Synonyms for spbm or Related words with spbm
Examples of "spbm"
The two flavors (SPBV and
) will be described separately although the differences are almost entirely in the data plane.
reuses the PBB data plane which does not require that the Backbone Core Bridges (BCB) learn encapsulated client addresses. At the edge of the network the C-MAC (client) addresses are learned.
is very similar to PLSB (Provider Link State Bridging) using the same data and control planes but the format and contents of the control messages in PLSB are not compatible.
We will work through
behavior on a small example, with emphasis on the shortest path trees for unicast and multicast.
Shortest Path Bridging - VID (SPBV) and Shortest Path Bridging - MAC (
) are two operating modes of 802.1aq, and are described in more detail below. Both inherit key benefits of link state routing:
Ethernet destination addresses (from UNI port attached devices) perform learning over the logical LAN and are forwarded to the appropriate participating B-MAC address to reach the far end Ethernet destination. In this manner Ethernet MAC addresses are never looked up in the core of an IEEE 802.1aq network. When comparing
to PBB, the behavior is almost identical to a PBB IEEE 802.1ah network. PBB does not specify how B-MAC addresses are learned and PBB may use a spanning tree to control the B-VLAN. In
the main difference is that B-MAC address are distributed or computed in the control plane, eliminating the B-MAC learning in PBB. Also
ensures that the route followed is shortest path tree.
Virtualisation is becoming an increasingly important aspect of a number of key applications, in both carrier and enterprise space, and
, with its MAC-in-MAC datapath providing complete separation between client and server layers, is uniquely suitable for these.
The first public interoperability tests of IEEE 802.1aq were held in Ottawa in October 2010. Two vendors provided
implementations and a total of 5 physical switches and 32 emulated switches were tested for control/data and OA&M.
Further events were held in Ottawa in January 2011 with 5 vendors and 6 implementations, at 2013's Interop event at Las Vegas where an
network was used as a backbone.
Failure recovery is as per normal IS-IS with the link failure being advertised and new computations being performed, resulting in new FDB tables. Since no Ethernet addresses are advertised or known by this protocol, there is no re-learning required by the
core and its learned encapsulations are unaffected by a transit node or link failure.
SPBV has been designed to manage a moderate number of bridges. SPBV differs from
in that MAC addresses are learned on all bridges that lie on the shortest path and a shared VLAN learning is used since destination MACs may be associated with multiple SPVIDs. SPBV learns all MACs it forwards even outside the SPBV region.
Service Identifier and Unicast Address TLV is used to introduce service group membership on the originating node and/or to advertise an additional B-MAC Unicast Address present on, or reachable by the node. The SPBV MAC Address TLV is the IS-IS sub-TLV used for advertisement of Group MAC Addresses in SPBV mode.
Individual MAC frames (unicast traffic) from an Ethernet attached device that are received at the
edge are encapsulated in a PBB (mac-in-mac) IEEE 802.1ah header and then traverse the IEEE 802.1aq network unchanged until they are stripped of the encapsulation as they egress back to the non participating attached network at the far side of the participating network.
802.1aq is the Institute of Electrical and Electronics Engineers (IEEE) sanctioned link state Ethernet control plane for all IEEE VLANs covered in IEEE 802.1Q. Shortest Path Bridging virtual local area network identifier (VLAN ID) or Shortest Path Bridging VID or (SPBV) provides capability that is backwards compatible with spanning tree technologies. Shortest Path Bridging Media Access Control (MAC) or (
), (previously known as Provider Backbone Bridge SPBB) provides additional values which capitalize on Provider Backbone Bridge (PBB) capabilities. SPB (the generic term for both) combines an Ethernet data path (either IEEE 802.1Q in the case of SPBV, or Provider Backbone Bridges (PBBs) IEEE 802.1ah in the case of
) with an IS-IS link state control protocol running between Shortest Path bridges (network-to-network interface (NNI) links). The link state protocol is used to discover and advertise the network topology and compute shortest path trees (SPT) from all bridges in the SPT Region.
, the Backbone MAC (B-MAC) addresses of the participating nodes and also the service membership information for interfaces to non-participating devices (user network interface (UNI) ports) is distributed. Topology data is then input to a calculation engine which computes symmetric shortest path trees based on minimum cost from each participating node to all other participating nodes. In SPBV these trees provide a shortest path tree where individual MAC address can be learned and Group Address membership can be distributed. In
the shortest path trees are then used to populate forwarding tables for each participating node's individual B-MAC addresses and for Group addresses; Group multicast trees are sub trees of the default shortest path tree formed by (Source, Group) pairing. Depending on the topology several different equal cost multi path trees are possible and SPB supports multiple algorithms per IS-IS instance.
Both SPBV and
inherit the rapid convergence of a link state control plane. A special attribute of
is its ability to rebuild multicast trees in a similar time to unicast convergence, because it substitutes computation for signaling. When an
bridge has performed the computations on a topology database, it knows whether it is on the shortest path between a root and one or more leaves of the SPT and can install state accordingly. Convergence is not gated by incremental discovery of a bridge’s place on a multicast tree by the use of separate signaling transactions. However,
on a node does not operate completely independently of its peers, and enforces agreement on the current network topology with its peers. This very efficient mechanism uses exchange of a single digest of link state covering the entire network view, and does not need agreement on each path to each root individually. The result is that the volume of messaging exchanged to converge the network is in proportion to the incremental change in topology and not the number of multicast trees in the network. A simple link event that may change many trees is communicated by signaling the link event only; the consequent tree construction is performed by local computation at each node. The addition of a single service access point to a service instance involves only the announcement of the I-SID, regardless of the number of trees. Similarly the removal of a bridge, which might involve the rebuilding of hundreds to thousands of trees, is signaled only with a few link state updates.
Figure 5 below is a quick way to understand what
is doing on the scale of the entire network. Figure 5 shows how a 7-member E-LAN is created from the edge membership information and the deterministic distributed calculation of per source, per service trees with transit replication. Head end replication is not shown as it is trivial and simply uses the existing unicast FIBs to forward copies serially to the known other receivers.
The forward and reverse paths used for unicast and multicast traffic in an IEEE 802.1aq network are symmetric. This symmetry permits the normal Ethernet Continuity Fault Messages (CFM) IEEE 802.1ag to operate unchanged for SPBV and
and has desirable properties with respect to time distribution protocols such as Precision Time Protocol (PTP Version 2). Also existing Ethernet loop prevention is augmented by loop mitigation to provide fast data plane convergence.
Shortest Path bridging enables shortest path trees for VLAN Bridges all IEEE 802.1 data planes and SPB is the term used in general. Recently there has been a lot of focus on
as explained due to its ability to control the new PBB data plane and leverage certain capabilities such as removing the need to do B-MAC learning and automatically creating individual (unicast) and group (multicast) Trees. SPBV was actually the original project that endeavored to enable Ethernet VLANs to better utilize mesh networks.
The two different flavors of data path give rise to two slightly different versions of this protocol. One (
) is intended where complete isolation of many separate instances of client LANs and their associated device MAC addresses is desired, and it therefore uses a full encapsulation (MAC-in-MAC a.k.a. IEEE 802.1ah). The other (SPBV) is intended where such isolation of client device MAC addresses is not necessary, and it reuses only the existing VLAN tag a.k.a. IEEE 802.1Q on participating network-to-network interface (NNI) links.
Avaya is currently the leading exponent of SPB-based deployments; their enhanced and extended implementation of SPB - including integrated layer 3 IP Routing and IP Multicast functionality - is marketed under the banner of the "Avaya VENA Fabric Connect" technology. Additionally, Avaya is supporting an IETF Internet Draft that defines a means of extended
-based services to end-devices via conventional Ethernet Switches, leveraging an 802.1AB LLDP-based communications protocol; this capability - marketing by Avaya as "Fabric Attach" technology - allows for the automatic attachment of end-devices, and includes dynamic configuration of VLAN/I-SID (VSN) mappings.
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