Hosting an Ark Monitor: Archipelago Memorandum of Cooperation (MOC) Between Hosting Sites and CAIDA

(version 2, 2023/08/20)

A site wishing to host an Ark node (Ark monitor) should first review and approve this Memorandum of Cooperation (MOC), which outlines the obligations and expectations of both CAIDA and the hosting site. See the FAQ for sites interested in hosting an Ark monitor for common questions about hosting.

A one-page flyer, "Why should my network host an Ark node?" is available for sharing.

This MOC concerns data collection and node usage between CAIDA and your organization as a Hosting Site for an Archipelago (Ark) node(s). CAIDA and your organization understand and agree that you are providing Ark hosting without fee in exchange for its use in valuable scientific research related to promoting a robust and scalable global Internet infrastructure.

For historical purposes, version 1 (2010/09/02) of this MOC is also made available.

CAIDA Obligations and Expectations

In pursuit of this research purpose, CAIDA aims to be a responsible steward of the measurement infrastructure hosted by your organization and will conduct measurements that are ethical, conform to best practices, respect your policies, and do not impose an unacceptable burden on your network.

CAIDA intends for Ark to support broad scientific study of the global Internet infrastructure. To this end, we are designing measurement capabilities for use by internal CAIDA researchers and suitably vetted third parties. All measurements are vetted to conform to community best practices regarding respect for network and system resources. The platform enforces reasonable limits on measurement rate and volume. CAIDA also maintains a “no probe” list for applicable measurements to comply with end-user requests to opt-out of future measurements. Hosting sites should forward to us any complaints they receive from end users who have received measurement traffic, and we will respond to the complaints (letting the hosting site know of our responses) and, if necessary, add destinations to our no-probe list to prevent future complaints. For over two decades, CAIDA has maintained and obligated users of CAIDA data and infrastructure to adhere to a no-probe list for topology measurements.

Typical uses of Ark nodes include:

  • topology measurements such as ICMP, TCP, and UDP traceroute and ping measurements to a broad cross section of the routed address space;
  • Performance measurements such as one-way delay, loss, and jitter; and,
  • Measurements of or leveraging DNS infrastructure
  • Measuring the prevalence of IP source-address filtering (BCP 38) among networks attached to the Internet.

An informative FAQ provides more details about expected usage patterns and incoming and outgoing traffic details at

CAIDA will remotely manage the Ark monitor (hardware or software) to fulfill our intention of minimizing the ongoing effort and involvement needed by the hosting site after initial installation and setup of the server. Specifically, this includes managing user accounts, installing software, applying security patches, and upgrading the container or operating system. However, CAIDA will provide a system administration account on the monitor for the hosting site if requested (note: dedicated hardware can be cleanly powered down on short notice without logging in by simply pushing the power button, and this feature satisfies the most common need for a local account).

Hosting Site Obligations and Expectations

To support the primary goal of comprehensive and continuous long-term measurements, CAIDA requests the following deployment environment and operational support, where possible:

  1. The Ark monitor is either a dedicated 1U server placed in a server rack, a small form-factor computer (such as a Raspberry Pi) placed in any suitable location, or an image running in a virtualized environment.
  2. For hardware deployments, the hosting site provides physical administration (“remote hands”) at the system console to troubleshoot and revive a nonfunctioning Ark monitor if a problem cannot be resolved by CAIDA remotely. We ask that the hosting site respond to these requests on a best-effort basis.
  3. The hosting site notifies CAIDA of any scheduled maintenance that may disrupt power to the system so that CAIDA may cleanly shut down the node.
  4. The hosting site whitelists the persistent contact address that CAIDA will use for all monitor-related communication; and,
  5. The hosting sites designates an email contact for Ark-related communication, and a physical address of the node for shipping replacement hardware/parts (and for geolocation of measurements), and notifies CAIDA of updates in the contact address.

In addition, the hosting site may need to make adjustments to the network environment to accommodate an Ark monitor. For example:

  1. The IP address of an Ark monitor may need to be put into an exception list for security monitoring and firewalls. In particular, the hosting site may need to relax firewall rules to allow the anticipated set of measurement probes and responses (please see the firewall configuration section of
  2. Rate-limiting of ICMP probes and responses to the system should be removed. Certain implementations of rate limiting (for example, dropping 50% of all ICMP packets) will significantly impair even low-rate measurements and thus the utility of the host.


This MOC will remain in effect until either CAIDA or the hosting site indicates in writing (email) its decision to terminate the cooperative arrangement described herein. Upon termination, CAIDA and the hosting site will discuss and agree to either dispose of or return any CAIDA-provided hardware.


CAIDA welcomes your comments and/or concerns regarding the obligations and expectations described in this MOC. If you believe that CAIDA or one of its Collaborators has not adhered to these provisions, or if you later determine a specific use to be unacceptable, please contact us at We will use best reasonable efforts to promptly work with you to determine and remedy any problem.

Complete the form to host an Ark monitor

If you are interested in hosting an Ark node, please complete the form below acknowledging the MOC along with some contact information so we can follow up with you about sending you an Ark node to deploy.

Acknowledgment of MOC

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