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A presentation given by RAD’s CTO, Dr. Yaakov Stein, at the 2012 MPLS and Ethernet World Congress. The presentation compares the two technologies in ten critical categories and grades them on suitability, coverage and maturity
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Ethernet vs. MPLS-TP in the Access Slide 1
Ethernet vs. MPLS-TPin Access Networks
Yaakov (J) Stein
CTO
RAD Data Communications
Ethernet vs. MPLS-TP in the Access Slide 2
Agenda
Is MPLS-TP ready to replace Ethernet as the packet technology that dominates access networks?
• Brief review of access networks
• Characteristics of Ethernet and MPLS-TP
• Technical comparison: Ethernet vs. MPLS-TP
Ethernet vs. MPLS-TP in the Access Slide 3
Access Networks
Ethernet vs. MPLS-TP in the Access Slide 4
Core:MPLS or IP
interface(and theoretically PBB)
Access Network Considerations
Access Network:Q-in-Q Ethernet?
MPLS-TP ?
Residential Customers
(IP)
Business Customers(IP or Ethernet)
Cell Sites(IP and/or Ethernet
and/or TDMand Timing)
Other customer
sites
Other customer
sites
InternetData
Centers
Ethernet vs. MPLS-TP in the Access Slide 5
CoreNetwork:
MPLS
Customer Network: Ethernet
Why Ethernet and MPLS-TP ?
• Ethernet started in customer networks (LAN) and over the years has moved into the access network (MEF)
• MPLS started in the core network and is now trying to conquer the access network
Access Network
First Mile
Last Mile
Ethernet vs. MPLS-TP in the Access Slide 6
Access Network Segmentation
A recent trend is to segment the access network into:• First/Last Mile
– Provides connectivity from customer site to first access node
– Leverages physical layer technologies such as DSL, active/passive fiber, microwave, HSDPA+, LTE, …
• Middle Mile– Collects and aggregates traffic from multiple access nodes
– Provides backhaul towards core
First/Last Mile Middle Mile
+Access Node
NTU/CLE
AggregationBackhaul
Access Network
Ethernet vs. MPLS-TP in the Access Slide 7
Access / Core Differences (1)
Differences between core and access networks may translate to protocol requirements differences:
Core Access Impact
No. of NetworkElements
Few – routers, LSRs, switches
Many – CPEs, NTUs, DSLAMs, aggregators
• Strong pressure on access NE price levels
• Access needs to be as “touchless” as possible
Data Rates Higher Lower • Core may guarantee QoS by resource over-provisioning
• Access needs QoS mechanisms
Ethernet vs. MPLS-TP in the Access Slide 8
Access / Core Differences (2)
Core Access Impact
Topology Richly connected Simple – typically trees or rings
• Fault in access network affects fewer people, but fewer bypass options
• Core can get away with fast rerouting
• Access network requires OAM and planned APS
Security “Walled garden”: • Strong security
to and from the outside world
• Loose security on the inside
Easily accessible • Customer networks alsoconsidered walled gardens
• Impractical to protect the entire access network
Ethernet vs. MPLS-TP in the Access Slide 9
Ethernet and MPLS-TP Overview
Ethernet vs. MPLS-TP in the Access Slide 10
Ethernet / MPLS-TP Differences (1)
While both Ethernet and MPLS are commonly used to carry IP,there are some fundamental protocol differences:
Ethernet MPLS-TP
OSI Layer L0-L2 (but may run over MPLS)
Requires a server layer to transport it (which may be Ethernet)
Packet Identification
Frames are inherently self-describing
No PID
Scope Destination address: Global, not aggregated
Only locally-meaningful labels
Source Identifier
Unique source address No source identifier
Clients IP and other IP and other
Transport Over SDH/SONET, OTN Over SDH/SONET, OTN
Ethernet vs. MPLS-TP in the Access Slide 11
Ethernet / MPLS-TP Differences (2)
Ethernet MPLS-TP
OAM and Protection
•Fault Management•Performance Monitoring•APS
•Fault Management•Performance Monitoring•APS
IP Protocols • No routing protocol defined
• A number of L2CPs
Leverages the entire IP suite of protocols
Loop Tolerance
No Can tolerate transient loops (has TTL field)
PriorityMarking
•3-bit (e.g., DiffServ)• “Drop Eligibility”
3-bit (DiffServ)
Additional Dedicated Tools
•Bandwidth Profiles•Timing over Packet•Security (MACSec)
None have been defined
Developed By • IEEE•Multiple competing SDOs
• IETF•Multiple competing SDOs
Ethernet vs. MPLS-TP in the Access Slide 12
Ethernet and MPLS-TP: Face-Off
Ethernet vs. MPLS-TP in the Access Slide 13
Comparison Criteria
1. Fault Management Functionality
2. Performance Management Functionality
3. Automatic Protection Switching Mechanisms
4. Quality of Service Mechanisms
5. Traffic – Handling Diverse Client Types
6. Timing – High Accuracy Time and Frequency Distribution
7. Integration with Surrounding Networks
8. CapEx
9. OpEx
10. Security
Each will be scored for:Suitability: 2 pointsCoverage: 4 pointsMaturity: 4 points
Ethernet vs. MPLS-TP in the Access Slide 14
Fault Management Functionality:The Arguments
The Need: Access networks require strong FM capabilities to minimize down-time
Ethernet• Two OAM mechanisms (Y.1731/CFM and EFM)• Unique source address, particularly amenable to trace-back functionality• Q-in-Q is not true client-server, but this is covered up by MEL• Y.1731 is full-featured – comprehensive set of FM TLVs • EFM is more limited, but adds dying gasp critical for CPEs• Interop issues of both OAMs have finally been resolved; remaining details
are resolved via implementation agreements (e.g., MEF-30)
MPLS-TP• Had basic heartbeats (BFD) and diagnostics (LSP-ping)• The IETF designed MPLS-TP FM based on the Generic Access Channel and:
• BFD for CC• LSP-ping for on-demand diagnostics• New frame formats to fulfill specific requirements
Ethernet vs. MPLS-TP in the Access Slide 15
Fault Management Functionality:The Verdict
Ethernet MPLS-TP
SuitabilityHighly suited (SA)
No true address, requires extra work
2 Points 1 Point
Coverage
Y.1731 is full featured, EFM fulfills its requirements
MPLS-TP FM similar to CFMbut missing dying gasp
4 Points 3 Points
Maturity
Y.1731 and EFM are interoperable and widely
deployed
Some MPLS-TP features are seeing initial trials
4 Points 1 Point
Total 10 Points 5 Points
Ethernet vs. MPLS-TP in the Access Slide 16
Performance Management Functionality:The Arguments
The Need: Useful tool for maintenance and diagnostics of the access network
Ethernet
• The ITU Y.1731 supports PM (loss, delay, PDV, …) using a request-response model; IEEE 802.1ag does not
• Y.1731 is used as the basis for commissioning procedures (Y.1564)
• Widespread vendor interoperability has been demonstrated
MPLS-TP• RFCs 6374, 6375 define a set of PM functions based on the GA Channel
• These functions were designed to be HW friendly, yet flexible- Support byte or packet counters- 1588 or NTP-style timestamps- Traffic-counters or synthetic loss
• Implementations have yet to be announced
Ethernet vs. MPLS-TP in the Access Slide 17
Performance Management Functionality:The Verdict
Ethernet MPLS-TP
SuitabilityNeither protocol has an inherent advantage or disadvantage
2 Points 2 Points
CoverageSupports all features
Supports all features (may be more flexible)
4 Points 4 Points
Maturity Y.1731 is finally interoperable
MPLS PM is not (widely) implemented
4 Points 0 Points
Total 10 Points 6 Points
Ethernet vs. MPLS-TP in the Access Slide 18
Automatic Protection Switching:The Arguments
The Need: APS is a complex subject, requiring careful protocol work and proper configuration. Solutions required for both linear and ring protection
Ethernet
• Ethernet has a particular problem with rings• There are many open loop ring protection (e.g., G.8032) but these are not
compatible with QoS mechanisms
MPLS-TP
• MPLS in the core exploits Fast ReRoute (RFC 4090) instead of APS• But FRR requires rich interconnection and so is usually not applicable
to access networks
• The IETF has standardized RFC 6378 for MPLS-TP linear protection• There are also proposals for ring protection
Ethernet vs. MPLS-TP in the Access Slide 19
Automatic Protection Switching:The Verdict
Ethernet MPLS-TP
SuitabilityNot suitable for ring protection
No particular strengths or weaknesses
0 Points 2 Points
Coverage
G.8031/G.8032 fulfill current requirements
RFC 6378 (linear protection); no ring protection RFC yet
3 Points 2 Points
Maturity
G.8031/G.8032 have been extensively debugged and
updated
MPLS-TP only partially finalized and not yet
deployed
4 Points 1 Point
Total 7 Points 6 Points
Ethernet vs. MPLS-TP in the Access Slide 20
Quality of Service:The Arguments
Two types of QoS need to be considered to manipulate traffic:1. Hard QoS (engineering): Connection Admission Control, Resource Reservation2. Soft QoS (conditioning): Priority marking, discard eligibility, queuing, bucketing
Ethernet
• PBB-TE (PBT) defines hard QoS, but is not widely implemented• P-bits for prioritization marking; discard eligibility marking in S-VLANs• MEF’s BW profile defines a bucketing algorithm• Ethernet headers are self-describing – support Traffic Awareness
MPLS-TP
• MPLS-TE supports resource reservation but traffic engineering may not be relevant for access networks
• Traffic Class (and L-LSPs) support DiffServ prioritization application awareness – MPLS packets are not self-describing
• DPI is required for Traffic Awareness
Ethernet vs. MPLS-TP in the Access Slide 21
Quality of Service:The Verdict
Ethernet MPLS-TP
SuitabilitySupports all QoS types
Does not define for (bucket-based) traffic conditioning
2 Points 1 Point
Coverage
MEF standards have been proven
Without bucketing,MPLS is at a disadvantage
4 Points 3 Points
Maturity
BW profiles are standardized;certification programs
MPLS-TP – nothing special
4 Points 0 Points
Total 10 Points 4 Points
Ethernet vs. MPLS-TP in the Access Slide 22
Traffic types:The Arguments
The Need: No transport protocol is useful if it can’t transport the required client traffic
Ethernet
• Differentiates traffic via Ethertype marking or LLC• Can directly carry IPv4, IPv6, MPLS, Ethernet, fiber channel, and low-
rate TDM (MEF-8)
• Does not directly carry other legacy traffic types (e.g., ATM, frame relay)• Can be carried indirectly via PHP’ed MPLS PWs
MPLS-TP
• Can carry IPv4, IPv6, MPLS, and PWs (and through which Ethernet, Fiber Channel and all legacy types)
• Defining a new PW type requires IETF consensus but the new packet-PWprovides more freedom
Neither is universal but existing mechanisms can be extended to cover new cases
Ethernet vs. MPLS-TP in the Access Slide 23
Traffic types:The Verdict
Ethernet MPLS-TP
Suitability
Supports arbitrary clients via Ethertypes
Supports arbitrary clients via PWs
2 Points 2 Points
Coverage
Does not support all legacy traffic types (ATM, FR)
Supports most traffic types via PWs
2 Points 3 Points
Maturity
Ethertypes have been widely deployed
PWs have been widely deployed
4 Points 4 Points
Total 8 Points 9 Points
Ethernet vs. MPLS-TP in the Access Slide 24
Timing:The Arguments
The Need: Distribution of highly accurate timing (frequency and Time of Day)is crucial for some access network applications, notably cellular backhaul
Ethernet
Two protocols have become standard for this purpose:1. Synchronous Ethernet (SyncE) is Ethernet-specific2. IEEE 1588-2008 (defined for Ethernet and UDP/IP) for Timing over
Packet; on-path support elements (Boundary Clocks or Transparent Clocks) have only been defined for Ethernet
MPLS-TP
• MPLS does not define a physical layer
• The IETF TICTOC WG is presently working on 1588oMPLS
Ethernet vs. MPLS-TP in the Access Slide 25
Timing:The Verdict
Ethernet MPLS-TP
Suitability
Supports ToP and defines a physical layer to support SyncE
May be able to support 1588 but there can be no
SyncMPLS
2 Points 1 Point
Coverage
Meets all requirements with SyncE, 1588, BC, TC
1588oMPLS to support ToP may be coming
4 Points 1 Point
Maturity
ITU-T has defined profile(s) for 1588 use
MPLS presently has no timing support
4 Points 0 Points
Total 10 Points 2 Points
Ethernet vs. MPLS-TP in the Access Slide 26
Integration:The Arguments
The access network needs to integrate with the core and customer networks. Cost and complexity will be minimized by a smooth hand-off, i.e., access protocol compatibility with other network protocols• Customer networks may have Ethernet or TDM interfaces (IP over Ethernet,
Ethernet over TDM, Ethernet over SDH)• Core networks are usually MPLS (IP over MPLS, MPLS over Ethernet, MPLS
over SDH)
Ethernet
• Ethernet in the access is a perfect match for customer networks
• Can not seamlessly interface with MPLS core
MPLS-TP• A reasonable match for customer network protocols since they can be
tunneled over MPLS• Reuses existing MPLS standards thus maximizing compatibility
Ethernet vs. MPLS-TP in the Access Slide 27
Integration:The Verdict
Ethernet MPLS-TP
Suitability
Perfect match for customer network, but not for core
Best match for core network, but not for
customer
1 Point 1 Point
Coverage
Ethernet Q-in-Q and MAC-in-MAC perfect customer hand-
off
Does not require GW for forwarding to core, but
control protocols may not interconnect
3 Points 2 Points
Maturity
Ethernet Q-in-Q presently widely deployed
Seamless MPLS still in its infancy
4 Points 1 Point
Total 8 Points 4 Points
Ethernet vs. MPLS-TP in the Access Slide 28
CapEx:The Arguments
The Need: Access network providers need to keep their costs down; due to the large number of Network Elements, access networks are CapEx-sensitive
Ethernet
• Ethernet switching fabrics are inherently non-scalable (long global addresses can’t be aggregated)
• Due to popularity, Ethernet switches are inexpensive (high volumes, large R&D investment in cost reduction)
• However, carrier-grade Ethernet switches need extra functionality• Ethernet supports CapEx-saving architectures (e.g., EPON)
MPLS-TP
• LSRs are complex and expensive – reducing the price of NEs (MPLS switchinstead of MPLS router) was the unstated motivation for MPLS-TP
• Pure MPLS NEs have simple forwarding engines and thus should be less expensive than Ethernet switches, but still require Ethernet or SDH or OTN interfaces
Ethernet vs. MPLS-TP in the Access Slide 29
CapEx:The Verdict
Ethernet MPLS-TP
Suitability
Inexpensive, but can not scale forever
Allows for significant cost reduction vs. full LSR
1 Point 2 Points
Coverage
R&D and volumes have driven down Ethernet CapEx
MPLS-TP-specific devices can be low cost
4 Points 4 Points
Maturity
MEF certification programs for carrier-grade Ethernet switches
Many trials are using LSRs; chip sets are starting to
come out to address
4 Points 2 Points
Total 9 Points 8 Points
Ethernet vs. MPLS-TP in the Access Slide 30
OpEx:The Arguments
• OpEx considerations that are taken into account:- Direct operations cost - Staffing- Minimizing “unchargeable” overhead
• Reduction of direct operations costs for networks with large number of NEs :- Equipment must work reliably and be interoperate- Minimum touch (auto-discovery, zero-touch configuration., etc.)- Use of FM, Control Plane or Management Plane protocols
• Maintaining competent staff requires:- Availability- Training- Employee retention
• Overhead minimization applies to: - Per packet overhead - OAM, CP/MP packets
Ethernet vs. MPLS-TP in the Access Slide 31
OpEx:The Arguments (Cont’)
Ethernet• Basic Ethernet is zero-touch by design but carrier-grade may add many
configuration parameters• A large number of useful L2CPs (STP, ELMI, GVRP) but no universal CP
protocol• In addition to equipment certification, MEF has initiated certification for
carrier Ethernet engineers• Main Ethernet overhead is large, but tags add only a small delta
MPLS-TP
• Basic MPLS relies on IP routing protocols but TP is designed to be able to function w/o CP
• GMPLS CP has been defined as an option• Can operate without IP forwarding (eliminating IP logistics); CP and MP
can be carried in GACh (although not yet developed)• Specific vendors have expert certifications but none specific to MPLS-TP• Same look and feel as other transport networks to minimize retraining• May leverage extensions to existing OSS
Ethernet vs. MPLS-TP in the Access Slide 32
OpEx:The Verdict
Ethernet MPLS-TP
Suitability
Metro Ethernets have been shown to be low OpEx
Designed to be inexpensively maintainable
2 Points 2 Points
Coverage
Inelegant CP, available staff, medium overhead
Learned from previous efforts
4 Points 4 Points
Maturity
Extensive experience and certification programs
Extensive operational experience only partially
applicable
4 Points 2 Points
Total 10 Points 8 Points
Ethernet vs. MPLS-TP in the Access Slide 33
Security:The Arguments
The Need: Security is perhaps the most important telecomm issue today
• OAM, APS, QoS mechanisms are powerless to cope with Denial of Service attacks
• Access network NEs are frequently physically unprotected, so:
1. Ports must be protected2. Packets must be authenticated and integrity checked 3. Confidentiality mechanisms may be needed4. MPs and CPs must be hard-state
Ethernet vs. MPLS-TP in the Access Slide 34
Security:The Arguments (Cont’)
Ethernet
• Ethernet packets carry unique authenticatable source addresses• MACsec and its 802.1X extensions define mechanisms that can be used to
protect carrier networks (although hop-by-hop security model may not always be ideal)
MPLS-TP
• MPLS was designed for core networks (walled gardens) with the assumption that there are no inside attacks
• Forwarding plane attacks based on lack of authentication/integrity• Control plane attacks based on soft state of protocols
Ethernet vs. MPLS-TP in the Access Slide 35
Security:The Verdict
Ethernet MPLS-TP
Suitability
Has an authenticatable unique SA
Has no source identifier and uses soft-state CPs
2 Points 0 Points
Coverage
MACsec and 802.1X, but may need more
Little positive support (but it does support attacks …)
3 Points 1 Point
Maturity
MACsec is starting to appear in standard chipsets
MPLS community is not addressing the TP security
problem
2 Points 0 Points
Total 7 Points 1 Points
Ethernet vs. MPLS-TP in the Access Slide 36
Summary: Final Score
Caveats:
• Deployments have particular (non)requirements, but all 10 considerations were given equal weight
• Some coverage and all maturity scores will change over time
Suitability Coverage Maturity Total
Ethernet 16/20 35/40 38/40 89
MPLS-TP 14/20 27/40 11/40 52
Note: MPLS-TP lost
• 29 points due to lack of maturity
• 9 points due to lack of security
Ethernet vs. MPLS-TP in the Access Slide 37
For information about RAD’s Ethernet Access solutions, visit www.ethernetaccess.com
www.rad.com