Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 278)

248 Multi-Service IronWare Switching Configuration Guide
53-1003036-02
Overview
10
By adding the PBB header, PBB isolates the Service Provider and customer address spaces. This
means that Ethernet switches in the core of the Service Provider network will no longer learn
customer MAC addresses or use customer MAC addresses to forward customer frames to their
destinations. This improves the scaling of the Service Provider network in terms of the number of
supported customers, since the number of supported customers is no longer directly tied to the
size of the MAC address tables of the core Ethernet switches. In addition, the Service Provider
network is now protected from customer network failures, since frame forwarding is now based on
its own PBB header. Moreover, customers benefit from added security, since the customer's MAC
addresses are no longer learned or used for frame forwarding decisions in the core of the Service
Provider network.
As additional benefits to the Service Provider, PBB has the potential to simplify operations, e.g., by
separating the customer and Service Provider addressing spaces, and to lower capital
expenditures by reducing the cost of Ethernet switches used in the core of the network, since
memory and processing power requirements are reduced by limiting MAC address learning to
backbone MAC addresses.
FIGURE 29 Customer, PB, and PBB frame formats
The new Backbone Service Instance Tag (I-TAG) contains a Backbone Service Instance Identifier
(I-SID), which is 24 bits long. The I-SID field allows a Service Provider to identify up to 2 to the power
of 24, that is, over 16 million service instances. In other words, over 16 million services or
customers can be uniquely identified using the I-SID field. Therefore, PBB's I-TAG allows for highly
scalable services by eliminating the 4090 service instances limitation of PB.
PB
PB PB
PBB
Network
PB
BEB
BEB BEB
BEB
S-Tagged
service
interface
B-Tagged
service
interface
C-TAG
S-TAG
C-SA
C-DA
Ethertype
Ethertype
Ethertype
Payload LLC
MAC
MAC
Relay
Customer
Network
Port
Provider
Instance
Port
MAC
LLC
I-Component S-Tagged
service
interface
MAC
Relay
Provider
Network
Port
Customer
Backbone
Port
MAC MAC
LLC LLC
I-Tagged
service
interface
B-Tagged
service
interface
B-Component
S-TAG
C-TAG
I-TAG
B-TAG
C-SA
C-DA
B-SA
B-DA
Ethertype
Ethertype
Ethertype
Ethertype
Ethertype
Payload
Backbone Edge Bridge (IB-BEB)
(PBB
Header
no B-TAG)