Remember, Hughes' DirecWay has a built-in 500-700ms lag (23,000 miles
each way to the satellite) so it will raise havoc with most enq/ack or
similar style protocols which are not designed for such latency.
Dennis Hassell
Dennis Hassell and Associates
(941) 746-4919
(941) 224-3981 - cell
-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On
Behalf Of Atwood, Tim (DVM)
Sent: Monday, August 11, 2003 3:42 PM
To: [log in to unmask]
Subject: Re: [HP3000-L] response time problem using Reflections or
qcterm
I wonder if it is a similar problem to what I have experienced with VPN
through Hughes' Direcway two-way satellite broadband. I am still trying
to
work out how to fix the problem, so any suggestions to concerning either
Bill's or my response problems would be of great interest to me.
I wonder if the same sort of optimization/aggregation of packets is
being
done by Bill's CDPD network as is done for satellite? Read on for what I
have found about satellite and VPN and the HP3000.
I will be first to admit network protocols and configurations are not my
field of expertise. So if anything I explain here sounds "wrong" to you,
please feel free to correct it. I am mostly repeating what I have been
told.
Since I'm not an expert I will not have known what to filter out.
From the Hughes site:
"Running a VPN client over a satellite network is not an ideal
configuration. Although most VPN clients will work, your speeds will be
affected significantly. While average download speeds are slightly
better
than dial-up, they will be reduced from typical DIRECWAY speeds by as
much
as 50 to 75 percent. Average upload speeds are comparable to dial-up
performance. "
And:
"Our communication satellite is located over 22,000 miles from Earth.
Each
data packet must be sent down separately and acknowledged by the remote
site. This process is very time-consuming. In order to expedite the
delivery
of data packets to our end-users, HUGHES has developed a patented
technology
for aggregating those packets and sending all of them down
simultaneously.
VPNs encrypt each data packet, which prevents our technology from
aggregating the data packets and reduces the throughput significantly."
This problem appears to increase significantly with the HP3000 character
mode. I have traditionally used Reflections connected VT-MGR and Qedit.
It
would appear VPN with standard character mode is encapsulating each and
every single character typed. The HP3000 then echoes back the same
character
as another separate VPN encapsulated packet. No wonder performance is
bad!
As a temporary solution until I get something better figured out, I have
done the following:
1) Do my log-on and initial typing with type-ahead turned on. Go have a
drink of coffee while I wait for a response.
2) As soon as possible enter Qedit Visual mode so I am in block mode. Do
everything including MPE commands from Qedit Visual so things are sent
as
blocks of characters. It appears VPN now encapsulates the entire block
as
one packet. And the HP3000 does not echo anything back. My response
times
are now back to what I would expect from a 56K modem.
I am sure there is a way to get the initial log on to be in block mode.
I am
also pretty sure there are other things I can do to speed this all up. I
just have not had time to figure it out yet. So would appreciate any
suggestions not already made to Bill. I have been reading all those
already
made with interest.
Timothy Atwood
Holtenwood Computing
http://www.holtenwood.bc.ca/computing/
for Domtar Vancouver Mill
(Opinions expressed are mine and do not reflect Domtar)
-----Original Message-----
From: Gavin Scott [mailto:[log in to unmask]]
Sent: Monday, August 11, 2003 10:24 AM
To: [log in to unmask]
Subject: Re: response time problem using Reflections or qcterm
James wrote:
> RE: response time problem using Reflections or qcterm
>
> ----------------------------------------Bill M writes--
> I pinged the MPE host from my home pc using a cable
> modem and linksys router and received packet times of
> about 20 ms. I then tried it from my air card and
> experienced packet times of 500 to 1000ms.
> -------------------------------------------------------
>
> Wow, 500 to 1000ms are long times... More typical from what I have
seen
> is 50-150ms with 1-4% data loss with 802.11b.
I'm pretty sure that the "air card" Bill talks about is not Wi-Fi but a
CDPD
or similar cellular data modem PC Card, so what he's talking about is
equivalent to an internet dial-up via a cell phone. These systems have
notoriously high latency.
G.
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