Section 13.10. Key Issues: Network Infrastructure for VoIP


13.10. Key Issues: Network Infrastructure for VoIP

  • The topology of a VoIP network rides atop that of an IP network.

  • Your IP network layout affects where you locate voice resources on the network and how resilient voice services will be to failure

  • Hub and spoke networks offer little remote redundancy but result in cheap connectivity

  • Meshed networks offer redundancy, but result in more expensive connectivity

  • Peered networks offer the least-expensive connectivity but are often the least capable of yielding positive results with IP telephony because call paths across peered networks are prone to latency

  • When choosing a location for a voice resource like a PBX server or media gateway, locate to conserve bandwidth, to save money, and to gain long-term capabilities, not because of superficial or short- term conveniences

  • The best way to survive a power failure is battery backup, but using multiphase power from the electric company can somewhat reduce the risks of power loss.

  • PSTN trunk failures almost always incur some manual failover, whether it's calling the phone company to get a line forwarded or physically juggling trunks around to compensate for a downed trunk

  • IP-based trunks (VoIP trunks) can be more easily failed over than PRIs and POTS lines

  • Remote site survivability , the ability to keep telephony applications at remote sites working when disconnected from the central PBX, is accomplished using application layer security. ALS techniques and failover protocols are proprietary to each IP telephony platform

  • Metro area bridging technologies like FSO and 802.11a/b/g don't offer automatic failover and must be used in combination with dynamic routing in order to accomplish it.

  • NAT firewalls impose a communications breakdown on protocols like H.323 and SIP that require multiple sockets. To get around this problem, you can employ a DMZ or use the IAX protocol (which requires only one socket per client), STUN, or a VPN

  • Peer-by-peer codec selection is necessary if you want to use bandwidth-conserving codecs across certain links and not across others. In Asterisk, this is configured in /etc/asterisk/sip.conf

  • Directory services are a crucial aspect of VoIP infrastructure. Using an XML-generating web site, you can create dynamic directories and other applications for Cisco IP phones that are tied to a database backend



Switching to VoIP
Switching to VoIP
ISBN: 0596008686
EAN: 2147483647
Year: 2005
Pages: 172

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