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Metro Ethernet:
Understanding Key Underlying
Technologies
Copyright 2007
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Metanoia, [email protected]+1-888-641-0082http://www.metanoia-inc.com
Metano ia, Inc .Critical Systems Thinking
http://www.metanoia-inc.com/http://www.metanoia-inc.com/http://www.metanoia-inc.com/http://www.metanoia-inc.com/8/13/2019 MetroEthernet MetanoiaInc Next Gen Workshop 2007-07-17
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Next-Generation Systems & Networks Workshop, 17thJuly. 2007, Bangalore, India 2
Who is Metanoia, Inc.?
Special ty techno logy con sultancyfounded in mid-2001, with HQ in Mountain View, California
Undertakes d eep-dive technical cons ult ingin telecom network, systems, software and chiparchitecture and design for clients across the world
Services have spanned4 cont inents, with clients in: North America, Europe, Asia, and Australia.
Principals provided services intechno logy strategies, architecture and design trade-of fs, productdevelopment, hardware/sof tware architecture, and know ledge enhancementto organizations thatinclude large equipment manufacturers, international, national and regional ISPs, premier metro/access
systems startups, network planning tool vendors, established software and technology houses andleading component and semiconductor vendors
Principals are technologis ts at the forefront of new developments, as leaders, creators,implementers, researchers, academics, strategists, and advisors in the US and abroad
Expertise spans Layer 1 through Layer 4, and wireline (optical, Ethernet, IP/ATM, SONET/SDH)through wireless (Wi-Fi, cross-layer design, Wi-Max, cellular data, 2.5-3G)
125+ man yearsof technology design and developm ent, and technology management experience,
having worked at leading global corporations, such as Apple, AOL Time Warner, BBN, Cisco, 3Com,Fujitsu, LSI Logic, Motorola, Tellabs, Siemens, Nokia, Tibco, and Qualcomm, and having workedat/consulted to corporates in the US and abroad for almost the last decade
70+ patents collectively issued/pending
Advanced graduate degrees from some of the most distinguished universities in the worldtheUniversity of California, Stanford University, Iowa State University, the University of Texas, theUniversity of Waterloo, and the Indian Institute of Technology
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Workshop Outline
Legacy networks & Ethernet over legacy networks Value propositions and business drivers
Ethernet over SDH/SONET
Metro Ethernet Forum (MEF)
MEF architecture
E-Line and E-LAN services
Native Ethernet as Carrier-class transport
Provider Bridges
Provider Backbone Bridges (PBB), Provider Backbone Transport (PBT)
MPLSan enabler for Ethernet services
Layer 2 VPNs: VPWS, VPLS, H-VPLS
Advanced concepts: traffic engineering, QoS, OAM, resilience
Conclusions
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Ethernet over
Legacy Networks
Metano ia, Inc .Critical Systems Thinking
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Issues with Legacy Networks
Low bandwidth
No flexibility to scale
High cost of installation
Slow provisioning
Bandwidth growth inflexible/non-linear Limited by multiplexing hierarchy
TDM-based access: inefficient for converged data
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Next-Generation SDH
NG ADM
NG ADM
NG ADM
Ethernet
Ethernet
Central
Office
Switch
Core
NetworkCustomer
NetworkSTM/4/16
RingCross
Connect
CustomerNetworkNG-SDH
NG-SDH
NG-SDH
Customer
Network
Customer
Network
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Ethernet-over-SDH
Framing protocol Encapsulates Ethernet frames in SDH payloads
Mapping of SDH payload to SDH channels
Vir tual concat.: for allocation of non-contiguous VCs
Flow control mechanism
Avoids packet drops due to speed mismatch between SDH and
Ethernet
Mechanism to increase/decrease allocated SDH bandwidth
Add or remove VCs
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Ethernet-over-SDH (contd)
Very popular in carriers with installed base of SDH rings E.g. BSNL in India
Good deployment choice when traffic primarily circuit
switched
Inefficient if major traffic is bursty packet-switched data
Solution: Carrier-class Ethernet!
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Metro Ethernet Value Propositions
Lower per-user provisioning costs Technically simple relative to TDM ckts.
Due to large installed base
Efficient and flexible transport
Wide range of speeds: 128 Kbps--10 Gbps
QoS capabilities
Ease of inter-working
Plug-and-play feature
Ubiquitous adoption
Thetechnology of choice in enterprise networks
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Ethernet Business Drivers
Business connectivity Storage networks
Data centers
Video conferencing
Residential services
Triple-play services (IPTV)
On-line gaming
High-speed Internet access
Wireless backhaul
Reduced cost, complexity for mobile operators
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Metro Ethernet Services
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Metro Ethernet Forum (MEF)
Industry forum at forefront of Carrier Ethernetstandardization
Carrier Ethernet architecture
Ethernet services
Founded in 2001. Currently approx. 120 members
Technical Sub-committees
Architecture
Services
Protocols and Transport
Management
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MEN Architectural Components
13
End
User
Customer
NetworkMEN
Customer
NetworkEnd
User
S
T T
S
UNI Reference Point UNI Reference Point
Ethernet Virtual Connection
End-to-End Ethernet Flow
End user Interface End user Interface
Ethernet Flow Unidirectional stream of Ethernet frames
UNI Interface used to interconnect MEN subscriber to provider
EVC Defines association between UNI for delivering Ethernet flow across MEN
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Application Service
Layer(IP, MPLS, PDH, E1/E3, SDH)
Ethernet ServiceLayer
Transport Service
Layer(802.1, SONET/SDH, MPLS)
MEN Layer Model
MEN Layer Model
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MEF Services Definition Framework
Service Type Construct used to create broad range of services
Service Attributes
Defines characteristics of a service type
Attribute Parameters
Set of parameters with various options
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Service Types
E-Line Point-to-point Ethernet Virtual
Circuit (EVC)
E-LAN
Multipoint-to-multipointEthernet Virtual Circuit
16
EVC1
EVC2
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Service Attributes
Physical Interface
Medium, speed, mode, MAC layer
Traffic Parameters
CIR, CBS, PIR, MBS
QoS Parameters
Availability, delay, jitter, loss
Service Multiplexing
Multiple instances of EVCs on a given physical I/F
Bundling
Multiple VLAN IDs (VID) mapped to single EVC at UNI
M t i I
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Ethernet Services
Ethernet Private Line (EPL) Uses E-Line
Does not allow service multiplexing
High degree of transparency
Low delay, delay variation, and packet loss ratio
Ethernet Virtual Private Line (EVPL)
Uses E-Line
Allows for service multiplexing
Need not provide full transparency
M t i I
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Service Types and Ethernet Services
Service Types
E-Line
(p2p connectivity)E-LAN
(mp2mp connectivity)
Ethernet Private
Line (E-line)
Ethernet Virtual
Private Line (E-VPL)Ethernet Private
LAN (E-LAN)
Ethernet Virtual Private
LAN (E-VPLAN)
Ethernet Services
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Native Ethernet as
Carrier-class Transport
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M t i I
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Requirements for Carrier-class Ethernet
Scalability
Network should support millions of subscribers
Protection and restoration
50ms resilience
Quality-of-Service (QoS)
Ability to offer differentiated levels of service
Service Monitoring and Fault Management
Support for TDM traffic
Seamless integration with legacy networks
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Ethernet Ring
Ethernet
Switch
Ethernet
Ethernet
Ethernet
Switch
Ethernet
Switch
Ethernet
Switch
1/10 GigabitEthernet Ring
Core
Network
Customer
Network
CustomerNetwork
Metano ia Inc
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Native Ethernet in Metro Access
How does one create the notion of a vir tual circu i t?
VLAN tagging with point-to-point VLAN
VLAN stacking
Outer tag service instance; Inner tag individual customer
802.1Q in 802.1Q (Q-in-Q) - IEEE 802.1ad
C-DA: Customer Destination MAC
C-SA: Customer Source MAC
C-TAG: IEEE 802.1q VLAN Tag
C-FCS: Customer FCS
S-TAG: IEEE 802.1ad S-VLAN Tag
C-DA C-TAGC-SA Client data FCSS-TAG
6bytes 6bytes 4bytes 4bytes 4bytes
Metano ia Inc
P id B id (IEEE 802 1 d)
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Customer
Network
Customer
Network
Customer
Network
24
Provider Bridge (IEEE 802.1ad)Architecture
CE: Customer Equipment
UNI: User-to-Network Interface
CES: Core Ethernet Switch/Bridge
P-VLAN: Provider VLAN
UNI-B
CES
CES
CE-A
UNI-A
UNI-C
CE-C
Spanning tree
CE-B
CES
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Limitations of Provider Bridge Scalability
Limited to 4096 service instances
Core switches must al lMAC addresses
Broadcast storms ensue due to learning
MAC address tables explode!
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Provider Backbone Bridging (802.1ah)
Encapsulate customer MAC with provider MAC at edge Edge switch adds 24-bit service tag (I-SID), not VLAN tag
Core switches need on ly learnedge switch MAC adds.
S-TAG: IEEE 802.1ad S-VLAN Tag
B-DA: IEEE 802.1ah Backbone Destination
B-SA: IEEE 802.1ah Backbone Source MAC
I-TAG: IEEE 802.1ah Service Tag
B-DA B-TAGB-SA I-TAG C-DA C-TAGC-SA Client data B-FCS
6bytes 6bytes 6bytes6bytes4bytes 5bytes 4bytes 4bytes
Metano ia Inc
P id B kb B id i (PBB)
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Provider Backbone Bridging (PBB)Architecture
CPE BCPE ACPE C
Provider backbonenetwork (802.1ah)
CPE BCPE A
802.1ad
CPE B
CPE B
802.1q
CPE C
Provider backbone
network (802.1ad)
CPE D
CPE D
CPE C
CPE A
Provider backbone
network (802.1ad)
Provider backbone
network (802.1ad)
Provider backbone
network (802.1ad)
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Benefits of PBB
Scalability Addresses limitations of 4096 service instances
Robustness
Isolates provider network from broadcast storms
Security
Provider need switch frames onlyon provider addresses
Simplicity
Provider & customers can plan networks independently
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Traffic Engineering in PBB
Via Multiple Spanning Tree Protocol (MSTP)
Maps a VLAN to ST or multiple VLANs to ST
Enables use of links that would otherwise be idle in ST
Eliminates wasted bandwidth but
Too slow for protection switching
Not suitable for complex mesh topologies
Difficult to predict QoS
Metano ia, Inc.
Ch ll ith All Eth t
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Challenges with an All-EthernetMetro Service
Restriction on # of customers
4096 VLANs!
Service monitoring
Scaling of Layer 2 backbone
Service provisioning
Carrying a VLAN is not a simple task!
Inter-working with legacy deployments
Need hyb r id archi tectures
Multiple L2 domains connected via IP/MPLS backbone
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What Solutions do we Have?
Ethernet-based Architecture
Provider Bridge (802.1ad) in edge
Provider Backbone Transport (PBT) in Core
Hybrid Architecture
802.1ad in the edge Multiprotocol Label Switching (MPLS) in core
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Provider Backbone Transport (PBT)
Connection-oriented, traffic-engineered Ethernet tunnels
Replaces spanning tree control plane with either a:
Management plane
External control plane
No learning !
Forwarding info. provided by management plane
Forwarding done on MAC + VID (60-bit) address
VID is not network global; however, MAC + VID is
B-MAC identifies destination
B-VID identifies per-destination alternate paths
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Customer
NetworkCustomer
Network
33
PBT Architecture
Central TE Module
SA : PE1
DA : PE2
VLAN 22
SA : PE1
DA : PE2
VLAN 33
PE1PE2
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Benefits of PBT
No learning Eliminates undesirable broadcast storms
Resolves MAC flooding problem
Addresses scaling by forwarding on MAC + VID-highly scalable
Protection
Sets-up backup paths
50ms restoration possible
QoS support available
M t i I
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MPLSAn Enabler forEthernet Services:
Fundamentals & Operations
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Basic Concept of MPLS
Routing fills routing table
Signaling fills label forwarding table
DA Next hoprouter
N/wInt.
129.89.10.x 198.168.7.6 1
179.69.x.x 198.168.7.6 1
128.89.10.x
1
179.69.x.x
2
1
128.89.10.12
179.69.42.3
198.168.7.6
In
label
Out
labelAddress Prefix N/w
Int.
Advertises binding
Advertises binding
128.89.10.x5 1179.69.x.x7 2
Advertises bindings
128.89.10.x3 1179.69.x.x4 1
34
X
X
DA Next hoprouter
N/wInt.
129.89.10.x 129.89.10.1 1
179.69.x.x 179.69.42.3 2
Routing Table
In
label
Out
labelAddress Prefix N/w
Int.
Label Table
R1 R2
R3
R4
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Basic Concept of MPLS
128.89.10.x
1
179.69.x.x
2
1
128.89.10.12
179.69.42.3
198.168.7.6
In
label
Out
labelAddress Prefix N/w
Int.
In
label
Out
labelAddress Prefix N/w
Int.
128.89.10.x5 1
179.69.x.x7 2128.89.10.x3 1
179.69.x.x4 1
3
4
X
X
3
5
Packet arrives
DA=128.89.10.25
3Push
Label
5Pop
labelForward
packet
553
Swap
Label
R2R1
R3
R3 R4
Metano ia, Inc.
So what about MPLS Control and
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So what about MPLS Control andForwarding?
Supersetof conventional router control
Distribute info. via n/w layer routing protocols (OSPF, BGP, etc.)
Algos. to convert routing info. into forwarding table:
Create binding from FEC label
Assign & distribute labels to peer LSRs via signaling
Label switching forwarding table (or label information base LIB)
Forwarding algo = label swapping, independentof control
component (implementable in optimized H/W or S/W)
Control
Component
ForwardingComponent
First Subentry Second Subentry
(for multicast or load balancing)
Incoming Label
Map
Next hop label forwarding entry (NHFLE)
Outgoing label
Outgoing inf.
Next hop address
Outgoing label
Outgoing inf.
Next hop address
Incoming
Label
Metano ia, Inc.C iti l S t Thi ki What does a Label Represent? The
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What does a Label Represent? TheIssue of Label Granularity
Packets form Forwarding Equivalence Class (FEC)
Treated identical lyby participating routers
Assigned the samelabel
Membership in FEC must be determinable from IP header + other info. thatingress router has about the packet
Entities that may be grouped into an FEC are flexible. E.g. FEC could be:
Connection between two IP ports on two hosts or between IP hosts
Traffic headed for a particular network with same TOS bits
All destination networks with a certain prefix
Manually configured connection
Traffic belonging to a customer or department VLAN
Traffic of a given applicationvoice, video, plain data, management traffic
and many others
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Lets Recap: Elements of MPLS
Label Forwarding
Use data link addressing. E.g. ATM VPI/VCI, FR DLCI
Shim header between data link and IP header
Label Creation and Binding Label Assignment and Distribution
Ride piggyback on routing protocols, where possible (BGP)
Separate label distribution protocolRSVP, LDP
Variable
L2 header L3 IP headerMPLS shim
header
Higher Layers
4 bytes 20 bytes
LabelEXP/
CoS TTLS
20 bits 3 bits 8 bits
Data
Plane
Control
Plane
1 bit
Metano ia, Inc.Critical Systems ThinkingPrimary Label Assignment and
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Primary Label Assignment andDistribution Modes
4
33
Edge LSR
Edge LSR
Downstream-on-demand
with Independent Control
1 Requests
2
2Assignments
Edge LSR
2
35
6
Edge LSR
Downstream-on-demand
with Ordered Control
1 Requests
4
Assignments
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Advantages of MPLS
Original justification
Availability of fast, amortized, ATM hardware; emergence of H/W
forwarding engines has practically eliminated this
Current justifications
Separates forwarding from control, allowing Routing functionality to evolve independent lyof forwarding algorithm
MPLS to control non-packettechnologies: SONET/SDH ckts., lightpaths
Provides explicit, manageable IP routes
Enables pol icy rout ingand t raf fic engineer ing
Offers TE for Ethernet tunnels in metro-Ethernet environments
Facilitates scalable hierarchical routing
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The Utility of Hierarchical Label Switching
Core LSRs
Edge LSRs
Swapand Push Pop
Swap
Concept is similar to VLAN stacking in PBT we saw earlier
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Hierarchical Label Stacking/Switching
Inside a transit AS, each co re rou termust keep track of all
networks that might be reached through it
With hierarchical labels, only edge routersneed know whatnetworks might eventually be reached through them
A lltransit traffic can be made to tunnel through core routers
using LSPs with stacked labels
Metano ia, Inc.Critical Systems ThinkingExplicit Manageable Routes -- Policy
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Explicit Manageable Routes -- Policyrouting, Traffic engineering
Carriers want certaintraffic to go over certainroutes. Suchnetwork engineering:
Keeps network loads balanced
Enhances network stability and reliability
Enables better QoS and performance assurances
Allows carriers to meet customer SLAs
Constraint-based routing together with MPLS allows carriers to
Bind Ethernet tunnelsto an LSP,
Place (or ro ute)LSP over the desired sequence of LSRs in the n/w
TE tunnels are helpful for VPLS-based carrier Ethernet n/ws
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IP/MPLS-based Layer 2 VPNs
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L2 VPN Components
A
B
A
PE1 PE2
B
PE3
Routed
backbone
Emulated
LAN A
Emulated
LAN B
VC LSP
AC
What does the P1-PE2
connection really look like?
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L2 VPN Component Details
PSN Tunnel
PWs
PE1 PE2
Emulated LAN
Interface
From CE
devices
PW Signaling
3
ForwarderBridgeModule
4
5
Emulated LAN
Instance
Routed backbone
with P routersFrom CE
devices
6
1 ACs 2
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VPLS Network Overview
B
A
CE
B
A
CE
VSI
VSI
VSI
VSI
VSI
LAN Service
LAN Service
PW
(full mesh)
Tunnel
(full mesh)
L3/MPLS
Backbone
AC
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VPLS Protocols Involved
B
A
CE
B
CE
PE PE
EthernetSTP
MP-iBGP (PW) + RSVP-TE /LDP (tunnel)Targeted LDP (PW) + LDP (tunnel)
EthernetSTP
ControlPlane
Data
Plane
EthernetEthernet or
Ethernet in IP/
ATM/FR/SDH/
SONET
Ethernet/MPLS
Ethernet/IPSec
Ethernet/GRE
EthernetEthernet or
Ethernet in IP/
ATM/FR/SDH/
SONET
BGP/Targeted LDP
LSP or PSN Tunnel
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Operational Characteristics of VPLS
Operational Requirement Realized Via
MAC address learning andswitching, work with 802.1p/qtags and VLANs
- VSI Forwarder- Bridge Module
Flooding pkts. with unknownsbroadcast, or multicast address
Frame replication on PWs
Provider edge signalinginformPE's to autoconfigure, and ofmembership, tunnelling
- Targeted LDP- BGP
VPLS membership discovery- BGP- Configuration
Inter-provider connectivity Globally unique VPLS ID
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Data Plane: Flooding, AddressLearning and Forwarding
All address unknown frames (unicast, multicast, broadcast)
flooded over corresponding PWs to all relevant PEs only
B
A
CE
BA
CE
VSI
VSI
VSI
VSI
VSI
PE1PE2
PE3 PE4
PWs
Src. MAC = 09:10:01:45:00:AB
Dest. MAC = 08:00:69:02:01:FC1
?2
2
3
3
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Address Learning
Layer 2 reachability directly learned in data plane
Use standard learning bridge functions for local MACs
PW-based association for remote MACs
Allow PE to determine from which physical port or LSP a given MAC
address came
VSI FIB keeps mapping between Ethernet MAC PW to use
Qualified Learning Unqualified Learning
- Each customer VLAN is its own
VPLS instance
- Has its own PW mesh and brdcast
domain
- All customer VLANs are part of
the same VPLS
- One PW mesh and single brdcast
domain
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Address Learning Example
ACE
VSI
VSI
PE1 PE2
PE3
i/f1 i/f2i/f1
Dest.
MAC
VC
LabelOut I/FTunnel
1 Inbound
VC LSP Label = 1002
Outbound
VC LSP Label = 2001
Src. MAC = 08:AA:FC:01:10:DE (S1)
Dest. MAC = FF:FF:FF:FF:FF:FF (D1)
(broadcast)
2
Local Learning
3
4
Remote
Learning
S1 1002 i/f1-
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Forwarding and Encapsulation
Forwarding requires ability to Dynamically learn MAC addresses on
Physical ports
Pseudowire VCs (VC LSPs)
Forward/replicate pkts. across physical ports and VC LSPs
Encapsulation
PW header applied to Ethernet packet w/o preamble + FCS VLAN tag denoting customers VPLS instance can be stripped at
ingress, reapplied at egress
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u e a d opo ogy a dLoop Freedom
Full mesh of PW and tunnels deployed
Tunnels
Help transport the PW payload
Aggregate traffic from multiple PWs
Pseudowiresdemultiplex the L2 traffic traversing tunnels
A
CEB
ACE
VSI
VSI
VSI
VSI
VSI
PW
(full mesh)
Tunnel
(full mesh)
AC
Dest. MAC = 08:00:69:02:01:FC
PE1 PE2
PE3 PE4
?
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Scaling VPLS: Hierarchical VPLS
Base VPLS requires full mesh of VC LSPs between PE routers
Adequate for PE routers in COmultiple customers aggregated
Inadequate for PE routers in MTU basements!
LSP explosion
Operational nightmare!
PE PE
PE
PEPE
MTU
MTU MTU
MTU
MTU
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Hierarchical VPLS Advantages
Benefits
Simplifies signaling
Reduces pkt. replication
Simplifies MTU
Scalable inter-domain VPLS
Simplifies new site addition
PE PE
PE
PEPE
MTU
MTU MTU
MTU
MTU
Spoke
VCs
Hub PE
Core VC
LSP mesh
(VLL or Q-in-Q)
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ya Metro Region
100 MTUs; 10 customers/MTU; 2 VPLS/cust.; 100 stations/VPLS
VPLSs/MTU = 10x2 = 20
MACs/MTU = 20x100 = 2000
No hierarchy PE supports
2000 MACs
LDP/BGP sessions = (100x99)/2 x
20 = 245,000
Hierarchy (10 MTU/PE) PE supports
2000 x 10 = 20,000 MACs
LDP/BGP sessions = (10x9)/2 x 200 = 9000
# of spoke VLLs = 10 x 20 = 200
PE
PE
PEPE
MTU40
MTU1
MTU99MTU2
PEMTU 100
PEMTU3
CE
CE
CECE
MTU40
Hub PE
MTU91
MTU81MTU10
CE
MTU100
CE
MTU1
CEMTU31
CE
MTU90
PEPE
PE
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Benefits of IP/MPLS-based L2 VPNs
Separation of administrative responsibilities
Migration from traditional L2 VPNs: seamless transport of Ethernet
services
Privacy of routing
Layer 3 independence
Less operational overhead
Ease of configuration (?)
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Advanced Features:Traffic Engineering,
Resilience, OAM, QoS
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Traffic Engineering Concepts
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Constraint Based Routing
A class of routing systems that computes routes through a
network subject to a set of constraints and requirements
QoS-based Routing
Path of flows determined by
Knowledge of resource
availability in network
QoS requirements of flows
Policy-based Rou ting
Path/routing decision based
on administrative policy
Can be on-line or off-line
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CB Routing System
Inputs
Flow/path attributes:
required b/w, hop count, ...
Resource attributes:
properties of nodes/links
Network topology & state
Outputs
Computed feasible path
Explicit route of the path
Constraint-Based
Routing Process
Attributes
Resources
Topology
Feasible Path
ERO {1,3,4,5}
1
3
4
5
2
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MPLS-based Resilience for the Metro
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Fundamental Characteristics of RSVP
Allows apps. to signal QoS requests to n/w, and n/w to respond
with success or failure
Designed to transport
Classification info. (Sender_Template)
Allows flows with specific QoS reqs. to be recognized
Traffic specs of source/sender (Tspec)
QoS needs of receivers (Rspec)
Soft-state protocol Path/Resv transmitted periodically to refresh reservation
Refresh Reduction [RFC2961] has practically eliminated original
scalability concerns with use of soft state
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Basic Operation of RSVP-TE
Path Message
Application for which RSVP
reservation is to be made
Identifies pkts. of the sender
Defines traffic output by sender
Request for label on this hop
Specific path to which flow isto be bound
LSP attributes for this sender
IP address of I/F that
transmitted Path Msg.
RSVP Header
SESSION
SENDER_TEMPLATE
SENDER_TSPEC
LABEL_REQUEST
SESSION_ATTRIBUTE
PHOP
ERO/RRO
Resv Message
Flow Descriptor
RSVP Header
SESSION
STYLE
LABEL
RRO
SENDER_TEMPLATE
NHOP
RSpec
Same as that in Path Msg.
Specifies senders that may
use the reserved resources
Label assigned to this hop
Record route taken by Path
QoS desired by receiver
Flow for which QoS is
desired
IP address of I/F originating
the Resv msg.
A B C D E
Path (Label_Req) Path (Label_Req)
Resv
Label=5Resv
Label=7
Resv
Label=49
Resv
Label=21
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LSP ID = L2
RSVP-TE
Rerouting is done when
A better path is available
Upon failure along LSP
Use SESSION Obj. & SE style
Tunnel uniquely identified by
Destination IP address
Tunnel ID
Ingress IP address
Tunnel ingress made to appear
as 2 different senders to the
RSVP session (via LSP ID)
Src
Rcvr
LSP ID = L1
On these links the
LSPs share resources
Tunnel ID in
Session Obj
Originates LSPs
with IDs 1 and 2
Here they are treated as di f ferent
LSPs within the same Session
LSPs 1 and 2 have a common SESSION Obj, but
a new LSP ID in the SENDER_TEMPLATE and a
different ERO (with possibly common hops)
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in a Nutshell
Route Computation
Process(on-line (CSPF) or offline)
Enhanced IGP
Process(OSPF-TE)
Signaling Process
(RSVP-TE)Standard IGP
Process (OSPF)
Link State
Database
(LSDB)
Routing Table
(RIB)Computed
feasible path(ERO)
Operator Input
(Flow or LSPAttributes)
MPLS LSPs
(Label Info. Base)
TED
Forwarding
Info. Base (FIB)
LSP
Establishment Link Attribute
Modification
Output
Resource
Attributes
Network
Topology + State
Demand or Traffic drivenLSP path selection
Control driven route computation
and LSP path selection
CONTROL PLANE
DATA PLANE
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How it All Fits Together
PE1
PE2
PE3
CE1
CE2
CE3
CE4
Last-mile Ethernet
PBB clouds
IP/MPLS Core
Pseudo-wires
Attachment circuits
-- Physical (PDH/SDN)
-- Logical (FR, ATM, VLANs, tunnels)
LSP Tunnels
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OAM: The Traditional Achilles Heel of
Ethernet
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,Critical Systems Thinking
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Why Ethernet OAM?
Current management protocols lack per-customer
granularity to handle Ethernet services
Most management protocols operate are point-to-point
Ethernet OAM can exploit multipoint capability
Link management required for last-mile connection
Similar to link mgt. in FR and ATM
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Ethernet OAM Types
Service OAM
e2e connectivity and fault mgt. per service instance
Part of IEEE 802.1ag, CFM project
Link OAM
Monitoring & fault mgt of individual Ethernet link (physical/emulated)
Part of IEEE 802.3, Clause 57 (formerly 802.3ah (not to be confused
with 802.1ah))
Ethernet Local Mgt. Interface (E-LMI)
Configuration & operational provisioning of customer edge device
Part of MEF Standard MEF-16
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Service OAM
Works on per-EVC basis
Independentof underlying transport technology
CFM messages
Continuity Check Message
Detects loss of service connectivity
Link Trace Message
Traces the path hop-by-hop (like IP traceroute)
Loopback Message Detects whether target point is reachable (like ICMP Ping)
AIS (Alarm Indication Signal) Message
Asynchronous notification to indicate fault
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Link OAM
Discovery
Identifies devices at both ends of the link
Link Monitoring
Detects link faults
Statistics of packet errors
Remote Failure Indication
Conveys loss-of-signal indication to peers, due to poor SNR, power
failure, or other critical events
Remote Loopback
Determines quality of link during installation and troubleshooting
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E-LMI
Provides local configuration & operational parameters to
customer edge
VLAN-EVC mapping
QoS profiles of EVC
Reduces configuration errors, improves performance
Dynamic EVC management
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Quality-of-Service: Ah! that elusive QoS
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Eth t S i
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Ethernet Services
MPLS supports (no textends) a packet-based QoS model
MPLS does notrun in hosts (only in metro/core routers)
QoS, however, is an end-to-endmechanism
MPLS helps carriers offer QoS-enabled services efficiently
Can support MEF QoS model via DiffServ QoS framework
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Diff ti t d S i F k
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Differentiated Services Framework
Traffic flows aggregated into small # of classes
Per-flow state is not required
More scalable than IntServ
EF
AF1x
AF2x
AF3x
AF4x
PriorityDrop Precedence
123
Class DSCP
001xx0
01xx10
1xxx10
11xx10
101110
Class encoded in IP header via
DiffServ Code Point (DSCP)
Edge router
Classifies packets to DifServ classes
DSCP identifies Per Hop Behavior(PHB)
Best Effort (BE)
Expedited Forwarding (EF)
Minimal delay & loss
Assured Forwarding (AF)
4 classes
3 drop precedences each
12 possibilities total
BE
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Diff ti t d S i A hit t
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Differentiated Services Architecture
Diffserv Domain
WFQ
Strict
Priority
EF
AF
BE
Core Functions
Queueing
Scheduling
Aggregate
PHBs
Colored packet
(marked DSCP)
Classifier Marker
Meter
Shaper
Traffic Conditioning
Edge Functions
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M i DSCP t LSP ( l b l )
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Mapping DSCPs to LSPs (or labels)
Map DSCP EXP bits in MPLS shim header
6 DS bits (64 PHBs) and only 3 EXP bits (8 classes)!
Complete mapping is infeasible
For many practical cases, 8 PHBs may suffice
Results in an LSP called an E-LSP
Label EXP TTLSDSCP
6 bits
IP Header
DSCP
3 bitsDS byte
MPLS shim header
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M i DSCP t LSP ( l b l )
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Mapping DSCPs to LSPs (or labels)
Map {PHB, FEC} MPLS Label
That is, provide the info. in the label itself!
Requires enhancing the label distribution protocols
Use EXP bits for drop precedence
That is to determine different PHBs of a PHB scheduling class
Label EXP TTLSDSCP
6 bits
DSCP
3 bitsDS byte
DS class dropprecedence
DS class: EF, AFx
IP Header MPLS shim header
Results in an LSP called an L-LSP
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Conclusions and Discussion
Critical Systems Thinking
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Conclusions
Ethernet poised to be dominant choice in metro networks
Reduces capex and opex for providers
Enables new revenue generating services
802.1ad provider bridge with OAM of 802.1ag a choice at the edge
Two architectures emerging for Ethernet in the metro core
Provider Backbone Transport (PBT)
IP/MPLS-based L2 VPNs
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Thank You!
Questions?
Critical Systems Thinking
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Glossary
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Glossary
AC Attachment CircuitACL Access Control ListAF Assured ForwardingAPI Application Programming InterfaceAS Autonomous SystemATM Asynchronous Transfer ModeBA Behavior AggregateB-DA Backbone Destination AddressB-DA Backbone Source AddressBE Best EffortB-FCS Backbone Frame Check SequenceBGP Border Gateway ProtocolCBS Committed Burst SizeCE Customer Edge (router)CES Core Ethernet Switch/BridgeCFMCIR Committed Information RateCO Central OfficeDA Destination AddressDS DiffServ
DS DiffServDSCP DiffServ Code PointEF Expedited ForwardingE-LMI Ethernet-Local Management InterfaceE-LSP EXP mapped LSPEPL Ethernet Private LineERO Explicit Route ObjectE-UNI Ethernet UNIEVC Ethernet Virtual CircuitEVPL Ethernet Virtual Private LineEXP Experimental (EXP bits in MPLS "shim"header)EXP Experimental BitsFCS Frame Check SequenceFEC Forwarding Equivalence ClassFIB Forwarding Information BaseFR Frame RelayGR Graceful RestartH-QoS Hierarchical Quality-of-ServiceH-VPLS Hierarchical VPLSIPTV IP Television
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Glossary
L2 Layer 2 (Data Link Layer; MAC Layer)L3 Layer 3 (Network or IP Layer)LAN Local Area NetworkLDP Label Distribution ProtocolLER Label Edge RouterLIB Label Information BaseL-LSP Label inferred LSPLSP Label Switched PathLSR Label Switching RouterMAC Medium Access ControlMBS Maximum Burst SizeMEF Metro Ethernet ForumMEN Metro Ethernet ArchitectureMPLS Multi-Protocol Label SwitchingMSTP Multiple Shortest Path TreeMTU Multi-Tenant UnitNG Next GenerationNGN Next-Generation NetworkNNI Network Network InterfaceOAM Operations, Administration, and Management
OSPF Open Shortest Path FirstP Provider (router)PB Provider BridgingPBB Provider Backbone BridgingPBT Provider Backbone TransportPDH Pleisosynchronous Digital HierarchyPE Provider Edge (router)PHB Per Hop BehaviorPIR Peak Information RatePSN Packet Switching NetworkP-VLAN Provider VLANPW Pseudo-WireQoS Quality-of-ServiceRIB Routing Information BaseRSTP Rapid Spanning Tree Protocol
RSVP-TEResource Reservation Protocol - Traffic
Engineering (RSVP protocol with MPLS
traffic engineering extensions)SA Source AddressSDH Synchronous Digital HierarchySONET Synchronous Optical Network
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Glossary
SPT Shortest Path TreeST Spanning Tree ProtocolSTP Spanning Tree ProtocolTDM Time-Division MultiplexingTE Traffic EngineeringTM Traffic ManagementTTL Time to LiveUNI User Network InterfaceVCI Virtual Circuit IdentifierVFI Virtual Forwarding InstanceVID VLAN IdentifierVLAN Virtual LANVLAN Virtual LANVOQ Virtual Output QueueVPI Virtual Path IdentifierVPLS Virtual Private LAN ServiceVPN Virtual Private NetworkVPWS Virtual Private Wire ServiceVR Virtual Router
VRF Virtual Routing and ForwardingVSI Virtual Switching InstanceWFQ Weighted Fair Queuing
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Readings and References (1)
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Readings and References (1)
MEF 4: Metro Ethernet Network Architecture Framework Part 1 Generic
Framework
MEF 6: Metro Ethernet Services Definition Phase 1
MEF 10.1: Metro Ethernet Services Attributes Phase 2
MEF 16: Ethernet Local Management Interface
IEEE 802.1d/q WG: Media Access Control (MAC) Bridges, IEEE 1998
IEEE 802.1s, Multiple Spanning Tree, IEEE 2002
IEEE 802.1ah, Provider Backbone Bridges, Work in Progress
Documents on the MEF and IEEE 802.1 and 802.3 WG web sites
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Readings and References (2)
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Readings and References (2)
L. Andersson and E. Rosen, Framework for Layer 2 Virtual Private
Networks (L2VPNs), RFC 4664, September 2006
K. Kompella and Y. Rekhter, Eds., Virtual Private LAN Service: Using
BGP for Autodiscovery and Signaling, RFC 4761, January 2007
V. Kompella and M. Lasserre, Eds., Virtual Private LAN Service: UsingLabel Distribution Protocol for Signaling, RFC 4762, January 2007
S. Bryant and P. Pate, Eds. Pseudo Wire Emulation Edge-to-Edge (PWE3)
Architecture, RFC 3985, March 2005
L. Martini et al, Eds., Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP), RFC 4447, April 2006
Documents on the L2 VPN, PWE3, MPLS, and CCAMP WGs of the IETF
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Additional Slides
Critical Systems Thinking
Metano ia, Inc.Critical Systems ThinkingLabel Assignment and Distribution
(control component)
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thJuly. 2007, Bangalore, India 92
(control component)
Downstream Upstream
Ordered Solicited (On Demand)Unsolicited
SolicitedUnsolicited
Independent Solicited (On Demand)Unsolicited
SolicitedUnsolicited
Directionfromwhich labels flow
Refers to whether LSR distributes
labels on demand or voluntarily
Whether LSR waits to hear from
its upstream/downstream nbrs.
before responding to a request
for label(s)
Label Retention: Liberal or Conservative
Whether LSR keeps labels from a neighbor
who is not currently the next hop for a FEC
Labels
Data
Labels
Data
Metano ia, Inc.Critical Systems Thinking
A Word on Reservation Styles
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thJuly. 2007, Bangalore, India 93
A Word on Reservation Styles
Always chosen by the receiver
Two styles apply with RSVP-TE
Fixed Filter (FF)
Dist inctreservation for traffic
from each sender Needs uniqu e labelper sender
Shared Explicit (SE)
Commonresvn. for traffic from
the senders specified by rcvr.
May assign unique label/sender
Useful for p2p or mp2p LSPs
Distinct reservationper sender
S1
S3
Link (i,j)
Unique label/sender
S2
Common reservation
shared by all senders
S1
S3
Link (i,j)
Different senders may
have different labels
S2
Metano ia, Inc.Critical Systems Thinking
LDP versus BGP Signaling
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thJuly. 2007, Bangalore, India 94
LDP versus BGP Signaling
LDP session full mesh b/ween PEs
PEs exchange labels directly
New PE reconfig. mesh at allPEs
FIB per VPLS per PE
RRs reduce full mesh to 2 sessions/PE
Cannot direct label mapping to a
specific peer need label ranges
New PE peering session only w/ RRs
BGP-based SignalingTargeted LDP
i-BGP
PE
PE
PE
PE
PERR
TargetedLDP
PE
PE
PE
PE
PE
Metano ia, Inc.Critical Systems Thinking
L2 VPNS with BGP
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L2 VPNS with BGP
Autodiscovery + signaling, together via BGP with RTs (per slide 74)
PE configured with its VPLS ID (if VPLS)
Transmits VPLD ID or identity of attached CEs to peer PEs
Includes demux value for each BGP NLRI (as a label range)
Selection algorithm allows each remote PE to pick correct label for
sending traffic to advertising PE
BGP NLRI for L2 VPNBGP NLRI for VPLS
Length (2 octets)
RD (8 octets)
VE ID (2 octets)
VE Block Offset (2 octets)
VE Block size (2 octets)
Label Base (3 octets)
Length (2 octets)
RD (8 octets)
CE ID (2 octets)
Label blk offset (2 octets)
Circuit Status Vector
Label Base (3 octets)
Metano ia, Inc.Critical Systems Thinking
BGP-based L2 VPN (VPWS)
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BGP-based L2 VPN (VPWS)
PE1
PE2
PE3
1003
3001
CE1
CE2
CE3
CE4
DLCI=[101, 102, , 120]
DLCI=[11,12,, 30]
IP/MPLS
Core
Label block offset=0
Label base = 3000
Label range = 20
Label block offset=0
Label base = 1000
Label range = 20
10311
12
3002
DLCI=[401, 402, , 420]
Label block offset=0
Label base = 2000
Label range = 20
403
2003
Metano ia, Inc.Critical Systems Thinking
BGP-based L2 VPN (VPLS)
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BGP-based L2 VPN (VPLS)
PE1
PE2
PE3
3001
CE1
CE2
CE3
CE4
IP/MPLS
Core
Label block offset=0
Label block size = 10
Label base = 3000
3002VE ID = 3