majority of requirements in SIPConnect 1.1.  In many cases, the level of support on the ESBC goes beyond the requirements of SIPConnect 1.1 and, in other cases, support for new functionality (such as GIN support as specified in RFC6140 for implicit registration) is also provided on the InnoMedia ESBC.

The InnoMedia ESBC also supports major PacketCable ESG requirements.  This has been well demonstrated during CableLabs SIP Interop events.  In fact, the InnoMedia ESBC goes well beyond CableLabs ESG Specification as shown in the diagram below.

PacketCable ESG and InnoMedia ESBC


InnoMedia’s ESBC product family is also IMS ready.  It has been tested against most of the major IMS servers.  Specifically, the InnoMedia ESBC products support the following features:

  • P-CSCF Discovery procedures
  • General IMS Registration requirements
  • RFC6140 (Martini GIN) support for implicit registration
  • IMS P-header support
  • SIP Digest authentication to SIP server with/without TLS
  • SUBSCRIBE/NOTIFY mechanisms
  • ‘reg-event’ package support
  • Tel/SIP URI support
  • Session Timer support
  • Various URI header formats for TN’s
  • PRACK/100rel support

InnoMedia ESBC Model Table

Model Name WAN 4LAN
4FXS ports Internal Battery B2BUA
(SIP Trunk)
(Hosted PBX)
Transcoding T1/PRI QoS
ESBC8528-4B DOCSIS 2.0 10/100BT Yes Yes Yes Yes Smart-DQoS™
ESBC9528-4B DOCSIS 3.0 Gigabit Yes Yes Yes Yes Smart-DQoS™
ESBC9578-4B DOCSIS 3.0 Gigabit Yes Yes Yes Yes Yes Smart-DQoS™
ESBC9580-4B DOCSIS 3.0 Gigabit Yes Yes Yes Yes Yes Smart-DQoS™
ESBC8328-4B 10/100BT 10/100BT Yes Yes Yes Yes ToS/DSCP
ESBC9328-4B Gigabit Gigabit Yes Yes Yes Yes ToS/DSCP
ESBC9378-4B Gigabit Gigabit Yes Yes Yes Yes Yes ToS/DSCP
ESBC9380-4B Gigabit Gigabit Yes Yes Yes Yes Yes ToS/DSCP

InnoMedia ESBC Advantages

The InnoMedia ESBC Advantages
Highest Level of Integration eCM, eSBC, FXS, Internal batteries, PRI
Advanced DOCSIS 3.0 8×4 channel bonding, 24 UGS SIDs for 24 QoS service flows
Complete Session Border Control features B2BUA and Registrar for SIP trunk, SIP ALG for hosted PBX,
NAT traversal, SIP normalization, IMS ready, SIPConnect compliant
DTMF transcoding (ESBC 9378/9578), Emergency Calling support
QoS Smart-DQoS™ for Cable – ESBC monitors and intelligently sets up service flows for SIP trunks, IP Centrex, and FXS lines to ensure QoS
VLAN & TOS/DSCP for Ethernet
Business Line features Ground start/loop start and CPC/Open Loop Disconnect → Key Phone Systems/Analog PBXs
Low-speed modem → Credit card reader
Fax with T.38
Complete with carrier-grade monitoring ESBC VoIP Performance Metrics → RTCP-XR and end-of-call syslog reporting:
Voice quality: R-factor, MOS scores
Network performance: Delay, packet loss, jitter
Element Management System (EMS) for device status monitoring, event reporting, remote access for device diagnostics, and VoIP performance metrics display and analysis

The InnoMedia ESBC Features and Benefits

Functional Blocks/Categories Features Benefits
High-Speed WAN I/F Embedded Cable Modem: DOCSIS 3.0 embedded cable modem:
1. ESBC 9528/9580: DOCSIS 3.0 with 8×4 channel bonding and 24 UGS SIDs 1. 300 Mbps downstream and 120 Mbps upstream BW
2. ESBC 8528: DOCSIS 2.0 2. 24 UGS SIDs for 24 QoS ensured voice sessions (DOCSIS 3.0)
Ethernet Interface:
1. ESBC 9380/9328: Gigabit Ethernet
2. ESBC 8328: 10/100 BT Ethernet
Quality of Service QoS: Smart-DQoS™:
1. WAN: Smart-DQoS™ for ESBC 9580/9528/8528 and VLAN/DSCP for ESBC 9380/9328/8328 Device initiated DQoS UGS for voice sessions with DQoS ensured service flows
2. LAN: VLAN with 1000 groups a. Instant service quality improvement
b. Minimum infrastructure investment
c. Time to market
Embedded Session Border Controller (eSBC) Registrar and B2BUA Highly interoperable between service provider and enterprise equipment
1. Implicit, explicit, and static (no) registration No interference with enterprise firewall setting
2. Header manipulation/SIP normalization Reliable and scalable SIP trunking service delivery
3. NAT traversal
4. SIPConnect compliant
5. IMS ready
SIP ALG Highly interoperable between service provider and enterprise equipment
1. Header manipulation No interference with enterprise firewall setting
2. NAT traversal Reliable and scalable hosted PBX/IP Centrex service delivery
3. SIPConnect compliant
4. IMS ready
High-speed bridge port Transparent Gigabit data port High-speed Internet data service delivery
FXS commercial voice ports Four FXS ports with commercial line features Business Friendly
1. T.38 1. Analog PBX interconnect
2. Low-speed (high-speed) modems 2. Fax
3. House wiring
4. Credit card reader
PRI ports (ESBC 9580/9380 only) 1. Support multiple switch types: 4ESS, 5ESS, NI1, NI2, Q.SIG, EuroISDN Supporting both TDM PRI PBX and IP UA (IPPBX), extending SIP trunking services to TDM customers.
Allowing co-existence of TDM and IP, or transitioning from TDM to IP.
Highly interoperable with different switch types, media formats, and signaling variations.
2. Media processing: DTMF transcoding, Codec transcoding, echo cancellation
3. Interoperability:
a. Ringback via ISDN alerting or B channel
b. Caller name discard option
Internal battery 4 hours of talk time Power backup for primary line services
Security Features 1. Stateful inspection 1. No intrusion into enterprise networks via SIP path
2. TLS for signaling 2. Secured signaling
3. Access control
Performance Monitoring & Management 1. VoIP performance metrics Allowing service providers to offer Service Level Agreement (SLA) based 1st tier quality services to enterprise customers
a. Voice: R-factor & MOS scores
b. Network: jitter, delay, packet loss
2. CDR records
3. SIP End-point Test Agent
Manual test calls
Pre-scheduled calls
Call performance reporting
4. SNMP traps for quality alarms
Emergency call handling 1. Line pre-emption Allowing service providers to offer SIP trunking services with Emergency calling support for primary line based services
2. SIP signaling
a. Emergency caller ID
b. Priority header
3. Media:
a. G.711
b. Disable VAD
4. QoS
a. DQoS pre-emption
b. DiffServ
5. Syslog and SNMP trap


The InnoMedia ESBC SIP ALG and B2BUA feature comparison table

Feature Description



Maximum # of concurrent sessions



NAT Traversal



Translating “User part” of the Contact header on outgoing messages*



Translating the “Host and port part” of the Contact header to ESBC’s “IP and port” on outgoing messages*



QoS Management – Smart-DQoS



QoS Management – Ethernet WAN & LAN: VLAN QoS traffic separation



QoS Management-Ethernet WAN/LAN: ToS QoS



RTP Timeout timer setting



SIP Expiration timer setting



SIP Server Redundancy



Emergency Call Handling



Call History



Digit translation



Test Agent



VQM Statistics



SIP Header Manipulation Rules (SHMR)



SIP Firewall Manipulation Rule



Media transcoding (Voice codec, DTMF, FAX)

Y (for 9578/9378)


PCAP packet capturing-LAN & WAN



SIP call flow Ladder Diagram per User-ID



SIP UA Registration Status Display



*: See Profile-Based SIP Normalization for additional header manipulation operations provided by B2BUA

Share Button