ATM LSR

Reference: A white paper from Juniper NetworksAppendix I: Cell-switched MPLS Operational Model

in“Migration Strategies for IP Service Growth: Cell-

switched MPLS or IP-routed MPLS” by Chuck Semeria

ATM LSR

ATM LSR

Unique features of ATM LSRs: • Must exchange control-plane IP packets over an

ATM-control VC. SAR is required• Use of VCI or VPI/VCI fields to carry label• Pushing or popping labels within an ATM LSR

domain is not supported• New mechanisms for detecting and preventing

loops

ATM LSRShips-in-the-Night

ATM LSRShips-in-the-Night

• Issues: – Label space partitioning– Resource partitioning– CoS and QoS support

ATM LSR

Using both VPI and VCI fields for direct connection:

ATM LSR

Using VCI Field for Indirect Connection:

ATM LSR

Frame based MPLS encapsulation:

ATM LSR

Cell based MPLS encapsulation:

ATM LSR

Label Merging at frame based LSR

ATM LSR

VC Merge at ATM LSR:

ATM LSR

Advantages of ATM MPLS over IP over ATM: • Single control plane• Removing the need for N^2 full meshed

connectivity among edge routers• Simplify the QoS management: now CoS to LSP

mapping is possible• Native ATM can be supported

Problems: • Cell tax• SAR bottleneck