Foundry Networks

Principal member of the MPLS Forum

Challenges Facing L2 VPN
MPLS Japan 11/8/2001
Gary BlankenshipFoundry Networks
Systems Engineer - JapanFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Agenda• L2 Technologies in MAN (Metro)• MPLS VLL Draft-Martini• MPLS VPLS
• Interoperability

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

L2 Technologies in Metro Area
Networks (MAN)• 802.1Q allows a maximum of 4,096 unique VLANs• SuperVLAN. A stack of two 802.1Q headers to be
carried in an Ethernet frame. 16 million unique VLANs– Potential solution through VLAN tag stacking –4096x4096 VLANs– Can work with Spanning Tree
– Customers can define their own VLAN ID– Core of the network remains limited to 4,096 VLANs– Large number of MAC addresses in the core
– Management of the VLAN hierarchy can becomerather complex

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

L2 Technologies in Metro Area
Networks (Cont.)• SuperVLAN– Lacks visibility of individual customer traffic within the network
core• Customers VLANs within the same Super VLAN must share
its resources (Aggregation = Loss of 802.1p information)• Broadcast/unknown unicast traffic may be forwarded tomore edge switches than necessary– Limited means for resources allocation and QoS treatment from802.1Q– STP provides only crude traffic placement ability andis not straightforward to manage• 802.1w – Rapid Spanning Tree Protocol for rapid
convergence time of 1 to 5 seconds• 802.1s – STP per VLAN Group provides VLAN and
STP scalability, and utilizes dark fiber efficiently
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Super VLAN Aggregation Solution to
VLAN Growth
VLAN 200: SVL 1000
VLAN 200: SVL 1000

Customer Access Backbone

VLAN 100: SVL 1000

Tag Type 9100

BigIronBigIronUT: SVL 1000

VLAN 100: SVL 1000

BigIronT

Customer1 Customer2
VLAN 100 VLAN 200

SVL: Super VLAN
T: Tagged interface
UT: Untagged interface

Foundry MPLS Tehnology, Confidential and Proprietary

Customer1 Customer2
VLAN 100 VLAN 200

November© 2001 Foundry Networks, Inc.

How 802.1s Works
STP with VLAN Grouping
Using 802.1 S
To Support 4 to 8 groups of Spanning Tree

(Tag ID=0x8100)

User-1VLAN 1-10

User-2VLAN 1-10

FWD
ALL VLANS

BI-Edge
Prio 5

BI-Edge
Prio 5VLAN 1011

Spanning Tree in Service
Provider’s network(Tag ID=0x9100)

BLK
VLAN 1011

VLAN 1025

Spanning Tree in Service
Provider’s network(Tag ID=0x9100)

VLAN 1025

BI-Core1
Prio 3, 0

BI-Core2
Prio 1

BI-Core3
Prio 2

BI-Core4
Prio 0, 3
BLK
VLAN 1025

BI-Edge
Prio 5User-2VLAN 1-10

VLAN 1011

BI-Edge
Prio 5User-1VLAN 1-10

VLAN 1-1024-> VLAN Group 1 =VLAN 1025-2048 -> VLAN Group 2 =VLAN 2049-3072 -> VLAN Group 3 =VLAN 3073-4096 -> VLAN Group 4 =All Core Switches forwarding unlessotherwise noted
Dash line indicates blocked state

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Foundry’s SuperSpan™

A Breakthrough For Layer 2 Network
Scalability and High Availability• Organizes Layer 2 Metro Core into smaller STP domainsthat are easy-to-manage and simple to configure• Localizes STP to the domain – Provides rapid convergence withineach domain with 802.1w Rapid STP• Dramatic improvements in scalability – By joining simple, fasterconverging STP domains, SuperSpan allows highly scalable large
Layer 2 Metro networks• Improves High Availability – A link failure is confined to the STP
domain as other STP domains will be unaffected• Allows any flexible topology within each STP domain – star, ring or
mesh networks• Interoperates with Super VLAN aggregation to allow end-to-end
VLAN based services
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

How Foundry’s SuperSpan Works
Easy-to-manage, scalable, highly available
Layer 2 Metro Core Networks!
Provides highly
scalable Layer 2
Metro networks
SuperSpan joins
STP domains

Each STP domain
can have any
topology

802.1w
provides rapid
convergence ineach domain

STP Domain 1

STP Domain 2

STP Domain 3

Linear Topology

Star Topology

Linear Topology

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

MPLS Layer-3 vs. Layer-2 VPNs
Layer-3• Provider has to do some routing
on the subscriber’s behalf on the
PE routers – extra burden for theprovider• Each PE router must havemultiple routing and forwarding
tables, one per customer site
• Introduces operational andmanagement complexity• Scalability challenges• IP-only solution as it is a routed
service

Layer-2
•

•
•
•

•

•

Provider doesn’t handle any routing
on the subscriber’s behalf, instead
only simple mapping of Layer-2
frames to VCs is done
No multiple routing and forwarding
tables, only the global routing table
Much simpler to operate and manage
No scalability challenges in point topoint mode
Scalability challenges in VPLS mode
Subscriber IP addresses are opaque
to the provider, that way overlapping
address spaces are handling without
any extra work on the provider side
Solution allows for carrying any
protocol contained within the Layer-2
framesFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Agenda• L2 Technologies in MAN• MPLS VLL Draft-Martini• MPLS VPLS
• Interoperability

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

What Is Virtual Leased Line/DraftMartini???
• “Draft-Martini” refers to two IETF Internet Drafts co-authored by
Luca Martini of Level3• draft-martini-l2circuit-encap-mpls-03.txt– Defines encapsulation formats for ATM, FR, Ethernet, Ethernet
VLAN, HDLC, and PPP– We focus on Ethernet and Ethernet VLAN for now• draft-martini-l2circuit-trans-mpls-07.txt– Proposes an extension to Label Distribution Protocol (LDP)– Purpose is to coordinate encapsulations between two routers– Introduces a new VC FEC TLV, to be used within Label Mapping
messagesFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

VLL Feature Highlights• Capable of selecting LSP tunnels based on COS criterion• Load balancing among multiple LSPs, tunnel failover• The two endpoints of a VLL can have
– Mixed tagged and untagged– Different tagged VLAN IDs• VLAN ID can be reused– Subject to same DMA restriction• Label withdrawal when local port goes down

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

The Martini Drafts• The Martini drafts introduce the concept of Virtual
Circuits (VCs)• LSP are used as tunnels, an LSP might carry multiple
VCs• To accomplish this, the drafts leverage the MPLS label
stacking ability by adding an extra MPLS label that
distinguishes the VC used
• An MPLS frame traversing a service provider network
has two labels:
For the LSP– Tunnel LabelFor the VC– VC LabelFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

The Martini Drafts• draft-martini-l2circuit-trans-mpls-07.txt– Distribution of VC labels via LDP– Introduces a new VC FEC TLV, to be used within
Label Mapping messages• draft-martini-l2circuit-encap-mpls-03.txt– Defines encapsulations for ATM, FR, Ethernet,
Ethernet VLAN, HDLC, and PPP
Format for Ethernet/VLAN Encapsulation:
PPP-MPLS
or
Enet Hdr.

Tunnel
Label

VC
Label

Optional
Control
Word

Tagged or untagged Ethernet payload

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

The Virtual Lease Line (VLL) Service• The mechanisms specified in the Martini drafts could
be used to offer a Virtual Leased Line (VLL) service forpoint to point connectivity• The Virtual Leased Line is just an abstraction of the
Virtual Circuits involved in realizing the point to pointconnectivity, making the service more manageable• A VLL is composed of two VCs one in each direction,
thus giving it bidirectionality
VLL

PE-A

LSP
VC

PE-B
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

What Draft-Martini Is and Is NOTMPLS backbone

PE-SF

PE-SJ
Customer-A
Endpoint-SF
Customer-A
Endpoint-SJ• Layer-2 packet relay between two customer endpoints
using MPLS encapsulation• The VLL is only known to the two Provider Edge (PE)routers involved• Point-to-Point ONLY
• Draft-Martini does not include Point-to-MultiPoint
support – it’s not transparent LAN switching (TLS)
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

What Draft-Martini Is and Is NOT(cont.)• No switching means– PE routers do not have to care and learn about MAC
addresses– Forwarding simplicity– No MAC table scalability concern

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Anatomy of a VLL

What Needs to Be Configured?
• VLL name and ID– VLL ID must be unique on the two PE routers – it allows thetwo PEs to know which VLL they are referring to– Name is just for user reference and is not signaled• VLL Peer
– IP address of the other PE router• Local Endpoint– Customer-facing interface– Can be either an untagged port or an tagged port with a
specified VLAN-ID– Benefit of tagged endpoint: can have multiple endpoints on
one physical port

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Sample Configurations• Untagged endpointrouter mpls
vll foundry-sj-to-sf 40000
vll-peer 192.168.2.100
untagged e 2/1

VLL ID• Tagged endpointrouter mpls
vll foundry-sj-to-la 50000
vll-peer 200.100.1.100
vlan 20
tagged e 3/1• Options: statically configured label
values, vll cos (class of service)
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Anatomy of a VLL

How Does a VLL Transport Packets?
• Peers forming a single virtual pipe
• Peers exchange VC-label to VLL-ID binding through LDP
session with Draft-Martini extension“To“Tosendsendpackets
packetsfor
forVLL-ID
VLL-ID1000
1000
to
me,
use
VC
label
X”
to me, use VC label X”“To“Tosendsendpackets
packetsfor
forVLL-ID
VLL-ID1000
1000
to
me,
use
VC
label
Y”
to me, use VC label Y”

PE-SF

PE-SJ

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Anatomy of a VLL

How Does a VLL Transport Packets?
• LSP tunnels, established by RSVP, provide the transport
through MPLS backbone
PE-SJ can be reached by LSP TL-20
Outgoing tunnel label is L

PE-SJ

PE-SF can be reached by LSP TL-10
Outgoing tunnel label is M

PE-SF

Outgoing MPLS packet generated by PE-SJ:
PPP
PPPHdrHdr
Type-MPLS
Type-MPLS

TunnelTunnel
Label
Label
MM

VC
VC
Label
Label
YY

TaggedTaggedororuntagged
untaggedEthernet
Ethernetpayload
payloadFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Anatomy of a VLL
VC Label Signaling• Once all configurations are complete, a PE router sends an LDPLabel-Mapping message to the other end (in downstream
unsolicited mode)• The message indicates the binding of a local VC label (in Label TLV)
to the VC FEC TLV (introduced by draft-martini)
012
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|
VC tlv|C|
VC Type|VC info Length |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|
Group ID|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
VC ID
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|
Interface parameters
|
|
"
|
|
"
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Anatomy of a VLL
VC Label Signaling
Local label X
Remote label Y

Local label Y
Remote label X“I bind label X to VLLVLL-ID 1000”
1000”“I bind label Y to VLLVLL-ID 1000”
1000”
PE-A

PE-B

• PE router sends an LDP Label-Mapping message to theother end
• May send Label-Withdraw message when local CE
interface goes down

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Anatomy of a VLL
How Does a VLL Get Up and Running?
Configuration
incomplete

Ready toforwardAdd configuration
Wait for local
endpoint port
to come up

Remote label received
Advertised local
Label; wait
for remote label

Endpoint ready

Wait for an LSPtunnel to peer

Tunnel foundSession ready
Wait for an LDP
sessionwith peer

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Fowarding Frames:
CE to Backbone
Apply VC andtunnel labels

MPLS Backbone
CE interface
PE-A
Inbound lookup
based on VLAN & port number
or just port number
Outgoing MPLS Packet Format:
PPP-MPLS
or
Enet Hdr.

Tunnel
Label
M

VC
Label
Y

Optional
Control
Word

Tagged or untagged Ethernet payload

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Forwarding Frames:
Backbone to CE

MPLS Backbone
CE interface
PE-A

Incoming MPLS Packet Format:
PPP-MPLS
or
Enet Hdr.

Tunnel
Label
M

VC
Label
Y

Incoming label X indicates VLL
payload and which CE interface to send toand VLAN-ID to use
Optional
Control
Word

Tagged or untagged Ethernet payload

Incoming MPLS Packet Format in Case of Pen-Ultimate Hop Popping:
PPP-MPLS
or
Enet Hdr.

VC
Label
X

Optional
Control
Word

Tagged or untagged Ethernet payload

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

VLL Example Application:
CE Device Handles Switching• Router at central location responsible for data
forwarding among all remotes; switches or routers at
remotes
RemoteCentral Site
Router

VLL for subnet 1

UT
The VLAN-ID’s on thesePEs are not required tomatch with the central sitePE

T
Multinetting
w/ one subnet
to each remote

VLL for subnet 2

UT
RemoteT: tagged
UT: untagged
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

VLL Example Application:
SP Handles Switching
Tagged interface
shared among VLANs

One VLAN per
customer

SP network

Customer 1
Site C
Customer 2
Site A

MPLS Backbone

Customer 1
Site A

Customer 2
Site C

Edge switches perform
SA learning, broadcasting/unknown unicasting, transit
forwarding, and STP

Foundry MPLS Tehnology, Confidential and Proprietary

Customer 1
Site B

Customer 2
Site B

November© 2001 Foundry Networks, Inc.

Service Provider View of the Service
PE-2
PE-1
PrivateVLAN 10
PrivateVLAN 20MPLS Backbone

PrivateVLAN 10
PrivateVLAN 20

Customer A
Site-2 CE Device

Customer A
Site-1 CE Device
taggedLSP Tunnel
Virtual Circuit

PE-3

PrivateVLAN 10
PrivateVLAN 20

Customer A
Site-3 CE Device
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Customer’s View of the Service
Customer’s CE devices think that they are all in the same subnet andthat they are connected through a switch

PrivateVLAN 10
PrivateVLAN 20

PrivateVLAN 10
PrivateVLAN 20

Customer A
Site-2 CE Device

Customer A
Site-1 CE Device
taggedPE-3

PrivateVLAN 10
PrivateVLAN 20

Customer A
Site-3 CE Device
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Agenda• L2 Technologies in MAN• MPLS VLL Draft-Martini• MPLS VPLS
• Interoperability

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Service Terminology• In this scenario, the provider is said to be offering:
A Virtual Private LAN Segment (VPLS)
or (alternative name):
A Transparent LAN Service

Foundry MPLS Tehnology, Confidential and Proprietary

Not to be confused with “Virtual
Private LAN Services” which isan IP only solution described in“draft-tsenevir-vpl-ip-00.txt”

November© 2001 Foundry Networks, Inc.

VPLS Defining Documents• RFC 2764 – “A Framework for IP Based Virtual Private Networks”:– Provides the general framework for IP Based VPNs – MPLS
included• draft-lasserre-tls-mpls-00.txt:– Describes the forwarding of Ethernet/802.3 frames between
multiple customer sites, as if they were in the same layer-2
broadcast domain– Defines a new parameter “VPN ID” to identify PE routersparticipating in the same customer VPN• draft-vkompella-ppvpn-vpsn-mpls-00.txt:– Describes MAC address learning and aging– Describes MAC address signaling• A single WG document will be formulatedFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Functional Requirements• As frames are transported over a provider backbone,
efficient use of resources is crucial• Frames should be forwarded only over the needed VCs• PE routers should be capable of learning Ethernet
source MAC addresses, just like a regular switch• A PE router keeps a VPLS Forwarding Table (quite
similar to a bridge’s MAC table) that distiguishes theentries belonging to the different VPNs
• Before forwarding a frame, the PE router checks its
VPLS forwarding table to determine which VCs theframe should go overFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Functional Requirements (Cont.)• Broadcast or unknown unicast frames are flooded over
all outgoing VCs belonging to the VPN• The PE routers have to be connected via VCs forming afull mesh topology• For loop prevention, running an instance of STP per
VPN in the provider network would not scale:– Solution:
When forwarding frames a PE follows a split-horizon
rule: it never forwards a frame from one VC toanother in the same VPN

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Handling Multicast Frames• Multicast frames are currently handled like broadcasts• Extensions for performing smarter mutlicasts are to be
developed in the future• Possible scenarios:– Interaction with 802.1 GMRP
– IGMP snooping– Static MAC multicast filters

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

PE Router Performs Source Address
Learning
PE-3 associates MAC X with the outgoing VC (VC Label N)
PE-2
PE-1

MPLS Backbone
SA

VC

=X
VC

Customer A
Site-1 CE Device

Lab

Lab

Customer A
Site-2 CE Device

el=
N

el=
M

LSP Tunnel
Virtual Circuit

PE-3

VPLS Forwarding
Table

Customer A
Site-3 CE Device
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

PE Router Performs ForwardingPE-3 Checks its VPLS forwarding table and selects VC Label N
PE-2
PE-1

LSP Tunnel
Virtual Circuit

DA=

Customer A
Site-1 CE Device

X

MPLS Backbone
DA
=X V
CL
abe
l=N
VC
Lab
el=
M

Customer A
Site-2 CE Device

PE-3

VPLS Forwarding
Table

Customer A
Site-3 CE Device
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Speeding up Convergence
For faster convergence:• Whenever a PE router learns a new MAC SA from thecustomer side, it signals it using an LDP Address
message to its peers• Should a MAC SA age out or should the CE device get
disconnected, the PE sends an LDP Address Withdraw
message to its peers

Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

MAC Signaling
PE-3 signals the new MAC to speed up convergence
PE-2
PE-1

LD
PM
sg

LDP
Ms

g

MPLS Backbone
Customer A
Site-2 CE DeviceSA=

LSP Tunnel
Virtual CircuitY

Customer A
Site-1 CE Device

PE-3

New MAC.
Notify peers.

Customer A
Site-3 CE Device
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Facilitating Provisioning• VPN membership:– Each customer VPN is assigned a unique 7 octet VPN
ID– It is defined as a new interface parameter includedin the LDP messages defined in the Martini drafts(VC FEC)– This allows PE routers to signal the VPNs they are
members of• Automatic discovery of VPLS capable routers:– IGP extensions might be used
– Still in the works
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

VPLS Example Application:
Providing TLS
Customer A
Site-1 Router
PE-2

UT
PrivateVLAN 10
PrivateVLAN 20

UT
Customer A
Site-2 Router

PE-1

PrivateVLAN 10
PrivateVLAN 20MPLS Backbone

T

Customer B
Site-2 Switch

T

Customer B
Site-1 Switch

UT
LSP Tunnel
Virtual Circuit
UT Untagged
T TaggedPE-3

PrivateVLAN 10
PrivateVLAN 20

Foundry MPLS Tehnology, Confidential and ProprietaryT

Customer A
Site-3 Router

Customer B
Site-3 Switch
November© 2001 Foundry Networks, Inc.

VPLS Example Application:
Dual Homing the Customer••

The customer might run and manage their own instance of STP
The provider does not run STP on their backbone, they just carry thecustomer’s BPDUs

STP used by the customer but not by the provider
PE-2
PE-1

MPLS Backbone

STP

STP

No STP

STP

Customer A
Site-1

STP

STP

STP
PE-3

PE-4

Customer A
Site-2

LSP Tunnel
Virtual Circuit
Foundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.

Q&A
Thank YouFoundry MPLS Tehnology, Confidential and Proprietary

November© 2001 Foundry Networks, Inc.