Edgio-specific HTTP headers for Azure Content Delivery Network rules engine

For Azure CDN Premium from Edgio products, when an HTTP request is sent to the origin server, the point of presence (POP) server can add one or more reserved headers (or proxy special headers) in the client request to the POP. These headers are in addition to the standard forwarding headers received. For information about standard request headers, see Request fields.

If you want to prevent one of these reserved headers from being added in the Azure content delivery network POP request to the origin server, you must create a rule with the Proxy Special Headers feature in the rules engine. In this rule, exclude the header you want to remove from the default list of headers in the headers field. If you've enabled the Debug Cache Response Headers feature, be sure to add the necessary X-EC-Debug headers.

For example, to remove the Via header, the headers field of the rule should include the following list of headers: X-Forwarded-For, X-Forwarded-Proto, X-Host, X-Midgress, X-Gateway-List, X-EC-Name, Host.

The following table describes the headers that you can add to the Edgio content delivery network POP in the request:

Request header	Description	Example
Via	Identifies the POP server that proxied the request to an origin server.	HTTP/1.1 ECS (dynamic content acceleration (DCA)/1A2B)
X-Forwarded-For	Indicates the requester's IP address.	10.10.10.10
X-Forwarded-Proto	Indicates the request's protocol.	HTTP
X-Host	Indicates the request's hostname.	cdn.mydomain.com
X-Midgress	Indicates whether the request was proxied through an extra content delivery network server. For example, a POP server-to-origin shield server or a POP server-to-ADN gateway server. This header is added to the request only when mid-gress traffic takes place. In this case, the header is set to 1 to indicate that the request was proxied through an extra content delivery network server.	1
Host	Identifies the host and the port where the requested content might be found.	marketing.mydomain.com:80
X-Gateway-List	ADN: Identifies the failover list of ADN Gateway servers assigned to a customer origin. Origin shield: Indicates the set of origin shield servers assigned to a customer origin.	icn1,hhp1,hnd1
X-EC-<name>	Request headers that begin with X-EC (for example, X-EC-Tag, X-EC-Debug) are reserved for use by the content delivery network.	waf-production

Via request header

The format through which the Via request header identifies a POP server gets specified by the following syntax:

Via: Protocol from Platform (POP/ID)

The terms used in the syntax are defined as follows:

• Protocol: Indicates the version of the protocol (for example, HTTP/1.1) used to proxy the request.

• Platform: Indicates the platform on which the content was requested. The following codes are valid for this field:

  Code	Platform
  ECAcc	HTTP Large
  ECS	HTTP Small
  ECD	Application delivery network (ADN)

• POP: Indicates the POP that handled the request.

• ID: For internal use only.

Example Via request header

Via: HTTP/1.1 ECD (dca/1A2B)

Host request header

The POP servers overwrite the Host header when both of the following conditions are true:

• The source for the requested content is a customer origin server.
• The corresponding customer origin's HTTP Host Header option isn't blank.

The Host request header is overwritten to reflect the value defined in the HTTP Host Header option. If the customer origin's HTTP Host Header option is set to blank, then the Host request header that gets submitted by the requester is forwarded to the customer's origin server.

X-Gateway-List request header

A POP server add/overwrite the X-Gateway-List request header when either of the following conditions are met:

• The request points to the ADN platform.
• The request is forwarded to a customer origin server that is protected by the Origin Shield feature.