Show 58 – The Packet Speaks!

In show 58, recorded August 27, 2011, Ethan Banks is joined by Tom Hollingsworth, Erik Peterson, and Amy Arnold for the Packet Pushers’ first discussion about voice technology. Think of this as a foundational show that will ramp you up if you’re a network engineer that doesn’t deal with voice much beyond a QoS policy tweak here and there.

I apologize in advance for any coughing/sniffling/clicking/crickets/hurricanes you notice. It seems this week’s Skype upgrade broke my mute button, at least as related to my recording plug-in, so there’s some environmental racket that wasn’t possible for me to edit out in this show.

First – The News:

Discussion – The Packet Speaks!

  • Voice – the redheaded stepchild of the networking world. Or is it? Why should network geeks pay attention to voice technology?
  • Let’s distinguish between voice and video.
  • So I bought this fancy VoIP system for my business. I can dump my phone company now, right?
  • How does a data T1 functionally differ from a voice T1?
  • When I order a voice T1 from my provider, what am I actually ordering? We discuss CAS vs. PRI.
  • Explain channelization of a voice T1 vs. a data T1…D-channels and B-channels, indeed.
  • Why is planning for peak load so critical when deploying voice networks?
  • What components take VoIP packets and turn them into TDM voice suitable for the plain old telephone system? We discuss gateways and DSPs.
  • Do I have to terminate my voice T1 on a router? Or can I terminate it on a call manager system directly?
  • What codecs should be used for what situations? G.711, G.729, and G.722 are discussed.
  • Let’s discuss vendor interoperability issues in the voice world. We mention a few religious discussions, proprietary vs. standard methodologies, and integrating a legacy PBX while migrating to a new VoIP system.
  • The voice world is acronym heavy, but we take a stab a grouping them into signalling protocols and media protocols.
Ethan Banks
Ethan Banks, CCIE #20655, has been managing networks for higher ed, government, financials and high tech since 1995. Ethan co-hosts the Packet Pushers Podcast, which has seen over 3M downloads and reaches over 10K listeners. With whatever time is left, Ethan writes for fun & profit, studies for certifications, and enjoys science fiction. @ecbanks
Ethan Banks
Ethan Banks
  • waltergibbons

    Another great show guys (+Amy)! Love to hear more about voice / VoIP / IP Telephony or whatever you call it, H.323, voice gateways, integration of Video Teleconferencing endpoint and firewall best practices to support all of the above. Keep up the awesome work!

  • Cristian


    Great show, thank you.

    I have two questions:

    1) What other options are available
    beside Cisco in the enterprise VOIP market?

    2) How well can be integrated in real
    life pieces of VOIP infrastructure from different vendors (for
    example Cisco phones on Procurve switches, non-Cisco phones with
    Cisco Call Manager, etc)

    Please bear with me if I don’t get all
    the acronyms right, I am not a “voice guy”.

    The good parts about Cisco VOIP:

    – it works, especially if the whole
    infrastructure is Cisco (the Cisco phone talks CDP with the Cisco
    switch, who assigns the voice VLAN, who automagically gets the right
    QOS markings …)

    – it covers all the possible
    situations, for example Cisco routers can serve voice traffic is the
    connection to Call Managers is down (SRST)

    The bad parts about Cisco:

    – it’s expensive, you get charged for
    all sorts of licenses. The number of licenses seems to increase with
    each new version of CallManager

    – some of the pieces of the puzzle are
    obviously acquisitions that were not fully migrated to a decent
    platform. The first example that comes to mind is UCC Enterprise.
    UCCE costs a lot of money and is supposed to run huge call centers.
    The software interfaces are DOS windows on Windows servers with
    messages scrolling.

    – I have the feeling that under the
    hood the Cisco software running on appliances/servers is less than stellar. I
    did an upgrade from CM version 5 to version 7. Based on the logs
    displayed, the upgrade process is a bunch of scripts with all sorts
    of errors displayed at almost at every step. The upgrade failed
    initially, we spent two weeks on the phone with Cisco TAC. The fifth
    engineer working on the case finally identified the problem as an issue with the database export function between versions.

    Something else (hopefully at least as stable and complete as the Cisco solution, but cheaper) should be available. Small companies can be served by
    Asterisk or similar low cost options. What options are available for
    companies with hundreds or thousands or phones and multiple
    locations? Nortel is gone, and based on what I heard on the show
    Avaya does not get a lot of love.

    Thank you,

  • Mrs. Y Iswhy

    Great show. I am always in awe of people who do voice, because it can be so esoteric. I felt like I was in the presence of enlightened Zen masters. Please do more shows on this subject, because then I’ll be able to talk to our voice engineers with more confidence.

  • gyrfalcon

    “…the problem is what happens two generations down the road. What happens when the word of apple or the management team decides that they’re going to give up on this form over function kinda idea, and start making mass produced devices”

    form over function?  apples only saving grace has been putting function over form.