Using CDN Attribution

The use of CDN attribution in Kentik is covered here.

Note: To use CDN attribution, at least one of your DNS servers must be running Kentik's Universal Agent with the DNS OTT Tap Capability enabled (see Universal Agents).

About CDN Attribution

Mapping IPs to CDNs is challenging in practice due to these two infrastructure scenarios:

• CDN-owned Infrastructure: Each CDN runs its own ASN(s), with their own PoPs running their own cache servers

• ISP-embedded infrastructure: Many CDNs rely on ISP-embedded caching servers for better last mile performance, typically by directing users of a given ISP to CDN nodes co-located at the local ISP, closer to the end-users.

Different CDNs blend these scenarios, e.g., commercial and multi-tenant CDNs vs. single-purpose CDNs. Kentik’s dynamic algorithms allow IP mapping across the spectrum: a base mapping lists ASNs by CDN and their originated IP ranges, while a more dynamic layer uses DNS traffic (upon ISP agreement) to deduce the remaining mappings.

Kentik’s CDN attribution system is self-learning and updates daily. It continuously discovers new CDNs and IPs (caching servers) as they emerge.

Enabling CDN Attribution

Preparing your Kentik setup for CDN attribution involves the following tasks:

• Deploy the Universal Agent software on at least one of your DNS servers (see Universal Agents).

• Enable the DNS OTT Tap Capability on each agent.

• Configure the corresponding device (in the Kentik portal or via Device API) to send DNS data to Kentik.

To configure CDN attribution in the Kentik portal:

1. Choose Settings » Networking Devices from the main nav menu to open the Devices page.

2. Open the Device settings dialog:

   1. To register a new DNS server with Kentik, click the Add Device button.

   2. To change the CDN attribution settings of an existing DNS server, click the Edit button (pencil icon) at the right of the device’s row in the Device List.

3. If you're registering a new device, on the General tab of the dialog set the Flow Device Type field to Kentik Host Agent.

4. On the General tab, turn on the Contribute to CDN Attribution switch.

5. Set the remaining settings on the dialog's tabs as needed (see Device Settings).

6. Click Save button to save changes and return to the Devices page. If you added a new device, it will now be shown in the Device list.

Note: DNS servers covering different geographical zones usually result in distinct, non-overlapping, IP-to-CDN mappings. Kentik recommends deploying Universal Agents on as many DNS servers as possible to export the best IP-to-CDN mapping data to KDE. This approach also provides granular NPM metrics for those devices.

Applying CDN Attribution

Once you've registered one or more DNS servers with Kentik and configured them for CDN attribution, the flow records stored for those devices in KDE (see KDE Tables) will include CDN Attribution Dimensions. You will now be able to use those dimensions in Kentik queries:

• To use source or destination CDN as a group-by dimension, see Dimension Selectors.

• To use source or destination CDN as a filter (as shown in the screenshot below), see Filters Pane.

Using CDN for filters or group-by dimensions in Data Explorer or Dashboard queries can reveal (among other things) how much of your traffic is coming from (shown in screenshot below) or going to various CDNs.

CDN Attribution Dimensions

CDN attribution makes it possible for Kentik to determine whether a given flow record originated or terminated with a commercial CDN, and to store that information for each record using the following two columns of the Kentik Data Engine (KDE):

• src_cdn: The commercial name of the CDN derived from the source IP (inet_src_addr) of an ingested flow.

• dst_cdn: The commercial name of the CDN derived from the destination IP (inet_dst_addr) of an ingested flow.

  Note: This dimension enables you to track "fill traffic" that is pointed toward a CDN server to fill a local cache.

Once stored in KDE (see KDE Tables), the columns can be used for both group-by dimensions and filters in Kentik queries (e.g., in Data Explorer, Dashboards) as described in Applying CDN Attribution.