Cisco 15327 - Manual (Page 436)

26-4
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 26 Configuring IEEE 802.17b Resilient Packet Ring
RPR-IEEE Framing Process
Figure 26-2 RPR-IEEE Data Frames
Table 26-1 defines the most important fields in the RPR-IEEE data frame.
1 TTL to Dest
Base Control
FCS
Service Data Unit
Protocol Type
MAC da
TTL Base
MAC sa
Extended Control
hec
6
1
1
6
1
2
2
n
4
Header
Payload
Trailer
1
6
1
1
6
1
2
6
6
2
TTL to Dest
Base Control
Protocol Type
Extended SA
Extended DA
MAC da
TTL Base
MAC sa
Extended Control
hec
FCS
Service Data Unit n
4
Header
Payload
Trailer
Basic Data Frame
Extended Data Frame
151965
Table 26-1 Definitions of RPR-IEEE Frame Fields
Field Definition
MAC Destination Address
(MAC da) A forty-eight-bit field specifying the destination as a multicast MAC
address or the MAC address of a specific ML-Series card in the
RPR-IEEE.
MAC Source Address (MAC sa) A fourth-eight-bit field specifying the MAC address of a specific
ML-Series card in the RPR-IEEE as the source.
Base Control A field that includes the ring indicator (RI) bit, the fairness eligible
(FE) bit, the frame type (FT) bit, and the service class (SC) bit.
TTL Base A field that contains the time to live (TTL) setting. The sending station
sets the TTL, which remains unchanged for the life of the packet.
Extended Control A field that contains the flood indicator (FI) bit and the strict order
(SO) bit.
Extended DA A forty-eight-bit field specifying the MAC address of the ultimate
destination.
Extended SA A forty-eight-bit field specifying the MAC address of the ultimate
source.