Author: John
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What is OpenSIPS?
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There are a number of open source applications available that are used to build IP Telephony solutions. OpenSIPS may not be as well-known as Asterisk, but it is widely used by service providers as a core part of their infrastructure because of its robustness, speed and capacity. In this article I will review the history of OpenSIPS, explain what it is, what features it offers and its core operational roles. This will include a summary of…
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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 a mistake to expect too much of QoS or to assume that it will always make a difference no matter what.…
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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 their place within the DiffServ packet prioritisation model. Recap I explained in part 1 how Layer 2 data can be tagged…
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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 Layer 2 network QoS settings; i.e. the settings associated with the VLAN tag in 802.1 Ethernet protocols. If you are looking…
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Setting up shared voicemail on Asterisk – part 2
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Part 1 laid the foundations for creating and accessing a shared voicemail box. In this, part 2, I explain how the lamp on the BLF key is switched on and off to show there are messages waiting in the shared box. Note that this is separate from any existing MWI lamp used for personal voicemail. It uses a custom device state within Asterisk switched by an external application. The external application in this case is a bash…
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Setting up shared voicemail on Asterisk – part 1
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It’s a requirement that people often seem to ask for – a single voicemail box, taking messages for a department, that can be easily monitored and accessed by several different users. A typical application would be to record out-of-hours messages which are then checked in the morning by any of a number of users, perhaps just depending who arrives first at the office. While it is fairly easy to configure Asterisk or Trixbox to record the messages, it is less…
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Using Custom Device States to control BLF lamps
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Do you want to know how to use a custom device state to control the lamp on a programmable key of an IP phone? In this article I explain how to set up the hints and make any number of IP phones subscribe to a custom device state and how to switch the custom status from within the Asterisk dial plan. In later articles I plan to show how this can be put to a practical use. I will explain how to…
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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. Summarising the design so far If you read the first two parts of this article, you will appreciate how and why we…
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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 to cluster two OpenSIPS servers and options for sharing common resources including the mediaproxy and MySQL database. An overview of far-end…
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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 use OpenSIPS as the primary public-facing portal into – and often out of – their voice infrastructure. This is fine as…
