Add IPFIX docs

Signed-off-by: Nick Yurchenko <koolzz@fb.com>

docs/readmes/lte/ipfix.md

@@ -0,0 +1,120 @@
+---
+id: ipfix
+title: Magma IPFIX Support
+hide_title: true
+---
+# Magma IPFIX Implementation
+
+## Overview
+
+Current AGW supports an OVS based Internet Protocol Flow Information Export(IPFIX) export. Magma does not provide the IPFIX collector, but there are plenty of open source free collectors to use.
+Current architecture supports 2 main use cases of IPFIX exports:
+ - Conntrack mode
+ - Default mode
+
+We sample packets by installing a special OVS flow rule with a sample action, that inspects the packets and creates an IPFIX record for it(or append to an existing record if such exists) and is then periodically sent over to the collector specified in the pipelined.yml.
+
+## Conntrack mode
+
+In Conntrack based sampling IPFIX only samples traffic two times for each unique flow.
+This is done by leveraging the linux conntrack events via the ConntrackD service and generating an internal packet every time a conntrack event is generated.
+The internal packet is recognized by the OVS flowtable as a special packet, gets forwarded to a specific IPFIX sampling table, hits the sampling rule, and is then dropped.
+
+## Default mode
+
+In default based sampling IPFIX only samples a specified percentage of the packets for each flow.
+
+### Custom fields
+
+We support a list of custom fields in the IPFIX export:
+   - imsi
+   - msisdn
+   - apn_mac_addr
+   - apn_name
+   - app_name
+
+Here is the nProbe config for the special custom fields
+Table is as follows:
+```text
+# Name    STANDARD_ALIAS	PEN     FieldId     Len         Format
+imsi            NONE       6888         899       8    dump_as_hex
+msisdn          NONE       6888         900      16    dump_as_hex
+apn_mac_addr    NONE       6888         901       6    dump_as_hex
+apn_name        NONE       6888         902      24    dump_as_asci
+app_name        NONE       6888         903       4    dump_as_hex
+```
+
+Additionally if DPI is enabled we support a few with optional DPI support)
+
+### Initialization
+
+Configure IPFIX collector destination IP/Port from the NMS
+
+Enable IPFIX in pipelined.yml
+```yaml
+# Add ipfix to static_services
+
+# Sample configuration for IPFIX sampling
+ipfix:
+  enabled: true
+  probability: 65
+  collector_set_id: 1
+  cache_timeout: 60
+  obs_domain_id: 1
+  obs_point_id: 1
+```
+
+If running with conntrackd:
+
+Add `connectiond` to magma_services in magmad.yml
+
+Add conntrackd configuration to pipelined:
+
+```yaml
+#Add conntrack to static_services
+
+# Sample configuration for conntrackd setup
+conntrackd:
+    enabled: true
+    zone: 897
+```
+
+## Debug and logs:
+
+Internal OVS Check:
+
+Check if the openvswitch flows are correctly created. With a user attached and having internet traffic check the ovs tables using the command.
+
+`ovs-ofctl dump-flows gtp_br0`
+
+If IPFix is properly working you should be able to see an entry in the table 203, the number of packets countered in this entry needs to increase as the user is consuming data, see the example below:
+
+```sh
+ovs-ofctl dump-flows gtp_br0 # Running First Time
+cookie=0x0, duration=3256.232s, table=203, n_packets=856, n_bytes=51370, priority=10 actions=sample(probability=65535,collector_set_id=1,obs_domain_id=1,obs_point_id=1,pdp_start_epoch=1,msisdn=default,apn_name=default,sampling_port=gtp0)
+
+ovs-ofctl dump-flows gtp_br0 # Running Second Time
+cookie=0x0, duration=3316.850s, table=203, n_packets=870, n_bytes=52210, priority=10 actions=sample(probability=65535,collector_set_id=1,obs_domain_id=1,obs_point_id=1,pdp_start_epoch=1,msisdn=default,apn_name=default8,sampling_port=gtp0)
+```
+
+### IPFix packets
+
+Check if the IPFIx packets are leaving the AGW source. In this example the collector IP and port were configured to 1.1.1.1 and 65010 make sure to change those to reflect your pipelined.yml. Run the tshark analyser to check if the IPFix records are shown as expected:
+
+```sh
+tshark -i any -d udp.port=65010,cflow dst 1.1.1.1
+1 0.000000000 172.17.3.151 → 1.1.1.1 CFLOW 439 IPFIX flow ( 395 bytes) Obs-Domain-ID=    1 [Data:281]
+2 1.035991689 172.17.3.151 → 1.1.1.1 CFLOW 439 IPFIX flow ( 395 bytes) Obs-Domain-ID=    1 [Data:281]
+```
+
+### nProbe collection:
+
+After running nProbe check if it is collecting the flows from the AGW, in this scenario nProbe is running at port 65010, and the AGW uses ip 172.17.3.151, you should see the the following log from your nProbe command
+
+```sh
+05/Jul/2021 20:52:03 [collect.c:206] Flow collector listening on port 65010 (IPv4/v6)
+05/Jul/2021 20:52:03 [export.c:545] Using TLV as serialization format
+05/Jul/2021 20:52:03 [nprobe.c:10773] nProbe started successfully
+05/Jul/2021 20:52:06 [collect.c:3038] Collecting flows from 172.17.3.151 [total: 1/4]
+```
+