Services
7750 SR OS Services Guide Page 37
SAP Encapsulation Types and Identifiers
The encapsulation type is an access property of a service Ethernet port or SONET/SDH or TDM
channel. The appropriate encapsulation type for the port or channel depends on the requirements
to support multiple services on a single port/channel on the associated SAP and the capabilities of
the downstream equipment connected to the port/channel. For example, a port can be tagged with
IEEE 802.1Q (referred to as dot1q) encapsulation in which each individual tag can be identified
with a service. A SAP is created on a given port or channel by identifying the service with a
specific encapsulation ID.
Ethernet Encapsulations
The following lists encapsulation service options 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. The encapsulation ID is
always 0 (zero).
• Dot1q — Supports multiple services for one customer or services for multiple customers
(Figure 7). For example, the port is connected to a multi-tenant unit (MTU) device with
multiple downstream customers. The encapsulation ID used to distinguish an individual
service is the VLAN ID in the IEEE 802.1Q header.
• QinQ — The qinq encapsulation type adds a IEEE 802.1Q tag to the 802.1Q tagged
packets entering the network to expand the VLAN space by tagging tagged packets,
producing a double tagged frame.
SONET/SDH Encapsulations
There are several encapsulation service options on SONET/SDH channels:
• Internet Protocol Control Protocol (IPCP) — Supports a single IP service on a SONET/
SDH port or a single service per channel (if the interface is channelized). This is typically
used for router interconnection using point-to-point protocol (PPP).
• Bridging Control Protocol (BCP-null) — Supports a single service on the SONET/SDH
port or a single service per channel (if the interface is channelized). This is used for
bridging a single service between two devices using PPP over SONET/SDH. The
encapsulation ID is always 0 (zero).
• Bridging Control Protocol (BCP-dot1q) — Supports multiple services on the SONET/
SDH port/channel. This encapsulation type is used for bridging multiple services between
two devices using PPP over SONET/SDH. The encapsulation ID used to distinguish
services is the VLAN ID in the IEEE 802.1Q header in the BCP-encapsulated frame.
• ATM — ATM, ATM-FR, ATM SAP-bridge encapsulation termination Epipe and VPLS.
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