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Interworking. Mesh Portal (MPP). A mesh network may be connected to an external network (IEEE 802 LANs) via an entity called a Mesh Portal (MPP) An MPP combines the functionality of an MP and that of an IEEE 802.1D bridge
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Mesh Portal (MPP) • A mesh network may be connected to an external network (IEEE 802 LANs) via an entity called a Mesh Portal (MPP) • An MPP combines the functionality of an MP and that of an IEEE 802.1D bridge • A mesh network may have 1 or more MPPs which may be connected to one of more LANs
Mesh Network as an IEEE 802 LAN Segment • The mesh MAC entity appears as a single port to • the MAC Relay entity in IEEE 802.1D • any higher-layer entity (e.g., Spanning Tree Protocol entity, layer-3 router, etc.) • The MPP is designed to transfer “proxy information” to the MAC relay entity in 802.1D • The learning process within the MAC Relay Entity learns the addresses of all MPs and their proxied stations
MPP Announcement Protocol • Used by an MPP to announce its presence in the mesh • MPP sends portal announcement elements (PANN) at regular intervals • portal announcement interval • MPs propagate PANNs • PANN propagation delay
Portal Announcement (PANN) Information Element • Hop Count: • Number of hops from the originator to the transmitting MP • Time to Live: • Maximum number of hops allowed • Originator Address: • MAC address of the MP collocated with the portal • Sequence Number: • Sequence number specific to the originator • Metric: • Cumulative metric from the originator to the transmitting MP
MP behavior in presence of MPP • MPs learn about active MPPs and record their addresses and path metrics • When an MP has a data frame to send • It first tries to determine an intra-mesh path to the destination address • If unable to do so, then the MP assumes that the destination is outside the mesh and forwards the frame to all active MPPs in the mesh • If the destination appears to be outside the mesh but there is no MPP, the frame is dropped
MPP Learning Process • An MPP learns the addresses of MPs and proxied devices through messages carrying proxy information • The bridge within an MPP learns via the Learning Process in the MAC Relay entity
MPP Data Forwarding Behavior • Frame received from an MP in the mesh: • If the DA is that of an MP or a proxied STA known to the MPP to be reachable through the mesh, then the MPP forwards the frame in the mesh • If the DA is known to the MPP to be outside the mesh, then the MPP forwards the frame on the external network • If the DA is unknown to the MPP, the MPP forwards the frame on the external network
MPP Data Forwarding Behavior • Frame received from outside the mesh • If the DA is that of an MP or a proxied STA known to the MPP to be reachable through the mesh, then the MPP forwards the frame in the mesh • If the DA is unknown to the MPP, the MPP forwards the frame on the mesh • MPP attempts to establish a path to DA • MPP broadcast the frame in the mesh
Proxy Protocol • The Proxy protocol is used by an MP to inform a destination MP of its proxied addresses • The MP sends a “Proxy Update” (PU) element • The MP repeats the PU every PU_TIMEOUT for a MAX_PU times or until it receives a Proxy Update Confirmation (PUC) from the destination.
Conditions for Sending a PU • An MP may send a PU • If it needs to inform a destination MP of its proxy information • When a change is made in the local proxy information (due to addition or deletion of proxy entries) • On a periodic basis to refresh the proxy information at the destination MP • May be useful in managing station mobility
Role of a Root MP • In proactive routing through a root MP, the root MP is relied on to maintain proxy information • In this case MPs send PUs to the root MP • If a root MP receives a PU with add proxy information, and the root already has proxy information for one or more of these proxied addresses, then it shall send a PU with delete proxy information to each of the old proxy MPs • Similarly if the root MP detects a new proxied address in its DS (e.g., through bridge learning)