Link Selection and OAM

Version 01

Stephen Haddock

July 18, 2012

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Example Scenario

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Server

Client

Co-Location Facility

Data CenterNetwork

CarrierNetwork

• Client connects to a Server in a Co-Location facility

• A single VLAN is used to carry this service within the Data Center Network• All frames transmitted and received by Server are untagged.

• VLAN is monitored using CFM with Up MEPs at each interface to the Data Center Network.

Server connects with Link Aggregation

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• Server connects using Link Aggregation• 5-tuple hash used to distribute frames among LAG links.

• Up MEP sits above Link Aggregation• In practice, separation of the physical ports of the LAG may complicate

implementation of the MEP, forcing it to be either distributed between the ports or centralized but not resident on a single physical port.

Server

MAC Relay

VLAN (6.9)

Link Agg

MACMAC

Server

Link Agg

MACMAC

Server connects with DRNI

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Distributed Relay (EmulatedSystem C)

VLAN (6.9)

Link Agg

MACMAC

Server

Link Agg

MACMAC

MACMAC

(6.9) (6.9)

Server

B

A

MAC

(6.9)

Relay (B)

MAC

(6.9)

Relay (A)

Gateway Links (virtual)

• Server connects to two physically separate nodes (Systems A and B)

• The logical view, as seen from the point of view of the Server and the Data Center Network, is that there the Server connects to a third node (Emulated System C) through a single logical port.

Distributed Relay as seen by Systems A and B

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Distributed Relay (C)*

(6.9)

LAG*

MACMAC

Server

Link Agg

MACMAC

MAC MAC

(6.9)(6.9)

MAC

(6.9)

Relay (B)

MAC

(6.9)

MAC

(6.9)

Distributed Relay (C)*

(6.9)

LAG*

MAC

MAC

(6.9)

Relay (A)

IPL

Selected Gateway for this VLAN

• Link Selection still based on 5-tuple hash, so both LAG links carry data.

• Where does the Up MEP go?

Options for MEP Implementation

1. Distribute MEP functionality across the physical DRNI ports.– Requires standardizing how MEP functionality gets distributed.

– Almost certainly requires support from the Intra-Portal Protocol.

2. Distribute MEP functionality across the Intra-Portal Port and the DRNI ports in the system with the selected Gateway.– Distributes MEP functionality among ports in the same physical

system (which is the same problem that arises with today’s LAG).

– Intra-Portal Link is not included in the MA monitored by the MEP.

– MEP functionality moves when the selected Gateway changes.

3. Constrain the Link Selection such that all frames that would pass through the same MEP use the same DRNI link.– VERY restrictive constraint.

4. Are there any other options?

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2nd Example: DRNI at an I-tagged service interface

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Carrier BNetwork

Carrier ANetwork

• The service ID on an I-tagged service interface is the I-SID.• Link selection is by I-SID

• Multiple I-SIDs map into a B-VLAN in the Carrier A Network• The B-VLAN is monitored using CFM with Up MEPs at each interface to the

Carrier A Network.

I-taggedServiceInterface*

B

A

B-components (B-BEBs)

* Reference: 802-1Q Figure 25-9 and 26.6.2

I-tagged DRNI as seen by Systems A and B

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Distributed Relay (C)*

(6.11)

LAG*

MACMAC

MAC MAC

(6.9)(6.9)

MAC

(6.9)

Relay (B)

MAC

(6.9)

MAC

(6.9)

Distributed Relay (C)*

(6.11)

LAG*

MAC

MAC

(6.9)

Relay (A)

IPL

Selected Gateway for this B-VLAN

• Link Selection based on I-SID, so I-SIDs from both LAG links could map to the B-VLAN.

• Where does the Up MEP go?

Thank You

.

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