metro ethernet: understanding key underlying technologies © copyright 2007 all rights reserved...

Metro Ethernet: Metro Ethernet: Understanding Key Underlying Understanding Key Underlying

TechnologiesTechnologies

© Copyright 2007All Rights Reserved

Metanoia, Inc. [email protected] +1-888-641-0082http://www.metanoia-inc.com

Metanoia, Inc.Critical Systems Thinking™

Next-Generation Systems & Networks Workshop, 17th July. 2007, Bangalore, India 2Copyright 2007

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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





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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


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


Inlabel

Outlabel


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



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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


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



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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


10311

12

3002

DLCI=[401, 402, …, 420]


403

2003

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