Virtual LAN Requirements


1.      A Virtual LAN (vLAN) is an administratively defined logical grouping
        of LAN stations independent of their physical location within a
	Bridged LAN infrastructure.

        - where a "Bridged LAN" is defined to be a collection of MSAPs that
	  can communicate at the Data Link layer.

2       vLANs are to be supported over all IEEE 802 media (both shared and
	point2point) and remote WAN bridging technologies.

3.      vLANs shall support bi-directional unicast communication between any
	two MSAPs and unidirectional communication from one MSAP to one or
	more other MSAPs within the same Virtual LAN topology (e.g. IGMP Group
	defined vLANs).

4.      vLANs must coexist and be backwards compatible with existing devices,
	end stations, hubs, routers etc.

5.      They facilitate adds/moves/changes. A LAN attached device can
	reconnect anywhere within the Bridged LAN and remain a member of that
	same Virtual LAN.

6.      vLANs enable logical segmentation of a Bridged LAN into autonomous
	broadcast domains; where a broadcast domain comprises all MSAPs
	belonging to the same Virtual LAN.

7.      Inter-vLAN communication between devices attached to different
	physical media shall require a Layer 3 or higher function.


8.      With regard to non-routable protocols where two or more vLANs are
	defined, a vLAN device may forward unicast frames between vLANs.

9.      Criteria for vLAN membership is defined by administrative policy
	and requires that each distinct vLAN be uniquely identified throughout
	the Bridged LAN.

10.     A single physical point of attachment via an 802 LAN interface may
	participate in multiple vLANs and may connect directly to a vLAN
	Trunk/Backbone.

        - where a vLAN Trunk/Backbone is defined to be a physical link
	  between vLAN intelligent devices over which is carried traffic from
	  one or more vLANs.

11.     In the absence of any vLAN configuration all MSAPs are able to
	communicate with all other MSAPs throughout the Bridged LAN domain.

12.     Once defined, static vLAN configuration should be non-volatile.

13.     vLAN capable devices may participate in a method for exchanging and
	distributing vLAN configuration information.

14.     Network Management devices would be able to create/delete/reconfigure
	vLANs and as such, all vLAN devices should be accessible to an NMS if
	present.

15.     vLAN devices may be capable of supporting redundant links (possibly
	for the purposes of load balancing) within the Bridged LAN
	infrastructure.

16.     Virtual LANs require no Quality of Service specification.

17.     Virtual LANs may support and be deployed in conjunction with
	multi-level security.

18.     Networks overlaid with vLAN topologies shall support attachment
	devices with multiple MAC interfaces which have the same MAC address
	on each interface (e.g. DECnet IV).

19.     Virtual LANs as defined by the IEEE shall be interoperable with
	other Virtual Networking technologies notably ATM's LAN Emulation.

20.     Automated VLAN reconfiguration, if supported, shall be done in such
	a way so as not to disrupt convergence of higher-layer protocols.

21.     Nothing in the standard shall preclude implementations which scale
	to many thousands of users.



Martin McNealis, Cisco Systems.
IEEE 802.1 Interim, 10/12/95