Standing While Working – Three Months

February 24, 2012 in Updates with 1 Comment

My second office. The raised desk at the Starbucks in Edina, MN.

It’s been three months since I converted the desk in my home office to a standing desk.

There are many expensive solutions out there, some even starting in the upper $800 price range. These desks have motors that raise the table up and down.

I’m too cheap for that.  Why spend $800 on a desk when it could be spent elsewhere (or saved for a future home)?

How did I do it?

I went to Home Depot and bought four cinder blocks for $2 each.  These cinder blocks raise any standard desk to a suitable height for someone 5’11″.  My solution cost me less than $10.

The Verdict

Here’s the summary of my reflections at the three month mark:

  • I need a good bar-stool or raised chair.  Just as the human body wasn’t designed to sit all day, it also wasn’t designed to stand in one place.  You need a good balance of alternating between sitting and standing.  I’m looking for a good quality steel chair like the one in the Starbucks near my house.  Must be sturdy.  Wobbles need not apply.
  • I have less back pain.  Standing for a few hours at a time helps my back get the movement it needs.  I’ve also experienced better digestive function (wink…wink…) which I believe is partly related to standing.
  • It feels good to be done with work at the end of the day.  I’m not a farmer like my ancestors of old, but  I can now appreciate the thought of sitting down for dinner with the family at the end of the day.  Standing makes me feel like I’ve actually done something during the day instead of simple crawling from a bed to a chair in the morning.

I’ll post another update once I have my chair in place.  If you’re interested in changing things up, give the raised desk idea shot.  If you follow my model, it’s a cheap experience that could have long-term benefits.

MeetMe Password Protection

February 22, 2012 in Tech with 4 Comments

Several months years ago, I came across a great script that combines UCCX/IP-IVR with MeetMe functionality.  This allows you to front-end MeetMe calls with a conference number and pin.  Call it a “poor man’s” version of Meeting Place.

Continue Reading…

How Much Downtime Exists in 5 Nines of Reliability?

February 21, 2012 in Tech with 0 Comments

The “five nines of reliability” is a term that you’ve likely heard if you’ve been in systems management for any length of time.  The promise of “five nines” is that the system will have a 99.999% uptime over a given period of time, usually a year.

But how much downtime does this leave me in a year?   Check out this useful chart below:

As you can see, 99.999% uptime annually leaves you five minutes for complete systems outages.

Another commonly used metric for measuring availability is Defects Per Million (DPM). While measuring the probability of failure of a network and establishing the service-level agreement (SLA) that a specific design can achieve is a useful tool, DPM takes a different approach. It measures the impact of defects on the service from the end user’s perspective. It is often a better metric for determining the availability of the network because it better reflects the user experience relative to event effects.

Click here to read more about DPM

Cisco TelePresence Fundamentals 05

February 20, 2012 in TelePresence with 0 Comments

Continuing the TelePresence notes series based on Cisco TelePresence Fundamentals by Cisco Press.

TelePresence Network Interaction

As highlighted in each TelePresence system connectivity schematic, the primary codec is the interface between the CTS system and the network infrastructure. The primary codec connects to the network access-edge switch through an RJ-45 10/100/1000 port. The access-edge Catalyst switch that it connects to provides IP services, 802.1Q/p VLAN serv- ices, QoS services, and security services to the TelePresence system.

TelePresence systems use a private network for internal communications between the primary and secondary codecs and between codecs and cameras. By default, the internal address range is 192.168.0.0/24 through 192.168.4.0/24; however, if the TelePresence codec receives a 192.168.x.x address from the network, the internal private net- work switches to 10.0.0.0/24 through 10.0.4.0/24.

Even though only 192.168.0.0/24 through 192.168.3.0/24 are illustrated, 192.168.4.0/24 is reserved within the system for future (internal) use.

Similarly, if the TelePresence system uses 10.0.0.0/24 through 10.0.3.0/24 for its internal net- working address range, 10.0.4.0/24 is reserved within the system for future (internal) use.

Following are three key points regarding the internal networking of TelePresence systems:

  • From the network’s perspective, the TelePresence primary codec appears as a single endpoint device with a single IP address. (Remember, the 7975G IP Phone also appears as a separate endpoint device with its own IP address).
  • The internal components (such as secondary codecs and cameras) do not receive a default gateway; therefore, they cannot route beyond the primary codec.
  • If the primary codec uses 192.168.0.0/24 through 192.168.4.0/24 as its internal networking addresses (which is the default), it cannot connect to external servers or end-points that uses these same addresses (because it will attempt to reach such addresses via its internal network, not its external default gateway). Conversely, if the primary codec has been assigned an IP address from the network in the 192.168.x.x range, it uses internal networking addresses in the range of 10.0.0.0/24 through 10.0.4.0/24 and similarly cannot connect to external servers or endpoints that might use these same addresses.

Cisco TelePresence network control, management, and signaling protocol:

Cisco TelePresence signaling and media paths:

When the TelePresence system completes these protocol interactions, it is ready to place and receive calls. When a call initiates, the following steps occur:

  1. The Cisco 7975G IP Phone sends an XML Dial message to its primary codec.
  2. The initiating TelePresence primary codec forwards the request as a SIP Invite message to the CUCM.
  3. The CUCM, in turn, forwards the SIP Invite message to the destination TelePresence primary codec (or Session Border Controller, in the case of business-to-business calls).
  4. The destination codec forwards the message as an XML Ring message to its associated 7975G IP Phone. (The TelePresence primary codec can optionally be set to automatically answer the incoming call, in which case the codec answers the call immediately and proceeds to Step 6, which is to send a SIP OK message to CUCM.)
  5. If auto-answer is not enabled, when the user presses the Answer softkey on the 7975G IP Phone, the 7975G IP Phone replies with an XML Answer message to the destination codec.
  6. The destination codec sends a SIP 200 OK message to the CUCM.
  7. The CUCM relays this SIP 200 OK message to the initiating TelePresence primary codec, and the call is established.
  8. Real-time media, both audio and video, passes between the TelePresence primary codecs over Real Time Protocol (RTP).

 

Cisco TelePresence Fundamentals 04

February 15, 2012 in TelePresence with 0 Comments

Continuing the TelePresence notes series based on Cisco TelePresence Fundamentals by Cisco Press.

Managing Latency, Jitter, and Loss

A few important facts about latency:

  • Latency: The human experience is round-trip in nature. This is referred to as conversational latency, or experience-level latency; 250 ms to 350 ms is the threshold at which the human mind begins to perceive latency and be annoyed by it.
  • Latency Target: To maintain acceptable experience-level latency, Cisco recommends that customers engineer their networks with a target of no more than 150 ms of network-level latency, in each direction, between any two TelePresence systems.
  • Latency Thresholds: When network-level latency exceeds 250 ms averaged over any 10-second period, the Cisco TelePresence system receiving those packets generates an alarm, and an onscreen message displays to the user.

If the latency from one TelePresence system in Hong Kong to the CTMS in London is 125 ms, and the latency from the CTMS in London to the other TelePresence system in San Francisco is 125 ms, the end-to-end latency from the Ethernet network interface of the Hong Kong system to the Ethernet network interface of the San Francisco system is 250 ms, plus approximately 10 ms added by the CTMS, for a total of 260 ms. The TelePresence System in San Francisco will not realize this and will think that the latency for that meeting is only 125 ms.

A few important facts about jitter:

  • Jitter Target: To maintain acceptable experience-level latency, Cisco recommends that customers engineer their networks with a target of no more than 10 ms of packet-level jitter and no more than 50 ms of video frame jitter in each direction between any two TelePresence systems.
  • Jitter Thresholds: Cisco TelePresence uses a quasi-adaptive jitter buffer.
    • At the beginning of every new meeting, the jitter buffer starts out at 85 ms in depth.
    • After monitoring the arrival time of the video frames for the first few seconds of the meeting, if the incoming jitter exceeds 85 ms average, the jitter buffer is dynamically adjusted to 125 ms.
    • After that, if the jitter exceeds 125 ms averaged over any 10-second period, the Cisco TelePresence system receiving those video frames generates an alarm and dynamically adjusts the jitter buffer to 165 ms. The alarm is written to the syslog log file of that TelePresence system, and an SNMP trap message is generated.
    • No onscreen message is displayed to the user.Any packets exceeding the 165 ms jitter buffer depth are discarded by the receiving TelePresence system and logged as “late packets” in the call statistics.

A few important facts about loss:

  • Loss Target: To maintain acceptable experience-level video quality, Cisco recommends that customers engineer their networks with a target of no more than .05 percent packet loss in each direction between any two TelePresence systems. This is an incredibly small amount, and given the complexity of today’s global networks, 0.05 percent loss is not always possible to accomplish.
  • Loss Thresholds: The Cisco TelePresence system has a multi-tiered loss thresholds:
    • When packet loss (or late packets) exceeds 1 percent averaged over any 10-second period, the Cisco TelePresence system receiving those packets generates an alarm, and an onscreen message appears.
    • When packet loss (or late packets) exceeds 10 percent averaged over any 10-second period, the Cisco TelePresence system receiving those packets generates a second alarm, and a second on-screen message appears (unless the hold timer is already in affect).
    • If loss (or late packets) exceeds 10 percent averaged over any 60-second period, in addition to the actions described, the system downgrades the quality of its outgoing video.
    • Finally, if loss equals 100 percent for greater than 30 seconds, the codec hangs up the call. If the packets begin flowing again anytime up to the 30-second timer, the codec immediately recovers.
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