1. Virtual Private LAN Service
Advanced Communications 2007 Week 11 Lecture 2
by Donald Neal

2. VPLS CE CE
AKL-PE1
TAU-PE1
AKL-P1
TAU-P1
HAM-P1
ROT-P1 CE
HAM-PE1

3. Layer 2 MPLS VPN 's
IGP
LSP's just like layer 3 VPN's – may be the same ones
LDP or RSVP or both
Two labels per packet
No customer IP routes
Layer 2 information passed among PE's instead

4. Layer 2 MPLS VPN 's Layer 2 information passed among PE's instead
Using LDP
Point-to-point RFC4447 “Martini”
VPLS – RFC4762
Using BGP
Point-to-point “Kompella”
VPLS - RFC4761

5. Same Parts, Mostly CE PE
U-PE P VE

6. Hi, Here's a VPLS
“A VPLS BGP NLRI has the following information elements: a VE ID, a VE
Block Offset, a VE Block Size, and a label base. The format of the
VPLS NLRI is given below. The AFI is the L2VPN AFI (25), and the
SAFI is the VPLS SAFI (65). The Length field is in octets.
| Length (2 octets) |
| Route Distinguisher (8 octets) |
| VE ID (2 octets) |
| VE Block Offset (2 octets) |
| VE Block Size (2 octets) |
| Label Base (3 octets) |
Figure 2: BGP NLRI for VPLS Information
A PE participating in a VPLS must have at least one VE ID. If the PE
is the VE, it typically has one VE ID. If the PE is connected to
several u-PEs, it has a distinct VE ID for each u-PE.”
- RFC4761

7. Multiprotocol Reachable NLRI
AFI 1 = IPv4
SAFI 1 = Unicast
SAFI 128 = Labelled VPN Unicast
AFI 25 = L2VPN
SAFI 65 = VPLS
NLRI
PE (VE) advertises it is a member of a VPLS

8. Encapsulation, etc. “.2.4. Signaling PE Capabilities
The following extended attribute, the "Layer2 Info Extended
Community", is used to signal control information about the
pseudowires to be setup for a given VPLS. The extended community
value is to be allocated by IANA (currently used value is 0x800A).
This information includes the Encaps Type (type of encapsulation on
the pseudowires), Control Flags (control information regarding the
pseudowires), and the Maximum Transmission Unit (MTU) to be used on
the pseudowires.
The Encaps Type for VPLS is 19.
| Extended community type (2 octets) |
| Encaps Type (1 octet) |
| Control Flags (1 octet) |
| Layer-2 MTU (2 octet) |
| Reserved (2 octets) |
Figure 3: Layer2 Info Extended Community”
- RFC4761

9. Encapsulation, etc. “ 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+
| MBZ |C|S| (MBZ = MUST Be Zero)
Figure 4: Control Flags Bit Vector
With reference to Figure 4, the following bits in the Control Flags
are defined; the remaining bits, designated MBZ, MUST be set to zero
when sending and MUST be ignored when receiving this community.
Name Meaning
C A Control word [7] MUST or MUST NOT be present when
sending VPLS packets to this PE, depending on whether C
is 1 or 0, respectively
S Sequenced delivery of frames MUST or MUST NOT be used
when sending VPLS packets to this PE, depending on
whether S is 1 or 0, respectively”
- RFC4761

10. VPLS, not VRF Route Distinguisher Route Target
Site Identifier in Site Range
Interface (to CE)
Routing Table
Forwarding Table (FIB)

11. Learning MAC Addresses
“the key distinguishing feature of VPLS is
that it is a multipoint service. This means that the entire Service
Provider network should appear as a single logical learning bridge
for each VPLS that the SP network supports. The logical ports for
the SP "bridge" are the customer ports as well as the pseudowires on
a VE. Just as a learning bridge learns MAC addresses on its ports,
the SP bridge must learn MAC addresses at its VEs.
Learning consists of associating source MAC addresses of packets with
the (logical) ports on which they arrive; this association is the
Forwarding Information Base (FIB). The FIB is used for forwarding
packets. For example, suppose the bridge receives a packet with
source MAC address S on (logical) port P. If subsequently, the
bridge receives a packet with destination MAC address S, it knows
that it should send the packet out on port P.”
- RFC4761
Can learn MAC or MAC plus VLAN tag - one VPLS per customer

12. And if in doubt ...
“When a bridge receives a packet to a destination that is not in its
FIB, it floods the packet on all the other ports. Similarly, a VE
will flood packets to an unknown destination to all other VEs in the
VPLS.
- RFC4761
With a Split Horizon rule

13. H-VPLS CE RFC4761 – VPLS signalled with BGP
talks about heirarchical BGP
RFC4762 – VPLS signalled using LDP
Heirarchical VPLS
Hub and Spoke, encapsulated with point-to-point MPLS L2VPN or Q-in-Q CE

14. VPLS CE CE
AKL-PE1
TAU-PE1
AKL-P1
TAU-P1
HAM-P1
ROT-P1 CE
HAM-PE1

15. IP Interworking – NOT VPLSCE
ETHERNET
VLAN
TAU-PE1
AKL-P1
TAU-P1
HAM-P1
ROT-P1 CE
HAM-PE1
FRAME
RELAY

16. Triple-Play Goblin Net
Customer
Database
RADIUS
Authentication
BNG
(PEP)
Brains
(PDP)
COPS
Portal
VIDEO
VoIP
INTERNET

17. Further Reading Next Week: Scaling BGP and Review
RFC Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery and Signaling
Broadband Network Architectures pp
Next Week: Scaling BGP and Review