Posts Tagged ‘latency’
Are You VoIP Ready? – Glossary
| Bandwidth Saturation | The point in which all available bandwidth on an Internet
connection is used up. |
| Bandwidth | The amount of data passing through a connection over a given time. It is usually measured in bps (bits-per-second) or Mbps (Megabits per Second). As a general rule, get as much as you can afford – and the make sure you are getting it. |
| Content Filtering | On the Internet, content filtering (also known as information
filtering) is the use of a program to screen and exclude from access or availability Web pages or e-mail that is deemed objectionable. Content filtering is used by corporations and governments as part of Internet firewall computers and also by home computer owners, especially by parents to screen the content their children have access to from a computer |
| Dropped Packets | Packets (i.e. small data “packages”) are occasionally dropped, or
lost, on the network for various reasons. For instance, two nodes may be communicating at widely disparate transfer rates. TCP packets are resent, UDP s are not. |
| Hop | In a packet-switching network, a hop is the trip a data packet takes
from one router or intermediate point to another in the network. On the Internet (or a network that uses TCP/IP), the number of hops a packet has taken toward its destination (called the “hop count”) is kept in the packet header. |
| ICMP | Internet Control Message Protocol is a message control and
error-reporting protocol between a host server and a gateway to the Internet. ICMP uses Internet Protocol (IP) datagrams, but the messages are processed by the IP software and are not directly apparent to the application user. |
| ISP | An ISP (Internet Service Provider) aka Carrier, aka Provider, is a
company that collects a monthly or yearly fee in exchange for providing the subscriber with Internet access. |
| Jitter | The difference in latency from one packet to the next measured in
milliseconds. |
| LAN | A Local Area Network is a computer network that spans a
relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN). |
| Latency | In a network, latency, a synonym for delay, is an expression of how
much time it takes for a packet of data to get from one designated point to another. Typically, latency is measured by sending a packet that is returned to the sender. The round-trip time – measured in milliseconds – is considered the latency. |
| NIU | A Network Interface Unit (sometimes called a network interface
device) is a device that serves as a common interface for various other devices within a LAN , or as an interface to allow networked computers to connect to an outside network. |
| Ping | Loosely, ping means “to get the attention of” or “to check for the
presence of” another party online. Ping operates by sending a packet |
| Point to Point | Point-to-point telecommunications generally refers to a connection
restricted to two endpoints, usually host computers. |
| PSTN | Public Switched Telephone Network is the world’s collection of
interconnected voice-oriented public telephone networks, both commercial and government-owned |
| QoS | Quality of Service. Describes the ability of a e.g. router to prioritize
certain packets |
| SIP | Session Initiation Protocol is an application-layer control
(signaling) protocol for creating, modifying, and terminating sessions with one or more participants. It can be used to create two-party, multiparty, or multicast sessions that include Internet telephone calls, multimedia distribution, and multimedia conferences. |
| TDM | Short for Time Division Multiplexing, a type of multiplexing that
combines data streams by assigning each stream a different time slot in a set. TDM telephone sets (often referred to as digital sets) differ from IP sets in that they do not go on a LAN s infrastucture are compatible with analogue wiring schemes and can work on cable runs oup to 1,600 feet. |
| VPN | (pronounced as separate letters) Short for Virtual Private Network,
is a private network that uses a public network (usually the Internet) to connect remote sites or users together. VPNs use “virtual” connections routed through the Internet from a company’s private network , a remote site or employee. |
| WIC | WAN Interface Card is installed in a router and is the component
that a Internet T-1 will physically plug in to. |
Are You VoIP Ready? – The Road to China: Content Filtering to the Max
Are You VoIP Ready? – What Stable Connections Look Like
Are You VoIP Ready? – The “X” Factor
Are You VoIP Ready? – QoS (Quality of Service)
Are You VoIP Ready? – Bandwidth
Are You VoIP Ready?
If you are considering VoIP for your company – or more to the point, if YOU are responsible for the implementation of VoIP for your company – here are the basics you will need to understand.
Voice over IP performance is a function of:
a) Bandwidth
b) Latency
Both components have to be within a certain tolerance in order to be usable and there are a multitude of factors that can adversely affect either. Many IT professionals who are first time VoIP-ers often think that given enough bandwidth, you can do anything – including voice. This is only half true. A lack of bandwidth can cause latency, but an abundance of bandwidth is not a guarantee of a clear conversation. Of the two, latency is not only a show stopper, it is also the hardest one to find and correct because there are many causes that are often times not within your control. Figure 1 is a great example of a company with a bonded 6M T-1 connection with such erratic latency – and jitter – that it is virtually unusable for
voice applications. In many cases like this, the most natural scapegoat is the carrier, however, in this case, hop 14 is the WAN side of the customer s router and hop 15 is a device behind it which implies a problem with the hardware. Here, the problem turned out to be one of the 4 T-1′s were in a permanent Admin Down mode and needed to have the WIC replaced.
WARNING TO THOSE JUST GETTING INTO VoIP – Voice is real time – using primarily UDP packets – and therefore much more affected by things like dropped packets, jitter and high latency than regular data. If there are issues on your Internet connections with these items, you will probably not realize it unless you specifically – and continuously – test for it. Most carriers only guarantee bandwidth and NOT latency. Trust me, the CEO, CFO, Customer Service manager and Sales manager will get upset if the email server or Internet is a little slow, but they will absolutely FREAK if their phones don’t work.