Switching to VoIP

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

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Chapter 13: Network Infrastructure for VoIP

is at capacity in order to make a prioritization decision or bandwidth reservation.

Consequently, these notions just don’t exist in wireless Ethernet.

Failing over from one 802.11 link to another is also complicated. Using 802.11 (or

FSO) by itself provides no way of knowing when an automatic failover is necessary,

because there are no built-in alert mechanisms that tell you when a link is down.

One possible solution is to place routers on either end of an 802.11 link pair, and

then use load-splitting or dynamic routing to deal with one of the links going down.

Beware of the potential for substantial jitter on 802.11 links, too. For a much more

elegant (and detailed) discussion of wireless networking, check out O’Reilly’s 802.11

Wireless Networks: The Definitive Guide.

Firewall Issues

In most networks, a firewall provides an access gateway to network resources that

need to be restricted and secured. The primary method firewalls use to secure a

resource is limiting network traffic to and from the resource by port number, by pro-

tocol, or by network address.

Another key use of firewalls is network address translation (NAT), which provides

an exchange point for data transmitted between privately and publicly addressed IP

networks. NAT keeps ...