content: Reorganize to better suit ananke theme

6 files changed, 861 insertions, 0 deletions

diff --git a/content/docs/tutorials/_index.md b/content/docs/tutorials/_index.md
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+---
+title: "Ouroboros Tutorials"
+date:  2019-06-22
+draft: false
+---
\ No newline at end of file
diff --git a/content/docs/tutorials/dev-tut-1.md b/content/docs/tutorials/dev-tut-1.md
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+---
+title: "Developer tutorial 1: Writing your first Ouroboros C program"
+draft: false
+---
+
+This tutorial will guide you to write your first ouroboros program. It
+will use the basic Ouroboros IPC Application Programming Interface. It
+will has a client and a server that send a small message from the client
+to the server.
+
+We will explain how to connect two applications. The server application
+uses the flow_accept() call to accept incoming connections and the
+client uses the flow_alloc() call to connect to the server. The
+flow_accept and flow_alloc call have the following definitions:
+
+```
+int flow_accept(qosspec_t * qs, const struct timespec * timeo);
+int flow_alloc(const char * dst, qosspec_t * qs, const struct
+timespec * timeo);
+```
+
+On the server side, the flow_accept() call is a blocking call that will
+wait for an incoming flow from a client. On the client side, the
+flow_alloc() call is a blocking call that allocates a flow to *dst*.
+Both calls return an non-negative integer number describing a "flow
+descriptor", which is very similar to a file descriptor. On error, they
+will return a negative error code. (See the [man
+page](/man/man3/flow_alloc.html) for all details). If the *timeo*
+parameter supplied is NULL, the calls will block indefinitely, otherwise
+flow_alloc() will return -ETIMEDOUT when the time interval provided by
+*timeo* expires. We are working on implementing non-blocking versions if
+the provided *timeo* is 0.
+
+After the flow is allocated, the flow_read() and flow_write() calls
+are used to read from the flow descriptor. They operate just like the
+read() and write() POSIX calls. The default behaviour is that these
+calls will block. To release the resource, the flow can be deallocated
+using flow_dealloc.
+
+```
+ssize_t flow_write(int fd, const void * buf, size_t count);
+ssize_t flow_read(int fd, void * buf, size_t count); int
+flow_dealloc(int fd);
+```
+
+So a very simple application would just need a couple of lines of code
+for both the server and the client:
+
+```
+/* server side */
+char msg[BUF_LEN];
+int fd = flow_accept(NULL, NULL);
+flow_read(fd, msg, BUF_LEN);
+flow_dealloc(fd);
+
+/* client side */
+char * msg = "message";
+int fd = flow_alloc("server", NULL, NULL);
+flow_write(fd, msg, strlen(msg));
+flow_dealloc(fd);
+```
+
+The full code for an example is the
+[oecho](/cgit/ouroboros/tree/src/tools/oecho/oecho.c)
+application in the tools directory.
+
+To compile your C program from the command line, you have to link
+-lourobos-dev. For instance, in the Ouroboros repository, you can do
+
+```
+cd src/tools/oecho
+gcc -louroboros-dev oecho.c -o oecho
+```
\ No newline at end of file
diff --git a/content/docs/tutorials/tutorial-1.md b/content/docs/tutorials/tutorial-1.md
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+---
+title: "Tutorial 1: local test"
+draft: false
+---
+
+This tutorial runs through the basics of Ouroboros. Here, we will see
+the general use of two core components of Ouroboros, the IPC Resource
+Manager daemon (IRMd) and an IPC Process (IPCP).
+
+![Tutorial 1 setup](/images/ouroboros_tut1_overview.png)
+
+We will start the IRMd, create a local IPCP, start a ping server and
+connect a client. This will involve **binding (1)** that server to a
+name and **registering (2)** that name into the local layer. After that
+the client will be able to **allocate a flow (3)** to that name for
+which the server will respond.
+
+We recommend to open 3 terminal windows for this tutorial. In the first
+window, start the IRMd (as a superuser) in stdout mode. The output shows
+the process id (pid) of the IRMd, which will be different on your
+machine.
+
+```
+$ sudo irmd --stdout
+==02301== irmd(II): Ouroboros IPC Resource Manager daemon started\...
+```
+
+The type of IPCP we will create is a "local" IPCP. The local IPCP is a
+kind of loopback interface that is native to Ouroboros. It implements
+all the functions that the Ouroboros API provides, but only for a local
+scope. The IPCP create function will instantiate a new local IPC
+process, which in our case has pid 2324. The "ipcp create" command
+merely creates the IPCP. At this point it is not a part of a layer. We
+will also need to bootstrap this IPCP in a layer, we will name it
+"local_layer". As a shortcut, the bootstrap command will
+automatically create an IPCP if no IPCP by than name exists, so in this
+case, the IPCP create command is optional. In the second terminal, enter
+the commands:
+
+```
+$ irm ipcp create type local name local_ipcp
+$ irm ipcp bootstrap type local name local_ipcp layer local_layer
+```
+
+The IRMd and ipcpd output in the first terminal reads:
+
+```
+==02301== irmd(II): Created IPCP 2324.
+==02324== ipcpd-local(II): Bootstrapped local IPCP with pid 2324.
+==02301== irmd(II): Bootstrapped IPCP 2324 in layer local_layer.
+```
+
+From the third terminal window, let's start our oping application in
+server mode ("oping --help" shows oping command line parameters):
+
+```
+$ oping --listen
+Ouroboros ping server started.
+```
+
+The IRMd will notice that an oping server with pid 10539 has started:
+
+```
+==02301== irmd(DB): New instance (10539) of oping added.
+==02301== irmd(DB): This process accepts flows for:
+```
+
+The server application is not yet reachable by clients. Next we will
+bind the server to a name and register that name in the
+"local_layer". The name for the server can be chosen at will, let's
+take "oping_server". In the second terminal window, execute:
+
+```
+$ irm bind proc 2337 name oping_server
+$ irm register name oping_server layer local_layer
+```
+
+The IRMd and IPCPd in terminal one will now acknowledge that the name is
+bound and registered:
+
+```
+==02301== irmd(II): Bound process 2337 to name oping_server.
+==02324== ipcpd-local(II): Registered 4721372d.
+==02301== irmd(II): Registered oping_server in local_layer as
+4721372d.
+```
+
+Ouroboros registers name not in plaintext but using a (configurable)
+hashing algorithm. The default hash is a 256 bit SHA3 hash. The output
+in the logs is truncated to the first 4 bytes in a HEX notation.
+
+Now that we have bound and registered our server, we can connect from
+the client. In the second terminal window, start an oping client with
+destination oping_server and it will begin pinging:
+
+```
+$ oping -n oping_server -c 5
+Pinging oping_server with 64 bytes of data:
+
+64 bytes from oping_server: seq=0 time=0.694 ms
+64 bytes from oping_server: seq=1 time=0.364 ms
+64 bytes from oping_server: seq=2 time=0.190 ms
+64 bytes from oping_server: seq=3 time=0.269 ms
+64 bytes from oping_server: seq=4 time=0.351 ms
+
+--- oping_server ping statistics ---
+5 SDUs transmitted, 5 received, 0% packet loss, time: 5001.744 ms
+rtt min/avg/max/mdev = 0.190/0.374/0.694/0.192 ms
+```
+
+The server will acknowledge that it has a new flow connected on flow
+descriptor 64, which will time out a few seconds after the oping client
+stops sending:
+
+```
+New flow 64.
+Flow 64 timed out.
+```
+
+The IRMd and IPCP logs provide some additional output detailing the flow
+allocation process:
+
+```
+==02324== ipcpd-local(DB): Allocating flow to 4721372d on fd 64.
+==02301== irmd(DB): Flow req arrived from IPCP 2324 for 4721372d.
+==02301== irmd(II): Flow request arrived for oping_server.
+==02324== ipcpd-local(II): Pending local allocation request on fd 64.
+==02301== irmd(II): Flow on port_id 0 allocated.
+==02324== ipcpd-local(II): Flow allocation completed, fds (64, 65).
+==02301== irmd(II): Flow on port_id 1 allocated.
+==02301== irmd(DB): New instance (2337) of oping added.
+==02301== irmd(DB): This process accepts flows for:
+==02301== irmd(DB): oping_server
+```
+
+First, the IPCPd shows that it will allocate a flow towards a
+destination hash "4721372d" (truncated). The IRMd logs that IPCPd 2324
+(our local IPCPd) requests a flow towards any process that is listening
+for "4721372d", and resolves it to "oping_server", as that is a
+process that is bound to that name. At this point, the local IPCPd has a
+pending flow on the client side. Since this is the first port_id in the
+system, it has port_id 0. The server will accept the flow and the other
+end of the flow gets port_id 1. The local IPCPd sees that the flow
+allocation is completed. Internally it sees the endpoints as flow
+descriptors 64 and 65 which map to port_id 0 and port_id 1. The IPCP
+cannot directly access port_ids, they are assigned and managed by the
+IRMd. After it has accepted the flow, the oping server enters
+flow_accept() again. The IRMd notices the instance and reports that it
+accepts flows for "oping_server".
+
+This concludes this first short tutorial. All running processes can be
+terminated by issuing a Ctrl-C command in their respective terminals or
+you can continue with the next tutorial.
diff --git a/content/docs/tutorials/tutorial-2.md b/content/docs/tutorials/tutorial-2.md
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@@ -0,0 +1,297 @@
+---
+title: "Tutorial 2: Adding a layer"
+draft: false
+---
+
+In this tutorial we will add a *normal layer* on top of the local layer.
+Make sure you have a local layer running. The network will look like
+this:
+
+![Tutorial 2 setup](/images/ouroboros_tut2_overview.png)
+
+Let's start adding the normal layer. We will first bootstrap a normal
+IPCP, with name "normal_1" into the "normal_layer" (using default
+options). In terminal 2, type:
+
+```
+$ irm ipcp bootstrap type normal name normal_1 layer normal_layer
+```
+
+The IRMd and IPCP will report the bootstrap:
+
+```
+==02301== irmd(II): Created IPCP 4363.
+==04363== normal-ipcp(DB): IPCP got address 465922905.
+==04363== directory(DB): Bootstrapping directory.
+==04363== directory(II): Directory bootstrapped.
+==04363== normal-ipcp(DB): Bootstrapped in layer normal_layer.
+==02301== irmd(II): Bootstrapped IPCP 4363 in layer normal_layer.
+==02301== irmd(DB): New instance (4363) of ipcpd-normal added.
+==02301== irmd(DB): This process accepts flows for:
+```
+
+The new IPCP has pid 4363. It also generated an *address* for itself,
+465922905. Then it bootstrapped a directory. The directory will map
+registered names to an address or a set of addresses. In the normal DHT
+the current default (and only option) for the directory is a Distributed
+Hash Table (DHT) based on the Kademlia protocol, similar to the DHT used
+in the mainline BitTorrent as specified by the
+[BEP5](http://www.bittorrent.org/beps/bep_0005.html). This DHT will use
+the hash algorithm specified for the layer (default is 256-bit SHA3)
+instead of the SHA1 algorithm used by Kademlia. Just like any
+Ouroboros-capable process, the IRMd will notice a new instance of the
+normal IPCP. We will now bind this IPCP to some names and register them
+in the local_layer:
+
+```
+$ irm bind ipcp normal_1 name normal_1
+$ irm bind ipcp normal_1 name normal_layer
+$ irm register name normal_1 layer local_layer
+$ irm register name normal_layer layer local_layer
+```
+
+The "irm bind ipcp" call is a shorthand for the "irm bind proc" call
+that uses the ipcp name instead of the pid for convenience. Note that
+we have bound the same process to two different names. This is to
+allow enrollment using a layer name (anycast) instead of a specific
+ipcp_name. The IRMd and local IPCP should log the following, just as
+in tutorial 1:
+
+```
+==02301== irmd(II): Bound process 4363 to name normal_1.
+==02301== irmd(II): Bound process 4363 to name normal_layer.
+==02324== ipcpd-local(II): Registered e9504761.
+==02301== irmd(II): Registered normal_1 in local_layer as e9504761.
+==02324== ipcpd-local(II): Registered f40ee0f0.
+==02301== irmd(II): Registered normal_layer in local_layer as
+f40ee0f0.
+```
+
+We will now create a second IPCP and enroll it in the normal_layer.
+Like the "irm ipcp bootstrap command", the "irm ipcp enroll" command
+will create the IPCP if an IPCP with that name does not yet exist in the
+system. An "autobind" option is a shorthand for binding the IPCP to
+the IPCP name and the layer name.
+
+```
+$ irm ipcp enroll name normal_2 layer normal_layer autobind
+```
+
+The activity is shown by the output of the IRMd and the IPCPs. Let's
+break it down. First, the new normal IPCP is created and bound to its
+process name:
+
+```
+==02301== irmd(II): Created IPCP 13569.
+==02301== irmd(II): Bound process 13569 to name normal_2.
+```
+
+Next, that IPCP will *enroll* with an existing member of the layer
+"normal_layer". To do that it first allocates a flow over the local
+layer:
+
+```
+==02324== ipcpd-local(DB): Allocating flow to f40ee0f0 on fd 64.
+==02301== irmd(DB): Flow req arrived from IPCP 2324 for f40ee0f0.
+==02301== irmd(II): Flow request arrived for normal_layer.
+==02324== ipcpd-local(II): Pending local allocation request on fd 64.
+==02301== irmd(II): Flow on port_id 0 allocated.
+==02324== ipcpd-local(II): Flow allocation completed, fds (64, 65).
+==02301== irmd(II): Flow on port_id 1 allocated.
+```
+
+Over this flow, it connects to the enrollment component of the normal_1
+IPCP. It sends some information that it will speak the Ouroboros
+Enrollment Protocol (OEP). Then it will receive boot information from
+normal_1 (the configuration of the layer that was provided when we
+bootstrapped the normal_1 process), such as the hash it will use for
+the directory. It signals normal_1 that it got the information so that
+normal_1 knows this was successful. It will also get an address. After
+enrollment is complete, both normal_1 and normal_2 will be ready to
+accept incoming flows:
+
+```
+==13569== connection-manager(DB): Sending cacep info for protocol OEP to
+fd 64.
+==13569== enrollment(DB): Getting boot information.
+==02301== irmd(DB): New instance (4363) of ipcpd-normal added.
+==02301== irmd(DB): This process accepts flows for:
+==02301== irmd(DB): normal_layer
+==02301== irmd(DB): normal_1
+==04363== enrollment(DB): Enrolling a new neighbor.
+==04363== enrollment(DB): Sending enrollment info (49 bytes).
+==13569== enrollment(DB): Received enrollment info (49 bytes).
+==13569== normal-ipcp(DB): IPCP got address 416743497.
+==04363== enrollment(DB): Neighbor enrollment successful.
+==02301== irmd(DB): New instance (13569) of ipcpd-normal added.
+==02301== irmd(DB): This process accepts flows for:
+==02301== irmd(DB): normal_2
+```
+
+Now that the member is enrolled, normal_1 and normal_2 will deallocate
+the flow over which it enrolled and signal the IRMd that the enrollment
+was successful:
+
+```
+==02301== irmd(DB): Partial deallocation of port_id 0 by process
+13569.
+==02301== irmd(DB): Partial deallocation of port_id 1 by process 4363.
+==02301== irmd(II): Completed deallocation of port_id 0 by process
+2324.
+==02301== irmd(II): Completed deallocation of port_id 1 by process
+2324.
+==02324== ipcpd-local(II): Flow with fd 64 deallocated.
+==02324== ipcpd-local(II): Flow with fd 65 deallocated.
+==13569== normal-ipcp(II): Enrolled with normal_layer.
+==02301== irmd(II): Enrolled IPCP 13569 in layer normal_layer.
+```
+
+Now that normal_2 is a full member of the layer, the irm tool will
+complete the autobind option and bind normal_2 to the name
+"normal_layer" so it can also enroll new members.
+
+```
+==02301== irmd(II): Bound process 13569 to name normal_layer.
+```
+
+![Tutorial 2 after enrolment](/images/ouroboros_tut2_enrolled.png)
+
+At this point, have two enrolled members of the normal_layer. What we
+need to do next is connect them. We will need a *management flow*, for
+the management network, which is used to distribute point-to-point
+information (such as routing information) and a *data transfer flow*
+over which the layer will forward traffic coming either from higher
+layers or internal components (such as the DHT and flow allocator). They
+can be established in any order, but it is recommended to create the
+management network first to achieve the minimal setup times for the
+network layer:
+
+```
+$ irm ipcp connect name normal_2 dst normal_1 comp mgmt
+$ irm ipcp connect name normal_2 dst normal_1 comp dt
+```
+
+The IPCP and IRMd log the flow and connection establishment:
+
+```
+==02301== irmd(DB): Connecting Management to normal_1.
+==02324== ipcpd-local(DB): Allocating flow to e9504761 on fd 64.
+==02301== irmd(DB): Flow req arrived from IPCP 2324 for e9504761.
+==02301== irmd(II): Flow request arrived for normal_1.
+==02324== ipcpd-local(II): Pending local allocation request on fd 64.
+==02301== irmd(II): Flow on port_id 0 allocated.
+==02324== ipcpd-local(II): Flow allocation completed, fds (64, 65).
+==02301== irmd(II): Flow on port_id 1 allocated.
+==13569== connection-manager(DB): Sending cacep info for protocol LSP to
+fd 64.
+==04363== link-state-routing(DB): Type mgmt neighbor 416743497 added.
+==02301== irmd(DB): New instance (4363) of ipcpd-normal added.
+==02301== irmd(DB): This process accepts flows for:
+==02301== irmd(DB): normal_layer
+==02301== irmd(DB): normal_1
+==13569== link-state-routing(DB): Type mgmt neighbor 465922905 added.
+==02301== irmd(II): Established Management connection between IPCP 13569
+and normal_1.
+```
+
+The IPCPs established a management flow between the link-state routing
+components (currently that is the only component that needs a management
+flow). The output is similar for the data transfer flow, however,
+creating a data transfer flow triggers some additional activity:
+
+```
+==02301== irmd(DB): Connecting Data Transfer to normal_1.
+==02324== ipcpd-local(DB): Allocating flow to e9504761 on fd 66.
+==02301== irmd(DB): Flow req arrived from IPCP 2324 for e9504761.
+==02301== irmd(II): Flow request arrived for normal_1.
+==02324== ipcpd-local(II): Pending local allocation request on fd 66.
+==02301== irmd(II): Flow on port_id 2 allocated.
+==02324== ipcpd-local(II): Flow allocation completed, fds (66, 67).
+==02301== irmd(II): Flow on port_id 3 allocated.
+==13569== connection-manager(DB): Sending cacep info for protocol dtp to
+fd 65.
+==04363== dt(DB): Added fd 65 to SDU scheduler.
+==04363== link-state-routing(DB): Type dt neighbor 416743497 added.
+==02301== irmd(DB): New instance (4363) of ipcpd-normal added.
+==02301== irmd(DB): This process accepts flows for:
+==02301== irmd(DB): normal_layer
+==02301== irmd(DB): normal_1
+==13569== dt(DB): Added fd 65 to SDU scheduler.
+==13569== link-state-routing(DB): Type dt neighbor 465922905 added.
+==13569== dt(DB): Could not get nhop for addr 465922905.
+==02301== irmd(II): Established Data Transfer connection between IPCP
+13569 and normal_1.
+==13569== dt(DB): Could not get nhop for addr 465922905.
+==13569== dht(DB): Enrollment of DHT completed.
+```
+
+First, the data transfer flow is added to the SDU scheduler. Next, the
+neighbor's address is added to the link-state database and a Link-State
+Update message is broadcast over the management network. Finally, if the
+DHT is not yet enrolled, it will try to do so when it detects a new data
+transfer flow. Since this is the first data transfer flow in the
+network, the DHT will try to enroll. It may take some time for the
+routing entry to get inserted to the forwarding table, so the DHT
+re-tries a couple of times (this is the "could not get nhop" message
+in the debug log).
+
+Our oping server is not registered yet in the normal layer. Let's
+register it in the normal layer as well, and connect the client:
+
+```
+$ irm r n oping_server layer normal_layer
+$ oping -n oping_server -c 5
+```
+
+The IRMd and IPCP will log:
+
+```
+==02301== irmd(II): Registered oping_server in normal_layer as
+465bac77.
+==02301== irmd(II): Registered oping_server in normal_layer as
+465bac77.
+==02324== ipcpd-local(DB): Allocating flow to 4721372d on fd 68.
+==02301== irmd(DB): Flow req arrived from IPCP 2324 for 4721372d.
+==02301== irmd(II): Flow request arrived for oping_server.
+==02324== ipcpd-local(II): Pending local allocation request on fd 68.
+==02301== irmd(II): Flow on port_id 4 allocated.
+==02324== ipcpd-local(II): Flow allocation completed, fds (68, 69).
+==02301== irmd(II): Flow on port_id 5 allocated.
+==02301== irmd(DB): New instance (2337) of oping added.
+==02301== irmd(DB): This process accepts flows for:
+==02301== irmd(DB): oping_server
+==02301== irmd(DB): Partial deallocation of port_id 4 by process 749.
+==02301== irmd(II): Completed deallocation of port_id 4 by process
+2324.
+==02324== ipcpd-local(II): Flow with fd 68 deallocated.
+==02301== irmd(DB): Dead process removed: 749.
+==02301== irmd(DB): Partial deallocation of port_id 5 by process 2337.
+==02301== irmd(II): Completed deallocation of port_id 5 by process
+2324.
+==02324== ipcpd-local(II): Flow with fd 69 deallocated.
+```
+
+The client connected over the local layer instead of the normal layer.
+This is because the IRMd prefers the local layer. If we unregister the
+name from the local layer, the client will connect over the normal
+layer:
+
+```
+$ irm unregister name oping_server layer local_layer
+$ oping -n oping_server -c 5
+```
+
+As shown by the logs (the normal IPCP doesn't log the flow allocation):
+
+```
+==02301== irmd(DB): Flow req arrived from IPCP 13569 for 465bac77.
+==02301== irmd(II): Flow request arrived for oping_server.
+==02301== irmd(II): Flow on port_id 5 allocated.
+==02301== irmd(II): Flow on port_id 4 allocated.
+==02301== irmd(DB): New instance (2337) of oping added.
+==02301== irmd(DB): This process accepts flows for:
+==02301== irmd(DB): oping_server
+```
+
+This concludes tutorial 2. You can shut down everything or continue with
+tutorial 3.
diff --git a/content/docs/tutorials/tutorial-3.md b/content/docs/tutorials/tutorial-3.md
new file mode 100644
index 0000000..2dd0645
--- /dev/null
+++ b/content/docs/tutorials/tutorial-3.md
@@ -0,0 +1,210 @@
+---
+title: "Tutorial 3: IPCP statistics"
+draft: false
+---
+
+For this tutorial, you should have a local layer, a normal layer and a
+ping server registered in the normal layer. You will need to have the
+FUSE libraries installed and Ouroboros compiled with FUSE support. We
+will show you how to get some statistics from the network layer which is
+exported by the IPCPs at /tmp/ouroboros (this mountpoint can be set at
+compile time):
+
+```
+$ tree /tmp/ouroboros
+/tmp/ouroboros/
+|-- ipcpd-normal.13569
+|   |-- dt
+|   |   |-- 0
+|   |   |-- 1
+|   |   `-- 65
+|   `-- lsdb
+|       |-- 416743497.465922905
+|       |-- 465922905.416743497
+|       |-- dt.465922905
+|       `-- mgmt.465922905
+`-- ipcpd-normal.4363
+    |-- dt
+    |   |-- 0
+    |   |-- 1
+    |   `-- 65
+    `-- lsdb
+        |-- 416743497.465922905
+        |-- 465922905.416743497
+        |-- dt.416743497
+        `-- mgmt.416743497
+
+6 directories, 14 files
+```
+
+There are two filesystems, one for each normal IPCP. Currently, it shows
+information for two components: data transfer and the link-state
+database. The data transfer component lists flows on known flow
+descriptors. The flow allocator component will usually be on fd 0 and
+the directory (DHT). There is a single (N-1) data transfer flow on fd 65
+that the IPCPs can use to send data (these fd's will usually not be the
+same). The routing component sees that data transfer flow as two
+unidirectional links. It has a management flow and data transfer flow to
+its neighbor. Let's have a look at the data transfer flow in the
+network:
+
+```
+$ cat /tmp/ouroboros/ipcpd-normal.13569/dt/65
+Flow established at:       2018-03-07 18:47:43
+Endpoint address:                    465922905
+Queued packets (rx):                         0
+Queued packets (tx):                         0
+
+Qos cube   0:
+ sent (packets):                             4
+ sent (bytes):                             268
+ rcvd (packets):                             3
+ rcvd (bytes):                             298
+ local sent (packets):                       4
+ local sent (bytes):                       268
+ local rcvd (packets):                       3
+ local rcvd (bytes):                       298
+ dropped ttl (packets):                      0
+ dropped ttl (bytes):                        0
+ failed writes (packets):                    0
+ failed writes (bytes):                      0
+ failed nhop (packets):                      0
+ failed nhop (bytes):                        0
+
+<no traffic on other qos cubes>
+```
+
+The above output shows the statistics for the data transfer component of
+the IPCP that enrolled into the layer. It shows the time the flow was
+established, the endpoint address and the number of packets that are in
+the incoming and outgoing queues. Then it lists packet statistics per
+QoS cube. It sent 4 packets, and received 3 packets. All the packets
+came from local sources (internal components of the IPCP) and were
+delivered to local destinations. Let's have a look where they went.
+
+```
+$ cat /tmp/ouroboros/ipcpd-normal.13569/dt/1
+Flow established at:       2018-03-07 18:47:43
+Endpoint address:               flow-allocator
+Queued packets (rx):                         0
+Queued packets (tx):                         0
+
+<no packets on this flow>
+```
+
+There is no traffic on fd 0, which is the flow allocator component. This
+will only be used when higher layer applications will use this normal
+layer. Let's have a look at fd 1.
+
+```
+$ cat /tmp/ouroboros/ipcpd-normal.13569/dt/1
+Flow established at:       2018-03-07 18:47:43
+Endpoint address:                          dht
+Queued packets (rx):                         0
+Queued packets (tx):                         0
+
+Qos cube   0:
+ sent (packets):                             3
+ sent (bytes):                             298
+ rcvd (packets):                             0
+ rcvd (bytes):                               0
+ local sent (packets):                       0
+ local sent (bytes):                         0
+ local rcvd (packets):                       6
+ local rcvd (bytes):                       312
+ dropped ttl (packets):                      0
+ dropped ttl (bytes):                        0
+ failed writes (packets):                    0
+ failed writes (bytes):                      0
+ failed nhop (packets):                      2
+ failed nhop (bytes):                       44
+
+<no traffic on other qos cubes>
+```
+
+The traffic for the directory (DHT) is on fd1. Take note that this is
+from the perspective of the data transfer component. The data transfer
+component sent 3 packets to the DHT, these are the 3 packets it received
+from the data transfer flow. The data transfer component received 6
+packets from the DHT. It only sent 4 on fd 65. 2 packets failed because
+of nhop. This is because the forwarding table was being updated from the
+routing table. Let's send some traffic to the oping server.
+
+```
+$ oping -n oping_server -i 0
+Pinging oping_server with 64 bytes of data:
+
+64 bytes from oping_server: seq=0 time=0.547 ms
+...
+64 bytes from oping_server: seq=999 time=0.184 ms
+
+--- oping_server ping statistics ---
+1000 SDUs transmitted, 1000 received, 0% packet loss, time: 106.538 ms
+rtt min/avg/max/mdev = 0.151/0.299/2.269/0.230 ms
+```
+
+This sent 1000 packets to the server. Let's have a look at the flow
+allocator:
+
+```
+$ cat /tmp/ouroboros/ipcpd-normal.13569/dt/0
+Flow established at:       2018-03-07 18:47:43
+Endpoint address:               flow-allocator
+Queued packets (rx):                         0
+Queued packets (tx):                         0
+
+Qos cube   0:
+ sent (packets):                             1
+ sent (bytes):                              59
+ rcvd (packets):                             0
+ rcvd (bytes):                               0
+ local sent (packets):                       0
+ local sent (bytes):                         0
+ local rcvd (packets):                       1
+ local rcvd (bytes):                        51
+ dropped ttl (packets):                      0
+ dropped ttl (bytes):                        0
+ failed writes (packets):                    0
+ failed writes (bytes):                      0
+ failed nhop (packets):                      0
+ failed nhop (bytes):                        0
+
+<no traffic on other qos cubes>
+```
+
+The flow allocator has sent and received a message: a request and a
+response for the flow allocation between the oping client and server.
+The data transfer flow will also have additional traffic:
+
+```
+$ cat /tmp/ouroboros/ipcpd-normal.13569/dt/65
+Flow established at:       2018-03-07 18:47:43
+Endpoint address:                    465922905
+Queued packets (rx):                         0
+Queued packets (tx):                         0
+
+Qos cube   0:
+ sent (packets):                          1013
+ sent (bytes):                           85171
+ rcvd (packets):                          1014
+ rcvd (bytes):                           85373
+ local sent (packets):                      13
+ local sent (bytes):                      1171
+ local rcvd (packets):                      14
+ local rcvd (bytes):                      1373
+ dropped ttl (packets):                      0
+ dropped ttl (bytes):                        0
+ failed writes (packets):                    0
+ failed writes (bytes):                      0
+ failed nhop (packets):                      0
+ failed nhop (bytes):                        0
+```
+
+This shows the traffic from the oping application. The additional
+traffic (the oping sent 1000, the flow allocator 1 and the DHT
+previously sent 3) is additional DHT traffic (the DHT periodically
+updates). Also note that the traffic reported on the link includes the
+FRCT and data transfer headers which in the default configuration is 20
+bytes per packet.
+
+This concludes tutorial 3.
diff --git a/content/docs/tutorials/tutorial-4.md b/content/docs/tutorials/tutorial-4.md
new file mode 100644
index 0000000..fd7db3a
--- /dev/null
+++ b/content/docs/tutorials/tutorial-4.md
@@ -0,0 +1,123 @@
+---
+title: "Tutorial 4: Connecting two machines over Ethernet"
+draft: false
+---
+
+In this tutorial we will connect two machines over an Ethernet network
+using the eth-llc or eth-dix IPCPs. The eth-llc use of the IEEE 802.2
+Link Layer Control (LLC) service type 1 frame header. The eth-dix IPCP
+uses DIX (DEC, Intel, Xerox) Ethernet, also known as Ethernet II. Both
+provide a connectionless packet service with unacknowledged delivery.
+
+Make sure that you have an Ouroboros IRM daemon running on both
+machines:
+
+```
+$ sudo irmd --stdout
+```
+
+The eth-llc and eth-dix IPCPs attach to an ethernet interface, which is
+specified by its device name. The device name can be found in a number
+of ways, we'll use the "ip" command here:
+
+```
+$ ip a
+1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
+group default qlen 1
+link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+...
+2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
+state UP group default qlen 1000
+link/ether fa:16:3e:42:00:38 brd ff:ff:ff:ff:ff:ff
+...
+3: ens6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
+state UP group default qlen 1000
+link/ether fa:16:3e:00:76:c2 brd ff:ff:ff:ff:ff:ff
+...
+```
+
+The output of this command differs between operating systems and
+distributions. The interface we need to use in our setup is "ens3" on
+both machines, but for you it may be something like "eth0" or
+"enp0s7f1" if you are on a wired LAN, or something like "wlan0" or
+"wlp2s0" if you are on a Wi-Fi network. For Wi-Fi networks, we
+recommend using the eth-dix.
+
+Usually the interface you will use is the one that has an IP address for
+your LAN set. Note that you do not need to have an IP address for this
+tutorial, but do make sure the interface is UP.
+
+Now that we know the interfaces to connect to the network with, let's
+start the eth-llc/eth-dix IPCPs. The eth-llc/eth-dix layers don't have
+an enrollment phase, all eth-llc IPCPs that are connected to the same
+Ethernet, will be part of the layer. For eth-dix IPCPs the layers can be
+separated by ethertype. The eth-llc and eth-dix IPCPs can only be
+bootstrapped, so care must be taken by to provide the same hash
+algorithm to all eth-llc and eth-dix IPCPs that should be in the same
+network. We use the default (256-bit SHA3) for the hash and 0xa000 for
+the Ethertype for the DIX IPCP. For our setup, it's the exact same
+command on both machines. You will likely need to set a different
+interface name on each machine. The irm tool allows abbreviated commands
+(it is modelled after the "ip" command), which we show here (both
+commands do the same):
+
+```
+node0: $ irm ipcp bootstrap type eth-llc name llc layer eth dev ens3
+node1: $ irm i b t eth-llc n llc l eth if ens3
+```
+
+Both IRM daemons should acknowledge the creation of the IPCP:
+
+```
+==26504== irmd(II): Ouroboros IPC Resource Manager daemon started...
+==26504== irmd(II): Created IPCP 27317.
+==27317== ipcpd/eth-llc(II): Using raw socket device.
+==27317== ipcpd/eth-llc(DB): Bootstrapped IPCP over Ethernet with LLC
+with pid 27317.
+==26504== irmd(II): Bootstrapped IPCP 27317 in layer eth.
+```
+
+If it failed, you may have mistyped the interface name, or your system
+may not have a valid raw packet API. We are using GNU/Linux machines, so
+the IPCP announces that it is using a [raw
+socket](http://man7.org/linux/man-pages/man2/socket.2.html) device. On
+OS X, the default is a [Berkeley Packet Filter
+(BPF)](http://www.manpages.info/macosx/bpf.4.html) device, and on
+FreeBSD, the default is a
+[netmap](http://info.iet.unipi.it/~luigi/netmap/) device. See the
+[compilation options](/compopt) for more information on choosing the
+raw packet API.
+
+The Ethernet layer is ready to use. We will now create a normal layer
+on top of it, just like we did over the local layer in the second
+tutorial. We are showing some different ways of entering these
+commands on the two machines:
+
+```
+node0:
+$ irm ipcp bootstrap type normal name normal_0 layer normal_layer
+$ irm bind ipcp normal_0 name normal_0
+$ irm b i normal_0 n normal_layer
+$ irm register name normal_layer layer eth
+$ irm r n normal_0 l eth
+node1:
+$ irm ipcp enroll name normal_1 layer normal_layer autobind
+$ irm r n normal_layer l eth
+$ irm r n normal_1 l eth
+```
+
+The IPCPs should acknowledge the enrollment in their logs:
+
+```
+node0:
+==27452== enrollment(DB): Enrolling a new neighbor.
+==27452== enrollment(DB): Sending enrollment info (47 bytes).
+==27452== enrollment(DB): Neighbor enrollment successful.
+node1:
+==27720== enrollment(DB): Getting boot information.
+==27720== enrollment(DB): Received enrollment info (47 bytes).
+```
+
+You can now continue to set up a management flow and data transfer
+flow for the normal layer, like in tutorial 2. This concludes the
+fourth tutorial.