Metro Ethernet: Metro Ethernet: Understanding Key Underlying Understanding Key Underlying
TechnologiesTechnologies
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Metanoia, Inc. [email protected] +1-888-641-0082http://www.metanoia-inc.com
Metanoia, Inc.Critical Systems Thinking™
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Who is Metanoia, Inc.? Specialty technology consultancy founded in mid-2001, with HQ in Mountain View, California
Undertakes deep-dive technical consulting in telecom network, systems, software and chip architecture and design for clients across the world
Services have spanned 4 continents, with clients in: North America, Europe, Asia, and Australia.
Principals provided services in technology strategies, architecture and design trade-offs, product development, hardware/software architecture, and knowledge enhancement to organizations that include large equipment manufacturers, international, national and regional ISPs, premier metro/access systems startups, network planning tool vendors, established software and technology houses and leading component and semiconductor vendors
Principals are technologists 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 years of technology design and development, 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 worked at/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 world – the University of California, Stanford University, Iowa State University, the University of Texas, the University 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)
MPLS – an enabler for Ethernet services
Layer 2 VPNs: VPWS, VPLS, H-VPLS
Advanced concepts: traffic engineering, QoS, OAM, resilience
Conclusions
Ethernet over Ethernet over Legacy NetworksLegacy Networks
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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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6
Next-Generation SDH
NG ADM
NG ADM
NG ADM
Ethernet
Ethernet
Central Office Switch
Core Network Customer
NetworkSTM/4/16
Ring Cross Connect
TDM Ckt
TDM Ckt
Customer Network
NG-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 Virtual 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 The technology 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
Metro Ethernet ServicesMetro Ethernet Services
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Metro Ethernet Forum (MEF)
Industry forum at forefront of Carrier Ethernet standardization 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
CustomerNetwork
MEN CustomerNetwork
EndUser
S
T TS
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 Service Layer
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-multipoint
Ethernet 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
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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
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Service Types and Ethernet Services
Service Types
E-Line(p2p connectivity)
E-LAN(mp2mp connectivity)
Ethernet PrivateLine (E-line)
Ethernet VirtualPrivate Line (E-VPL)
Ethernet PrivateLAN (E-LAN)
Ethernet Virtual PrivateLAN (E-VPLAN)
Ethernet Services
Native Ethernet as Native Ethernet as Carrier-class TransportCarrier-class Transport
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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
EthernetSwitch
Ethernet
Ethernet
EthernetSwitch
EthernetSwitch
EthernetSwitch
1/10 Gigabit Ethernet Ring
Core Network
Customer Network
Customer Network
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Native Ethernet in Metro Access
How does one create the notion of a virtual circuit? 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
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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 all MAC 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 only learn edge 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
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Metanoia, Inc.Critical Systems Thinking™Provider Backbone Bridging (PBB)
ArchitectureCPE BCPE A
CPE C
Provider backbone network (802.1ah)
CPE BCPE A
802.1ad
CPE BCPE B
802.1q
CPE C
Provider backbone network (802.1ad)
CPE D
CPE DCPE 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 only on 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
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Metanoia, Inc.Critical Systems Thinking™Challenges with an All-Ethernet
Metro 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 hybrid architectures …
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 Network
Customer Network
33
PBT Architecture
Central TE Module
SA : PE1DA : PE2VLAN 22
SA : PE1DA : PE2VLAN 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
MPLS – An Enabler for MPLS – An Enabler for Ethernet Services:Ethernet Services:
Fundamentals & OperationsFundamentals & 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
21
128.89.10.12
179.69.42.3
198.168.7.6
Inlabel
Outlabel
Address Prefix N/wInt.
Advertises binding<5, 128.89.10.x>
Advertises binding<7, 179.69.x.x>
128.89.10.x 5 1
179.69.x.x 7 2
Advertises bindings<3, 128.89.10.x> <4, 179.69.x.x>
128.89.10.x 3 1
179.69.x.x 4 1
3
4
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
Inlabel
Outlabel
Address Prefix N/wInt.
Label Table
R1 R2
R3
R4
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Basic Concept of MPLS
128.89.10.x
1
179.69.x.x
21
128.89.10.12
179.69.42.3
198.168.7.6
Inlabel
Outlabel
Address Prefix N/wInt.
Inlabel
Outlabel
Address Prefix N/wInt.
128.89.10.x 5 1
179.69.x.x 7 2128.89.10.x 3 1
179.69.x.x 4 1
3
4
X
X
3
5
Packet arrives DA=128.89.10.25
3Push Label
5Pop label
Forward packet
553
Swap Label
R2R1
R3
R3 R4
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Metanoia, Inc.Critical Systems Thinking™So what about MPLS Control and
Forwarding? Superset of 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, independent of control component (implementable in optimized H/W or S/W)
ControlComponent
ForwardingComponent
First Subentry Second Subentry(for multicast or load balancing)
Incoming Label Map
Next hop label forwarding entry (NHFLE)
Outgoing labelOutgoing inf.Next hop address
Outgoing labelOutgoing inf.Next hop address
Incoming Label
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Metanoia, Inc.Critical Systems Thinking™What does a Label Represent? The
Issue of Label Granularity Packets form Forwarding Equivalence Class (FEC)
Treated identically by participating routers Assigned the same label
Membership in FEC must be determinable from IP header + other info. that ingress 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 application – voice, video, plain data, management traffic
… and many others
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Let’s 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 protocol – RSVP, LDP
Variable
L2 header L3 IP header MPLS “shim” header
Higher Layers
4 bytes 20 bytes
Label EXP/CoS TTL S
20 bits 3 bits 8 bits
Data Plane
Control Plane
1 bit
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Metanoia, Inc.Critical Systems Thinking™Primary Label Assignment and
Distribution Modes
4
33’
Edge LSR
Edge LSR
Downstream-on-demand with Independent Control
1 Requests
2
2’Assignments
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 independently of forwarding algorithm
MPLS to control non-packet technologies: SONET/SDH ckts., lightpaths
Provides explicit, manageable IP routes Enables policy routing and traffic engineering
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
Swap and 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 core router must keep track of all networks that might be reached through it
With hierarchical labels, only edge routers need know what networks might eventually be reached through them
All transit traffic can be made to tunnel through core routers using LSPs with stacked labels
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Metanoia, Inc.Critical Systems Thinking™Explicit Manageable Routes -- Policy
routing, Traffic engineering
Carriers want certain traffic to go over certain routes. Such network 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 tunnels to an LSP,
Place (or route) LSP over the desired sequence of LSRs in the n/w
TE tunnels are helpful for VPLS-based carrier Ethernet n/ws
IP/MPLS-based Layer 2 VPNsIP/MPLS-based Layer 2 VPNs
Metanoia, Inc.Critical Systems Thinking™
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L2 VPN Components
A
B
A
PE1 PE2
B
PE3
Routedbackbone
EmulatedLAN A
EmulatedLAN 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 LANInterface
From CEdevices
PW Signaling
3
Forwarder
BridgeModule
4
5
Emulated LANInstance
Routed backbonewith P routers From 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/MPLSBackbone
AC
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VPLS Protocols Involved
B
A
CEB
CE
PE PE
EthernetSTP
MP-iBGP (PW) + RSVP-TE /LDP (tunnel)Targeted LDP (PW) + LDP (tunnel)
EthernetSTP
ControlPlane
DataPlane
EthernetEthernet or
Ethernet in IP/ATM/FR/SDH/
SONET
Ethernet/MPLSEthernet/IPSecEthernet/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 and switching, work with 802.1p/q tags and VLANs
- VSI Forwarder - Bridge Module
Flooding pkts. with unknowns broadcast, or multicast address
Frame replication on PWs
Provider edge signaling – inform PE's to autoconfigure, and of membership, tunnelling
- Targeted LDP - BGP
VPLS membership discovery - BGP - Configuration
Inter-provider connectivity Globally unique VPLS ID
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Metanoia, Inc.Critical Systems Thinking™Data Plane: Flooding, Address
Learning 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
VCLabel
Out I/FTunnel
1 InboundVC LSP Label = 1002
OutboundVC LSP Label = 2001
Src. MAC = 08:AA:FC:01:10:DE (S1)
Dest. MAC = FF:FF:FF:FF:FF:FF (D1)(broadcast)
2
Local Learning3
4
RemoteLearning
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 customer’s VPLS instance can be stripped at ingress, reapplied at egress
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Metanoia, Inc.Critical Systems Thinking™Tunnel and PW Topology and
Loop Freedom
Full mesh of PW and tunnels deployed
Tunnels Help transport the PW payload
Aggregate traffic from multiple PWs
Pseudowires – demultiplex 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 CO – multiple customers aggregated
Inadequate for PE routers in MTU basements!
LSP explosionOperational 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
SpokeVCs
Hub PE
Core VCLSP mesh
(VLL or Q-in-Q)
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Metanoia, Inc.Critical Systems Thinking™Hierarchical VPLS: Case Study for
a Metro Region100 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 (?)
Advanced Features: Advanced Features: Traffic Engineering, Traffic Engineering,
Resilience, OAM, QoSResilience, OAM, QoS
Metanoia, Inc.Critical Systems Thinking™
Traffic Engineering ConceptsTraffic 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 Routing
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-BasedRouting Process
Attributes
Resources
Topology
Feasible PathERO {1,3,4,5}
1
3
4
5
2
MPLS-based Resilience for the MetroMPLS-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 RSVPreservation 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 thattransmitted 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 mayuse the reserved resources
Label assigned to this hop
Record route taken by Path
QoS desired by receiver
Flow for which QoS isdesired
IP address of I/F originatingthe Resv msg.
A B C D E
Path (Label_Req) Path (Label_Req)
ResvLabel=5
ResvLabel=7
ResvLabel=49
ResvLabel=21
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LSP ID = L2
Fast Re-Route (FRR) using 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 theLSPs share resources
Tunnel ID inSession Obj
Originates LSPswith IDs 1 and 2
Here they are treated as differentLSPs within the same Session
LSPs 1 and 2 have a common SESSION Obj, buta new LSP ID in the SENDER_TEMPLATE and adifferent ERO (with possibly common hops)
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Metanoia, Inc.Critical Systems Thinking™TE with Constraint-based Routing
in a Nutshell
Route ComputationProcess
(on-line (CSPF) or offline)
Enhanced IGPProcess
(OSPF-TE)
Signaling Process(RSVP-TE)
Standard IGPProcess (OSPF)
Link StateDatabase(LSDB)
Routing Table(RIB)
Computedfeasible path
(ERO)
Operator Input(Flow or LSPAttributes)
MPLS LSPs (Label Info. Base)
TED
ForwardingInfo. Base (FIB)
LSPEstablishment Link Attribute
Modification
Output
ResourceAttributes
NetworkTopology + State
Demand or Traffic drivenLSP path selection
Control driven route computationand 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 EthernetPBB clouds
IP/MPLS Core
Pseudo-wires
Attachment circuits-- Physical (PDH/SDN)-- Logical (FR, ATM, VLANs, tunnels)
LSP Tunnels
OAM: The Traditional Achilles Heel of OAM: The Traditional Achilles Heel of
EthernetEthernet
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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 Independent of 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
Quality-of-Service: Ah! that elusive QoSQuality-of-Service: Ah! that elusive QoS
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Metanoia, Inc.Critical Systems Thinking™MPLS and Quality-of-Service for
Ethernet Services
MPLS supports (not extends) a packet-based QoS model
MPLS does not run in hosts (only in metro/core routers)
QoS, however, is an end-to-end mechanism
MPLS helps carriers offer QoS-enabled services efficiently
Can support MEF QoS model via DiffServ QoS framework
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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
Priority Drop Precedence
1 2 3
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 precedence’s each
12 possibilities total
BE
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Differentiated Services Architecture
Diffserv Domain
WFQ
StrictPriority
EF
AF
BE
Core Functions
Queueing
Scheduling
AggregatePHBs
Colored packet (marked DSCP)
Classifier Marker
Meter
Shaper
Traffic Conditioning
Edge Functions
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Metanoia, Inc.Critical Systems Thinking™MPLS Support of DiffServ:
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
TTL
S
DSCP
6 bits
IP Header
DSCP 3 bits
DS byte
MPLS “shim” header
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Metanoia, Inc.Critical Systems Thinking™MPLS Support of DiffServ:
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
TTL
SDSCP
6 bits DSCP 3 bits
DS byte
DS class drop precedence
DS class: EF, AFx
IP Header
MPLS “shim” header
Results in an LSP called an L-LSP
Conclusions and DiscussionConclusions and Discussion
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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
Thank You!Thank You!Questions? Questions?
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Glossary
AC Attachment Circuit
ACL Access Control List
AF Assured Forwarding
API Application Programming Interface
AS Autonomous System
ATM Asynchronous Transfer Mode
BA Behavior Aggregate
B-DA Backbone Destination Address
B-DA Backbone Source Address
BE Best Effort
B-FCS Backbone Frame Check Sequence
BGP Border Gateway Protocol
CBS Committed Burst Size
CE Customer Edge (router)
CES Core Ethernet Switch/Bridge
CFM
CIR Committed Information Rate
CO Central Office
DA Destination Address
DS DiffServ
DS DiffServ
DSCP DiffServ Code Point
EF Expedited Forwarding
E-LMI Ethernet-Local Management Interface
E-LSP EXP mapped LSP
EPL Ethernet Private Line
ERO Explicit Route Object
E-UNI Ethernet UNI
EVC Ethernet Virtual Circuit
EVPL Ethernet Virtual Private Line
EXPExperimental (EXP bits in MPLS "shim" header)
EXP Experimental Bits
FCS Frame Check Sequence
FEC Forwarding Equivalence Class
FIB Forwarding Information Base
FR Frame Relay
GR Graceful Restart
H-QoS Hierarchical Quality-of-Service
H-VPLS Hierarchical VPLS
IPTV 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 Network
LDP Label Distribution Protocol
LER Label Edge Router
LIB Label Information Base
L-LSP Label inferred LSP
LSP Label Switched Path
LSR Label Switching Router
MAC Medium Access Control
MBS Maximum Burst Size
MEF Metro Ethernet Forum
MEN Metro Ethernet Architecture
MPLS Multi-Protocol Label Switching
MSTP Multiple Shortest Path Tree
MTU Multi-Tenant Unit
NG Next Generation
NGN Next-Generation Network
NNI Network Network Interface
OAM Operations, Administration, and Management
OSPF Open Shortest Path First
P Provider (router)
PB Provider Bridging
PBB Provider Backbone Bridging
PBT Provider Backbone Transport
PDH Pleisosynchronous Digital Hierarchy
PE Provider Edge (router)
PHB Per Hop Behavior
PIR Peak Information Rate
PSN Packet Switching Network
P-VLAN Provider VLAN
PW Pseudo-Wire
QoS Quality-of-Service
RIB Routing Information Base
RSTP Rapid Spanning Tree Protocol
RSVP-TE
Resource Reservation Protocol - Traffic Engineering (RSVP protocol with MPLS traffic engineering extensions)
SA Source Address
SDH Synchronous Digital Hierarchy
SONET Synchronous Optical Network
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Glossary
SPT Shortest Path Tree
ST Spanning Tree Protocol
STP Spanning Tree Protocol
TDM Time-Division Multiplexing
TE Traffic Engineering
TM Traffic Management
TTL Time to Live
UNI User Network Interface
VCI Virtual Circuit Identifier
VFI Virtual Forwarding Instance
VID VLAN Identifier
VLAN Virtual LAN
VLAN Virtual LAN
VOQ Virtual Output Queue
VPI Virtual Path Identifier
VPLS Virtual Private LAN Service
VPN Virtual Private Network
VPWS Virtual Private Wire Service
VR Virtual Router
VRF Virtual Routing and Forwarding
VSI Virtual Switching Instance
WFQ Weighted Fair Queuing
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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)
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: Using Label 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 WG’s of the IETF
Additional Slides Additional Slides
Metanoia, Inc.Critical Systems Thinking™
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Metanoia, Inc.Critical Systems Thinking™Label Assignment and Distribution
(control component)
Downstream Upstream
Ordered Solicited (On Demand)Unsolicited
SolicitedUnsolicited
Independent Solicited (On Demand)Unsolicited
SolicitedUnsolicited
Direction from which 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 requestfor 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
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A Word on Reservation Styles
Always chosen by the receiver
Two styles apply with RSVP-TE
Fixed Filter (FF)
Distinct reservation for traffic from each sender
Needs unique label per sender
Shared Explicit (SE)
Common resvn. 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 reservationshared by all senders
S1
S3
Link (i,j)
Different senders mayhave different labels
S2
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LDP versus BGP Signaling
LDP session full mesh b/ween PE’s
PE’s exchange labels directly
New PE reconfig. mesh at all PE’s
FIB per VPLS per PE
RR’s 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
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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 CE’s to peer PE’s
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)
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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/MPLSCore
Label block offset=0Label base = 3000Label range = 20
Label block offset=0Label base = 1000Label range = 20
10311
12
3002
DLCI=[401, 402, …, 420]
Label block offset=0Label base = 2000Label range = 20
403
2003
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BGP-based L2 VPN (VPLS)
PE1
PE2
PE3
3001
CE1
CE2
CE3
CE4
IP/MPLSCore
Label block offset=0Label block size = 10Label base = 3000
3002VE ID = 3