Diameter Protocol

Theory

Diameter is an AAA protocol, mainly used in telecom.

Authentication

Authorization

Accounting

Diameter follows two-layer structure.

Base Protocol Layer - Infrastructure.

Application Layer - Business Logic.


Message Format

A diameter message contains a header and a payload.
The payload is a list of attribute–value pairs (AVPs).

A diameter node can act as a client, server or agent.

Diameter Client Node

Server

Agent


Diameter uses TCP or SCTP as transport protocol.

Lab 01: Erlang Diameter

Step 1: Install erlang.

$ apt install -y erlang

$ dpkg -l | grep erlang
erlang
erlang-diameter
erlang-examples

Step 2: Build diameter example code.

$ dpkg -L erlang-examples
/usr/lib/erlang/lib/diameter-2.2.4/examples/code/server.erl
/usr/lib/erlang/lib/diameter-2.2.4/examples/code/client.erl

$ cd /usr/lib/erlang/lib/diameter-2.2.4/examples/code/

$ erlc *.erl
# build .erl file to .beam

Step 3: Start server.

$ cd /usr/lib/erlang/lib/diameter-2.2.4/examples/code

$ erl -pa .
> application:start(diameter).
> server:start().
> server:listen(tcp).

# server listening at 127.0.0.1:3868
$ lsof -n -i :3868
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
beam.smp 11825 root   17u  IPv4  91515      0t0  TCP 127.0.0.1:3868 (LISTEN)

Step 4: Start server.

$ cd /usr/lib/erlang/lib/diameter-2.2.4/examples/code

$ erl -pa .
> application:start(diameter).
> client:start().
> client:connect(tcp).
> client:call().

{ok,['ACA'|
     #{'Accounting-Record-Number' => 0,
       'Accounting-Record-Type' => 1,
       'Origin-Host' => <<"server.example.com">>,
       'Origin-Realm' => <<"example.com">>,'Result-Code' => 2001,
       'Session-Id' => <<"client;1831359964;1;nonode@nohost">>}]}

> client:stop().

Step 5: Capture pcap.

# tcpdump -i lo -w hello.pcap 'tcp port 3868' --print
$ tshark -i lo -w hello.pcap -f "tcp port 3868" -P -l

$ tshark -r hello.pcap -Y 'diameter'
4   0.001318243  127.0.0.1 → 127.0.0.1  DIAMETER 190 cmd=Capabilities-Exchange Request(257) flags=R--- appl=Diameter Common Messages(0) h2h=acb06dc3 e2e=acb06dc3 | 
6   0.002841007  127.0.0.1 → 127.0.0.1  DIAMETER 202 cmd=Capabilities-Exchange Answer(257)  flags=---- appl=Diameter Common Messages(0) h2h=acb06dc3 e2e=acb06dc3 | 
8  28.409234033  127.0.0.1 → 127.0.0.1  DIAMETER 134 cmd=Device-Watchdog Request(280)       flags=R--- appl=Diameter Common Messages(0) h2h=acb06dc4 e2e=acb06dc4 | 
9  28.410384934  127.0.0.1 → 127.0.0.1  DIAMETER 146 cmd=Device-Watchdog Answer(280)        flags=---- appl=Diameter Common Messages(0) h2h=acb06dc4 e2e=acb06dc4 | 
11 34.159011885  127.0.0.1 → 127.0.0.1  DIAMETER 222 cmd=Accounting Request(271)            flags=RP-- appl=Diameter Common Messages(0) h2h=acb06dc5 e2e=acb06dc5 | 
12 34.161076648  127.0.0.1 → 127.0.0.1  DIAMETER 214 cmd=Accounting Answer(271)             flags=-P-- appl=Diameter Common Messages(0) h2h=acb06dc5 e2e=acb06dc5 | 
14 48.667674359  127.0.0.1 → 127.0.0.1  DIAMETER 146 cmd=Disconnect-Peer Request(282)       flags=R--- appl=Diameter Common Messages(0) h2h=acb06dc6 e2e=acb06dc6 | 
15 48.668208006  127.0.0.1 → 127.0.0.1  DIAMETER 146 cmd=Disconnect-Peer Answer(282)        flags=---- appl=Diameter Common Messages(0) h2h=acb06dc6 e2e=acb06dc6 |

$ tshark -r hello.pcap -O 'diameter' -Y diameter > hello.txt

Sample: hello.pcap, hello.txt.


References