[tahoe-dev] tahoe over satellite

Aleksandr Milewski zandr at allmydata.com
Fri Jun 20 19:12:04 UTC 2008


Those are precisely the sorts of network conditions we were designing  
for both at DF and later at Aspera. I'm actually very surprised things  
are working as well as they are, since TCP is mostly useless under  
those conditions.

I wouldn't be the least bit surprised if there were some sort of TCP  
proxying going on to enable that to work at all.

-Z
On Jun 20, 2008, at 11:42 AM, zooko wrote:

> Folks:
>
> I'm uploading lots of pictures and movies from my mom's farmhouse.
> Her Internet connection is through a geostationary satellite owned by
> a company named "WildBlue".  When we're not doing too much with it,
> we get ping times like this:
>
> 28 packets transmitted, 26 packets received, 7% packet loss
> round-trip min/avg/max/stddev = 1155.724/1428.105/1756.191/169.410 ms
>
> When I'm heavily loading it by doing many simultaneous Tahoe uploads
> and downloads as well as ssh and other web requests, we get ping
> times like this:
>
> 49 packets transmitted, 44 packets received, 10% packet loss
> round-trip min/avg/max/stddev = 2740.267/3571.314/4553.213/493.893 ms
>
> It is interesting to see how Tahoe handles these unusually large
> round trip times and unusually large packet loss.  In general, it
> handles it simply by being patient -- there are no timeouts, fail-
> overs or other mode changes that occur in response to this network
> behavior.
>
> Here are a few statistics results from my local Tahoe node -- a
> directory update (completed), and a download in progress.
>
>                           Mutable File Publish Status
>
>      * Started: 11:17:32 20-Jun-2008
>      * Storage Index: mmn63ajdghwqnen6o546icgvim
>      * Helper?: No
>      * Current Size: 1382
>      * Progress: 100.0%
>      * Status: Done
>
> Retrieve Results
>
>      * Encoding: 3 of 10
>      * Sharemap:
>           * 0 -> Placed on [wy7w3sls]
>           * 1 -> Placed on [xiktf6ok]
>           * 2 -> Placed on [trjdor3o]
>           * 3 -> Placed on [fcmlx6em]
>           * 4 -> Placed on [wfninubk]
>           * 5 -> Placed on [ckpjhpff]
>           * 6 -> Placed on [2y7ldksg]
>           * 7 -> Placed on [6fyx5u4z]
>           * 8 -> Placed on [q5l37rle]
>           * 9 -> Placed on [sgh4c5cr]
>      * Timings:
>           * Total: 33.36s (41Bps)
>                * Setup: 369us
>                * Encrypting: 72us (19.19MBps)
>                * Encoding: 87us (15.71MBps)
>                * Packing Shares: 35ms (39.0kBps)
>                     * RSA Signature: 33ms
>                * Pushing: 33.32s (41Bps)
>           * Per-Server Response Times:
>                * [ckpjhpff]: 15.09s
>                * [fcmlx6em]: 25.77s
>                * [q5l37rle]: 20.63s
>                * [sgh4c5cr]: 34ms
>                * [trjdor3o]: 25.50s
>                * [wfninubk]: 31.48s
>                * [wy7w3sls]: 7.18s
>                * [xiktf6ok]: 33.32s
>                * [2y7ldksg]: 17.57s
>                * [6fyx5u4z]: 24.22s
>    Return to the Welcome Page
>
>                               File Download Status
>
>      * Started: 11:15:24 20-Jun-2008
>      * Storage Index: uv7kpwj6v4hkwfhuzlacw5jgve
>      * Helper?: No
>      * Total Size: 113554221
>      * Progress: 5.3%
>      * Status: Downloading segment 47 of 867
>
> Download Results
>
>      * Servers Used: [xiktf6ok], [trjdor3o], [q5l37rle]
>      * Servermap:
>           * [ckpjhpff] has share: #8
>           * [fcmlx6em] has share: #5
>           * [lwkv6cji] has share: #9
>           * [q5l37rle] has share: #6
>           * [trjdor3o] has share: #7
>           * [uf7kq2sv] has share: #1
>           * [wfninubk] has share: #0
>           * [xiktf6ok] has share: #2
>           * [2y7ldksg] has share: #3
>           * [7tlov7eg] has share: #4
>      * Timings:
>           * File Size: 113554221 bytes
>           * Total: ()
>                * Peer Selection: 33.99s
>                * UEB Fetch: 7.13s
>                * Hashtree Fetch: 3.65s
>                * Segment Fetch: ()
>                     * Cumulative Fetching: 1395.52s (81.4kBps)
>                     * Cumulative Decoding: 33ms (3429.94MBps)
>                     * Cumulative Decrypting: 635ms (178.63MBps)
>                * Paused by client: 0us
>           * Per-Server Segment Fetch Response Times:
>                * [q5l37rle]: 5.85s, 7.94s, 10.22s, 10.83s, 8.79s,
> 6.11s,
>                  2.94s, 6.99s, 12.19s, 18.08s, 10.55s, 9.07s,
> 17.86s, 26.49s,
>                  2.35s, 6.14s, 7.50s, 8.89s, 10.31s, 28.59s, 2.33s,
> 3.34s,
>                  7.19s, 12.86s, 10.56s, 19.14s, 1.92s, 2.37s, 8.72s,
> 5.02s,
>                  8.33s, 8.67s, 8.55s, 16.23s, 4.29s, 7.24s, 7.28s,
> 9.68s,
>                  4.21s, 2.89s, 4.24s, 13.57s, 7.23s, 3.56s, 19.65s,
> 7.36s,
>                  6.65s
>                * [trjdor3o]: 37.12s, 35.54s, 27.57s, 27.41s, 11.26s,
> 12.08s,
>                  11.62s, 7.03s, 20.03s, 32.34s, 18.47s, 22.98s,  
> 27.87s,
>                  38.52s, 15.31s, 6.19s, 9.38s, 10.50s, 37.48s, 30.39s,
>                  13.95s, 10.28s, 21.23s, 14.55s, 14.90s, 20.84s,  
> 2.02s,
>                  5.39s, 11.04s, 5.07s, 16.83s, 23.25s, 8.68s,
> 25.65s, 17.63s,
>                  22.17s, 26.57s, 44.66s, 10.80s, 33.90s, 14.72s,
> 14.82s,
>                  29.48s, 3.70s, 37.88s, 21.56s
>                * [xiktf6ok]: 67.08s, 34.63s, 29.03s, 15.74s, 17.35s,
> 15.79s,
>                  31.65s, 22.71s, 31.81s, 45.63s, 14.83s, 17.14s,
> 25.75s,
>                  33.62s, 27.52s, 30.70s, 34.56s, 34.06s, 30.21s,
> 32.83s,
>                  30.59s, 31.02s, 29.23s, 38.74s, 28.72s, 23.40s,
> 15.23s,
>                  15.13s, 30.82s, 22.61s, 29.38s, 22.66s, 16.33s,
> 40.87s,
>                  32.62s, 35.30s, 36.10s, 34.96s, 12.08s, 45.91s,
> 30.44s,
>                  34.83s, 19.97s, 3.51s, 49.49s, 36.60s
>    Return to the Welcome Page
>
>
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