The fields are not used.
?– The Protocol Field is not used.
Figure 12.21 MAC relationship with the physical sublayers
Application
Presentation
Session
Transport
Network
Data-link
Physical
OSI reference
model layers
MAC data path
PRS-1 or PRS-10 GRS SRS
PHY service
interface
SPI-X
HDLC-like
adaptation
GFP adaptation
SONET/SDH PHY
Packet PHY
GMII
XGMII
XAUI
MDI
Medium Medium
Resilient Packet Ring (RPR) 355
?– The FCS is neither computed nor appended to the frame.
?– The asynchronous control character map (ACCM) is not used.
LAPS framing for RPR complies with ITU-T X.85 /Y.1321.
Drivers for This Solution
The Ethernet we use today is significantly different than the Ethernet that was originally
created in the IEEE 802.3 group. It is now full duplex and has lost CSMA/CD
as an access method. It has new physical interfaces, different data rates, new port aggregation
features, VLAN functions and many other modifications that have been introduced
over the years to facilitate new applications and uses. In many ways the RPR
MAC is another case of an IEEE standard that facilitates the evolution of Ethernet, in
this case, to the WAN environment.
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