# 13.3. IPOP2 (IP-over-P2P)¶

IPOP (IP-over-P2P) is a software-defined virtual network that can be used as a basis for creating virtual private clusters across multiple cloud providers and administrative domains. IPOP is architected as a peer-to-peer (P2P) overlay for tunneling and routing of encapsulated IP packets that are captured/injected into virtual network interfaces (v-NICs). The IPOP software consists of P2P routers that run on endpoints that are connected to the virtual network, such as virtual machines (VMs) distributed across multiple cloud providers.

This tutorial provides step-by-step instructions for deploying a minimal independent P2P overlay upon which you can run IP-over-P2P (IPOP) virtual private networks. This tutorial is a follow-up to the introductory IPOP tutorial, which guides you through the process of connecting two VMs by using a public P2P overlay that runs on PlanetLab resources. In this follow-up tutorial, you will learn how to deploy your own P2P overlay which can be used instead of PlanetLab’s public overlay. This is useful if you plan to deploy your own isolated IPOP overlays for private overlay networks.

## 13.3.1. Prerequisites:¶

• It is a pre-requisite that you have gone through the introductory IPOP tutorial
• Basic knowledge of Unix/Linux command line tools

## 13.3.2. Step 1: Bringing up Alice and Bob VMs¶

The first step in this tutorial is to deploy at least two virtual machines which will be connected by an IPOP virtual network. Please follow the instructions of the introductory IPOP tutorial before you continue; is assumed you have started two VMs “Alice” and “Bob” as described in that tutorial before proceeding to the next step.

## 13.3.3. Step 2: Disconnecting Alice and Bob VMs from the PlanetLab P2P overlay¶

The instructions of the introductory IPOP tutorial work by connecting Alice and Bob through an IPOP configuration where the P2P overlay runs on PlanetLab. You will now disconnect the two VMs from this IPOP network before you configure them to connet through a different P2P overlay - one which you will set up in the next step.

Disconnect Alice and Bob from IPOP and make sure IPsec is disabled, by running these commands, as root, on both Alice and Bob:

/etc/init.d/groupvpn.sh stop
/etc/init.d/racoon stop
setkey -F
setkey -FP


## 13.3.4. Step 3: Deploy Pam, a P2P Bootstrapping VM¶

Now you will deploy a VM that will run a small P2P overlay from which you can bootstrap your independent IPOP system - we will refer to this third VM as “Pam” in the rest of the tutorial.

Any of the options described in the introductory IPOP tutorial work (FutureGrid, EC2, VMware) will work here, as long as the “Pam” VM can be reached by both “Alice” and “Bob” through the Internet. In general, “Pam” should be a machine deployed with a public IP interface (e.g. in EC2 or FutureGrid). (If you run “Pam” on your own desktop using VMware/VirtualBox, it is likely not to have a public IP interface - but it should work for this tutorial, as long as Alice and Bob are also deployed in the same computer).

Before you continue to the next step:

• Deploy the Pam VM using the method of your choice
• This can be found by using the “ifconfig” command and looking for the “eth0” interface.
• We will refer to this IP address as IP_Pam in the remainder of this tutorial.

## 13.3.5. Step 4: Configure Pam to run P2P Bootstrapping Overlay¶

First, download a zip archive with template configuration files and scripts prepared for this tutorial, on Pam, as root:

wget http://www.acis.ufl.edu/~renato/ipopdemo/bootstrap/bootstrap\_demo.zip
apt-get install unzip
unzip bootstrap\_demo.zip


Now run the configuration script; you need to provide three parameters: a P2P namespace string, the IP_Pam address, and a port.

• The P2P namespace is akin to the IPOP namespace of the previous tutorial, but it establishes a name that P2P nodes joining the same overlay agree on. For simplicity, you can use the same namespace you chose in the previous tutorial
• The IP_Pam address and port configure the network endpoint that other nodes (Alice and Bob) will use to join the P2P overlay. By default, we’ll use port 40000 in this tutorial, but you are free to choose another number if you’d like.
Configure these parameters by running *on Pam, as root, and

replacing Namespace and IP_Pam as appropriate*:

./bootstrap\_demo\_prepare.sh P2PNamespace IP\_Pam 40000


This creates a XML configuration file called “bootstrap.config”. You can take a look at this file and check where the information is stored; it should look like this:

<?xml version="1.0"?>
<NodeConfig>
<BrunetNamespace>P2PNamespace</BrunetNamespace>
<EdgeListeners>
<EdgeListener type="udp">
<port>40000</port>
</EdgeListener>
</EdgeListeners>
<RemoteTAs>
<Transport>brunet.udp://IP\_Pam:40000</Transport>
</RemoteTAs>


Brunet is the name of the P2P software “under the hood” of IPOP. This configuration tells Brunet to listen on endpoint, IP_Pam:40000, on protocol UDP. It is possible to also configure the P2P overlay to use TCP, but UDP is preferrable in most cases as it supports NAT traversal. Other nodes (Alice, Bob), will be configured to contact these endpoints. Now run the P2P bootstrapping code with this configuration, as follows:

(Note: this command first installs mono, if it’s not already installed on the VM, which may take a few minutes to complete):

./run\_bootstrap\_node.sh ./bootstrap.config


## 13.3.6. Step 5: Configure Alice and Bob to use Pam as P2P overlay¶

Now you will change the configuration of IPOP on Alice and Bob to use Pam instead of PlanetLab for bootstrapping. To do so, run the following commands, on Alice and Bob, as root:

mkdir tmp
cd tmp
wget http://www.acis.ufl.edu/~renato/ipopdemo/bootstrap/bootstrap\_demo.zip
unzip bootstrap\_demo.zip


For the following command, *make sure you use the same exact parameters you configured for Pam*:

./bootstrap\_demo\_prepare.sh P2PNamespace IP\_Pam 40000


Place the configuration file where IPOP can find it:

cp bootstrap.config /opt/ipop/etc/node.config


Start IPOP:

/etc/init.d/groupvpn.sh start


## 13.3.7. Step 6: Send messages between Alice and Bob¶

The Alice and Bob VMs are now configured with the same virtual IP addresses as in the previous tutorial, and the same operations you have done then (ping, IPsec, etc), should also work here - the main difference being that your overlay is not confined to Alice, Bob, and Pam, and is independent of PlanetLab.

## 13.3.8. 7.1) Inspecting the P2P network¶

The previous steps show how you can create a separate overlay network; from a user’s perspective (Alice and Bob), it does not look very different from the previous tutorial. If you are curious as to whether the overlay is indeed connected through Pam, you can run the following command:

/opt/ipop/bin/crawl.py


This will “crawl” the P2P network node by node and dump statistics about nodes and connections. You should see an output that looks like this:

Total Nodes: 18
Consistent Nodes: 18
Consistency: 1.0
Connections: 296
SecurityAssociations: 0
WrappedEdges: 0
Edges: 469
RelayEdges: 15
SubringEdges: 0
TcpEdges: 54
UdpEdges: 400
Crawl took: 1.07016801834


There should be a total of 18 P2P nodes; 16 of the nodes are running in a single VM (Pam) to create a small overlay-in-a-node, while the remaining two nodes are Alice and Bob.

You can also check how the mapping between IPOP IP and P2P identifiers mapping works by querying the DHT. On Alice, check what P2P identifier it has been assigned by executing:

grep node /opt/ipop/etc/node.config


You should get an output that looks like this:

<NodeAddress>brunet:node:X33YDT5FA3GTBQ3Q5AJ3PNE3YQSRNRBQ</NodeAddress>


Alice’s P2P identifier is a self-assigned randomly generated 160-bit long integer encoded as a string (X33YDT5FA3GTBQ3Q5AJ3PNE3YQSRNRBQ). If you check Bob, you will see its identifier is a different 160-bit number.

If you query the DHT for the IPOP namespace you chose, and for Alice’s IP address, you will see that it maps to this P2P identifier. Query the DHT with this command, replacing the IPOP namespace appropriately:

/opt/ipop/bin/bget.py dhcp:IPOPnamespace:192.168.10.10


And you will see it maps to Alice’s P2P identifier. Substitute for Bob’s IPOP address and query the DHT again.

## 13.3.9. 7.2) Adding fault tolerance by deploying multiple bootstrap nodes¶

In this example, we only deployed one overlay bootstrapping VM - Pam. In practice, this is not a very good idea, as Pam becomes a central point of failure - if it crashes, the network loses connectivity. In practice, IPOP bootstrap overlays span across multiple nodes; the network is then resilient to failures of a fraction of the nodes. The PlanetLab overlay used in the previous tutorial, for instance, runs hundreds of nodes where it is not uncommon for dozes of nodes to crash/reboot every day.

If you want to deploy a multi-node IPOP overlay, the overall approach is to add to the bootstrap.config file of each bootstrapping node the IP:port endpoints of all the other bootstrapping nodes, and use this list of endpoints in the /opt/ipop/etc/node.config files of each node that joins IPOP.