How to support multiple "eNodeB and SGW-U" pairs with one MME

[s5uishida]

Please let me ask one question.

Is it possible to place one set of Open5GS EPC in DC or Cloud and manage multiple eNodeB and SGW-U pairs with one MME?

Since the IP address and port number of SGW-U are passed to eNodeB via S1-AP, I would like to know if it is possible to control different eNodeB and SGW-U pair for each tenant.

Thank you very much in advance.

[kbarlee]

Hey. Short answer, yes. There are a couple of options setup for SGW-C (SGW-U) and SMF (UPF) selection, so you can ensure that each UE is assigned to the correct userplane server.

open5gs/configs/open5gs/sgwc.yaml.in

Lines 55 to 105 in 15e42bc

	# sgwu:
	#
	# <PFCP Client>>
	#
	# o PFCP Client(127.0.0.6:8805)
	#
	# pfcp:
	# addr: 127.0.0.6
	#
	# <SGWU_SELECTION_MODE - EPC only>
	#
	# o Round-Robin
	# (note that round robin can be disabled for a particular node
	# by setting flag 'rr' to 0)
	#
	# sgwu:
	# pfcp:
	# - addr: 127.0.0.6
	# - addr: 127.0.0.12
	# rr: 0
	# - addr: 127.0.0.18
	#
	# o SGWU selection by eNodeB TAC
	# (either single TAC or multiple TACs, DECIMAL representation)
	#
	# sgwu:
	# pfcp:
	# - addr: 127.0.0.6
	# tac: 1
	# - addr: 127.0.0.12
	# tac: [3,5,8]
	#
	# o SGWU selection by UE's APN (either single APN or multiple APNs)
	#
	# sgwu:
	# pfcp:
	# - addr: 127.0.0.6
	# apn: ims
	# - addr: 127.0.0.12
	# apn: [internet, web]
	#
	# o SGWU selection by CellID(e_cell_id: 28bit)
	# (either single e_cell_id or multiple e_cell_id, HEX representation)
	#
	# sgwu:
	# pfcp:
	# - addr: 127.0.0.6
	# e_cell_id: 463
	# - addr: 127.0.0.12
	# e_cell_id: [123456789, 9413]
	#

open5gs/configs/open5gs/smf.yaml.in

Lines 236 to 275 in 15e42bc

	# o Round-Robin
	# (note that round robin can be disabled for a particular node
	# by setting flag 'rr' to 0)
	#
	# upf:
	# pfcp:
	# - addr: 127.0.0.7
	# - addr: 127.0.0.12
	# rr: 0
	# - addr: 127.0.0.19
	#
	# o UPF selection by eNodeB TAC
	# (either single TAC or multiple TACs, DECIMAL representation)
	#
	# upf:
	# pfcp:
	# - addr: 127.0.0.7
	# tac: 1
	# - addr: 127.0.0.12
	# tac: [3,5,8]
	#
	# o UPF selection by UE's DNN/APN (either single DNN/APN or multiple DNNs/APNs)
	#
	# upf:
	# pfcp:
	# - addr: 127.0.0.7
	# dnn: ims
	# - addr: 127.0.0.12
	# apn: [internet, web]
	#
	# o UPF selection by CellID(e_cell_id: 28bit, nr_cell_id: 36bit)
	# (either single enb_id or multiple enb_ids, HEX representation)
	#
	# upf:
	# pfcp:
	# - addr: 127.0.0.7
	# e_cell_id: 463
	# - addr: 127.0.0.12
	# nr_cell_id: [123456789, 9413]
	#

[s5uishida]

Hi @kbarlee

Thank you very much!

Also, sorry for asking the question without checking sgwc.yaml and smf.yaml.

[kbarlee]

No worries!

[s5uishida]

Please let me ask for an additional question.

Is it possible to combine two or more types of conditions with AND?

For example: SGWU selection by eNodeB TAC AND UE's APN.

sgwu:
  pfcp:
    - addr: 127.0.0.6
      tac: 1
    - addr: 127.0.0.12
      tac: 3                 <==
      apn: ims               <==
    - addr: 127.0.0.20
      tac: 3                 <==
      apn: [internet, web]   <==

Thank you very much in advance.

[acetcom]

The related code is as follows.

static bool compare_ue_info(ogs_pfcp_node_t *node, sgwc_sess_t *sess)
{
    sgwc_ue_t *sgwc_ue = NULL;
    int i;

    ogs_assert(node);
    ogs_assert(sess);
    sgwc_ue = sess->sgwc_ue;
    ogs_assert(sgwc_ue);

    for (i = 0; i < node->num_of_apn; i++)
        if (strcmp(node->apn[i], sess->pdn.apn) == 0) return true;

    for (i = 0; i < node->num_of_e_cell_id; i++)
        if (node->e_cell_id[i] == sgwc_ue->e_cgi.cell_id) return true;

    for (i = 0; i < node->num_of_tac; i++)
        if (node->tac[i] == sgwc_ue->e_tai.tac) return true;

    return false;
}

So, only ORing is supported. Basically, we can consider three ways for this.

1. AND
2. OR
3. Both AND and OR

The third method requires a flag in the configuration file to distinguish AND and OR.

Anyway, I have no experience in live environment, so I implemented only OR first. Is an AND condition necessary in a real? Or do I need to support both AND and OR? Do you know how to support in other commercial EPC or 5GC?

If other settings are needed, I'll implement this part.

Thanks you for raising this issue.
Sukchan!

[kbarlee]

I feel the current setup would be sufficient in all cases; as when an attach with ims apn is requested it would use 127.0.0.12; internet or web would use 127.0.0.20?

#560 (comment)

Logic for the SMF(UPF) and SGWC(SGWU) selection is:

1. Search through node list to see if any are dedicated to support the APN
   -- round robin between nodes that support the APN && are PFCP associated
   -- if there are none, move to 2

2. Search through node list to see if any are dedicated to support the e_cell_ID
   -- round robin between nodes that support the e_cell_ID && are PFCP associated
   -- if there are none, move to 3

3. Search through node list to see if any are dedicated to support the nr_cell_ID ((SMF ONLY))
   -- round robin between nodes that support the nr_cell_ID && are PFCP associated
   -- if there are none, move to 4

4. Search through node list to see if any are dedicated to support the TAC
   -- round robin between nodes that support the TAC && are PFCP associated
   -- if there are none, move to 5

5. Round robin full list. Use next PFCP associated node. If rr: 0 the node will be skipped. This is to avoid the dumb RR choice.

[s5uishida]

Hi @acetcom and @kbarlee

Thank you very much for your replies.

I thought it would be good if UEs connecting to the same eNodeB (or rather TAC) for private LTE could use different U-Planes due to different APNs. But l will think a little about whether it's really necessary.

I will withdraw it once.

[s5uishida]

I may think too much about private LTE.

So, I think the current logic is OK.

Thanks!