Ethernet, MPLS, Where and How
Much?
Tim Pearson
Leader, Asia Business Development
timp@nortel,com

MPLS JAPAN 2007

Introduction> How far you push MPLS from the WAN into the MAN is akey decision facing service providers> Robust new developments in ethernet technologies
change the question from “how far” you push MPLS into
the metro, to “how much and why?”> The relationship of MPLS and Ethernet will dominate thisdecision due to technology and architecture fundamentals> An Ethernet metro solution that offers transit for nonEthernet services based on MPLS adaptations is thescalable next generation solution.
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Metro Ethernet Applications
Overview of Deployment Scenarios
Ethernet Access in the First Mile

Business Service Delivery(Ethernet VPNs)

E-Line E-Tree

Residential Service Aggregation

MERS
8600

E-LAN

Wireless Aggregation

MERS
8600

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MPLS in 2007
> Defined in such a way that it touches most othernetworking technologies• E.g. GMPLS into L1 and optical, ubiquitous shim for packet
processing> A fundamental value is the combination of automation andautonomous resiliency offered by the set of MPLS control
planes.
> MPLS dominates the WAN, the question has become will
the virtues of MPLS automation stand up to the scaling
requirements of the MAN.
> A key value of MPLS is the control plane, so question
becomes how does control plane fare when pushed to theedge.
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Nature of LDP> LDP is a label flooding mechanism> Each device when it learns of a FEC offers a local label for
the FEC to it’s peers• either via routing/Independent mode, or via LDP peers/ordered mode

> Per platform labels/liberal label retention is most commonusage• Minimizes per-peer state, and simplifies FIB refresh as it produces acommon per platform FIB> Amount of state per LSR per interface goes up linearly withthe number of PE /32 FECs in the network

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Liberal/IndependentNature of RSVP-TE> RSVP-TE is focused on P2P and more recently P2MP
> RSVP-TE hellos giving way to FRR or e2e BFD> RSVP-TE + FRR is N-squared LSPs plus backup per
potential point of failure• Per link for facility, per LSP per hop for detours

FRRPrimary andFacility backup

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Nature of BGP> BGP in an MPLS context is basically a flooding
mechanism for service information between PEs> Primary uses are auto-discovery (L2VPN) and to relay
customer reachability information (L3VPN)> Basic “route target” receiver filtering paradigm and nominal
full mesh of adjacencies needs route reflectors to scale
RR

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Network build> What does the network look like the closer to the edge youget?
• Order of magnitude more devices• Progressively smaller community of interest for any given device• Increased price pressure• Increased difficulty of craftsperson access• Unmanned sites• Desire for reduced complexity, footprint and powering requirements• Real estate and enclosure start to dominate overall cost

So what sort of MPLS options exist for the MAN?
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Option 1: MPLS to the Edge
> This means• relatively flat LDP PSN (/32 labels)• Multi area solutions to achieve some degree of isolation• Large number of labels on any given interface• VPLS N-squared becomes a problem->H-VPLS->resiliency• RSVP-TE N-squared becomes a problem• Amount of BGP configuration and route reflectors is a concern
MANMPLSMAN

The wall you will hit is the amount oftelemetry collected that is of little value
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Option 2: MPLS L2-L3 Islands> We’re seeing a trend to L3 WANs and Emulated L2 MANs
• 2547 in the core, VPLS in the metro> We assume VPLS is the current choice in the perceived
absence of other solutions> Produces a decoupled solution• L2 MAN, L3 WANVPLSMANMPLS
WAN

VPLS
MAN

This produces a complex metro simply
because L2 is emulated instead of natively
recreated

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Option 3: Ethernet PSN> Third option is to produce decoupled islands but using
Ethernet instead of MPLS
> Much of the world already doing Ethernet• Swiss Army Knives have Ethernet RJ45 on the back• Broadband is already going Ethernet• DOCSIS, DSLF “TR-101 migrating to Ethernet aggregation”> Issue is other legacy services, and how far do you invest
in continuing to support/transition declining markets• FR/ATM, CES etc.
Ethernet
MAN
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MPLSWAN

Ethernet
MANMPLS JAPAN 2007

MPLS and Ethernet> MPLS initially defined as IP helper, so universal carriage
over any link layer is defined• If it carries IP, it carries MPLS

> Ethernet is ubiquitous, so universal carriage over any linklayer is defined• 802.3, 802.17, GFP/SONET/SDH, MPLS etc.
• Ethernet has it’s own link layers as well

> MPLS & Ethernet each can encapsulate and carry theother> PEs have Ethernet UNIs and NNIs
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However…
… not all semantics of the relationship translate evenly> Ethernet carrying MPLS starts as a broadcast medium andfilters to produce more selective behaviors• The atomic unit is a broadcast LAN segment> When MPLS PEs are directly connected by Ethernet,
MPLS declares itself redundant• PHP> MPLS carrying Ethernet clones P2P tunnels to produce asplit horizon “full” mesh
• The atomic unit is a P2P PW
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Emulating Broadcast with a PW Mesh
> Places a lot of burden on the PEs> May keep some state out of the core
• But at the expense of multicast inefficiency AND• N-squared PW control, OAM and telemetry> H-VPLS improves the situation, but does not change thefundamentals• “many” MPLS PWs to emulate Ethernet “one” Ethernet segment> Clearly carrying MPLS with Ethernet is different than carrying
Ethernet with MPLS

Why emulate broadcast with connections built on
a broadcast media?
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So, when considering the network…
>It is the relationship between MPLS and Ethernetthat will dominate choices>If MPLS recreation of Ethernet LAN segments has
clear scaling issues, lets take that off the table>Lets do Ethernet WITH Ethernet and leave MPLS
to do what it does well
Eliminate the scaling burden that Ethernet as
the dominant service will place on MPLS
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Ethernet Tools to Scale> Defined solutions:••

Link layer: LAG, RPR etc.
802.1ad QinQ,> Separation of “Ethernet as a service” from “Ethernet as
infrastructure”..802.1ah MACinMAC••••

Secure the MAN/WANPush customer state to the edgesEasy to instrument known end points
Carrier in complete control of all aspects of Ethernet forwarding> OAM… 802.1ag CFM/Y.1731•

Fault and performance management OAM for Ethernet> Configure “Ethernet infrastructure”…802.1Qay PBB-TE•

Engineered p2p and p2mp
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Future Innovations – 2008/2009> Infrastructure• L1/L2 clock distribution via Ethernet PHY/Ethernet frame• eDCO – DSP dispersion compensation for optical• 1600km reach with no regeneration or engineering of fiber• Control plane• Routing for link state bridging plus connection automation> Services• PW adaptations of legacy L2 onto Ethernet directly• “Dry Martini”• Simple and scalable L2VPN side by side with PBT• MACinMAC + PBT + Routing system + loop suppression• near zero-config ELAN +ETREE
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The vision – Converging on Ethernet

Legacy/Clocked(Private line, wireless)

MPLS Services(RFC 2547 VPN, PWs etc.)

Ethernet Services(EVPL, ELAN, ELINE, Multicast)

Ethernet
Ethernet with LANs and connections as the infrastructure of choice
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In Conclusion…
> Ethernet is fundamentally the most flexible networking
technology• It is a commodity with vast untapped capabilities> We can re-purpose Ethernet switches with new control
software to broaden their role in the network• TE, SPF in addition to bridging and multicast….

> This can be done with minimal changes to Ethernet
standards• And they are well underway> This lets us radically delayer and simplify the network
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For Further Reading
Fedyk, Don, David Allan, et. al. “GMPLS control of Ethernet” IETF Draft
June 2006 <http://www.ietf.org/internet-drafts/draft-fedyk-gmplsethernet-pbt-01.txt>.
Allan, David, Nigel Bragg, et. al. "Pseudo Wires over Provider Backbone
Transport. " IETF Draft July 2006 <http://www.ietf.org/internetdrafts/draft-allan-pw-o-pbt-01.txt>.
Allan, Bragg, McGuire, Reid. "Ethernet as Carrier Transport
Infrastructure." IEEE Communications 44(2006): 134-139.
Allan, Bragg “Taking Control: The evolving role of control and dataplanes”
Nortel Technical Journal, Issue 4
http://www2.nortel.com/go/technicaljournal_index.jsp?locale=en-US
Fedyk, Bottorff “Provider Link state Bridging”,
http://www.ieee802.org/1/files/public/docs2007/aq-fedyk-provider-linkstate-bridging-0107-01.pdf

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Questions?