Introduction to Shortest Path Bridging
g g
IEEE 802.1aq
Don Fedyk, PLM Alcatel-Lucent, Editor IEEE 802.1aq
donald fedyk@alcatel lucent com
[email protected]
October 12
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AGENDA
•Introduction
•What is SPB
•SPB Details
•SPB Applications/Futures
•References
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Acknowledgements
• SPB was a large Project in IEEE 802 over a number of years ~6. One of
the longer
g running
g 802. projects.
p j
• Many people contributed from many companies to get the work of
standardization done.
• This
Thi presentation
i uses some material
i l from:
f
- Peter Ashwood-Smith Huawei[ [email protected]]
• Other notable contributors to the project were:
- Mick Seaman, Janos Farkas , Nigel Bragg, Paul Unbehagen, David Allan
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Ethernet Network Challenges
• Layer 2 networks that scale.
• Use of arbitraryy mesh topologies.
p g
• Use of (multiple) shortest paths.
• Efficient broadcast/multicast routing and replication points.
• Avoid
A id address
dd
learning
l
i by
b tandem
t d
devices.
d i
• Get recovery times into 100’s of millisecond range for larger topologies.
• Good scaling without loops.
• Allow creation of very many logical L2 topologies (subnets) of arbitrary
span.
properties
p
within the logical
g
L2 topologies
p g
• Maintain all L2 p
• Reuse all existing Ethernet OA&M 802.1ag/Y.1731
B tM
But
Moore’s
’ llaw and
d ttechnology
h l
ttrends
d are on our side!
id !
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The Problem:
Scaling Native Ethernet (Spanning Tree)
Inneficient
routes
2
MACs
M1…M100
Destination-2
S
Source
ROOT
bridge
3
1
All the nodes on the
route need to learn
MAC’s M1-M100
Cannot use
these links
Destination-1
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The IEEE 802.1 Solution: SPB
• SPB is a Link State Control protocol for Ethernet
• Specifically an instance of IS-IS
IS IS protocol for exchanging Bridge Properties:
• SystemIDs + Priority = Bridge Identifiers
• Link Attributes (Metrics)
• Backbone MAC addresses & Multicast II-SIDs
SIDs (SPBM)
• SPB Has Two Modes
• SPB for MACs (SPBM) for PBB or MAC in MAC (MAC Learning on the Edge)
• SPB for VIDs (SPBV) for QinQ of VLAN bridges. (MAC Learning)
• All Ethernet data planes existed prior to SPB (next Chart)
• What SPB provides Topology for:
• Shortest path Unicast/Multicast
• Efficient Multicast replication
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What are Ethernet data planes?
Provider
Backbone
Bridges
802.1ah
Ethernet
VLAN
SA = Source MAC address
DA = Destination MAC address
VID = VLAN ID
C-VID = Customer VID
S-VID = Service VID
I-SID = Service ID
B-VID
B
VID = Backbone VID
B-DA = Backbone DA
B-SA = Backbone SA
Provider
Bridges
802.1ad
Ethernet
802.3
Ethertype
SA
DA
Ethertype
C-VID
Q TAG
Q-TAG
SA
DA
1998
Ethertype
C-VID
C-TAG
S-VID
S TAG
S-TAG
SA
DA
Ethertype
C-VID
C-TAG
S-VID
S-TAG
SA
DA
I-SID
I-TAG
B-VID
B TAG
B-TAG
B-SA
B-DA
Encapsulation for
virtualization is
important in
many networks
Consistent
C
i t t
Forwarding
2005
2008
Standard Approved
It is a very good Data Plane!
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Pushing Scale in Ethernet Single Domain networks
IEEE 802.1aq
SPBM
SPBV
Enterprise
p
Network
Metro Core Network
Access Network
• Plug & Play
• Easy to operate
• Unknown addresses
MAC learning
in data plane
• Reliability
• Bandwidth efficiency
• Unknown or managed
addresses
D t Center
Data
C t
• Reliability
• Auto-discovery
• Load sharing
• Managed addresses
MAC learning
in control plane
VLANS
Using Scale today of IS-IS (one SPBM Domain of 1000 nodes)
Easily address Millions of devices
Why? Orthogonal Address, Service and Topology
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Properties of the Ethernet Data Plane
• Congruency
- Multicast and Unicast
• Symmetry
- Forward path and Reverse Path
• Determinism
- Allows parallel computation of paths
• MAC Learning/Flood Containment
- Plug and play operations
- Contain MAC Learning in SPBM BMACs distributed,
distributed Edge learning only
• OAM Capable
- Congruency, Determinism, Symmetry enable CCM, LBM, LTM, performance etc
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Congruency & Symmetry
D
Shortest path between any
two points is both the same
and symmetrical for unicast
and multicast
E
H
C
A
G
Bridge “A”
J
B
I
F
Same Forward and Reverse Shortest Path
Learning SPBV, OAM, Frame Ordering
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Implementation of
Congruency & Symmetry
• Tie-breaking extension to Dijkstra for the case of equal cost multiple paths
- Sorted List of transit node IDs comprising a path are unique/deterministic.
Ranking them produce deterministic default winner.
- {2,6} < {3,7} < {4,7}
1
Bridge3
1
1
1
Bridge7
Bridge1
1
Bridge4
1
Bridge5
1
Bridge2
1
Bridge6
• Same algorithm is used both for unicast and multicast
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Equal Cost Trees (ECTs)
D
Green and Blue Costs are
equal A
A-C-D
C D and A-B-D
ABD
E
H
C
A
G
Bridge “A”
J
B
I
F
Optional Multipath Load Balancing different services
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Implementation of ECTs
• 16 trees are created by applying the previous algorithm
AFTER XORing BridgeID’s with 16 different bit-masks.
• Example XORing with 0xff
0xff…ff
ff (invert) selects largest ranked path so {~7
{~7,~4}
~4} wins
wins..
1
Bridge3
1
Low
1
Bridge7
Bridge1
1
1
Bridge4
1
Bridge5
1
Bridge2
1
Bridge6
• Each mask is assigned to a B-VID (SPBM mode)
High
MASKS | B-VID
0x00
0 11
0x11
0x22
0x33
0x44
0x55
0x66
0x77
0x88
0x99
0xAA
0xBB
0xCC
0xDD
0xEE
0xFF
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SPBM Multicast Groups
I-SID 5
Multicast
Forwarding for
I-SID 5
I-SID 5
D
E
H
C
A
G
Bridge “A”
J
B
I-SID 5
I
F
I-SID 5
No Multicast
Forwarding for ISID 5 (Shortest
path
th to
t E but
b t nott
part of the tree)
I-SIDs define efficient subsets
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SPBM Multicast P2MP
Multicast
Forwarding for
I-SID 45
D
E
I-SID 45
Leaf
H
C
A
G
Bridge “A”
I-SID 45
Root
I-SID 45
Leaf
J
B
I
F
I-SID 45
Leaf
E-TREE I-SIDs Root to/From Leaf only
y
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SPBM Multicast Addresses
The SPBM Trifecta
• By constructing local IEEE Multicast Addresses the Control Plane has
complete
p
flexibilityy to build multicast trees.
• Computation, Source Identification, Service Identification
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Loop Prevention
• Loop Prevention (Not new)
- Policyy : Loop
p Free byy never allowing
g a loop
p to form
- “Never forward a Frame unless the neighbor node has agreed to accept it”
- Mechanism: Don’t populate an FDB entry until you synchronize with next-hop
neighbor.
• Loop Mitigation (New for Ethernet)
- Policy: Discard potential looping frames
- “Never
Never accept a Frame from a neighbor node that you do not expect”
expect
- Mechanism: Ingress check. Source DA/VID must be expected. Local Policy.
- Loop Prevention is sufficient, but Loop Mitigation is faster during changes
- Loop Prevention for Multicast and Loop Mitigation for Multicast and Unicast
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Load Sharing - Visually
All links usable
Slide Courtesy of Peter Ashwood-Smith
Huawei
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Applications
• Spanning Tree Protocol replacement in native Ethernet networks
• Data Center or layer
layer-2
2 Internet Exchange Point
- Allows the creation of a large and scalable layer-2 fabric in the DC where all the
links are used (active/active topologies) and VM/servers/routers can freely move
anywhere
• Layer-2 VPNs transport
- Enhances scalabilityy and flexibilityy for layer-2
y
VPNs
- All the MEF services are supported: ELINE, ELAN, ETREE*
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Is SPB Real ?
• SPBM Data path (PBB) and OA&M already wide spread use.
• Multiple Vendors shipping product,
product Alcatel-Lucent,
Alcatel Lucent Avaya
INTERWORKING:
- Three Inter-working
g events. Last one June 27 2011 : Huawei (host),
(
), AlcatelLucent, Avaya, Solana, Spirent
BASE STANDARDS:
- IETF:
- RFC 6329.
- IEEE:
- IEEE 802.1aq Published June 2012
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SPBM Futures
• 802.1Qpb Equal Cost Multiple Path
- Some Ethernet networks have many paths (Fat Tree
Tree, Dense Mesh etc
etc.))
- ECMP enables per hop load balancing
- Shared Trees for multicast
- Reduces multicast state
- Enable ECMP for multicast on per Tree Basis
-O
OAM Enhancements
a
- Loss of Symmetry and Congruency needs OAM enhancements to maintain OAM
capability.
- Data Plane Enabler
- New TAG with Flow ID and TTL.
• Traffic Engineering? 802.1 AVB group interest
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References
• “IEEE Std 802.1aq-2012” Media Access Control (MAC) Bridges and Virtual
Bridged Local Area Networks—Amendment 20: Shortest Path Bridging
• RFC 6329 “IS-IS
IS IS Extensions Supporting IEEE 802.1aq
802 1aq Shortest Path
Bridging” http://datatracker.ietf.org/doc/rfc6329/
• “IEEE 802.1Qbp Task Group Project” Virtual Bridged Local Area Networks
— Amendment: Equal Cost Multiple Paths (ECMP) Work in Progress.
Progress
• “IEEE 802.1aq” : www.wikipedia.org:
http://en.wikipedia.org/wiki/IEEE_802.1aq
• “Shortest Path Bridging – Efficient Control of Larger Ethernet Networks” :
IEEE Communications Magazine – Oct 2010
• “Provider
Provider Link State Bridging”
Bridging :
IEEE Communications Magazine V46/N9– Sept 2008
• http://ieee802.org/1/files/public/docs2011/aq-ashwood-smith-spbm-3rdi t
interop-0718-v01.pdf
0718 01 df
•
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Thank You
Questions?
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Glossary
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
B MAC Backbone MAC
B-MAC
BEB Backbone Edge Bridge
BCB Backbone Core Bridge
CCM Continuity Check Message
C-VID Customer VID
CFM Connectivity Fault Management 802.1ag
ELINE Ethernet Point to Point Service
ELAN Ethernet LAN Service
ETREE Ethernet Hub and Spoke
p
Service
FDB Filtering Data Base
I-SID (802.1ah) Service Identifier
IS-IS Intermediate System to Intermediate
System (IGP)
LAN Local
L
l Area
A
Network
N t
k
LTM Link Trace Message
LBM Loop back Message
MAC Media Access Control
MACinMAC see PBB
• OAM Operations, Administration and
Maintenance
• P2MP Point to Multipoint
• PB Provider Bridges IEEE 802.1ad
• PBB Provider Backbone Bridging IEEE 802.1ah
• QinQ see PB
• S-VID Service VID
• SPB Shortest Path Bridging IEEE 802.1aq
• SPBM Shortest Path Bridging MAC
• SPBV Shortest Path Bridging VID
• SPT Shortest Path Tree
• STP Spanning tree protocol
• RSTP Rapid Spanning tree protocol
• TTL Time
Ti
To
T Live
Li
• VID VLAN Identifier
• VLAN Virtual LAN
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