352 Chapter 12
Figure 12.18 Data frame formats
Basic frame format
ttl
ttl
base vontrol
base vontrol
da
da
sa
sa
ttl base
ttl base
extended control
extended control
hec
hec
protocol type protocol type
sdu sdu
facs facs
1
1
6
6
1
1
2
2
n
4
Extended frame format
da extended
sa extended
Covered by HEC
Covered by HEC
Covered by FCS
Covered by FCS
1
1
1
1
6
6
6
6
2
2
n
4
Figure 12.19 Control frames format
Basic frame format
ttl
base vontrol
da
sa
ttl base
extended control
hec
protocol type
sdu
facs
1
1
6
6
1
1
2
2
n
4
Covered by HEC
Covered by FCS
Control type
value
Name
01 CT_STATION_ATD
02 CT_TOPO_PROT
03 CT_TOPO_CHKSUM
04 CT_LRTT_REQ
05 CT_LRTT_RSP
06 CT_FDD
07 CT_OAM_ECHO_REQ
08 CT_OAM_ECHO_RSP
09 CT_OAM_FLUSH
0A CT_OAM_ORG
Resilient Packet Ring (RPR) 353
Figure 12.20 illustrates the fairness and idle frame formats. For fairness frames, the
saControl field specifies the station that provided the values contained in the fairness-
Header and fairRate fields. This station is not necessarily the station that generated
this frame, which is always the upstream neighbor.
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