Category: VoIP
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VoIP QoS in practice: About Network Congestion
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My previous two articles explored QoS tagging of voice data packets using ToS/DiffServ values and of Ethernet frames using CoS or Priority values. QoS is often advocated as an essential part of any self-respecting VoIP solution and there is no doubt it can make a big difference in the right circumstances. However, it would be […]
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VoIP QoS Settings – part 2
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In part 1, we examined the Layer 2 QoS settings available on most VoIP equipment. In this second part, I will explore the Layer 3 parameters and offer practical suggestions for the values that should be assigned to them. We will briefly look at the history and structure of the ToS and DSCP fields and […]
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VoIP QoS Settings – part 1
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The QoS settings on VoIP phones and related equipment can be perplexing. Here, I will attempt to explain what parameters like CoS, ToS, DiffServ and DSCP really mean and offer practical suggestions for the values that should be assigned to them. Part 1 of this article starts with a broad overview and then focuses on […]
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Clustering OpenSIPS for High Availability – Part 3
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In this, part 3, we examine how a virtual IP address can be switched between two Linux servers to provide an active/standby failover and how this impacts on OpenSIPS. Part 2 investigated the implications for far-end NAT traversal of clustering two OpenSIPS servers and concluded that the best solution is the use of a virtual IP address. […]
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Clustering OpenSIPS for High Availability – Part 2
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In this, part 2, we investigate the implications of using more than one IP address on an OpenSIPS server and how this impacts on far-end NAT traversal. We will also see how the use of a virtual IP address can overcome these problems when clustering two OpenSIPS servers. Part 1 reviewed why we might want […]
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Clustering OpenSIPS for High Availability – Part 1
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Why cluster OpenSIPS? Unlike Asterisk, a typical OpenSIPS server is able to handle a very large number of simultaneous SIP calls. It is generally very reliable and will keep running for many months, or even years, with little or no attention. As a consequence, it is the preferred choice for many VoIP service providers who […]
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IP Phone Configuration: User Account Settings
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Manufacturers different naming conventions While SIP is an industry standard protocol, the names assigned to the configuration fields on an IP phone are far from standardised. The tables below show the text labels that you can expect to see on the web interface configuration forms next to the boxes where you must enter your settings. […]
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Using SIP Devices behind NAT
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SIP Devices behind NAT: What solutions are available? When an IP phone is installed behind NAT, problems can be created by the NAT device itself, by the phone’s inability to correctly understand its own networking environment or from a combination of the two. Because it is such a common problem, most IP Phones have built-in […]
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SIP and NAT: Why is it a problem?
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Why is it a problem using SIP Clients behind NAT? What is NAT? To understand why SIP Clients behind NAT are a problem, you need to first have some understanding of what NAT is and what it does. NAT stands for Network Address Translation. Unless you are using One-to-one NAT, then a NAT device may […]
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SIP Outbound Proxy Server Explained
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Why do IP Phones require a setting for ‘Outbound Proxy Server’? Outbound Proxy Server When you look at the configuration options on most IP phones, you will see a field called “Outbound Proxy” or “Outbound Proxy Server”. In this field you can enter an IP address, a host.domain name or just a domain name (as […]
