Ip Bandwidth Considerations
You can determine how much voip bandwidth to set aside for voice traffic using simple math. However, in a converged voice and data network, you have to make decisions on how much voip bandwidth to give each service. These decisions are based on careful consideration of your priorities and the available voip bandwidth you can afford. If you allocate too little voip bandwidth for voice service, there might be unacceptable quality issues.
Another consideration is that voice services are less tolerant to voip bandwidth depletion than that of Internet traffic. Therefore, voip bandwidth for voice services and associated signaling must take a priority over that of best-effort Internet traffic.
If a network were to use the same prevailing encoding (CODEC) scheme as the current PSTN system, voip bandwidth requirements for Voip networks would tend to be larger than that of a circuit-switched voice network of similar capacity. The reason is the overhead in the protocols used to deliver the voice service.
Typically, you would need speeds of OC-12c/STM-4 and higher to support thousands of call sessions. However, Voip networks that employ compression and silence suppression could actually use less voip bandwidth than a similar circuit-switched network. The reason is because of the greater granularity in voip bandwidth usage that a packet-based network has in comparison to a fixed, channel size TDM network.
Allocations of network voip bandwidth are based on projected numbers of calls at peak hours. Any over-subscription of voice voip bandwidth can cause a reduction in voice quality. Also, you must set aside adequate voip bandwidth for signaling to ensure that calls are complete and to reduce service interruptions. The formula for calculating total voip bandwidth needed for voice traffic is relatively straightforward. The formula to calculate RTP bearer voice voip bandwidth usage for a given number of phone calls is as follows:
Bits per sec = packet creation rates per sec x packet size x number of calls x 8 bits per sec
Where samples per sec = 1,000 ms / packet creation rate
Example: 2,000 full-duplex G.711 encoded voice channels that have a packet creation
Rate of 20 ms, with a packet size of 200 bytes (40 byte IP header + 160 byte payload)
50 samples per second = 1,000 ms / 20 ms
160 Mbps = 50 x 200 x 2,000 x 8
Note that this number is a raw measure of Voice over IP traffic and does not take in account the overhead used by the transporting media (links between the routers) and data-link layer protocols. Add this raw IP value to that of the overhead to determine the link speeds needed to support this number of calls. Note this value represents only the bearer (voice) content. Signaling voip bandwidth requirements vary depending on the rate at which the calls are generated and signaling protocol used. If a large number of calls are initiated in a relatively short period, the peak voip bandwidth needs for the signaling could be quite high. A general guideline for the maximum voip bandwidth requirement that an IP signaling protocol needs is roughly three percent of all bearer traffic. Using the previous example, signaling voip bandwidth requirements if all 2,000 calls were initiated in one second would be approximately 4.8 Mbps (3 percent of 160-megabits).
With the calculation of bearer and signaling, the total voip bandwidth needed to support two thousand G.711 encoded calls would be an approximate maximum of 164.8 MB. This voice over ip bandwidth requirement is a theoretical maximum for this specific case. If the parameters change, such as call initiation rate, voice encoding method, packet creation rate, employment of compression, and silence suppression, the voip bandwidth requirements would change as well. With large Voice over IP implementations requiring sizable voip bandwidth, it becomes imperative that the IP network delivers the needed service at predictably high performance.
Jim Francisto
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Voice Over Ip Voip Accelerators Requirements List
Accelerator products can help enterprises a lot in addressing the performance requirements of all enterprise applications including voip. First, Accelerators change the economics of wide area networking by squeezing an average of 100% - 400% more bandwidth with peaks of 1000% depending on traffic mix. This frees up link bandwidth to support high quality IP services - and it does it without expensive WAN upgrades.
It is also worthy to note that Accelerators do not actually use lossy compression schemes that might degrade voice quality and they add less than one millisecond of latency. In fact, the Accelerator’s compression actually reduces end-to-end latency by reducing serialization delays on WAN links. For example, it takes 125 ms to serialize a 1,000 byte packet on a 64 kbps link, but if an Accelerator increases the effective bandwidth by 4X to 256 kbps, the serialization delay is reduced by a factor of four to 31 ms. The following formula can be used to calculate the serialization delay for any combination of packet size and link speed:
Packet Size (in bytes) x 8 / Speed (in kbps) = Serialization Delay (in ms)
In addition to freeing up the bandwidth normally consumed by data applications, Accelerators are able to reduce WAN bandwidth requirements for different voip codecs. In fact, tests have shown that Accelerators reduced G.711 bandwidth requirements by 20% and G.729 by 70%. As a result, WAN links can carry more simultaneous voice calls and the performance of other applications may also be improved.
Accelerators solve increased jitter and latency caused by large data packets over slow WAN links by fragmenting large data packets and injecting voip packets at regular intervals. This feature allows voip and data to co-exist even on branch office WAN links. For example, normally, a voip packet “stuck” behind a 1,500 byte packet on a 64kbps lin will be delayed by 188ms.
Using the Accelerator’s packet fragmentation will result in the data packet being reduced in size (accelerated - say from 1500 bytes to 500b bytes) and then fragmented into smaller data packets (say - 2 packets of 250 bytes each). In this case, the latency for the voip packet will go down from 188 ms to 31ms! In addition to increasing WAN capacity for both data and voip while reducing latency and jitter, Accelerators also manage WAN bandwidth to ensure that critical applications like voip get the bandwidth they need.
Accelerators include an Instant QoS feature that prioritizes application access to WAN bandwidth. Without such priorization, the additional effective bandwidth provided by Accelerators could be consumed by aggressive, non-critical applications such as file sharing. Accelerator’s AppView feature provides graphical visibility for all application traffic sharing a link. AppView can be used to monitor WAN utilization and to plan future capacity requirements.
And finally, voip accelerators have a set of data integrity features that are designed to stop the packet loss that can degrade voice quality. A flow control mechanism reduces packet loss caused by link congestion and a packet recovery feature ensures that any lost packets are transparently recovered at the link level before they can cause voice quality problems.
Jim Francisto
Finding Out About Ldap Directory Servers
As companies have grown, and migrated from just using telephones to email and web based systems, so the comon company directory has needed to expand and grow. In the 1980s telecommunication companies created the X.500 specification, which is a collection of protocols to create and distribute a directory of information.
X.500 directory services were accessed via the X.500 Directory Access Protocol (DAP) which used the Open Systems Interconnect (OSI) protocol stack. As companies [spi]began|started[/spin] to implement TCP/IP networks, many found the complexity of managing a large OSI/DAP infrastructure too much. The Lightweight Directory Access Protocol (LDAP) was created to access X.500 directory servers via TCP/IP.
An LDAP server uses the idea of an organisational structure to organise information, which can include usernames, telephone numbers, office locations, photos, and more. This directory structure can be based on an organisation’s structure, making LDAP directories an obvious fit for replacing an organisation’s phonebook. The initial X.500 specification was deliberately designed with this scalable organisation of information in mind, which is one of the main factors behind the success of LDAP.
With the development of Voice Over IP (VOIP) systems an entire company’s information can exist within LDAP, allowing access from email clients, instant messaging applications, and HR systems. Even products like Microsoft’s Active Directory are based on LDAP and X.500 directory structures. LDAP’s power makes it an indispensiblemodern infrastructure.
What To Look For In A Spyware Blocker
Scanning your computer system to remove any spyware invaders that may be present is a good first step to protecting yourself from potential threats on the Internet; however, it simply is not enough. All too often, spyware components can come back just as easily after they are removed. To provide future protection for your computer system you need a thorough spyware blocker. This article is being brought to you by Network installation Cape Town
Your computer, just like your pets and kids, needs to be immunized against potential threats. Spyware blocker programs are designed to provide that very protection and immunization.
Ideally, spyware blocker programs should have a variety of protection features to ensure your computer receives more than adequate immunization. Consider this for a moment. Which would you prefer, protection from ever developing a disease or a cure after you have it and become ill? It’s not an understatement to say that just about everyone would say they would prefer to never get the disease in the first place. That’s why we all line up at the doctor’s office as kids to receive immunizations and booster shots. This article is being brought to you by Network installation Cape Town
To keep your computer from becoming ill, you need to select a spyware blocker with real time protection. This type of feature will detect a threat as soon as it attempts to attack your computer and stop it right in its tracks; thus preventing your computer from ever becoming infected.
One of the number one ways that many spyware and adware components work is by sort of hijacking your home page. In some cases, you may have to turn on your computer one day to realize that your homepage has been changed or reset without your permission and in other cases you may not realize anychange at all, yet the problem is still there. To combat this, be sure to look for a spyware blocker that will prevent your home page from being hijacked. This feature works by sort of low-jacking your home page so that it can’t be reset without your permission.
Some of the best spyware blocker programs out there actually work by containing a list of restricted sites that prevent your computer from accessing sites that have been determined to be dangerous. If lack of control has you concerned, rest assured that many programs with such features also have a manual control option that gives you a choice of whether you want to visit the site but also informs you at the same time that this site may be dangerous. This article was brought to you by Network installation Cape Town
Try Free Network Performance Monitoring Software
If you are looking for ways or tools that can help you manage your networks effectively, you can try using some network monitoring software. There are free Network Performance Monitoring Software available on the internet. Try downloading some of the programs and try them on your network, just to check which one will best work for you. Just make sure that you are getting them on safe sites. To be safe, try reading some of the review posts on these programs, by doing that you can download the ones that you think will be useful on your network. LAN, Bandwith, and server monitoring software are some of the example of this kind of software.