Link Selection and OAM
Version 02
(added a Conclusion slide capturing the results of the
discussion following presentation on 9/12/12)
Stephen Haddock
September 13, 2012
1
Example Scenario
Co-Location Facility
Carrier
Network
Data Center
Network
Server
Client
• 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.
2
Server connects with Link Aggregation
MAC Relay
Server
VLAN (6.9)
Server
Link Agg
MAC
MAC
Link Agg
MAC
MAC
• 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.
3
Server connects with DRNI
B
Server
A
• 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.
Relay (B)
Relay (A)
Distributed Relay
(EmulatedSystem C)
(6.9)
Server
MAC
(6.9)
MAC
(6.9)
(6.9)
VLAN (6.9)
MAC
MAC
Link Agg
MAC
MAC
Link Agg
MAC
MAC
Gateway Links (virtual)
4
Distributed Relay as seen by Systems A and B
Relay (A)
Relay (B)
(6.9)
MAC
(6.9)
MAC
Selected Gateway for this VLAN
Distributed Relay (C)*
Distributed Relay (C)*
Server
(6.9)
(6.9)
(6.9)
(6.9)
(6.9)
(6.9)
MAC
LAG*
MAC
MAC
LAG*
MAC
MAC
MAC
Link Agg
MAC
MAC
IPL
• Link Selection still based on 5-tuple hash, so both LAG links carry data.
• Where does the Up MEP go?
5
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?
6
2nd Example: DRNI at an I-tagged
service interface
I-tagged
Service
Interface*
Carrier A
Network
Carrier B
Network
B
A
B-components (B-BEBs)
• 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.
* Reference: 802-1Q Figure 25-9 and 26.6.2
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I-tagged DRNI as seen by Systems A and B
Relay (A)
Relay (B)
(6.9)
MAC
(6.9)
MAC
Selected Gateway for this B-VLAN
Distributed Relay (C)*
Distributed Relay (C)*
(6.9)
(6.11)
(6.9)
(6.9)
(6.11)
(6.9)
MAC
LAG*
MAC
MAC
LAG*
MAC
MAC
MAC
IPL
• 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?
8
Conclusion on 9/12/12
• The conclusion of the discussion in the 802.1 Interworking
session on 9/12/12 was to favor a slightly different
expression of option 2:
The system that acts as the selected Gateway for a VLAN is
responsible for implementing an Up MEP monitoring that
VLAN (if such a MEP is configured).
– How the system implements the MEPs, i.e. whether the
functionality is distributed across multiple physical ports or
centralized somewhere in the system, is implementation dependent
and will not be specified in the standard.
– The Intra-Portal Link is outside the MA monitored by this MEP.
– The MEP functionality moves when the Gateway changes.
• The MEP state is not synchronized during such a move, which may result in
things such as a discontinuity in counters maintained by the MEP.
9
Thank You
.
10