Service Entities
Page 44 7705 SAR OS Services Guide
The encapsulation ID is an optional suffix that is appended to a port-id to specify a logical
sub-element for a SAP. For example, a port can be tagged to use IEEE 802.1Q encapsulation
(referred to as dot1q), where each individual tag can identify with an individual service. The
encapsulation ID for an ATM SAP is a special case because it requires that a channel group
identifier (which always uses the value 1) precede the VPI/VCI value.
Ethernet Encapsulations
The following encapsulation service options are available on Ethernet ports:
• null — supports a single service on the port; for example, where a single customer
with a single service customer edge (CE) device is attached to the port.
• dot1q — supports multiple services for one customer or services for multiple
customers (see Figure 3). An example of dot1q use might be the case where the
Ethernet port is connected to a multi-tenant unit device with multiple downstream
customers. The encapsulation ID used to distinguish an individual service is the
VLAN ID in the IEEE 802.1Q header.
SONET/SDH Encapsulations
The following service encapsulation option is available on SONET/SDH ports:
• atm — supports multiple services for one customer
Notes:
• Throughout this guide, the term “channel group” is often simplified to “channel”.
• Do not confuse the term “encapsulation ID” (described here) with the term “Encapsulation
ID”, which is used with the SNMP and MIBs for the 7705 SAR.
Figure 3: Multiple SAPs on a Single Port/Channel
19480
Customer
27
Customer
27
Customer
9
Network
SDP
Service
Service
SAP
1/1/5
dot1q
SAP
1/1/6
dot1q
SAP
1/2/3
dot1q
Service
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