Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
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Fabric Connect and Fabric Attach
The Fabric Connect name is often used to designate the entire Extreme SPB-based fabric solution,
including the other variants, Fabric Attach & Fabric Extend, touched on below. However, in this section,
Fabric Connect (FC) is the Extreme Networks name given to the core SPB-based fabric technology that is
based on IS-IS and Mac-in-Mac (SPBM). A node running in Fabric Connect mode will need to run the IS-IS
control plane protocol, form IS-IS adjacencies with its Fabric Connect neighbors, and will then be
knowledgeable about the physical topology and how all Fabric Connect nodes are interconnected. This will
allow it to calculate shortest paths to every other Fabric Connect node in the network and to react fast and
recalculate those shortest paths should any change be detected in the active topology. Given that Mac-in-
Mac is the encapsulation used by SPBM, any device running in Fabric Connect mode will need to have Mac-
in-Mac capable hardware/chipsets. The IS-IS SPB control plane also allows it to advertise a desire to
participate in a service type by announcing the corresponding I-SID for the relevant service type.
As the naming implies, Fabric Attach is all about attaching users and devices to the inner Ethernet SPB
Core Fabric, that is, Fabric Connect. You can think of Fabric Attach as a subset of Fabric Connect, where the
IS-IS control plane is removed (and with it its ability to calculate shortest paths) and traditional Ethernet
based MAC encapsulation and MAC learning are used (without any requirements for Mac-in-Mac). Only the
ability to attach users to I-SID based services is preserved and this service attachment signalling is now
handled by LLDP. A further restriction of Fabric Attach is that only L2 I-SIDs can be signalled; that is, users
and applications must always be Fabric Attached to some L2 VSN segment that needs to exist on at least
one Fabric Connect node somewhere.
Tip
L3 I-SIDs for L3 VSN attachment are only relevant and will only exist on Fabric Connect
nodes that are acting as IP routers with VRF support. It is perhaps on these nodes that L2
I-SID VSN segments have been defined and bound to a particular VRF and thus L3 VSN.
Fabric Attach at the edge can be used to place users and applications in the desired L2
VSN segment belonging to the desired L3 VSN tenant IP routing domain.
Table 5 – Properties of Fabric Connect vs. Fabric Attach
Property
Fabric
Connect
Fabric
Attach
Able to pre-provision Fabric access port based on edge user/device type
no
yes
Allows node to compute shortest path/trees across Fabric using IS-IS/SPB
yes
no
Allows node to signal end-point Service Attachment to Fabric L2 I-SID
yes
yes
Allows node to signal end-point Service Attachment to Fabric L3 I-SID
yes
no
Node counts towards maximum scaling limit of SPB Nodes per Region
yes
no
Requires node’s hardware chipset to be SPB (Mac-in-Mac) capable
yes
no
At the same time, Fabric Attach enhances the Fabric Connect end-point provisioning by being able to
detect what edge device type is being connected, which allows for automatic configuration of the fabric
access port to accept the end device into the correct VSN. Therefore, edge devices, such as virtual
switches, ExtremeWireless Access Points, video surveillance cameras, etc., can be Fabric Attach enabled
and act as FA Clients, which then allows them to advertise their identities securely. This information can
either be used directly by the Fabric Attach access switch or relayed to the RADIUS server for secured MAC
based authentication and authorization onto the desired Fabric I-SID via Fabric Attach RADIUS outbound
attributes.