Endace DAG 5.2X, User Manual

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EDM01-33v1 DAG_7.5G4_Card_User_Guide
58 ©2008 Endace Technology Ltd. Confidential - Version 1 - November 2008
Extension Headers (EH)
Introduction
The addition of an Extension Header into the ERF record allows extra data relating to the
packet to be transported to the host. The extension header allows certain features to be added
independently of ERF types, for example, features shared by different ERF records do not
have to be implemented separately. This results in automatic support across ERF types.
Bit 7 of the ERF type field is used to indicate that Extension Header's are present. If set to '1'
Extension Headers are present. The Extension Header type field indicates the type and
format of the Extension Header. It also indicates whether further Extension Headers are
present. If bit 7 of the Extension Header is set to '1' further Extension Headers exist in the
record. The Extension Headers are 8 bytes in length.
The following diagram shows presence of an Extension Header in addition to the ERF record.
The following diagram shows presence of two Extension Headers with Bit 7 of the first
Extension Header set to '1'.