1/13/2009 January Interim New Orleans 1 802.1aq Shortest Path Bridging Recap Don Fedyk [email protected] János Farkas [email protected]
Mar 27, 2015
1/13/2009 January Interim New Orleans 1
802.1aq Shortest Path Bridging Recap
Don Fedyk [email protected]
János Farkas [email protected]
1/13/2009 January Interim New Orleans 2
Shortest Path BridgingProject Authorization Request
• Scope :VLAN Bridges– Shortest Path within a region– Interwork with Spanning Tree Protocols, RSTP,
MSTP bridges• This standard specifies shortest path bridging of unicast and
multicast frames, including protocols to calculate multiple active topologies that can share learnt station location information, and support of a VLAN by multiple, per topology, VLAN identifiers (VIDs).
– Compatibility• This amendment will not change the conformance of IEEE
Std 802.1Q to Std 802. Overview and Architecture, or its relationship to that specification.
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802.1Q Data Planes
SA = Source MAC addressDA = Destination MAC addressVID = VLAN IDC-VID = Customer VIDS-VID = Service VIDI-SID = Service IDB-VID = Backbone VIDB-DA = Backbone DAB-SA = Backbone SA
Supports Data Plane OAM (CFM, MIP, MEPs)
We have a long standing Data Plane
2005 2008Standard Approved
1998
B-VIDI-TAG
B-TAG
B-DA
B-SA
DA
SA
Payload
EthertypeC-VID
Payload
Ethertype
Q-TAG
DA
SA
C-VID
S-VID
Payload
Ethertype
C-TAG
S-TAG
DA
SA
I-SID
Payload
Ethertype
S-TAG
DA
SA
S-VIDC-TAGC-VID
Ethernet
ProviderBackboneBridges802.1ah
ProviderBridges802.1ad
EthernetVLAN
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Applicability
Small VLANNetworks
2-100 bridges
Large PBBNetworks
2-1000 backbone bridges
Plug and playEfficientLow delayBackwards Compatible
Carrier GradeFast convergenceEfficient use of resourcesB-VLAN Partitioned Forwarding Compatible
IEEE 802.1aq
Shortest Path Bridging (SPB) Shortest Path Backbone Bridging (SPBB)
E-Line, E-Tree, E-LAN Services Provider E-Line, E-Tree, E-LAN Services
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Motivation
• RSTP/MSTP forwarding– Detours appear
– Manual configuration isneeded for disjoint trees
– Forwarding can be onlyoptimized by manual configuration
• Shortest path forwarding– Each bridge only sends
frames on its own Shortest Path Tree (SPT)
– Automatic SPT management
– Controlled by IS-IS
BA
DC
C
C
C
C
CC
Spanning tree forwarding
SPB forwarding
BA
DC
C
CC
C
CC
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SPT Region
MST Region
Interworking with RSTP and MSTP
• Common Spanning Tree (CST)• Internal Spanning Tree (IST)• Common and Internal Spanning Tree
RSTP bridges
SPT Region
IST
MST Region
IST CST
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IEEE 802.1aq variants
• Shortest Path Backbone Bridging (SPBB) is aimed to be deployed in PBB networks where all addresses are managed
• Shortest Path Bridging (SPB) is applicable in customer, enterprise or storage area networks
SPB SPBB
Metro Core Network• Reliability• Auto-discovery• Load sharing• Managed addresses
Access Network• Reliability• Bandwidth efficiency • Unknown or managed addresses
Enterprise Network• Plug & Play• Easy to operate• Unknown addresses
MAC learningin data plane
MAC learningin control plane
IEEE 802.1aq
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IS-IS controls IEEE 802.1aq
• Topology discovery– Each bridge is aware of the physical topology of the SPT Region
• Service discovery– I-SID registrations are included into a new TLV
• Shortest Path Tree computation• Maintenance of SPTs and CIST• SPTs can be set according to the discovered I-SID
membership information– MRP is not needed
• VID allocation to VLANs
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Source tree identification
VLAN ID• An SPT is identified by
the SPVID assigned to the source bridge
Applicable to both 802.1Q and 802.1ah bridges
Ingress check on VID Consumes VLAN space Unidirectional VIDs
MAC address• B-SA and its Nickname incorporated
into Group MAC DA identifies an SPT
Two VIDs only used for a whole set of Shortest Path Trees(Base VID and another VID) Each ECMT uses one more VID
Bidirectionality of VID is preserved Only applicable to 802.1ah bridges Ingress check on SA All multicast addresses take the local
bit mapping
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VID
VLAN assignmentVLAN Base VID
identified by
MSTISPT Set
SPVIDBase VIDB-SA
Group B-DA
IST CST
Base VID Base VID
LearningNon-learningSPBB
Base VID
ID
LearningNon-learningPBB-TE
LearningNon-learningSPBB
Non-learningSPBB
allocated to
supported bysupported by
Learning
IDID ID
MSTI CIST
Learning
SPT Set
VID*B-SA
Group B-DA
MSTI
Non-learningSPBB
IST
Base VID
LearningNon-learningSPBB
IEEE 802.1aq implements
SPVID
Non-Learning
SPBB
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Tree implementation
• By Port Roles
• SPT is formed from the Root Bridge
• By Filtering Entries
• Source rooted SPTs applied in 802.1aq
Root Bridge Source Bridge
Designated,Forwarding
Root,Forwarding
Alternate,Blocking
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MAC learning
• MAC learning in the data plane (Learning)
• MAC learning in the control plane (Non-learning)
Bridge
FD
B
Bridge
FD
B
Bridge
FD
B
Frames
IS-IS IS-ISIS-IS
Addresses
Add
ress
es
Frames
Addresses
Add
ress
es
Bridge
FD
B
IS-IS
Bridge
FD
B
IS-IS
Bridge
FD
B
IS-ISControl Messages Control Messages
Addresses Addresses Addresses
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SPB
• SPB (802.1Q compliant)– Uses VID for source identification, don’t own the C-
MAC– Solution Attributes
• VID Trees, one source per bridge, distributed in IS-IS• SVL learning of unicast forwarding supported
– Solution Requirements• Must Interwork at edges with RSTP, MSTP• The region may default to a single instance MSTP
(associated with the “Base VID”) if the VID allocation fails or detects errors
• Must support loop prevention, may support ingress check
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SPB ConceptsSPT Region
SPVID = 45
SPVID = 41
VID = 6
DASA
Payload
45
DASA
Payload
22
DASA
Payload
41
DASA
Payload
22
DASA
Payload
22
CSTIST
DASA
Payload
45
DASA
Payload
41
SPVID = 71
SPVID = 66SPVID = 44
SPVID = 22
DASA
Payload
22
Base VID 22
SPB Region Identifier!= Base VID
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SPBB
• SPBB (Shortest Path Backbone Bridging)– Solution Attributes
• Single VID for an SPT Region (may use VID Trees)
• Does not use learning of B-MACs – Provider addresses will all be known allows for more
efficient flooding (no B-MAC broadcast storms),
• Reduction in forwarding space Shared Forwarding,
– Solution Requirements• Must use Multicast loop Prevention, • Must use ingress check for unicast
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SPBB Operation
IS-IS IS-IS IS-IS
IS-ISIS-IS
IS-IS
BEB
BEBBEB
BCB BCBBEB “A”
BEB Backbone Edge Bridge BEB
PBBN
IS-IS
IS-IS IS-IS
Backbone Core Bridge BCB
Shortest Path Tree from “A”
Shortest path between any two points is both the same and symmetrical for unicast
and multicast
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SPBB Shortest Path Tree to/from “A”
IS-IS IS-IS IS-IS
IS-ISIS-IS
IS-IS
BEB
BEBBEB
BCB BCBBEB “A”
BEB Backbone Edge Bridge BEB
PBBN
IS-IS
IS-IS IS-IS
Backbone Core Bridge BCB
Uses the full mesh network
Shortest path between any two points is both the same and symmetrical for unicast
and multicast
All pairs shortest path computation
performed in parallel
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SPBB Multicast Groups
IS-IS IS-IS IS-IS
IS-ISIS-IS
IS-IS
BEB
BEBBEB
BCB BCBBEB “A”
BEB Backbone Edge Bridge BEB
PBBN
IS-IS
IS-IS IS-IS
Backbone Core Bridge BCB
I-SID 5
I-SID 5I-SID 5
MMAC for 5 from A
I-SIDs define efficient subsets
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Forward and Reverse path Congruency
• Necessary if MAC learning is in the data plane• Not necessary if MAC learning is in the control plane• Going to be assured by both SPB and SPBB
Bridge5
11
1
1
1
1
2
Bridge2
Bridge1
Bridge3
Bridge4
Bridge6
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Unicast and Multicast Congruency
• Necessary for MAC learning in data plane• Necessary for the proper operation of OAM• Going to be assured by both SPB and SPBB
Bridge5
11
1
1
1
1
2
Bridge2
Bridge1
Bridge3
Bridge4
Bridge6
unicast
multicast
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Implementation ofCongruency
• Tie-breaking extension to Dijkstra for the case of equal cost multiple paths– List of node IDs comprising a path are unique– {1,6,5} < {1,2,3,5} < {1,2,4,5}
• Same algorithm is used both for unicast and multicast
Bridge5
11
1
1
1
1
2
Bridge2
Bridge1
Bridge3
Bridge4
Bridge6
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Load sharing
• Two trees are calculated taking advantage of equal cost multiple paths: {1,6,5} < {1,2,3,5} < {1,2,4,5}
• SPT Primary Set Primary Base VID • SPT Alternate Set Secondary Base VID
Bridge5
11
1
1
1
1
2
Bridge2
Bridge1
Bridge3
Bridge4
Bridge6
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Loop Prevention and Mitigation
• Inconsistent view on network topology at different nodes may cause transient loops in case of a link-state control protocol
• Loop prevention– Tree Agreement Protocol (TAP)– Handshake mechanism between neighbors– Extension to MSTP’s handshake
• Loop mitigation– Ingress Checking (e.g. RPFC)– Frames not arriving on the shortest path from the Source Bridge are
discarded– Makes the tree directed– Good for loop prevention in most cases– Transient loops may appear
• Severe problem for multicast traffic• A chance of network melt-down remains if one does not care
– Ingress filtering has to be modified
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Neighbor handshake mechanism
• Let’s make it sure that bridges having different view on network topology do not exchange frames
• The link between adjacent neighbors has to be blocked after a topology change until they agree that both of them have the same topology database
• The agreement between neighbors is implemented by a handshake mechanism
• A digest of the topology database is exchanged– CRC– Cryptographic hash function (e.g. SHA-256)
• Agreements at different part of the network are independent of each other
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Handshake: MSTP extension
• Tree Agreement Protocol (TAP)
• Two-way Agreement = three-way handshake
• No per tree handshake• BPDUs contain
– Digest of LSP database– Info on the CIST
• Proposal-Agreement– Explicit on the CIST– Computed for SPTs
Pro
posa
l
Agr
eem
ent
Agreem
ent
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Handshake: Filtering entry manipulations
• SPBB networks• STPs are implemented by
Filtering Entries• Do not implement the TAP
extension to MSTP• Implement link-state database
synchronization (TAP logic)• Loops for unicast flows are
mitigated by Ingress Checking (RPFC)
• Remove ‘unsafe’ entries if neighbors are unsynchronized
Wait for LSP update
Unicast computation
Install Unicast andremove ‘unsafe’
Multicast FDB entries
Update Digest andsend it to neighbors
Multicast computation
Install ‘safe’ Multicast FDB entries
Wait for Digest synch
Install ‘unsafe’Multicast FDB entries
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Two Options
• BPDUs
• Link State
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SPB IS-IS TLVS 8
Per Adjacency
c) SPB Link Metric Sub TLVIS-IS Reachability TLV
SPB-Link Metric
Res
S Reserved16
16
M-T ID
24
Port Identifier 16
Source MAC
d) SPB Multicast Group TLV
Per Bridge
VID
Number of records
Res
S Reserved
M-T ID 16
12
48
Destination MMAC48
Number of VIDs
8
8
SPT Set 4
8
a)Hello PDU BASE-VID TLV
Per Bridge
8
16
12
4
12
8
M-T ID
Base VID
Number of-VIDs
Res
S Reserved
SPT SET
B
Algorithm
Reserved
4
VID
SPT Set
8
4
12
8
0
Algorithm
Reserved
Per Bridge
Nickname
b)SPB Instance TLV
Nickname Priority
Nickname Flags
SP-VID
Bridge Identifier
32
20
64
4
M-T IDResS Reserved
1616
12
SPT Set
Res 4
O
For the CIST
For the SPT
For the ST
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SPBB IS-IS TLVS8
Per Adjacency
c) SPB Link Metric Sub TLVIS-IS Reachability TLV
SPB-Link Metric
Res
S Reserved16
16
M-T ID
24
Port Identifier 16
e) SPBB I-SID & UnicastMAC TLV
Per Bridge
VID
Number of I-SIDs
Res
S Reserved
M-T ID 16
8
12
24I-SID
RT Res 8
8
Number of VIDs 8
MAC Address 48
TYP Res 8
SPT Set 4
a)Hello PDU BASE-VID TLV
Per Bridge
8
16
12
4
12
8
M-T ID
Base VID
Number of-VIDs
Res
S Reserved
SPT SET
B
Algorithm
Reserved
4
VID
SPT Set
8
4
12
8
0
Algorithm
Reserved
Per Bridge
Nickname
b)SPB Instance TLV
Nickname Priority
Nickname Flags
SP-VID
Bridge Identifier
32
20
64
4
M-T IDResS Reserved
1616
12
SPT Set
Res 4
O
For the CIST
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SPVID Allocation
• How to control the allocation? • Master Bridge
– Need a communication path before the allocation• SPVID neighbor is a proxy
– Need an allocation protocol– Need to deal with Master Bridge changing
• Deterministic Distributed algorithm– Neighbor performs the computation locally based on the Link
state database– Need a collision mechanism– Need an aging mechanism that is much slower than other aging
mechanism– SPVIDs are commited to some NVRAM
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SPVID Allocation
0 4096SPVID Set 1 SPVID Set 2
VID space
Configure Sets an let the allocation be from the set
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SPVID Allocation
0 4096
VID space
Configure an SPVID pool and sets come from the pool
SPVID Pool
VIDs VIDs
SPVID Region
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IEEE 802.1aq ProjectWhere are we now?
• Topology Distribution– IS-IS
• Loop Prevention– TAP or SPBB Multicast Loop Prevention
• Loop Mitigation – Optional Forwarding change Ingress Check
• SPVID allocation– Leverage link State
• SPBB – Multicast Source Tree identification
• SPVID or B-VID&Source DA• MRP and Link State
• Path Computation– Convergence time/algorithms
• MSTP/RSTP/STP backwards/forwards interoperability & coexistence• Provisioning
– Tree types (Shared Trees or Tree per source, etc) – MIBs– Mis-provisioning
• CFM – SPB CFM– SPBB CFM
Document Both
Only IS-IS need TLVs
Documenting compliance
Documenting options
Proposals in works
TBD
Proposal in works
TBD
Seems complete
Documented Clause 13
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What do we need from IS-IS?
• Some TLVs and Sub TLVS– Per SPT Region
– BASE VID (IST)– Shortest path tree algorithm– Define Single VIDs
• Per Bridge– Bridge Identifier– Per Base VID
» Define SPVID» Bridge Priority » Supported Multicast Groups/I-SIDs» Supported Unicast
• Per Port– Per Base VID
» Link Metric, Port Priority
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Other information and Pointers
• http://www.ieee802.org/1/
• http://www.ieee802.org/1/files/public/
• SPB-ISIS mailing list for SPB IS-IS related discussions– If you want to subscribe to the spb-isis list you
can subscribe by sending to:
With subscribe in the body.
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GlossaryB-MAC Backbone MACBEB Backbone Edge BridgeBCB Backbone Core BridgeC-VID Customer VIDCFM Connectivity Fault ManagementCST Common Spanning TreeELINE Ethernet Point to Point ServiceELAN Ethernet LAN ServiceETREE Ethernet Hub and Spoke ServiceFDB Filtering Data BaseI-SID (802.1ah) Service IdentifierIGP Interior Gateway Protocol (Typically link state) IS-IS Intermediate System to Intermediate System
(IGP)IST Internal Spanning TreeLAN Local Area NetworkMAC Media Access ControlMACinMAC see PBBMEP Maintenance End point
MIP Maintenance Intermediate pointMMAC Multicast MACMSTP Multiple Spanning tree protocol MMRP Multiple MAC Registration Protocol OAM Operations, Administration and
Maintenance PB Provider Bridges IEEE 802.1adPBB Provider Backbone Bridging IEEE 802.1ahPBB-TE PBB Traffic Engineering IEEE
802.1QayQinQ see PBS-VID Service VIDSPB Shortest Path Bridging IEEE 802.1aqSPBB Shortest Path Backbone Bridging SPT Shortest Path TreeSTP Spanning tree protocol RSTP Rapid Spanning tree protocol TTL Time To LiveVID VLAN IdentifierVLAN Virtual LAN