Services
7750 SR OS Services Guide Page 49
SDP Encapsulation Types
The Alcatel-Lucent service model uses encapsulation tunnels through the core to interconnect
service edge routers. An SDP is a logical way of referencing the entrance to an encapsulation
tunnel.
The following encapsulation types are supported:
• Layer 2 within generic routing encapsulation (GRE)
• Layer 2 within RSVP signaled, loose hop non-reserved MPLS LSP
• Layer 2 within RSVP signaled, strict hop non-reserved MPLS LSP
• Layer 2 within RSVP-TE signaled, bandwidth reserved MPLS LSP
• Layer 2 with LDP signaled
GRE
GRE encapsulated tunnels have very low overhead and are best used for best-effort (be) class of
service. Packets within the GRE tunnel follow the IGP (interior gateway protocol) shortest path
from edge to edge. If a failure occurs within the service core network, the tunnel will only
converge as fast as the IGP itself. If ECMP (equal cost multi-path) routing is used in the core,
many loss-of-service failures can be minimized to sub-second timeframes.
MPLS
Multi-Protocol Label Switching (MPLS) encapsulation has the following characteristics:
• LSPs (label switched paths) are used through the network, for example, primary,
secondary, loose hop, etc. These paths define how traffic traverses the network from point
A to B. If a path is down, depending on the configuration parameters, another path is
substituted.
Paths can be manually defined or a constraint-based routing protocol (e.g., OSPF-TE or
CSPF) can be used to determine the best path with specific constraints.
• An MPLS 7750 SR router supports both signaled and non-signaled LSPs through the
network.
• Non-signaled paths are defined at each hop through the network. This is also referred to as
static LSPs.
• Signaled paths are communicated via protocol from end to end using resource reservation
protocol (RSVP).
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