Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
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The third standard is IEEE802.1ag, which is the new foundation for Operations, Administration &
Management (OAM) over Ethernet-based networks for Connectivity and Fault Management (CFM). Defined
by carriers for use on carrier-grade networks (including MPLS-based ones), this standard brings to Ethernet
and SPB a far more sophisticated troubleshooting toolkit than Enterprise customers are used to with IP.
Ethernet-based CFM can test for the most basic connectivity tests (ping) to path tracing (traceroute) over
both unicast and service-specific multicast trees (tracetree & tracemroute), as well as network performance
monitoring (latency/jitter measurements) via Continuity Check Message (CCM) and Y.1731 extensions.
Figure 2 Comparison of SPB’s Simplicity with Traditional Protocol Stack
The benefits of delivering MPLS service types over an SPB-based Fabric are many. To start, MPLS is
complex and relies on a multitude of control plane protocols each with its own complexities and protocol
layer dependencies. Being able to deliver an Ethernet-based Fabric with a single control plane (IS-IS)
supporting all of the same service types as MPLS/EVPN but without needing to engineer the backbone with
OSPF, Multiprotocol BGP, BGP Route Reflectors, LDP, and PIM-SM makes for an easier life for enterprise
network administrators, both in terms of design and maintenance, but inevitably in terms of cost.
Layer 3 Virtualization Overview
L3 Virtualization is designed to support the concept of multi-tenancy. Enterprise networks can separate
portions of the network into separately addressed “communities of interest,” or logical segments. This
improves enterprise security by isolating unrestricted communications to only those members of the
specific logical segment. Inter-segment communications may be controlled by using stateful firewalls with
interfaces residing in each of the network segments, or through carefully applied inter-segment route
leakage policies, or a combination of both.
The deployment of virtualized L3 routing domains over an SPB Ethernet Fabric is achieved in a manner that
bears many similarities with the MPLS-based IPVPNs. Virtualized L3 routing domains in Fabric Connect are
called Layer 3 Virtual Service Networks (L3 VSNs). Every L3 routing domain is terminated on a Virtual
Router and Forwarding (VRF) entity on a BEB, usually located on the distribution layer nodes. These nodes
exchange I-SID-IPv4 (or I-SID-IPv6) routes via IS-IS well defined Type Length Values (TLVs). These TLVs
exist in the IS-IS Link State Data Base (LSDB) of the SPB Fabric, but will only be inspected by nodes where
the same L3 VSN I-SID is terminated.
Core nodes (BCBs) take no notice of these TLVs and simply forward packets based on the shortest path
towards the destination BMAC. The BEB distribution nodes participating in the L3 VSN service have directly
connected interfaces for access layer subnets that can be extended to edge switches or Fabric Attached
switches. If attached to a Fabric Attached switch, the corresponding L2 VLAN can be derived either via