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VOIP VPN
February 03, 2012 @ 12:08:45 AM EST |
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Good VPN for VOIP.
Voice Over IP is not always easy under a Virtual Private Network.
A VOIP VPN combines voice over IP and virtual private network technologies.
Because VOIP transmits digitized voice as a stream of data, the VOIP VPN solution accomplishes voice encryption.
The VOIP gateway-router first converts the analog voice signal to digital form, encapsulates the digitized voice within IP packets,
then encrypts the digitized voice using IPsec, and finally routes the encrypted voice packets securely through a VPN tunnel.
At the remote site, another VoIP router decodes the voice and converts the digital voice to an analog signal for delivery to the phone.
A VOIP VPN can also run within an IP in IP tunnel or using SSL-based OpenVPN.
There is no encryption in former case,
but traffic overhead is significantly lower in comparison with IPsec tunnel.
The advantage of OpenVPN tunneling is that it can run on a dynamic IP and may provide up to 512 bits SSL encryption.
What is good about it:
Security is not the only reason to pass Voice over IP through a virtual private network.
Session Initiation Protocol, a commonly used VoIP protocol is notoriously difficult to pass through a firewall
because it uses random port numbers to establish connections.
A VPN is also a workaround to avoid a firewall issue when configuring remote VoIP clients.
Some VOIP standard STUN, ICE and TURN eliminate natively some NAT problems of VOIP.
What is not good:
The protocol overhead caused by the encapsulation of VoIP protocol within IPSec dramatically increases the bandwidth requirements for VOIP calls.
VoIP over VPN protocols too "fat" to be used over a mobile data connections like GPRS, EDGE or UMTS.
VoIP over VPN is not as usable in mobile environments, it is sometimes used to create "encrypted VOIP trunk"
between different sites of a corporations, running VoIP PBX interconnections over a VPN connection.
New standards:
The recent publication of new VoIP encryption standards built into the protocol, such as ZRTP and SRTP,
allow the VOIP client to run without the VPN overhead, integrating with standard features of VOIP PBX
without having to manage both the VPN gateway and the PBX. No more VPN overhead.
You can do it for free:
VOIP VPN solution may be accomplished using open source software like Linux distribution,
or BSD, as an operating system, a VoIP server, and an IPsec server.
VOIP Definition:
VOIP or Voice over Internet Protocol is methodology in which the Internet users transmit their voice data over the Internet Protocol (IP).
Different terms have been developed for the VoIP like Internet telephony; Internet phone, IP telephony and IP phone.
This is the latest technology in which fax, text, SMS and voice is transmitted over the Internet after it is converted in to IP data packets.
Working of VoIP:
VOIP uses the Internet to transmit the voice messages rather than the Public Switched Telephone Network (PSTN).
The basic steps involve for the process are signaling and media channel setup, digitization of the analog voice signal,
encoding, packetization, and transmission as Internet Protocol (IP) packets over a packet-switched network.
On the receiver side these same steps are used but in the reverse order.
VOIP systems employ session control protocols to control the set-up and tear-down of calls as well as audio codecs which encode speech allowing
transmission over an IP network as digital audio via an audio stream.
VPN and VOIP:
VOIP is considered as unsafe because the protocol used can be easily broken down.
So to improve the security of the VoIP channel VPN technique is integrated with the VoIP network.
Users can connect and send and receive calls using a VoIP channel without any concern of a security lapse using the VPN connection.
VPN allows encrypts the data sent over the channel using the 128-bit AES technique which is still unbreakable
and as voice is transmitted as data packets so they can also be encrypted through the AES technique and transmitted.
In this way whatever you speak is safe and secure.
Any kind of broadband internet connection from your local ISP can be use:
ADSL modem, Cable modem, Satellite, ISDN, T1/E1, DDN etc.
Your ISP blocks the VOIP calls? Not a problem.
VPN for VOIP service works 100% with any ISP.
VPN service works with private IP (behind NAT router) or dynamic IP (PPPoE) environment.
A VPN router just works like plug-and-play; connect it to your home network or office network where DHCP is enabled,
and you are online with connection to a VPN network where all network parameters are optimized for VOIP traffic.
VOIP Traversal (nobody can block your VOIP traffic) - your local ISP can't block your VOIP calls any more.
Your VOIP traffic doesn't run on famous VOIP ports, no H.323 or SIP signal packet pattern can be matched by ISP.
Privacy & Security (nobody can find out that you are running VOIP traffic)
your local ISP can't figure out what applications you are running with the internet connection,
and the highest encrypted VPN packet doesn't make any sense to the network monitor.
No one can find that you are running VOIP traffic through the network, and no one can sniff the VOIP phone call conversation.
Flexibility (you can run VOIP service with any kind of internet connection)
People may get surprised but it's true, that in professional tests, under the same network condition,
SSL VPN network provides better voice quality than regular network.
In high-bandwidth, low-latency environments, there is virtually no difference in quality between an unencrypted VoIP call
and the same call made over an SSL VPN.
In every case, adding an SSL VPN to a VoIP call over a good broadband network improved call quality.
Run over a bad, slow network, showed that when the network is horrible, nothing helps.
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2 Comments so far - |
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VOIP across an SSL VPN said...
February 19, 2012 @ 9:37:06 AM EST
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VOIP across SSL-based VPN can improve call quality.
You get improvement by encapsulating the UDP VOIP packets ( SIP and RTP ) in TCP/IP.
VPN has no negative influence on latency, jitter and packet loss.
in the case of the g7.11 codec and compressed VPN it is even possible to gain 10% bandwidth compared to non-VPN traffic.
Different common VPN solutions have big difference on the available throughput,
which is due to the rather small packet sizes and greatly increased overhead:
With enabling authentication, encryption, HMAC, anti-replay attack, and initialization vector,
and use small RTP size for Codec, the vpn overhead is high:
g723 with 30ms RTP size and using VPN tunneling: approx. 85% overhead;
g729a with 20ms RTP size and using VPN tunneling: approx. 80% overhead;
But when making some adjustments on the encryption/authentication settings and double the RTP size,
the overhead can go down to about 20%-30%.
Comparing to SRTP as encryption method for VoIP: approx. 5% additional overhead. |
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