All Rights Reserved © Alcatel-Lucent 2008 (G)ELS - Ethernet VLAN-label Switching (ELS) (G)ELS -...

All Rights Reserved © Alcatel-Lucent 2008

(G)ELS - (G)ELS - Ethernet Ethernet VLAN-label Switching (ELS) VLAN-label Switching (ELS)

Benchmarking Carrier Ethernet Technologies Workshop

Session MII.1

Krakow, PolandApril 30, 2008

Dimitri Papadimitriou<[email protected]>

<[email protected]>

All Rights Reserved © Alcatel-Lucent 20082 | NGI 2008 - Workshop | April 2008

Evolution of Ethernet paradigmsTwo main scalability concerns: VLAN ID space - can not be solved with Provider bridges (IEEE 802.1ad) MAC address space & learning - (hierarchical) hash-based table lookup (=> simple but limited MAC table size due to memory consumption & non-deterministic lookup time)

Main “networking” concern: Loop avoidance (STP) - can not be solved with STP 802.1d or RSTP 802.1w Convergence time of STP - idem

Main performance concern: STP “blocks” network trunks - not solved with MSTP 802.1s

Spanning Tree Protocol (STP)(VLAN-)Bridges

Multiple STP (MSTP)Provider Bridges (PB)

Multiple STP (MSTP)Provider Backbone Bridges

(PBB)

Ethernet LAN/MAN bridging branch


Ethernet MAC and Ethernet v2

Ethernet 802.3 MAC Frame

Ethernet v2 Frame

Preamble SDDestination

AddressSource Address Length Information Pad FCS

7 1 6 6 2 4

64 to 1518 bytesSynch Startframe

• MAC address (6 bytes) is either • Single address (0x0….)• Group address (broadcast = 111...111)

• MAC addresses are defined • on local (0) or global (1) basis (second bit)• 246 possible global addresses

Preamble SDDestination

AddressSource Address Type Information Pad FCS

7 1 2 4

64 to 1518 bytesSynch Startframe

6 6

No TTL (time to live) => impossible to detect

looping Ethernet MAC frames


Spanning Tree Protocols: Count-to-infinity

Spanning tree: a connected, acyclic subgraph (no cycles) containing all the vertices of a graph

Minimum spanning tree (aka shortest spanning tree): a weighted graph which contains all of the graph's vertices

Count-to-infinity problem (as for any other Distance-Vector routing protocol)

Temporary forwarding loop (cycle) that con persist for O(10s)

(R)STP does not provide for fast convergence (and no - known - suitable technique to improve distance vector convergence properties)

Note: steiner tree = a minimum-weight tree connecting a designated set of vertices, called terminals, in an undirected, weighted graph or points in a space. The tree may include non-terminals.

Source: Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology. 17 July 2006.

Root Root unreachablecycle


Evolution of Ethernet paradigms: PBB

Two main scalability concerns: VLAN ID space - solved: S-VID (12 bits) -> I-SID (24bits) MAC address space & learning - solved: MAC-in-MAC tunneling (MAC learning still required)

Main “networking” concern: Loop avoidance (STP) - not solved Convergence time of STP - not solved

Main performance concern: STP “blocks” network trunks - not solved




(PBB)

Ethernet LAN/MAN Bridging branch


Ethernet Transport technologies

Switching Bridging

Ethernet • ELS: Ethernet VLAN-label switching (link local label): VLAN ID Label

• PBB-TE: Provider Backbone Bridges - Traffic engineering (domain wide label): DA_MAC + VLAN ID Label

Evolution of both Ethernet control and forwarding paradigm

• Legacy: VLAN Bridged Ethernet (MSTP)

Provider bridges: IEEE 802.1q/.1adPBB Provider Backbone Bridge: IEEE 802.1ah

• Shortest Path Bridging: IEEE 802.1aq ( link-state)

Evolution of Ethernet control paradigm only

Shim header (sub-layer)

• Legacy: Ethernet Pseudo-wire over MPLS Packet Switched Network (PSN)

Routing bridges (Rbridges)

Ethernet packet-switched technology with two possible variants: Ethernet Bridging: 802.1ah (PBB), 802.1aq (SPB) Ethernet Switching (ongoing efforts):

MAC + VID based (domain-wide labels): 802.1Qay (PBB-TE) VID based (link-local labels): Ethernet VLAN label switching


Problem statement

Management

Spanning Tree, Learning, FilteringForwarding Plane Ethernet Control (MSTP)

Provisioning(Policy, etc)

Provisioning(Forwarding Components)

Existing IEEE 802.1 forwarding components and their control does not fulfil requirements associated to Carrier Ethernet metro (and core) networks


Evolution of control and forwarding paradigms: Ethernet VLAN-label Switching (ELS)




(PBB)

Ethernet Bridging branch (Distance

vector)

Ethernet Switching branch (Link State

routing)

S-VID (encapsulation) +

Constraint-based switched data paths

Link-local labels


Ethernet LER (E-LER) function: take an incoming Ethernet MAC frame, add or remove the label (encoded in the TAG field)

Ethernet LSR (E-LSR): take incoming labelled Ethernet MAC frame and perform label swap (VID in VID out) => forwarding independent of destination MAC address

Ethernet: point-to-point and point-to-multipoint data paths

Ethernet VLAN-label Switching (ELS) - Overview

Ethernet 802.1ad Switch

E-LSR E-LSR E-LSR

Source Dest

Router

S-VID swapS-VID push S-VID popEthernet

LSP

Ethernet MAC frame

Ethernet MAC frame

Eth. PHYEth. PHY Ethernet 802.1ad Switch

Ethernet 802.1ad Switch

Router

PHY

MAC header + S=VID

Payload (Eth, X, Y)


Ethernet VLAN-label Switching (ELS) - Framing

Ethernet Frame Format

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // +-+-+-+-+-+-+-+-+-+| MAC_DA | MAC_SA | S-TAG | C-TAG | ET| Payload | CRC |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // +-+-+-+-+-+-+-+-+-+

IEEE 802.1 TAG format

Oct: 1 2 3 4+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+| TPID | TCI |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

bit: 8 1 8 1 8 1 8 1

TPID (16 bits): TAG Protocol IdentificationTCI (16 bits): TAG Control Information

S-VLAN TAG Control Information (TCI)

Oct: 1 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ PCP (3 bits): Priority Code Point | PCP |D| S-VID | D (1 bits): Drop Eligible Indicator (DEI) bit+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ S-VID (12 bits): S-VLAN Identifier

bit: 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1


Traffic engineering adapt traffic routing to network conditions with joint traffic and resource-oriented performance objectives

Effectively control usage of available network resources (put traffic where unused capacity is)

Efficiently re-/direct selected traffic flows from IGP shortest path onto an alternative path

Rapidly redistribute traffic in response to changes in network topology

Performance objectives (provisioning and recovery) Resource-oriented Traffic-oriented: packet loss, delay (and variation)

Approaches Proactive (longer-term): anticipating traffic changes Reactive/adaptive (shorter-term): responsive to traffic

changes

ELS Control Paradigm: Traffic Engineering


Use RequestConstraints

Explicit Route Representation

(GMPLS) RSVP-TE Signaling

Traffic engineeringDatabase (TEDB)

Traffic engineeringDatabase (TEDB)

Routing table

(GMPLS) OSPF-TE

Operations performed by a LSP head-end (G)MPLS-TE capable node

Constrained-SPF Computation

1 2

3

6

4

5(GMPLS) OSPF-TE ExtensionsDistributed (piggybacked) using Opaque Link State Advertisements (LSA) & encoded as Link sub-TLVMetrics: Unreserved Bandwidth, Maximum Reservable Bandwidth, TE Metric, Resource Class and ISCD (Max. LSP Bandwidth, Switching Cap., LSP Enc. Type)

(1) Store information from IGP flooding in the Link State DB (LSDB)

(2) Store traffic engineering information in the TE Link State DB (TEDB)

(3) Examine user defined constraints for the incoming connectivity requests (=> QoS routing)

(4) Path computation for the data path (LSP) through the TE link topology (=> Policy routing)

(5) Representation of the computed path as an Explicit Route (=> Source routing)

(6) Pass Explicit Route to (GMPLS) RSVP-TE engine for signaling

Constrain-based Routing (Policy-based + QoS source routing)


Ethernet VLAN-Label Switching (ELS)

S-VID Label (link local)

Positioning ELS

Ethernet (Untagged, C-/S-VID)

Shim (I-SID)

Ethernet + B-VID

Provider Backbone Bridges (PBB)

Provider Backbone Bridges (PBB-TE)

Ethernet (Untagged, C-VID)

[Ethernet] + S-VID


Shim (CW + PW label)

PSN Tunnel (MPLS)

Ethernet PW over MPLSMPLS Label (link local)

PayloadPayloadPayload

IEEE: PBB/PBB-TEEthernet VLAN-label

Switching (ELS)Ethernet PW over

MPLS

4k LSP per port (max.)

LSP merging

Unique payload type per LSP

Encapsulating LSP can not be merged (as PW labels are node specific)

PBB: same issues as for any other 802.1 based technologyPBB-TE: Single domain (MAC unicity) and no multicast support (single VID space segmentation)


Positioning ELS vs PBB-TE (1)

ELS (Ethernet VLAN-label

Switching)Provider Backbone Bridges (PBB-

TE)

Paradigm

Ethernet frame forwarding independent from destination MAC address (no learning)

Constraint-based routing

Add traffic engineering capabilities to PBB networks

Connection ID encoded in the data frame

Label encoding S-VID (12 bits) B-VID + B-MAC DA (requires MAC-in-MAC)

Label semantic Link local Domain wide

Hierarchy Single level Single level

PathUnidirectional, Bi-directional P2P

Unidirectional: MP2P (merge), P2MP (multicast)

Unidirectional, Bi-directional P2P

Unidirectional MP2P (multiplexing requires SA MAC lookup =/= classical label merging)

No P2MP data path support

Provisioning

RecoveryControl-plane based (GMPLS RSVP-TE)

Management or optionally control-plane based (GMPLS RSVP-TE)

Data plane linear protection based on (ongoing efforts on ring protection)

Load balancing No (in order delivery) No (in order delivery)

OAMBFD, Ping, Traceroute

ETH OAM (based on Y.1731)

ETH OAM (based on Y.1731)

CC/CV OAM requires SA MAC lookup


Router

Frame Filtering

I-SID

B-VID

B-DA

IP/MPLS

ETH + S-VID

Router

PWoMPLS LER

IP/MPLS

ETH+S-VID

IP/MPLS

ETH

IP/MPLS

ETH

Ethernet LSR

Ethernet Transport

Ethernet Transport

Positioning ELS vs PBB-TE (2)

PB (BCB)

VLAN label Switching

Ethernet Label Switching <B-DA, B-

VID>

S-VID Label Switching

Frame forwarding independent of MAC

address

Same Ethernet MAC address

space

Disjoint Ethernet MAC address

spaces

ETH PHY

PBB (BEB)

IP/MPLS

ETH + S-VID

IP/MPLS

ETH + S-VID

B-SA


Positioning ELS vs Ethernet PW over PSN (1)

Ethernet Label Switching (ELS)

Ethernet (Untagged, C-VID)

[Ethernet] + S-VID


Shim (CW + PW label)

PSN Tunnel (MPLS)

Ethernet Pseudo-Wires (PW)

Connectivity Service

Network Emulation & Adaptation

Network PE-to-PE Connection

Data link layer

Ethernet P2P, P2MP, MP Segment

Pseudo-Wire (PW) label

MPLS/T-MPLS

Network Intermediate Trunks MPLS Tunnel/T-MPLS Tunnel

Ethernet MAC/PPP-HDLC

Ethernet PW over PSN

Client Payload Outside scope

Physical layer Ethernet PHY/SONET-SDH

Ethernet Transport

Ethernet P2P, P2MP Segment

Ethernet Path (PE-to-PE) Append S-VID to Ethernet frames

IP, IP/MPLS, etc.

Ethernet PHY/SONET-SDH


Router

PWoMPLS LER

IP/MPLS

PW

ETH

MPLS

MPLS

DLL

IP/MPLS

ETH

IP/MPLS

ETH

MPLS LSR

Router

PWoMPLS LER

IP/MPLS

ETH+S-VID

IP/MPLS

ETH

IP/MPLS

ETH

Ethernet LSR

Ethernet (connectivity) Service

Ethernet Transport

Positioning ELS vs Ethernet PW over PSN (2)

MPLS Label Switching


MPLS Label Switching

Same Ethernet MAC address

space


spaces

ETH PHY

S-VID Label Switching

Frame forwarding independent of MAC

address


Resolving the Ethernet Paradox

Ethernet Paradox Ethernet evolves as intra-domain aggregation technology for metro & core

networks (by better adapting transport to Ethernet as MPLS is adapted to IP)

Ethernet forwarding plane Ethernet switching technology e.g. ELS Moving Ethernet "networking" properties (linked to LAN / campus networks)

toward metro-aggregation networks - but also core - definitely transform intrinsic nature of Ethernet

Ethernet routing paradigm (control) use of unified control e.g. GMPLS

Consequences Ethernet control:

From distance vector routing protocol (spanning tree protocol) to link state routing protocol

As IP routing evolved from RIP (distance vector) to OSPF (link state) Ethernet forwarding:

Ethernet forwarding without specific mechanisms suitable/dedicated for LAN (campus, enterprise, etc.) environments

Mechanisms fitting specific needs of aggregation


Router

IP/MPLS

Optical

ETH

IP/MPLS

ETH

IP/MPLS

ETH

Router

IP/MPLS

ETH+S-VID

IP/MPLS

ETH

IP/MPLS

ETH

Ethernet LSR

Ethernet (connectivity) between routers using OWS network

ELS and Architectural evolution: IP over Optics IP over Carrier Ethernet

Optical Switching


Optical Switching

S-VID VLAN Label Switching (802.1ad)

Same Ethernet MAC address space + Same admin domain


spaces+ Service boundary

ETH PHY

Ethernet (connectivity) between routers using carrier Ethernet switching network


Architectural evolution: IP over Optics IP over Carrier Ethernet

IP routers traffic aggregation (level 1) networking (single peering point), IP fast re-routing (not MPLS), and multi-topology routing, and

BFD (OAM) Carrier Ethernet: robust, resilient, flexible and cost-effective traffic aggregation (level 2) Optical equipment/switching: (internal long distance) connectivity

IP router

Carrier Ethernet

Optical

Domain boundary

Long distance, Ethernet switch interconnection

Domain boundary IP router

ETH PHY ETH PHY ETH PHY

ETH PHY ETH PHY


Tomorrow’s situation

< 5,5 km < 50 km < 100 km < O(100 km)

O(10) nodes

LargeCO

RegionalPOP

Ethernet aggregation

Ethernet metro switch

Core

Metro-Aggregation

Metro Access

First Mile

< 10 nodes

IP edge routers

CustomerPremises

IP Access router

IP Access router

SP1..i-1

SPi…n

Internet

Ethernet aggregation

Ethernet core switch

100GbE

100GbE


Conclusion: Evolution of Ethernet control and forwarding paradigms

Forwarding component

control

Provisioning(TE data paths, re-routing, etc)

Management

Forwarding Plane Unified Ethernet Control (e.g. GMPLS)

The ultimate goal toward Carrier Ethernet …

Provisioning(Forwarding Components)


Several issues for further investigation

Ethernet Forwarding Plane Ethernet label space and scalability ( Label/LSP merging ?) - specific

to link-local label switching based Ethernet forwarding Ethernet CoS mechanisms (DSCP to Ethernet PCP mapping DCP ?) -

common Ethernet multicast traffic (connectivity and adaptation) - common

Ethernet Control - common Unified traffic engineering (including fast re-routing) lighter protocol

suite(*) ? Adaptive traffic engineering and resource allocation including

Bandwidth Constraint Models (BCM) Lightweight measurement/monitoring capabilities including

performance

(*) fundamental issue: developing, deploying and operating metro Ethernet using unified

control must remain time-, resource- and cost-efficient (prevent over-engineering)


Thanks !

AcknowledgementsThis work was carried out within the framework of the IWT TIGER project sponsored by

the Flemish government institute for Innovation through Science and Technology in Flanders (IWT)

All Rights Reserved © Alcatel-Lucent 2008 (G)ELS - Ethernet VLAN-label Switching (ELS) (G)ELS -...

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