VOIP & Its Challenges

Problems with VoIP at present are:

a. not getting a dial tone

b. not sure that the call is going to the correct party

c. echo

d. caller ID reporting a completely different number

e. poor sound dropped calls

f. intermittent loss of service

g. voice or data packets getting lost

h. latency*, jitter**, delay***, and dropped packets

i. problems with internet routers affecting the quality of the call

j. VoIP goes down when your power, internet connection, broadband connection goes down; also depend on the resources of the computer if you are using "soft phones" like Skype

k. viruses, worms, hack attacks that bring down the internet can also bring down your phone system when it is IP-based

You can increase VoIP reliability by:

a. power backups

b. redundant internet connections

c. dedicated internet connection from VoIP; separate from your data network

d. redundant VoIP lines

The technology that VoIP & PSTN use...

PSTN uses circuit switching technology; whereas VoIP uses packet switching technology

In circuit switching technology (PSTN), there is a dedicated circuit that stays open between the caller and receiver for the entire time; that circuit cannot be used by anyone else during that time.

In packet-switched network (VoIP), there is no constant connection maintained; the voice signal is digitized and broken into small packets that are sent through a series of routers. The packets are reassembled at the destination and turned back into voice.

In total, the small amount of bandwidth used by one PSTN phone call can be shared by several VoIP calls.

The security strategy that should be implemented to protect VoIP from hacks...

Multi-layered security strategy of your VoIP, which slows down the process involves:

a. firewall packet filters

b. application filters

c. encryption protocols

d. decryption protocols

e. authentication access control mechanism

Although each of these layers delays the process a little bit, you should not skimp on your VoIP security as the effect is cumulative and can be enough to affect call quality.

The first step in creating a more secure VoIP network is to separate VoIP network from your data network using VLAN-capable switches. This means:

a. put VoIP phones on a separate virtual LAN with non-routable (private) addresses

b. do not allow interaction between Internet-connected PCs and VoIP components

c. use access control lists (ACLs) to prevent communication between the VLANs

VoIP is more vulnerable to attacks than the PSTN network because of the public nature of the IP network and its protocols; but by taking carefully planned, multi-layered approach security strategies, companies can make VoIP as secure as traditional phone systems.

*Latency refers to amount of time it takes for a packet to reach its destination. According to ITU, the maximum acceptable delay for work for voice transmissions is about 150 ms. Even dialup is adequate in regard to lag time; however, cellular, with delays of up to 600 ms, does not work so well until you get up to the 3G level.

**Jitters refer to uneven transmissions, with data flowing in quickly at times and being delayed at other times. Jitter results in echo.

***Delay results in high latency. Packets can be delayed at a router or other gateway that they pass through or travel more slowly along a low-bandwidth link or one that is crowded with a large amount of traffic.

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