IEEE 802.1 and ITU-T Q.9/15
Ethernet Transport issues
(Geneva, 27 May 2010)
Port group model in G.8021
Akira Sakurai
G.8021 Co-editor
Background
The introduction of the Port Group construct in
Ethernet Flow Forwarding (ETH_FF) process in
ITU-T Recommendation G.8021 Amendment 2 is
based on 12 months study and the development
of a set of requirements based on carriers and
vendors contributions to support E-Tree and ELAN services.
These services have already been specified in
G.8011.x series of Recommendations.
G.8011 - Ethernet Services Framework
G.8011.4 - Ethernet Virtual Private Rooted
Multipoint Service
G.8011.5 - Ethernet Private LAN Service
Requirements for
E-Tree/E-LAN services
1.
2.
3.
4.
5.
A single Ethernet Virtual Connection (EVC) to
support E-Tree and E-LAN services
Capability to reduce latency in EVC
Capability to support Y.1731 OAM for EVC and
server/EVC adaptation functions located in NNI
ports
Capability to traffic-engineered rmp and mp2mp
EVCs by means of performing Traffic
Conditioning (TC) at the ingress of each EVC link
connection
Support of EVC by a mix of server layer
technologies such as:
•
•
•
•
ETH
MPLS-TP
SDH VC-n
OTN ODUk
Principle of the Port Group
Frames arriving via an input port in a Port Group
may be forwarded to one or more output ports,
with the exception of the output ports that are
member of the Port Group.
Frames arriving on an input port which is not a
member of the Port Group may be forwarded to
one or more output ports, with exception of the
port over which the frame arrived.
ETH_FF {A,B,C,X,Y,Z}
A
X
B
Y
C
Port Group {A,B,C}
Z
Applications for the Port Group
Primary is to allow for configuration of a
rooted-multipoint EVC.
Additional application is Split horizon.
Root
Port group
Leaf
Leaf
Leaf
Port group
Rooted multipoint EVC
Split horizon
Reduction of latency
Full mesh of ETH VC link connections in a domain
contributes to the reduction of latency for
forwarding frames. However, it does require an
additional loop-prevention mechanism.
The Port Group performs this mechanism at the
bridging points without changing any of
MEP/MIP/TC functionalities.
VC T
VC T
D1
VC SW
Metro 1
VC SW
VC SW
Port group
VC SW
Port group
Metro 4
VC SW
Port group
VC T
Port group
VC SW
VC T
VC T
D2
Core B
Core A
VC SW
VC T
VC SW
Port group
Metro 2
VC SW
VC SW
VC SW
VC SW
VC T
D5
VC T
D4
VC T
MetroVC
3 SW
VC T
VC T
Port group
VC SW
VC T
VC T
VC T
VC SW
VC T
VC SW
VC SW
VC SW
VC SW
VC T
VC T
D3
VC T
VC SW
VC T
Location of
the Port Group functionality
Option1 - between the ETH_FF process and the
ETH MEP/MIP/TC functions in the interface ports
The Port Group functionality is collocated with the
original ETH_FF process inside an ETH Connection
(ETH_C) function.
Option 2 - inside a Server/ETH_A function
This does not support the possibility of traffic
conditioning at the Ingress of the EVC link connections,
nor the use of different server layer technologies.
ETH
ETH_C
ETH_FF
ETH_FF
ETH
Option1
For these reasons,
G.8021 selected the option 1
to achieve the Port Group
functionality.
ETH
ETH
ETH
ETH
ETH/ETHm
ETH
ETH
ETH
ETH
Srv/ETH
Srv/ETH
Srv/ETH
Srv/ETH
Srv/ETH
Srv
Srv
Srv
Srv
Srv
ETH ETH
Option2
Conclusion
The introduction of the Port Group defined
in G.8021 Amd2 enables operators to
deploy E-Tree/E-LAN services efficiently.
ITU-T SG15 Q9 would like to express its
appreciation for the continued useful
exchange of information with IEEE 802.1
on Ethernet technology standards. We
look forward to continuing this
coordination in the future.