Relationship between peer link and physical link Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2007 Relationship between peer link and physical link Date: 2007-09-19 Authors: M. Bahr, Siemens AG John Doe, Some Company

Month Year doc.: IEEE 802.11-yy/xxxxr0 September 2007 Abstract Background information on the resolution for comments CID 418 and 465 is given. These comments are concerned with the relationship between peer links and physical links. The resolution proposes a logical peer link concept as described in 11-07/0861r0, where the logical peer link is used for mesh discovery, mesh membership, and security setup, but the physical link and the management of the connectivity is left to the path selection protocol. The changes to the draft are minimal. M. Bahr, Siemens AG John Doe, Some Company

September 2007 Some slides from 11-07/0861r0 M. Bahr, Siemens AG

Requirements for IEEE 802.11s communication over a link September 2007 Requirements for IEEE 802.11s communication over a link Sending a frame to what neighbor (MAC address)? next hop provided by path selection protocol am I allowed to send to that neighbor? information provided by peer link establishment and initial MSA authentication secure communication? key material provided by MSA authentication over peer link IEEE 802.11 Link is implicitly defined DATA-ACK handshake  if received ACK, link has been available and communication has been successful M. Bahr, Siemens AG

Relation of HWMP to Links September 2007 Relation of HWMP to Links HWMP refers to (allowed) physical links HWMP does not need explicit state information on links HWMP discovers links on-demand through probing during path discovery (PREQ, PREP)* receiver of PREQ, PREP needs to associate a metric value to last hop airtime link metric, hop count path discovery is only done over links that are allowed* derived from peer link establishment / MSA security association „link close“ is done/detected by path timeout, missing ACK delete next hop information * In practice, the mesh will provide the set of links that are allowed, and the path selection protocol will work on that subset of links. M. Bahr, Siemens AG

Peer Link Establishment September 2007 Peer Link Establishment only MPs can setup a peer link passive / active scanning (beacons, probe request) 1 or 2 messages peer link management protocol for peer link establishment 4 messages for setting up the peer link (2 messages for closing the peer link) peer link establishment is needed for secure setup of key material (MSA authentication) Initial MSA authentication EAP authentication (2+ messages) 4-way handshake (4 messages) group keys  11+ messages, message exchanges takes time M. Bahr, Siemens AG

Peer Link vs. Physical Link September 2007 Peer Link vs. Physical Link necessary for secure (MSA) authentication and mesh membership security association has long lifetime 30 minutes, hours, one day, several days lifetime depends on external events revocation of keys timeout of security association necessary for communication Physical Link has wide range of lifetimes short, long, in some cases even very long lifetime depends on dynamics of wireless topology mobility fluctuations of radio environment Peer link/security association and physical link have lifetimes on different time scales, and lifetimes vary independently and unpredicably in case of physical link. M. Bahr, Siemens AG

Dependency Models between Peer Link – Physical Link September 2007 Dependency Models between Peer Link – Physical Link Peer Link requires existing Physical Link Peer Link is closed if Physical Link is lost incurs overhead in terms of packets, delay to mobile MPs maybe additional overhead for testing the physical link longer processing of events decreases the level of mobility to be supported by 802.11s Peer Link does not require existing Physical Link existing physical link required for peer link establishment established Peer Link is not closed if Physical Link is lost Peer Link is required for sending frames to peer MP no overhead in terms of packets, delay to mobile MPs due to repeated peer link establishment path selection protocols can deploy their own, optimized path maintenance procedures higher level of mobility can be supported M. Bahr, Siemens AG

September 2007 Interface between general functionality and path selection protocols / metrics path selection protocols have different, optimized methods for detecting physical links HWMP: on-demand link discovery with PREQ, PREP; implicit link through DATA-ACK RA-OLSR: Hello messages with willingness, MPR state additional specific state variables associated with link (forwarding willingness, MPR state in RA-OLSR) M. Bahr, Siemens AG

Proposal: Logical Peer Link Concept September 2007 Proposal: Logical Peer Link Concept a peer link between two MPs means: logical link the two MPs are allowed to communicate (transmit frames to each other) peer link is necessity for mesh membership the two MPs have exchanged the necessary security material after establishment, a physical link is not required peer link is closed through timeout or revocation of security material, explicit close, not closed if physical link is lost M. Bahr, Siemens AG

Advantages of Logical Peer Link Concept September 2007 Advantages of Logical Peer Link Concept clear and secure mechanism for determining MPs with which a node can communicate discovery/maintenance of physical link left to specialized path selection protocol / path selection metric use of optimized and enriched mechanisms for physical link discovery/maintenance possible no repetition of same functionality for physical link discovery/maintenance in general peer link management and specific path selection protocol (e.g. periodic testing for availability of physical link) no overhead in terms of frames and delay due to repeated peer link establishment for mobile nodes no inconsistencies between (physical) link state of peer link and in path selection protocol M. Bahr, Siemens AG

Straw Poll in Montreal May 2007 September 2007 Straw Poll in Montreal May 2007 Should 802.11s go into the direction of such a logical peer link concept? yes: 13 no: 1 abstain: 10 M. Bahr, Siemens AG

Changes to IEEE 802.11s Draft D1.06 September 2007 Changes to IEEE 802.11s Draft D1.06 Revised definitions neighbor MP MPs in direct communication range not all neighbor MPs are peer MPs peer MP not all peer MPs are neighbor MPs peer MPs – link between MPs established through peer link management protocol neighbor peer MP peer MPs in direct communication link peer link established with mesh peer link management protocol not necessarily in direct communication range mesh link peer link AND physical link (i.e. peer MPs are in direct communication range) M. Bahr, Siemens AG

Changes to IEEE 802.11s Draft D1.06 September 2007 Changes to IEEE 802.11s Draft D1.06 make changes to use peer link, mesh link, peer MP, neighbor MP, neighbor peer MP in the right context throughout the document where appropriate change constants of mesh peer link establishment protocol starting with MESH_LINK_... to PEER_LINK_... removed strong coupling of logical peer link and physical link connectivity in introductory clause of mesh discovery (clause 11A.1.1) Revised definitions proposed changes to normative text in 11-07/2569r0 changes are minimal (but tedious ) M. Bahr, Siemens AG

September 2007 Motion Move to adopt the changes proposed in 11-07/2569r0 as resolution to comments CID 418 and 465 and to instruct the editor to incorporate them into the draft. yes: no: abstain: M. Bahr, Siemens AG

September 2007 References 11-07/0861r0 „ Architectural Considerations for IEEE 802.11s” 11-07/2569r0 “Text changes for relationship between peer link and physical link“ IEEE P802.11s™/D1.06: Draft STANDARD Amendment <number>: Mesh Networking M. Bahr, Siemens AG