User`s guide

6: ADCCP NRM Line-Monitor Function
DC 900-1317J 111
The normal ICP response to the Configure Monitor command is the same command
(
usProtCommand field set to DLI_PROT_START_LINK_TRACE). However, if the command was
sent to a Link Session, a
DLI_PROT_RESP_ERROR response (Section 3.4.28 on page 80) is
returned to the client. Apart from Attach and Detach, only the Configure Monitor
command is valid for the Monitor Session. If any other command is sent to the Monitor
Session, a
DLI_PROT_RESP_ERROR response is returned to the client.
6.3 Reporting Frames to the Client
All transmitted and received frames for the monitored links are reported to the client
on the Monitor Session, with a Monitor Data Notification (
usProtCommand field set to
DLI_PROT_MONITOR_DATA). The usProtLinkID and iProtModifier fields are not used. The rest
of the Optional Arguments are set per Figure 3–1 on page 51.
The data reported with the Monitor Data Notification consists of an image of the entire
transmitted or received frame. There is one exception to this: transmitted frames are
conveyed to the client without their FCS octets, since the FCS is generated on the fly by
hardware operations as each octet is released to the line, without being made available
to the software.
A fixed 24-byte header precedes the frame image. This header is rendered as a “C”-lan-
guage structure in Figure 6–1. Its fields are described next.
typedef struct {
unsigned int usTime; // time-stamp
unsigned char usEvent; // event type (1,2)
unsigned char usLinkID; // link ID (0-7)
unsigned short usLength; // length of frame
unsigned short usSequence; // seq. # for rcvd I-frames
unsigned char usFiller[2]; // 0-fill to 12 bytes
FRAME_ABSTRACT Abstract; // 12-byte abstract
} MESSAGE_HEADER; // total of 24 bytes
Figure 6–1: Monitor Data Notification Header