Switching to VoIP

This is the Title of the Book, eMatter Edition

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

802.1q VLAN

|

203

LTC on a softPBX

It can also be used, on a Linux-based softPBX, to tag traffic with the EF class. This

way, the DiffServ decision point and the softPBX can reside on the same machine.

For more details, an excellent book on using Netfilter firewalls is Linux iptables

Pocket Reference (O’Reilly). Another is Building Secure Servers with Linux (O’Reilly).

LTC-specific resources are available at the Linux Advanced Routing and Traffic Con-

trol web site (http://www.lartc.org).

802.1q VLAN

Ordinarily, Ethernet provides one common broadcast domain per network segment.

This means that when a packet comes across the segment destined for a local host

whose hardware (MAC) address has not yet been resolved (ARPed) and associated

with a certain switch port on the Ethernet segment, a broadcast to all ports is done in

order to find a host with the right MAC address that’s supposed to receive the

packet. Once the port with the correct recipient is found, an ARP record is recorded

in the switch so that all future traffic destined for that MAC address can go to that

port rather than being broadcast.

One problem with this is that the broadcast traffic, while only a small percentage on

most networks, can be a waste of bandwidth. Another problem is that, when broad-

casts occur, every device ...