Source:
Title:
IEEE P802.1 & P802.17 Working Group
Communication to ITU-T SG15 from IEEE P802.1 & 802.17
TO:
COMMUNICATION STATEMENT
Ghani Abbas, rapporteur Q9/15, ghani.abbas@marconi.com
Malcolm Betts, rapporteur Q12/15, betts01@nortel.com
COPY:
Paul Nikolich, IEEE 802 Chair, p.nikolich@ieee.org
APPROVAL:
FOR:
DEADLINE:
CONTACT:
Agreed to at IEEE P802.1 & P802.17 Plenary meeting, Dallas, November 2006
Information
N/A
Mike Takefman, chair IEEE 802.17, tak@cisco.com
Tony Jeffree, chair IEEE 802.1, tony@JEFFREE.CO.UK
Subject: Ethernet Protection & Restoration
Reference: ITU-T Q9/15, Q12/15 Liaison LS1
We would like to thank you for your liaison that further explains work on Ethernet ring protection.
The 802.1 Working Group uses an architectural approach that separates the mechanisms that perform
network path selection from those that reserve and control the bandwidth use on a particular path, so
does not recognize distinct categories of protection and restoration, but leaves the related issues in the
hands of the network designer and administrator. In some cases, e.g. use of some dual redundant ‘riser’
connections to wiring closet switches on an Enterprise campus, a spanning tree protocol can clearly be
providing ‘protection’ in the terms you describe, as the network design has reserved a full amount of
matching bandwidth that the protocol will select upon link failure. In other cases bandwidth will be
shared, and the network design provides fault tolerance that is somewhere on the continuum from
‘protection’ to ‘restoration’ for classes of traffic that are subject to admission control, and ‘restoration’
only for best effort traffic.
The 802.17 Working Group appreciates your explanation of protection and restoration. As we have
indicated before, RPR provides ring protection per your definitions.
The 802.17 Working Group would like to update you on our progress. We have agreed that the next
stage in the evolution of RPR is to consider protected inter-ring connections. Among the aspects that
we will be considering is interactions of this mechanism with STP. We have chartered an 802.17c
Study Group on this topic at our November plenary and ITU-T experts are invited to join us. We would
also appreciate understanding any additional requirements you have for protected inter-ring
connections.
As we indicated in a previous liaison, 802.17 is willing to provide assistance should you require it during
development of your recommendation to describe Ethernet ring protection using RPR.
We wish to thank the leadership and the members of ITU-T SG15 for the inquiry into our work programs
and look forward to the continuation of the exchange of information on topics of common interest to our
organizations.
Regards,
Mike Takefman
Tony Jeffree
APPENDIX on RPR
802.17 Layer Structure
Upper Layers/Logical Link Control
802.17 Medium Access Control (MAC)
Topology/
Protection
Fairness
OAM
MAC Datapath
GFP
RS
(GRS)
POS
RS
(PRS)
GFP
Adaptation
GE (GERS)
10GE (XGERS)
HDLCHDLC-Like
Adaptation
Other
RS
GMII/XGMII/XAUI
SDH PHY (STM1–
(STM1–STM64, VCAT)
Ethernet PHY 11-10G
Other PHYs
1
Ethernet Service over RPR: Protocol View
Bridge Relay
IP / MPLS
802.3 MAC
1GE
PHY
10GE
PHY
802.17 MAC
1GE
PHY
10GE
PHY
802.3 MAC
1GE
PHY
10GE
PHY
802.17 MAC
1GE
PHY
10GE
PHY
Architectural Characteristics:
Layer 3 Model
Layer 2 Model
• IP/MPLS internetworking across • 802.1D bridging and learning
ring
• 802.17b spatially aware extensions
• 802.1D/Q Internetworking
2
802.17 Protocol: Packet Format
Extended Packet Format: Bridging Operation
1
TTL
1
Base Control
6
Ring DA
6
Ring SA
1
TTL Base
1
Extended Control
2
HEC
6
Extended DA
6
Extended SA
2
Protocol Type
n
Service Data Unit
4
FCS
• RPR Header containing ring
addressing information and
RPR frame control
Header
Payload
• Original Ethernet Frame
Trailer
3
Ethernet Frame
Ethernet Service over RPR : Frame Format View
DA
SA
Protocol Type
TTL
Base Control
Ring DA
Ring SA
TTL Base
Extended Control
HEC
Extended DA
Extended SA
Protocol Type
DA
SA
Protocol Type
Service Data Unit
Service Data Unit
Service Data Unit
FCS
FCS
H
H
H
B1
FCS
H
H
B2
B3
B4
B5
B6
H
H
H
B7
4
Layer 2 RPR Internetworking
802.17b Spatially Aware Sublayer
CE#1
CE#2
Unicast Ethernet frame
to Ring
CE#3
DA SA
Payload
B1
B2
DA SA DA SA
CE#7
CE#6
DA SA
CE#5
Payload
Payload
CE#4
• Frame travel is scoped on the ring using the RPR MAC addresses to hold ring station
DA/SA
• Stations running 802.17b learn MAC SA of stations in the CE Edge networks that are
reachable on each ring port
• At the same time, the Ring Station SA from which the Frame originated is also stored in
the FDB
• Once learned, the DA lookup provides the Ring Station MAC address behind which the
host station resides. Frame travel can be scoped by using this address as the Ring DA.
• Spatial reuse is maintained
5
Proposed Project: Inter-Node Protection
1G RPR
10G RPR
1G RPR
1G RPR
• Protection protocol that insures a forwarding path
exists between rings by using multiple nodes
• Similar to subtending rings with matched nodes in
SDH/SONET
6