I'm very new to VoIP and have been researching the implementation of VoIP on my network. I have a bunch of questions however I will limit it to a couple. I have 17 locations all with Cisco 2801 routers (IOS v12.4(c1), 61MB flash, 128mb memory) and it appears that IP is the only available feature on my device. Is this okay for Voice? Or do I need to upgrade the IOS or hardware?