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SBC 'traffic cop' controls VoIP streams at the border

Session border controllers, complex and costly, offer widely varying capabilities.
By Edwin Mier, Anthony Mosco, Robert Tarpley and Robert Smithers, Network World
April 14, 2006 10:44 AM ET
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Is there a session border controller in your enterprise's VoIP future? If you're looking to expand your organization's VoIP reach - to VoIP-based service providers, to other enterprises or even to VoIP-interconnected distributed sites via the Internet - there very well may be.

A word about performance

In this inaugural test of session border controllers (SBC), it was not our intent to get into the minutiae of product performance, because SBCs have disparate feature sets and deployment options. That said, we can make some general assessments about SBCs based on the results of our sending modest levels of Session Initiation Protocol call traffic through them. SBCs' effects on call quality varied from essentially no degradation (mean opinion score [MOS] of 4.5, R-factor of 93) to measurable degradation (MOS of 3.9, R-factor of 85). SBCs also could add to call-setup time and latency; the extent appears to vary based on the power of the SBC hardware platform.
Click to see:

Functionally, an SBC is a traffic cop: It facilitates and mediates VoIP flows in real time, in both directions between private VoIP domains: an enterprise and a VoIP-based service provider - the environment we tested here - or two service providers. SBCs came of age by providing peering connectivity between different carriers' VoIP services and only recently have begun penetrating enterprises.


How we tested SBCs
Archive of Network World tests
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There is no universal job description for an SBC. Certainly there has to be versatile handling of VoIP call-control protocols, such as Session Initiation Protocol (SIP) and H.323, especially amid different firewall and network address translation (NAT) configurations. And there needs to be some security safeguards - hiding the network topology of the private network, for example. But overall, SBCs are complex and costly components, coming from diverse backgrounds and offering widely varying capabilities.

We invited more than a dozen vendors who were touting new SBC wares earlier this year to submit their packages for testing in Miercom's New Jersey lab. Four accepted our challenge for this feature-based testing: Ditech Communications, Ingate Systems, Mera Systems and NexTone Communications.

Despite many differences in the feature sets of these products (see "What SBCs do"), their general orientations lie in a few similar, basic areas, including VoIP call handling, QoS handling and security capabilities. Based on our assessment in these areas, our Clear Choice Test Award goes to NexTone's package, the Multiprotocol Session Controller (MSC) coupled with its iView Management System (iVMS). NexTone's dynamic VoIP session control, real-time monitoring with active error and threshold-limit notification, call-level reporting system, and integrated firewall features make it the best of the enterprise-focused SBCs we tested. We note, though, that the NexTone package costs considerably more than the competition (more than $100,000, compared with $25,000 to $38,000 for the others).

What session border controllers do: Comparative feature checklist
Note: A check mark (√) indicates the product fully addresses this feature.
VoIP signaling and call handling
Ditech PeerPoint C100
Ingate SIParator 60
Mera MVTS
NexTone MSC and iVMS
Call load, bandwidth optimization        
Full-featured firewall traversal  
Session Initiation Protocol (SIP) to H.323 conversion
H.323 gatekeeper services    
SIP proxy, redirect, other services
Real-time Transport Protocol/RTP Control Protocol termination and regeneration
 
Transcoding (G.711-G.729, etc.)    
 
IP address resolution/management
Security        
Native, integral firewall  
 
Topology hiding
Authenticate VoIP calls and callers
Open and close legacy firewall ports
   
VoIP network address translation
Prevention of denial-of-service attacks
 
QoS, quality monitoring, reporting        
Differentiated Services/types of services QoS handling
Monitors each VoIP call
Per-call quality rating (i.e., mean opinion score)    
Issue call detail records  
TCall-quality trend reports      
Click to see:

Next: NexTone Communications >

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