How useless is UMTS?

Štefan, one of our CCIEs, was working with a customer who wanted to have UMTS backup for his primary link. They’ve got it to work, including IPSec+GRE running over UMTS to provide the necessary privacy/security. However, it turned out that all wireless solutions (at least as offered by nearby Service Providers) are ridden with ridiculous round-trip times. For example, UMTS transmission delay is equivalent to the time it takes to send an IP packet from Central Europe to US West coast.

Štefan’s conclusions were modest: obviously UMTS technology is not ready to provide backup for VoIP traffic (which prompts an interesting question: how do the Service Providers plan to provide reasonable quality IP-based voice calls over UTMS?). The reality is way worse than that: a few hundred millisecond round-trip time can kill web browsing performance if you have awfully-designed web sites (and a lot of intranets are not well-designed because the developers never considered the delay impact).

5 comments:

  1. Hi,

    Some of my customers have a running UMTS like Štefan scenario a branch office with IPSec+GRE to the central office. We used German Telecom and Vodafone. With a good connection or in other words with HSDPA it works well, even with VOIP (Siemens Highpath). We have a round trip time of ~100Ms and a ugly jitter but it works...
    With EDGE or GPRS was no way for VOIP and normal working was not satisfying.

    My Opinion: UMTS Backup is ugly. Some (most?) providers assigning RFC-1918 IP adresses and/or filter inbound traffic. There is no way to get always the same IP (public) adress. The Connections are not reliable because of rain, snow, breathing cells, to many cell-user or whatever. But there some pro's: the cost is relatively low and sometimes there are no alternative (no means no or high priced) lines available.

    If possible i prefer any other cable based Backup.

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  2. hello,

    Latency is well known problem since 3g (2000). It improved with HSDPA...

    3gpp LTE looks to solve this...

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  3. A lot of the latency is at the RF edge. But the carriers try and compensate with extremely high speed IP backbones. A lot of it is going to have to do with your location, obviously, and how close you are to a Internet peering point on the carrier's network.

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  4. ...sure if you see something like https://www.swe.siemens.com/belux/portal/en/press/press/releases/cc/PublishingImages/012_umts_antenna_1102517.jpg
    from the position of your umts device you have a good chance of success ;-)

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  5. Anonymous is not entirely correct. True the latency comes at the edge. But I don't see how having high speed backbones makes any difference or compensates in any form.

    They tend to be over-provisioned and look like any other fixed line carrier backbone. ie. MPLS

    Latency in the backbone is basically the propagation delay which is fixed to physics and any additional latency would be variable queueing delay but this is designed in as to not be excessive, certainly in low latency classes.

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Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.