Posts Tagged ‘IP’

postheadericon Are You VoIP Ready? – The “X” Factor

One X factor you will need to consider when looking at a VoIP solution is your network s vulnerability to viruses, worms and Trojans. The first thing I caution customers about when they want to go all out and purchase a pure  IP telephony solution is that as a general rule, you want to keep your local voice and local data traffic separate. In practice, this means if you already have a voice infrastructure (i.e. jacks specifically for telephone
sets that home run to a main telephone room or the IT Head End  room without connecting to the LAN wiring), put your voice on that with TDM sets instead of abandoning the wires that are in place.
Voice and data packets going out to other offices that are linked to you through a Point to Point or VPN connection will inevitably share time on the same Internet circuit. However, TDM sets are not affected by anything on the LAN until they have to connect to some off site device through VoIP. Regular local traffic such as voice mail retrieval, intercom calls, paging to the warehouse or calling a supplier over the PSTN will occur with or without a data switch or server in place.
If you do decide to go all IP, then do it when you can make a fresh wiring start and run a separate cable for voice and data sets. Also, keep the voice devices on their own subnet separated from the other LANs by a decent router. RonEK is not a Cisco reseller but we like their routers and recommend them in cases like this.
Many IT people would take issue with this approach but I have personally witnessed and been victim to what can happen as shown in Figure 4. As you can see, everything looks great until the main server on the LAN was hit by a very aggressive virus. For about 2 hours it created such havoc on the LAN in the form of broadcast storms that all network traffic was reduced to a crawl and VoIP was stopped cold.

postheadericon Are You VoIP Ready? – QoS (Quality of Service)

Normally, when packets are serialized out the router to the Internet, they are sent in a first come first serve  fashion. If your router is equipped with QOS, packets from your PBX or SIP server* can be prioritized ahead of the other non-voice packets thereby keeping the flow of
voice traffic relatively smooth. Most carriers that offer a combined package of voice and data services do just that. RonEK is a partner with several ISPs and one of the first questions on the vendor check list is the IP address of the PBX. Most of the higher end carriers will provide an
end to end managed circuit  which means that they can control the connection from your office to their space in the central office. From there, packets are routed out on their backbone or someone else s backbone depending on the carrier s capacity and the final destination.
Keep in mind that QOS prioritizes packets going out to the other end. Once a packet leaves your premise or your provider s backbone, it is no longer prioritized and subject to the winds and tides of the Internet just like all the other packets. So, when designing a multi-site
network, try to stick with one provider and, if possible, try to do it on an MPLS platform. Usually if you stay within a provider s backbone from end to end, the prioritization will be maintained throughout the connection. Also, there is no way to prioritize packets coming to you until they actually get to you. Many times customers think that if they simply implement QOS that all their voice issues will go away not realizing that they only addressed half of the potential problem. Your connection and QOS is just part of the overall voice session that YOU control. The rest is in the hands of the intermediary (often there is more than one) that controls the path of the packets and then finally, the ISP and equipment at the final destination.
* More about SIP servers in coming articles.

postheadericon 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.