25 Feb
2017
25 Feb
'17
3:16 a.m.
Hi all
I have got trough the pcs 1900 nano bts if you have any doubts pls let me ... and these
days I am trying to resolves OML issues with RBS 2308 ericson bts
Thank you very much
Regards
Rajitha peiris
Sent from my iPhone
On Feb 24, 2017, at 9:42 PM,
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Today's Topics:
1. Re: Ki and OPC values change when programming MCC and MNC
(Holger Freyther)
2. Re: Virtual layer 1 - Questions (Harald Welte)
3. OsmoHLR and IPA unit id (Neels Hofmeyr)
4. Re: Handover and load balancing on SysmoBTS 2050 (Keith)
5. Re: OsmoHLR and IPA unit id (Harald Welte)
6. Re: Handover and load balancing on SysmoBTS 2050 (Keith)
----------------------------------------------------------------------
Message: 1
Date: Thu, 23 Feb 2017 15:25:56 +0700
From: Holger Freyther <holger@freyther.de<mailto:holger@freyther.de>>
To: Neels Hofmeyr <nhofmeyr@sysmocom.de<mailto:nhofmeyr@sysmocom.de>>
Cc: "openbsc@lists.osmocom.org<mailto:openbsc@lists.osmocom.org>"
<openbsc@lists.osmocom.org<mailto:openbsc@lists.osmocom.org>>
Subject: Re: Ki and OPC values change when programming MCC and MNC
Message-ID:
<31579AC7-F837-49F1-9EDC-C0B8D2CCC85C@freyther.de<mailto:31579AC7-F837-49F1-9EDC-C0B8D2CCC85C@freyther.de>>
Content-Type: text/plain; charset=us-ascii
On 23 Feb 2017, at 09:53, Neels Hofmeyr
<nhofmeyr@sysmocom.de<mailto:nhofmeyr@sysmocom.de>> wrote:
On Wed, Feb 22, 2017 at 05:06:20PM +0100, Sylvain Munaut wrote:
--help will tell you defaults for Ki and OPC is to randomize ...
Ah, indeed, I never saw that. Could also be misunderstood. IMHO it should say
right at the top that you normally want to pass -k and -o when calling pysim.
After all, none of the other options do that. anyway...
"normally".. for the batch mode as used at XC3 events the "normal" is
to
generate a random KI, you wouldn't want to do that by hand 4k times. :)
holger
------------------------------
Message: 2
Date: Thu, 23 Feb 2017 15:41:24 +0100
From: Harald Welte <laforge@gnumonks.org<mailto:laforge@gnumonks.org>>
To: Sebastian Stumpf
<sebastian.stumpf87@googlemail.com<mailto:sebastian.stumpf87@googlemail.com>>
Cc: openbsc@lists.osmocom.org<mailto:openbsc@lists.osmocom.org>,
baseband-devel@lists.osmocom.org<mailto:baseband-devel@lists.osmocom.org>
Subject: Re: Virtual layer 1 - Questions
Message-ID: <20170223144124.mdba7w7avdujy23g@nataraja>
Content-Type: text/plain; charset=us-ascii
Hi Sebastian,
On Sun, Feb 19, 2017 at 06:16:01PM +0100, Sebastian Stumpf wrote:
I also see that the RACH requesets all are sent with a bogus frame
number: 42. This will not work. The RACH request needs to be sent with
the current frame number at the time being.
I fixed that and calculate the proper rach fn like in
https://github.com/osmocom/osmocom-bb/blob/master/src/target/firmware/layer…
good.
Also, RACH retransmissions are happening way too quick.
Calculating a proper frame number didn't fix the fast retransmissions.
They are caused by sending the channel request over the virtual um
immediately after getting the rach-request from layer23. Thus also the
rach-confirm is sent to l23 immediately, so layer23 thinks "oh fine its
already transmitted" and will generate the next rach-request for my
layer 1.
i see. the confirmation should probably be delayed somehow. As a quick
intermediate hack you might simply add a timer.
I think one can do without on the MS side, but then the BTS must
basically queue the incoming frames until the respective frame number
indicated in the frame matches the current frame number.
I think to fix the problem with the quick retransmission , I need some type
of scheduling. Because if I queue the incoming uplink-msgs in the
bts-virtual-layer1 instead, I don't know when they are processed on the ms
side and thus don't know when to send the rach-confirm to layer23...
My idea for a simple scheduler would be:
-- no timing and timer interrupts on ms side, but just set the current fn in
the ms state each time we receive a message on downlink to the fn of
the received message, which is accessible in the gsmtap header.
yes, that makes sense.
-- queue the outgoing uplink messages with their confirm callback to l2
and process all that with a smaller fn than the current fn in the
scheduling function.
yes, but please keep in mind that the frame number is wrapping every so
often, so "smaller" must consider that modulo-arithmetic, or you will
(after fn wrap) have pending downlink messages for much higher fn which
are not sent as the wrapped fn is now very small.
-- calling the scheduling function each time we receive a msg on downlink
(so I do not need to handle timer interrupts)
yes. I think it is reasonable to not have any actual timers on the ms
side and always depend on the frame numbers in the downlink messages
from the BTS. After all, in the worst case you have periodic messages
like the BCCH messages that can be used to update the fn.
I hope that will be sufficent and try it out tomorrow. I am a bit
afraid of trouble caused by the frame number skipping values with the
upper incrementation logic.
I don't think skips are that problematic. But then, I haven't tried it ;)
--
- Harald Welte <laforge@gnumonks.org<mailto:laforge@gnumonks.org>>
http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
------------------------------
Message: 3
Date: Fri, 24 Feb 2017 06:43:26 +0100
From: Neels Hofmeyr <nhofmeyr@sysmocom.de<mailto:nhofmeyr@sysmocom.de>>
To: openbsc@lists.osmocom.org<mailto:openbsc@lists.osmocom.org>
Subject: OsmoHLR and IPA unit id
Message-ID:
<20170224054326.GB1368@my.box<mailto:20170224054326.GB1368@my.box>>
Content-Type: text/plain; charset="us-ascii"
I just ran my first tests of both OsmoNITB and OsmoSGSN connecting to OsmoHLR.
It turns out OsmoHLR uses the ipaccess_unit data a.k.a. CCM (whatever CCM
means) to route GSUP replies back to its sender.
It looks like "NAME-00-00-00-00-00-00".
However, all of our GSUP client code simply sets the unit id to:
"SGSN-00-00-00-00-00-00".
The result is that the VLR never receives an UPDATE LOCATION RESULT, because it
is sent to the SGSN instead, since that was the first one to say that it is
"SGSN-00...".
I would extend the GSUP clients to allow setting an ID from VTY, or maybe a
random ID. At this point it would suffice to make the MSC side say it is
"MSC-00-00-00-00-00-00" but that's beside the point.
Do we really want to do that? Any peer could come along and say it is someone
else, very easy to misconfigure (and not very security sensitive when thinking
of OAP -- which we're not using but maybe we will one day).
For some messages, OsmoHLR uses the conn pointer from msg rx to route the
response back -- that works. AFAICT it just receives messages and replies to
them right away (but haven't seen / understood all of it). For the case of the
UPDATE LOCATION RESULT, it would also be possible to use the same conn pointer,
but the code chooses to resolve by id and then sends to the wrong peer. If it
used the peer's IP address and port instead, things would work out.
With the attached and possibly very stupid patch, OsmoHLR works for me with
both MSC and SGSN talking to it even though they have identical IPA IDs: I
bluntly store the conn in struct lu_operation and re-use it later.
Which way shall we resolve this?
~N
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------------------------------
Message: 4
Date: Fri, 24 Feb 2017 16:42:35 +0100
From: Keith <keith@rhizomatica.org<mailto:keith@rhizomatica.org>>
To: Alexander Chemeris
<alexander.chemeris@gmail.com<mailto:alexander.chemeris@gmail.com>>
Cc: OpenBSC Mailing List
<openbsc@lists.osmocom.org<mailto:openbsc@lists.osmocom.org>>
Subject: Re: Handover and load balancing on SysmoBTS 2050
Message-ID:
<39e245c4-ba1a-600b-8e38-cb300c10133f@rhizomatica.org<mailto:39e245c4-ba1a-600b-8e38-cb300c10133f@rhizomatica.org>>
Content-Type: text/plain; charset=utf-8
Hi Alexander, seeing as how you came in on the thread, as a side topic,
you may have noticed I mentioned meas_json and meas_web in the OP. I
fixed up a small thing with meas_json that was producing unparseable
json in the neighbours array. I also did some stuff server side to
filter for either SDCCH or TCH, although I think I would make this a
clientside javascript filter option, rather than running multiple websocketd
I added the neighbour levels to the displayed data. I hardcoded the
ARFCNs for the site in question, but I would make that happen dynamically.
I found this quite useful for monitoring in relation to analysis on this
site and the would-be handover scenario.
I'm wondering what to do with this work.
Should I make a commit of meas_json to master? In that case I would
appreciate some minor help getting the Makefile right.
Maybe meas_json is not a candidate for the master branch, as it doesn't
currently do anything particularly useful without the external
dependencies, ie meas_web and websocketd or alternative.
I can publish my work on meas_web to github.
Keith.
------------------------------
Message: 5
Date: Fri, 24 Feb 2017 16:53:03 +0100
From: Harald Welte <laforge@gnumonks.org<mailto:laforge@gnumonks.org>>
To: Neels Hofmeyr <nhofmeyr@sysmocom.de<mailto:nhofmeyr@sysmocom.de>>
Cc: openbsc@lists.osmocom.org<mailto:openbsc@lists.osmocom.org>
Subject: Re: OsmoHLR and IPA unit id
Message-ID: <20170224155303.tuidxovd4qbzp5go@nataraja>
Content-Type: text/plain; charset=us-ascii
Hi Neels,
IPA CCM made sense on the Abis interface, where each BTS reports with
its unit_id and MAC address. I'm not quite sure how much sense that
makes in the core network. I also don't know if existing
implementations of e.g. A interface over IPA multiplex actually use it.
In terms of future outlook, the MSC/VLR/SGSN should register at the HLR
with some kind of identity. In MAP, it is the SCCP Address that is used
for this purpose. In absence of SCCP on GSUP, I used the CCM identity
as a replacement. However, it is used as an opaque string, so that any
GSUP/MAP gateway might simply translate the SCCP address into a string
of its choosing, and then talk to OsmoHLR. OsmoHLR would then simply
do a strcmp() on the string to match the identity.
Sooner or later, OsmoHLR will have to store this identity in the
database, e.g. for imlpementing message-waiting-lists of SMSCs in case
of MT-SMS from real SMSCs.
All-in-all, I think the string approach is not too bad in terms of
keeping GSUP simple while having a clan approach to interworkng with
MAP.
On Fri, Feb 24, 2017 at 06:43:26AM +0100, Neels Hofmeyr wrote:
I just ran my first tests of both OsmoNITB and OsmoSGSN connecting to OsmoHLR.
It turns out OsmoHLR uses the ipaccess_unit data a.k.a. CCM (whatever CCM
means) to route GSUP replies back to its sender.
It looks like "NAME-00-00-00-00-00-00".
However, all of our GSUP client code simply sets the unit id to:
"SGSN-00-00-00-00-00-00".
The result is that the VLR never receives an UPDATE LOCATION RESULT, because it
is sent to the SGSN instead, since that was the first one to say that it is
"SGSN-00...".
this is of course not good.
I would extend the GSUP clients to allow setting an ID from VTY, or maybe a
random ID. At this point it would suffice to make the MSC side say it is
"MSC-00-00-00-00-00-00" but that's beside the point.
A random ID would not be permissible, as it has to be persistent accross
MSC/VLR/HLR re-starts, in order to make above-mentioned mechanisms
working.
I would say, why not simply use the same approach as in OsmoBTS, i.e. use
the MAC address (together with the MSC or SGSN prefix). The MAC address
is unlikely to change frequently or on short notice. For people who
know what they're doing, we can have a VTY command to override the
identity with a manually-specified string. If that option is not set,
the default "(SGSN|MSC)-MAC" is used.
Do we really want to do that? Any peer could come along and say it is someone
else, very easy to misconfigure (and not very security sensitive when thinking
of OAP -- which we're not using but maybe we will one day).
I don't think we are aiming for anyone to use those protocols on
public[ly accessible] networks. There's no message authentication or
other cryptographic protection anyway. OAP seems like a funny but
futile minor obstacle, but nothing that can provide any reasonable level
of security.
For some messages, OsmoHLR uses the conn pointer from msg rx to route the
response back -- that works.
This should be done in all request-response style procedures, I think.
AFAICT it just receives messages and replies to them right away (but
haven't seen / understood all of it). For the case of the UPDATE
LOCATION RESULT, it would also be possible to use the same conn
pointer, but the code chooses to resolve by id and then sends to the
wrong peer. If it used the peer's IP address and port instead, things
would work out.
Looking up by ID would also work in case meanwhile the old connection
has died and a new connection has been established
With the attached and possibly very stupid patch, OsmoHLR works for me with
both MSC and SGSN talking to it even though they have identical IPA IDs: I
bluntly store the conn in struct lu_operation and re-use it later.
For synchronous responses (i.e. no asynchronous activity in between)
this will work. So I think it's an optimization for those cases, and we
shouldn't rely on this to always work for all transactions at all time
in the future. Rather, we should make sure it works even without that
optimization?
--
- Harald Welte <laforge@gnumonks.org<mailto:laforge@gnumonks.org>>
http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
------------------------------
Message: 6
Date: Fri, 24 Feb 2017 17:12:02 +0100
From: Keith <keith@rhizomatica.org<mailto:keith@rhizomatica.org>>
To: Harald Welte <laforge@gnumonks.org<mailto:laforge@gnumonks.org>>
Cc: OpenBSC Mailing List
<openbsc@lists.osmocom.org<mailto:openbsc@lists.osmocom.org>>
Subject: Re: Handover and load balancing on SysmoBTS 2050
Message-ID:
<ca4d6dc2-fa43-8eaa-8c39-821939d87e52@rhizomatica.org<mailto:ca4d6dc2-fa43-8eaa-8c39-821939d87e52@rhizomatica.org>>
Content-Type: text/plain; charset=windows-1252
On 21/02/2017 16:14, Harald Welte wrote:
Just a quick response: jolly implemented "traffic handover" aka "load
balancing" 3 years ago as part of a branch (I believe for a customer),
but unfortunately this never was merged back to master.
Reading the commit log, this looks terrific...
Meanwhile, we already have all the code for execution of hand-overs in
place. We also have dynamic timeslots in place. So the "mechanics"
should all be there to add the two missing features from those old
branches:
a) de-fragmenting of channels (i.e. merging two separate TCH/H into one
timeslot, so the other timeslot can be switched to TCH/F or PDCH on
demand
b) load/traffic based hand-over
So essentially everything I was talking about is already implemented!
My question then would be, and I understand maybe the answer is not so
easily available without a full code review, but
Was it unfortunately never merged back to master because
Simply no one ever made the effort to do so.
OR
There were problems with the code, disagreement on the implementation or
incompatibilities with other developments etc..
If it's the former, I'll have a go at this.
If it is the latter, it's probably beyond my skills.
The general strategy I would normally assume is to
* switch to half-rate channels with AMR whenever possible
* use dynamic channel switching to switch between TCH/H (default) and
TCH/F (if neded)
Absolutely, I must revisit this one.
It was shelved for us due to my understanding a few months ago that if
we implemented AMR, then we couldn't also use FR.
As that's all now resolved, I can implement, test and report. :-)
------------------------------
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