Ace ACE-3105, Инструкция по установке и эксплуатации

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Chapter 1 Introduction Installation and Operation Manual
1-22 Functional Description ACE-3105, ACE-3205 Ver. 5.2
• ATM pseudowire (PW) over Ethernet
•
ATM cross-connect (XC) over E1 UNI/IMA or STM-1 UNI.
MPLS Utilization
ACE-3105, ACE-3205 provides the following MPLS-related features:
• Label Distribution Protocol (LDP)
• Penultimate Hop Popping (PHP)
.
Label Distribution Protocol (LDP)
With an appropriate license, ACE-3105, ACE-3205 optionally allows using the label
distribution protocol (LDP) to automatically assign and distribute pseudowires
and tunnel labels between MPLS peers (up to 32 peers). When LDP is enabled,
labels (tunnels or PWs) are set automatically.
Figure 1-15. LDP Definitions and Connectivity
For more information, refer to
Configuring the LDP Signaling Protocol
in
Chapter 4.
Penultimate Hop Popping (PHP)
Penultimate Hop Popping (PHP) is a packet-level modification process in which
the label switched router (LSR) removes (pops) the last label of MPLS packets
before they are passed to an adjacent label edge router (LER). The PHP mode is
relevant only when some signaling protocols are in use.
When PHP mode is enabled:
• The receiving LER advertises an implicit null label (a reserved label value of 3)
for directly connected routes. The implicit null label causes the previous hop
(penultimate) router to remove the most outer label before transmitting the
packet to the LER.
• Every packet received over MPLS (regardless of the number of labels) is
regarded as data packet and is forwarded to the PW module.
• The control (IP) traffic is received as raw IP.
•
Configuration of PW connections with static ingress tunnel label is allowed in
order to allow backward compatibility.