Alcatel-Lucent 7705 Service Manual page 50

Service Entities
With MPLS, the MTU for the network port permits the addition of labels for transmission
across the MPLS network. Ethernet frames that are sent out of a network port toward the
MPLS core network (or a P router) are allowed to be oversized in order to include the MPLS
labels without the need to fragment large frames. See
information.
The following ways of configuring an MPLS tunnel are supported:
GRE Encapsulation
Generic routing encapsulation (GRE) is one of the most common tunneling techniques in the
industry. GRE tunnels are used to transport various network layer packets and are especially
useful for facilitating pseudowires over IP networks. Since MPLS is a Layer 2.5 protocol,
MPLS packets cannot be natively transported over a Layer 3 (IP) network. Therefore, GRE
is the ideal alternative for applications where traffic must travel over a Layer 3 network; for
example, in DSL applications.
For the HSDPA offload application (see
are transported over IP using GRE tunneling. For other applications, Ethernet and TDM
pseudowires over GRE are also supported.
GRE SDPs are supported on any port of the 8-port Ethernet Adapter card (for the
7705 SAR-8) or any Ethernet port on the 7705 SAR-F. Up to 64 GRE tunnels are supported
per chassis.
GRE Format
In accordance with RFC 2784, a GRE encapsulated packet has the following format:
Delivery Header
The delivery header is always an IP header.
Page 50
• LDP signaled
• RSVP-TE signaled
• user-configured (static LSP)
• delivery header
• GRE header
• payload packet
MTU Settings on page 186
HSDPA Offload on page
7705 SAR OS Services Guide
for more
57), ATM pseudowires