Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
© 2019 Extreme Networks, Inc. All rights reserved. 12
The SPB (IEEE802.1aq) standard leverages this addressing hierarchy, replacing the Spanning Tree
protocols, and bringing to Ethernet-based networks the well-known and much appreciated IS-IS Link State
Routing protocol. IS-IS computes the shortest paths between all BMACs within the Ethernet fabric. As such,
an SPB fabric behaves with similar properties that network administrators expect to see from a traditional
IP-based network using either OSPF or IS-IS as the IGP.
Tip
SPB is an Ethernet based fabric and is sometimes referred to as an L2 fabric. It is
important to understand that L2-specific flooding and learning mechanisms, which
naturally have a negative connotation for L2 networks, are not used in the SPB fabric
infrastructure. Like MPLS, SPB uses a non-IP header to route packets through the fabric
between fabric nodes. Like a traditional IP routed network, it is using an IGP routing
protocol (IS-IS) to calculate shortest paths for which forwarding entries (FDB) are then
programmed into the data plane.
Table 1 – SPB IEEE Relevant Standards
Original IEEE
Standard
Amendment
Year
Published
Incorporated into
IEEE Standard
Standard Name
802.1ag
2007
802.1Q-2011
Connectivity Fault Management (CFM)
802.1ah
2008
802.1Q-2011
Provider Backbone Bridging (Mac-in-Mac)
802.1aq
2012
802.1Q-2014
Shortest Path Bridging (SPBM & SPBV)*
* SPBM uses Mac-in-Mac Ethernet encapsulation and SPBV uses 802.1ad Q-in-Q encapsulation.
Note
Extreme Networks only implements SPBM in its current products. SPBV was implemented
in Extreme EOS S/K series legacy products.
The technology discussed in this design document makes use of SPBM, which leverages
802.1ah Mac-in-Mac encapsulation. Throughout this document, any reference to Shortest
Path Bridging or SPB is always referring to SPBM.
Perhaps the most important innovation that IEEE802.1ah introduces to Ethernet is the addition of a new 24-
bit Service-ID (I-SID) field in the Mac-in-Mac encapsulation. The I-SID is a fabric-wide global service
identifier, in contrast to the VLAN identifier, which in SPBM becomes only locally significant to the node or
access port. This brings the ability to virtualize and transport any of the network service types that
previously only MPLS-based backbones were capable of supporting, directly over an Ethernet-based
network.