Inter-network Ethernet Service Protection
Zehavit Alon
Nurit Sprecher
John Lemon
Slide 1
Agenda
• Inter-network Ethernet Service Protection
– Overview
– Requirements
– Network architecture
▪ Possible connectivity constructions between Ethernet Networks
▪ Recommended construction
– Proposed solution
• Open discussion and next steps
Slide 2
Ethernet Services over Interconnected Networks
• Carrier Ethernet services are delivered over interconnected
Ethernet networks - untagged, C-VLAN, S-VLAN, B-VLAN
• Interconnected networks may, for example, consist of:
– a customer’s network connected to a service provider's network
– that is also connected to other service providers' networks.
PB
PBB-TE
PBB
PBB-TE
PB
• An end-to-end carrier Ethernet service can span several
interconnected packet networks.
Slide 3
Ethernet Services over Interconnected Networks
• Each Ethernet network may deploy a different packet
transport technology which provides its own mechanisms
aimed at ensuring network survivability. Examples are:
– Bridged Ethernet with MSTP or SPB or G.8032
– Traffic Engineered Ethernet with PBB-TE protection switching
PB
PBB-TE
PB xSTP
Interconnected Zone
1:1
Interconnected Zone
PBB
PBB-TE
SPB
1:1
Interconnected Zone
PB
PB xSTP
Interconnected Zone
• A protection mechanism is required for the interconnected
zone.
Slide 4
Interconnected Networks
Protection Mechanism: Requirements
• Protect against any single failure or degradation of a facility
(link or node) in the interconnected zone
• Support all standard Ethernet frames: 802.1D, 802.1Q,
802.1ad, 802.1ah
• Support interconnection between different network types
(e.g. CN-PBN, PBN-PBN, PBN-PBBN, PBBN-PBBN, etc.)
• Provide 50ms protection switching
• Provide a clear indication of the protection state
• Maintain an agnostic approach towards:
– the Ethernet technology running on each of the interconnected
networks, and
– the protection mechanism deployed by each of the interconnected
networks
Slide 5
Interconnected Networks
Protection Mechanism: Requirements (cont’d.)
• Avoid modification of the protocols running inside each of the
interconnected networks
• Ensure that multicast and broadcast frames are delivered
only once over the interconnected zone
• Allow load balancing between the interfaces that connect the
networks to ensure efficient utilization of resources
Slide 6
Possible Topologies
Mesh
Slide 7
Ring
Dual Attached Connectivity
Mesh
Two links are required
Slide 8
Ring
Three links are required
Enhanced Resiliency
Mesh
Resiliency is enhanced by adding a
node with dual attachment to the
adjacent network. This provides
protection against node failure (with
no traffic disruption).
Dual attachment is widely deployed.
Slide 9
Ring
Resiliency is enhanced by adding a
node and two links, and by removing
the redundant link. This operation
may cause traffic disruption (if a
facility fails during the upgrade
operation).
Connectivity between adjacent networks
Mesh
Ring
Adjacent networks are connected by Adjacent networks are connected by
4 direct (single-hop) connections:
8 connections:
A-D, A-C, B-D, B-C
2 direct connections A-D, B-C
2 indirect connections A-D, B-C
2 indirect connections B-D
2 indirect connections A-C
A
D
B
C
A
D
B
C
The network local link may also be used to transmit
internal traffic in the network (which may result in the
utilization of BW required for protection).
Slide 10
Protection Path Load
Mesh
Ring
Load sharing is supported across all
four links.
Load sharing is supported across
two links.
When a link fails, traffic is shared
between the three other links.
When a link connecting the
networks fails, all traffic between the
networks is transmitted via the other
single link connecting the networks.
When a node fails, traffic is shared
between two links.
When a node fails, all traffic
between the networks is transmitted
via the other single link connecting
the networks.
Slide 11
Load Sharing
Mesh
Ring
Capable of supporting more than two Capable of supporting only two
nodes and two links in each network, nodes in each network
for connecting the networks with
Although nested rings are possible,
support for load sharing
they can significantly complicate the
solution and the operation.
Slide 12
Protection Path Cost
Mesh
The cost of the protection path (in
terms of the number of hops) is
identical to that of the working path.
(Revertive functionality is optional.)
Working
Protection
Slide 13
Ring
The cost of the protection path (in
terms of the number of hops) is
higher than that of the working path.
(Revertive functionality is
recommended.)
Multiple Failures
Mesh
Mesh topology provides better
resiliency in the event of multiple
failures. Examples are:
Slide 14
Ring
Interconnection with Rings (G.8032)
Mesh
Ring
Shared Link
G.8032
G.8032
Protection in the interconnection zone A super loop is created.
is agnostic with regard to failures
Protection in the interconnection zone
inside the ring.
is not agnostic with regard to failures.
A mechanism is required to prevent
the transmission of internal traffic from
the network in the west (shown above)
to the two nodes in the network in the
east.
Slide 15
Proposed Topologies
Mesh that supports dual-homing and that provides enhanced
protection in the double dual-homing configuration
Slide 16
Solution Principles
Blue traffic (VLAN X) is
only sent through port 1
(which is protected by
port 2).
A
C
Blue traffic is sent through
port 2 in the event of failure
of link 1-3, or of node B
3
1
4
2
5
7
6
Interconnect zone
8
B
D
Blue traffic is sent through node C in
the event that node A fails.
• The protection mechanism is available per Ethernet service in the interconnected zone (i.e. per
VLAN).
• An Ethernet service is carried only over one of the interfaces which connects the two adjacent
networks.
• In the event of a fault condition on the link or the peer node, traffic is redirected to the
redundant interface.
• The service may also be protected by another node to avoid a single point of failure. If a node
is no longer able to carry traffic, traffic is redirected over the redundant node.
Slide 17
Solution Principles
A
10
C
F
3
1
B
4
2
9
5
7
6
11
12
8
Interconnect Area
11
13
D
E
• The interconnected zone may include additional nodes, interfaces and links
• Each protected VLAN is configured, (independently of other VLANs) on:
– Total of three nodes and four ports - on one of the networks, one node with two ports; on
the other network, two nodes with one port on each (i.e. dual-homing)
– Total of four nodes and eight ports - on both networks, two nodes with two ports each
(i.e double dual-homing)
• Each protected VLAN can be transmitted over one out of two/four links. However, at
any given time, it is only transmitted over one of the links crossing the
interconnected zone.
Slide 18
Solution Principles
• For each protected VLAN, one of the nodes is responsible for selecting
the interface over which the traffic will be transmitted. This node functions
as a master.
• The master is connected to two nodes. These two nodes follow the
master’s decisions and function as slaves.
• The master node can be protected by a redundant node. In the event that
the master fails, the redundant node functions as the master. This node is
called a deputy. The deputy is connected to the same two slaves as the
master.
SD
M
SM D
The same node may function as a master
node for some VLANs (blue), as a deputy
node for other VLANs (red), and a slave for
other VLANs (green), thus enabling load
sharing between the nodes.
Slide 19
S
S
SD
SM
The role of each node
(master, deputy and
slave) is set for each
VLAN by administrative
configuration.
Solution Principles
For each VLAN, the master/deputy/slave nodes are configured according to
the following options:
M
S
M
S
S
D
S
(a)
S
(c)
(b)
M
S
M
D
S
D
(d)
• Additional parameters must be configured for the master and deputy
nodes (not for the slaves):
– working port – the default port to use for traffic
– protection port – the port to use when the working port can not be used.
Slide 20
Solution Principles
• The interface selection algorithm for each VLAN is based on
– local configuration
– Information provided by link-level CCMs
• The protection state of all the protected VLANs is
synchronized between peers by means of a single link-level
CCM message.
Slave1 follows master’s
decision and uses port 3
for VLAN X
Master chooses the configured
working port 1 for VLAN X
Master uses this port
for VLAN X
M
Master uses another
port for VLAN X
1
2
Slave1 uses this port
3 for VLAN X
Slave1 is active, and uses
4 another1port for VLAN X.
S
Slave2 follows master’s
decision and does not use
any of its ports for VLAN X
Master is working so
deputy does not need
to take over
Deputy is not active for VLAN X
D
Deputy is not active for VLAN X
Slide 21
5
6
7
8
Slave2 is not active for
VLAN X
S
Slave2
2 is not active for
VLAN X
Solution Principles
• If a link fails, the master node uses the protection port (port 2)
for VLAN X
Link on port 1 is not
working, Master chooses
the configured protection
port 2 for VLAN X
Slave1 does not receive anything
from the master. It does not use
any of its ports for VLAN X
M
1
2
Master uses this port for VLAN X
3
1 active for
4Slave is not
S
VLAN x
Master is working so
deputy does not need
to take over
Deputy is not active for VLAN X
D
Deputy is npot active for VLAN X
Slide 22
5
6
7
8
Slav2 follows master’s
decision and uses port 7
for VLAN X
Slave2 uses this port for VLAN X
S
Slave2
2 is actctive and uses another
port for VLAN X
Solution Principles
• If the master fails, the deputy is informed about it by the
slaves and it becomes active
Does not receive anything
from master so it doesn't use
any port for VLAN X
Master failed.
Does not send
anything
Deputy sees that
both slaved are not
working. It
understands that
the master is not
working so deputy
takes over using its
working port (6)
does not use any of its ports
for VLAN X
Deputy uses another
port for VLAN X
M
1
2
D
5
6
Deputy uses this port for
VLAN X
3
4
S
Slave1
does
not
work for
Slave1
does
not
1 work for
VLAN
X X
VLAN
Does not receive
anything from master so
it doesn't use any port
for VLAN
7
Slave2 follows
does
notthis
work
for
Slave2
uses
this
2
8 Slave2
deputy’s
decision and
VLAN
X for VLAN X
port
S
uses port 8 for VLAN
X
Slide 23
Solution Principles
• A protected VLAN x is defined on 2 ports: On port A, VLAN x is
configured as working entity, while on port B, VLAN x is
configured as protection entity
Port A
VLAN x Working
Port B
VLAN x Protection
• In a live system, the VLAN is transmitted only on one of the ports
(working or protection entity).
Port A
VLAN x
Port B
VLAN x
• The 2 ports on which the VLAN is protected are grouped into a
VLAN Protection Group (VPG). The VPG is a logical bridge port
(as defined in 802.1Q + ad + ah).
VPG
Port A
VLAN x
Slide 24
Port B
VLAN x
Solution Principles
• The VPG forwards VLAN traffic to the port selected by the
algorithm.
VPG
Port A
VLAN x
Port B
VLAN x
• VLAN traffic received on a port is forwarded to the VPG. Learning
occurs at the VPG level.
VPG
Port A
VLAN x
Port B
VLAN x
• The CCMs are sent and received by ports A and B, and the
selection algorithm is implemented on the VPG, based on the
information received on both ports.
Slide 25
Solution Principles
Location of the new shim
Slide 26
Intention
• Start a new project in the IEEE802.1 aimed at
defining a protection mechanism for interconnected
networks in the proposed topologies. The
mechanism should comply with the requirements
introduced in this presentation.
• Decide whether we should send a liaison to the MEF
in order to receive feedback on (1) the proposed
connectivity construction and (2) the requirements.
Slide 27
Thank You
zehavit.alon@nsn.com
nurit.sprecher@nsn.com
jlemon@ieee.org
Slide 28