5G/NR - Network Architecture - NRF

NR CORE - NRF

NRF stands for Network function Repository Function. Simply put, it works as a central registration center (registra) for all the Core Network Components. As shown in the following diagram, NRF has connected to all the 5G Core components in HPLMN and get connected to another NRF in VPLMN with N27 interface.

< 29.510 - Figure 4-1: 5G System architecture >

Followings are the name of each network component.

AMF Access and Mobility Management Function ==> Equivalent to MME in 4G

AUSF Authentication Server Function

DN Data Network

NEF Network Exposure Function

NRF Network Repository Function

NSSF Network Slice Selection Function

PCF Policy Control Function ==> Equivalent to PCRF in 5G

(R)AN (Radio) Access Network

SMF Session Management Function

UDM Unified Data Management==> Equivalent to HSS in 4G

UPF User Plane Function ==> Equivalent to PGW in 4G

SMSF SMS Function

SEAF SEcurity Anchor Function ==> part of AMF function

Since NRF is connected almost every components (Network Functions) and provide various services to all of them. Descriptions on this NF(Network Function) can be complicated. I may not be able to put all of the functionalities in this note. I will just write down those things which I have some hands-on experience with.

NF Registration to NRF

Structured Data Types

NFProfile

NF Registration to NRF

Each NF(Network Function) is supposed to register to NRF so that NRF can coordinate all the NFs whenever necessary.

< 29.510-Figure 5.2.2.2.2-1: NF Instance Registration >

NF Service Consumer : Every Network Function (Core Network Components) except NRF itself.

URI : The URI of the NF that wants to get registered

nfInstanceID : UUID within the PLMN (e.g, 4947a69a-f61b-4bc1-b9da-47c9c5d14b64)

NFProfile : Network Function Profile which can carry a huge list of information as defined here.

The example messages shown below is from open5gs log. (For Official documentation of open5gs, go to open5gs.org. For basic tutorial about open5gs on sharetechnote, see the notes : Installation on Virtual Machine, Installation and test on Google Cloud, WebUI, Run)

Example : AMF Registration

PUT

07/09 21:21:05.476: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/0ab51768-ffcd-41ec-a11e-7954f71c156f (../lib/sbi/nghttp2-server.c:770)

07/09 21:21:05.476: [sbi] DEBUG: RECEIVED: 672 (../lib/sbi/nghttp2-server.c:773)

07/09 21:21:05.476: [sbi] DEBUG: {

"nfInstanceId": "0ab51768-ffcd-41ec-a11e-7954f71c156f",

"nfType": "AMF",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.5"],

"allowedNfTypes": ["SMF"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "0ab6167c-ffcd-41ec-a11e-7954f71c156f",

"serviceName": "namf-comm",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.5",

"port": 7777

}],

"allowedNfTypes": ["SMF"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

}

201 Created

07/09 21:21:05.476: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/09 21:21:05.476: [sbi] DEBUG: SENDING...: 157 (../lib/sbi/nghttp2-server.c:355)

07/09 21:21:05.476: [sbi] DEBUG: {

"nfInstanceId": "0ab51768-ffcd-41ec-a11e-7954f71c156f",

"nfType": "AMF",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

}

Example : AUSF Registration

PUT

07/08 02:45:18.834: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/fa64abc8-fe67-41ec-b3d5-a934c5d291a8 (../lib/sbi/nghttp2-server.c:770)

07/08 02:45:18.834: [sbi] DEBUG: RECEIVED: 676 (../lib/sbi/nghttp2-server.c:773)

07/08 02:45:18.834: [sbi] DEBUG: {

"nfInstanceId": "fa64abc8-fe67-41ec-b3d5-a934c5d291a8",

"nfType": "AUSF",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.11"],

"allowedNfTypes": ["AMF"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "fa64b79e-fe67-41ec-b3d5-a934c5d291a8",

"serviceName": "nausf-auth",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.11",

"port": 7777

}],

"allowedNfTypes": ["AMF"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

}

201 Created

07/08 02:45:18.834: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/08 02:45:18.834: [sbi] DEBUG: SENDING...: 158 (../lib/sbi/nghttp2-server.c:355)

07/08 02:45:18.834: [sbi] DEBUG: {

"nfInstanceId": "fa64abc8-fe67-41ec-b3d5-a934c5d291a8",

"nfType": "AUSF",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

}

Example : UDM Registration

PUT

07/08 03:22:31.370: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/33ae29b8-fe6d-41ec-9216-8d673c526000 (../lib/sbi/nghttp2-server.c:770)

07/08 03:22:31.370: [sbi] DEBUG: RECEIVED: 1512 (../lib/sbi/nghttp2-server.c:773)

07/08 03:22:31.370: [sbi] DEBUG: {

"nfInstanceId": "33ae29b8-fe6d-41ec-9216-8d673c526000",

"nfType": "UDM",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.12"],

"allowedNfTypes": ["AMF", "SMF", "AUSF"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "33ae6342-fe6d-41ec-9216-8d673c526000",

"serviceName": "nudm-ueau",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.12",

"port": 7777

}],

"allowedNfTypes": ["AUSF"],

"priority": 0,

"capacity": 100,

"load": 0

}, {

"serviceInstanceId": "33ae6360-fe6d-41ec-9216-8d673c526000",

"serviceName": "nudm-uecm",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.12",

"port": 7777

}],

"allowedNfTypes": ["AMF"],

"priority": 0,

"capacity": 100,

"load": 0

}, {

"serviceInstanceId": "33ae636a-fe6d-41ec-9216-8d673c526000",

"serviceName": "nudm-sdm",

"versions": [{

"apiVersionInUri": "v2",

"apiFullVersion": "2.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.12",

"port": 7777

}],

"allowedNfTypes": ["AMF", "SMF"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

201 Created

07/08 03:22:31.371: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/08 03:22:31.371: [sbi] DEBUG: SENDING...: 157 (../lib/sbi/nghttp2-server.c:355)

07/08 03:22:31.371: [sbi] DEBUG: {

"nfInstanceId": "33ae29b8-fe6d-41ec-9216-8d673c526000",

"nfType": "UDM",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

}

Example : UDR Registration

PUT

07/09 21:21:05.726: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/0adb7b56-ffcd-41ec-8ac9-0f5331342d1b (../lib/sbi/nghttp2-server.c:770)

07/09 21:21:05.726: [sbi] DEBUG: RECEIVED: 686 (../lib/sbi/nghttp2-server.c:773)

07/09 21:21:05.726: [sbi] DEBUG: {

"nfInstanceId": "0adb7b56-ffcd-41ec-8ac9-0f5331342d1b",

"nfType": "UDR",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.20"],

"allowedNfTypes": ["PCF", "UDM"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "0adc404a-ffcd-41ec-8ac9-0f5331342d1b",

"serviceName": "nudr-dr",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.20",

"port": 7777

}],

"allowedNfTypes": ["PCF", "UDM"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

}

201 Created

07/09 21:21:05.726: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/09 21:21:05.726: [sbi] DEBUG: SENDING...: 157 (../lib/sbi/nghttp2-server.c:355)

07/09 21:21:05.726: [sbi] DEBUG: {

"nfInstanceId": "0adb7b56-ffcd-41ec-8ac9-0f5331342d1b",

"nfType": "UDR",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

}

Example : PCF Registration

PUT

07/09 21:21:05.723: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/0adae7a4-ffcd-41ec-aff0-b734789f4477 (../lib/sbi/nghttp2-server.c:770)

07/09 21:21:05.723: [sbi] DEBUG: RECEIVED: 1146 (../lib/sbi/nghttp2-server.c:773)

07/09 21:21:05.723: [sbi] DEBUG: {

"nfInstanceId": "0adae7a4-ffcd-41ec-aff0-b734789f4477",

"nfType": "PCF",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.13"],

"allowedNfTypes": ["AMF", "SMF", "NEF", "AF"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "0adb8b96-ffcd-41ec-aff0-b734789f4477",

"serviceName": "npcf-am-policy-control",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.13",

"port": 7777

}],

"allowedNfTypes": ["AMF", "NEF"],

"priority": 0,

"capacity": 100,

"load": 0

}, {

"serviceInstanceId": "0adb8baa-ffcd-41ec-aff0-b734789f4477",

"serviceName": "npcf-smpolicycontrol",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.13",

"port": 7777

}],

"allowedNfTypes": ["SMF", "NEF", "AF"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

}

201 Created

07/09 21:21:05.723: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/09 21:21:05.723: [sbi] DEBUG: SENDING...: 157 (../lib/sbi/nghttp2-server.c:355)

07/09 21:21:05.723: [sbi] DEBUG: {

"nfInstanceId": "0adae7a4-ffcd-41ec-aff0-b734789f4477",

"nfType": "PCF",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

}

Example : SMF Registration

PUT

07/09 21:21:06.081: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/0adf454c-ffcd-41ec-9f8e-25aaf51f9b14 (../lib/sbi/nghttp2-server.c:770)

07/09 21:21:06.081: [sbi] DEBUG: RECEIVED: 678 (../lib/sbi/nghttp2-server.c:773)

07/09 21:21:06.081: [sbi] DEBUG: {

"nfInstanceId": "0adf454c-ffcd-41ec-9f8e-25aaf51f9b14",

"nfType": "SMF",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.4"],

"allowedNfTypes": ["AMF"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "0b11ac76-ffcd-41ec-9f8e-25aaf51f9b14",

"serviceName": "nsmf-pdusession",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.4",

"port": 7777

}],

"allowedNfTypes": ["AMF"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

}

201 Created

07/09 21:21:06.081: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/09 21:21:06.081: [sbi] DEBUG: SENDING...: 157 (../lib/sbi/nghttp2-server.c:355)

07/09 21:21:06.081: [sbi] DEBUG: {

"nfInstanceId": "0adf454c-ffcd-41ec-9f8e-25aaf51f9b14",

"nfType": "SMF",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

}

Example : NSSF Registration

PUT

07/08 03:20:40.354: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/eaf3a41e-fe6c-41ec-9185-39782a1733b6 (../lib/sbi/nghttp2-server.c:770)

07/08 03:20:40.354: [sbi] DEBUG: RECEIVED: 683 (../lib/sbi/nghttp2-server.c:773)

07/08 03:20:40.354: [sbi] DEBUG: {

"nfInstanceId": "eaf3a41e-fe6c-41ec-9185-39782a1733b6",

"nfType": "NSSF",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.14"],

"allowedNfTypes": ["AMF"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "eaf42bd2-fe6c-41ec-9185-39782a1733b6",

"serviceName": "nnssf-nsselection",

"versions": [{

"apiVersionInUri": "v2",

"apiFullVersion": "2.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.14",

"port": 7777

}],

"allowedNfTypes": ["AMF"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

}

201 Created

07/08 03:20:40.354: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/08 03:20:40.354: [sbi] DEBUG: SENDING...: 158 (../lib/sbi/nghttp2-server.c:355)

07/08 03:20:40.354: [sbi] DEBUG: {

"nfInstanceId": "eaf3a41e-fe6c-41ec-9185-39782a1733b6",

"nfType": "NSSF",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

} (../lib/sbi/nghttp2-server.c:356)

Example : BSF Registration

PUT

07/09 21:21:06.262: [sbi] DEBUG: [PUT] /nnrf-nfm/v1/nf-instances/0b2e7414-ffcd-41ec-9c59-a56e64429106 (../lib/sbi/nghttp2-server.c:770)

07/09 21:21:06.262: [sbi] DEBUG: RECEIVED: 680 (../lib/sbi/nghttp2-server.c:773)

07/09 21:21:06.262: [sbi] DEBUG: {

"nfInstanceId": "0b2e7414-ffcd-41ec-9c59-a56e64429106",

"nfType": "BSF",

"nfStatus": "REGISTERED",

"ipv4Addresses": ["127.0.0.15"],

"allowedNfTypes": ["PCF"],

"priority": 0,

"capacity": 100,

"load": 0,

"nfServices": [{

"serviceInstanceId": "0b2e7aa4-ffcd-41ec-9c59-a56e64429106",

"serviceName": "nbsf-management",

"versions": [{

"apiVersionInUri": "v1",

"apiFullVersion": "1.0.0"

}],

"scheme": "http",

"nfServiceStatus": "REGISTERED",

"ipEndPoints": [{

"ipv4Address": "127.0.0.15",

"port": 7777

}],

"allowedNfTypes": ["PCF"],

"priority": 0,

"capacity": 100,

"load": 0

}],

"nfProfileChangesSupportInd": true

}

201 Created

07/09 21:21:06.262: [sbi] DEBUG: STATUS [201] (../lib/sbi/nghttp2-server.c:347)

07/09 21:21:06.262: [sbi] DEBUG: SENDING...: 157 (../lib/sbi/nghttp2-server.c:355)

07/09 21:21:06.262: [sbi] DEBUG: {

"nfInstanceId": "0b2e7414-ffcd-41ec-9c59-a56e64429106",

"nfType": "BSF",

"nfStatus": "REGISTERED",

"heartBeatTimer": 10,

"nfProfileChangesInd": true

}

Structured Data Types

There are various structured data type being used in communication between NF and NRF. These data types are specified in 39.510-6.1.6.2. This section is mostly direct copies of those tables that I am interested. If you don't find any of those structures, refer to 39.510

NFProfile

< 29.510 - 29.510-Table 6.1.6.2.2-1: Definition of type NFProfile >

Reference :