osmocom Kernel GTPU module - Support for incoming DL packets for idle mode users in S-GW /SGSN
18 Feb
2017
18 Feb
'17
1:03 a.m.
Hi ,
Posting question related to capability to implement user plane (GTP tunnel) for S1-U and
Iu-PS interface between S-GW & eNB and SGSN & RNC respectively via osmocom kernel
GTP-U module.
At present it seems if TE-ID is not valid packet is dropped in kernel GTP-U module. So in
order to use this for S1-U/Iu-PS interface it is required to add support for following
use-case:
* Down link packet arrival in S-GW /SGSN for UE which is in idle mode - Buffer the
packet and trigger paging to move the UE to connected.
a. When UE moves to idle mode - S1-U or IuPS bearer is released. In this case IP
address and TE-ID of eNB/RNC becomes invalid.
b. DL Packet is received for the idle mode UE in S-GW/SGSN - In this case , kernel
GTP-U module should deliver packet to user-space application (SGW/osmoSGSN) so that these
packets can be buffered in user space and paging can be initiated.
Question - Is there any plan to support above in near-future in osmocom kernel GTP-U
module or larger question would be to plan to enable usage of kernel GTP-U module in
SGSN and SGW towards RAN ?
Thanks,
Anoop
18 Feb
18 Feb
12:58 p.m.
Hi Anoop,
On Sat, Feb 18, 2017 at 12:03:37AM +0000, Anoop Singh Tomar wrote:
Posting question related to capability to implement
user plane (GTP
tunnel) for S1-U and Iu-PS interface between S-GW & eNB and SGSN & RNC
respectively via osmocom kernel GTP-U module.
The current kernel GTP-U module has been designed explicitly for the use
case of a GGSN/P-GW. This was what the original requirement was, and
where Pablo and I received some funding from a customer to implement it.
The requirements for a SGSN/S-GW are completely different, and I don't
think the current module is any good match for this. Please see the
discussion starting from
http://marc.info/?l=linux-netdev&m=148611438811696&w=2 for the rationale
about this, specifically my post at
http://marc.info/?l=linux-netdev&m=148638986910316&w=2
If you think otherwise, please let me know. I'd be happy to undeerstand
why.
At present it seems if TE-ID is not valid packet is
dropped in kernel
GTP-U module.
This is a bug/mis-feature that has been fixed already and the patch is
currently in net-next, waiting to be merged into the next linux kernel
merge window:
https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/driv…
Question - Is there any plan to support above in
near-future in
osmocom kernel GTP-U module or larger question would be to plan to
enable usage of kernel GTP-U module in SGSN and SGW towards RAN ?
There are no such plans, at least not from Pablo and my side. I don't
know about Andreas, but I think he is also primarily focussing on
various (more complex) P-GW use cases, rather than S-GW. The module was
developed to fulfill certain requirements under a customer contract.
Neither Pablo or I currently have any customers who have above
requirement, so there's no related agenda.
I would love to work on the kernel GTP code, but I cannot afford to do
so in my limited spare time (which is already occupied by way too many
projects getting too little attention), sorry.
In general, I don't think the current GTP "tunnel endpoint" module fits
the S-GW/SGSN use case at all (see my linked post above). The S-GW/SGSN
is not a node visible in Layer3 of the user-IP payload, it must not
terminate the user IP tunnel. A completely different architecture
should be used for the SGSN/S-GW use case, where it is all about
forwarding encapsulated packets between MME and P-GW without
decapsulating the inner (user) IP layer.
Regards,
Harald
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
19 Feb
19 Feb
3:38 p.m.
Hi Anoop,
----- On Feb 18, 2017, at 1:03 AM, Anoop Singh Tomar <anooptomar(a)fb.com> wrote:
Hi ,
Posting question related to capability to implement
user plane (GTP tunnel) for
S1-U and Iu-PS interface between S-GW & eNB and SGSN & RNC respectively via
osmocom kernel GTP-U module.
At present it seems if TE-ID is not valid packet is
dropped in kernel GTP-U
module. So in order to use this for S1-U/Iu-PS interface it is required to add
support for following use-case:
· Down link packet arrival in S-GW /SGSN for UE which
is in idle mode – Buffer
the packet and trigger paging to move the UE to connected.
a. When UE moves to idle mode – S1-U or IuPS bearer is
released. In this case IP
address and TE-ID of eNB/RNC becomes invalid.
b. DL Packet is received for the idle mode UE in
S-GW/SGSN - In this case ,
kernel GTP-U module should deliver packet to user-space application
(SGW/osmoSGSN) so that these packets can be buffered in user space and paging
can be initiated.
Question – Is there any plan to support above in
near-future in osmocom kernel
GTP-U module or larger question would be to plan to enable usage of kernel
GTP-U module in SGSN and SGW towards RAN ?
We (Travelping) have some ideas about implementing a S-GW based
on the current ergw code [1]. This would also involve implementing kernel
side support.
The current idea for extending the kernel part is to change the PDP
context logic from a 'GTP-U to network device' reeation to a 'GTP-U
to something' relation. The 'something' then would be the existing network
device, another GTP-U socket (including TEID's), a L2TP tunnel, a IPsec
session, .... an so on. My current understanding is that the LWT infrastructure
should be suitable for that.
This implementation would support the S1-U use case. For Iu-PS, a user
space only implementation would IMHO be more suitable. Anyhow, the
current kernel implementation is passing all packets that it can't handle
(has no PDP context for them) onto the user space process.
But all that are only halve backed ideas, nothing concrete, yet.
Regards
Andreas
[1]: https://github.com/travelping/ergw
Anoop
2630
days inactive
2631
days old
osmocom-net-gprs@lists.osmocom.org
2 comments
3 participants
participants (3)
-
Andreas Schultz -
Anoop Singh Tomar -
Harald Welte