Hi Alex, Indeed, 'reachability' is not listed in many directories. However, the IETF seems to accept it as a word. For instance:
RFC 1273 "Measurement Study of Changes in Service-Level Reachability in the Global TCP/IP Internet" RFC 5549 "Advertising IPv4 Network Layer Reachability Information with an IPv6 Next Hop" Cheers, Dominik On Wed, May 13, 2009 at 11:58 AM, Alexandru Petrescu <[email protected]> wrote: > Dominik Kaspar a écrit : >> >> Hi, >> >> Would 'non-reflexive' (better called 'irreflexive') reachability > > 'Irreflexive' sounds good to my dictionary, and to me better than > non-reflexive. > > 'Reachability' is absent from many dictionaries. > > Alex > >> mean that a node can not reach itself? If so... I think the term >> still makes sense, because 6LoWPAN nodes usually cannot send and >> receive at the same time (except if they had two physical radio >> interfaces). >> >> By the way, typo: assymetric -> asymmetric. >> >> Greetings, Dominik >> >> >> On Tue, May 12, 2009 at 11:53 AM, Burnett, Peter >> <[email protected]> wrote: >>> >>> Zach, I'm wondering if the term 'non-reflexive' in RFC4861 should >>> have been 'non-symmetric'. Mathematically, an equivalence >>> relationship is defined as being reflexive, symmetric and >>> transitive. Symmetric is the property which is untrue on a >>> unidirectional link not reflexive. Apologies if this is nonsense, >>> I'm new to this list. Thanks Peter >>> >>> -----Original Message----- From: [email protected] >>> [mailto:[email protected]] On Behalf Of Zach Shelby Sent: >>> 2009 May 12 10:38 To: 6lowpan Subject: [6lowpan] Terminology >>> >>> Hi, >>> >>> I am working on an updated terminology set for the nd draft. The >>> terminology is now split with 6LoWPAN general terminology now in >>> its own section. I would like comments on this updated set (below) >>> where I have tried to find a solution based on the constructive >>> discussions we had on the list. >>> >>> After looking through all the background RFCs in detail, it >>> actually turns out this is not as hard as we thought. RFC4861 >>> actually does cover the wireless case as it defines assymetric >>> properties of wireless links including non-transitivity (see >>> Section 2.2). In fact RFC4861 actually mentions that the protocol >>> (ND) will presumably be extended in the future to deal with links >>> that are assymetric (non-reflexive, non-transitive). That is what >>> we are doing with ND for 6LoWPAN! >>> >>> Therefore I have now defined link as being non-transitive and >>> complex NBMA, which can be somewhat overcome using link-layer mesh >>> techniques or by with IP routing. This greatly simplifies the >>> definition of a subnet (whew!), as we keep the RFC4291 where subnet >>> <= link. As we are performing IP routing to overcome the >>> non-transitive nature, the subnet does exhibit one aspect of >>> multi-link subnet mentioned in RFC4903. >>> >>> IP routing has been defined as Alex recommended as it has specific >>> properties to 6LoWPAN. In the architecture section of nd-03 we will >>> include LoWPAN IP routing examples including topology and what is >>> in the table. >>> >>> >>> >>> >>> General 6LoWPAN Terminology: >>> >>> This section defines additional general terms related to the >>> 6LoWPAN architecture used in this specification: >>> >>> IP Routing >>> >>> The forwarding of datagrams at the IP layer between arbitrary >>> source-destination pairs, during which the hop limit is decremented. In the >>> LoWPAN context, IP routing is performed by LoWPAN Routers on a single >>> interface within the same link to overcome the non-transient nature of the >>> link. Exact match search is performed on the dst address of the IP packet >>> to find the next- hop to the destination. Referred to as routing in this >>> document. >>> >>> Link >>> >>> The link is a communication facility or medium over which nodes can >>> communicate at the link-layer, i.e., the layer directly below IP >>> ([RFC4861]). 6LoWPAN assumes the use of low-power and lossy wireless >>> links such as IEEE 802.15.4, which is a special type of link as described in >>> [RFC4861] exhibiting severe assymetric reachability with both non-reflexive >>> and non-transitive qualities. Furthermore complex Non-broadcast Multi-Access >>> (NBMA) behaviour is exhibited as these links do not support native >>> multicast, and broadcast reaches only a subset of nodes on the link. The >>> use of link-layer mesh technology (see Mesh Under) emulates transitivity >>> across the link but still has problems with non-reflexitivity. Multicast on >>> a link-layer mesh is usually implemented as a broadcast flood. >>> >>> Link-local >>> >>> Standard IPv6 link-local scope as defined in [RFC4291] and [RFC4861] is >>> supported by the 6LoWPAN link and subnet model. Link-local scope is achieved >>> by setting the hop limit to 1, using link-local prefix or link-local >>> multicast scope. If a link is non-transient then link-local scope includes >>> only a subset of nodes >>> on the link (the set of nodes within assymetric radio range of a >>> node). Nodes in the link-local scope of a node are its neighbors, >>> and this link-local scope may be different for each node on a link. >>> >>> >>> LoWPAN Host >>> >>> A node that only sources or sinks IPv6 datagrams. Referred to as a >>> host in this document. >>> >>> LoWPAN Node >>> >>> A node that composes a LoWPAN and is used to refer to both hosts and >>> routers. Referred to as a node in this document. >>> >>> LoWPAN Router >>> >>> A node that forwards datagrams between arbitrary source- destination >>> pairs using a single 6LoWPAN interface performing IP routing on that >>> interface. >>> >>> Mesh Under >>> >>> A term referring to a configuration where the link-local scope is defined >>> by the boundaries of the LoWPAN and includes all the 6LoWPAN interfaces >>> within it. Forwarding and multihop routing functions are achieved at the >>> link layer. In this configuration the link may still exhibit assymetric >>> behaviour. >>> >>> Route Over >>> >>> A term referring to a configuration where the link is non- transient and >>> the link-local scope reaches only a subset of the LoWPAN nodes. IP routing >>> is performed by LoWPAN Routers to overcome to the non-transient nature of >>> the link. This configuration may consist of both routers nad hosts. >>> >>> Subnet >>> >>> A subnet is the collection of interfaces having the same IPv6 subnet >>> prefix on a link, as defined in [RFC4291]. A LoWPAN is made >>> up of the interfaces of LoWPAN Nodes and Edge Routers sharing the >>> same subnet prefix. Due to the non-transient nature of 6LoWPAN >>> links, IP routing may be used on the link to provide transitivity. >>> This exhibits a multi-link subnet feature with regard to hop limit >>> as defined in [RFC4903], and thus 6LoWPAN applications should make >>> no assumptions about the hop limit as it may be decremented in a >>> LoWPAN. >>> >>> >>> -- http://www.sensinode.com http://zachshelby.org - My blog "On the >>> Internet of Things" Mobile: +358 40 7796297 >>> >>> Zach Shelby Head of Research Sensinode Ltd. Kidekuja 2 88610 >>> Vuokatti, FINLAND >>> >>> This e-mail and all attached material are confidential and may >>> contain legally privileged information. If you are not the intended >>> recipient, please contact the sender and delete the e-mail from >>> your system without producing, distributing or retaining copies >>> thereof. _______________________________________________ 6lowpan >>> mailing list [email protected] >>> https://www.ietf.org/mailman/listinfo/6lowpan >>> >>> The information contained in this message may be confidential and >>> legally protected under applicable law. The message is intended >>> solely for the addressee(s). If you are not the intended recipient, >>> you are hereby notified that any use, forwarding, dissemination, or >>> reproduction of this message is strictly prohibited and may be >>> unlawful. If you are not the intended recipient, please contact the >>> sender by return e-mail and destroy all copies of the original >>> message. _______________________________________________ 6lowpan >>> mailing list [email protected] >>> https://www.ietf.org/mailman/listinfo/6lowpan >>> >> _______________________________________________ 6lowpan mailing list >> [email protected] https://www.ietf.org/mailman/listinfo/6lowpan >> > > > _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
