Re: [SWMP] Re: faster field messages
john_patterson@us.ibm.com Fri, 31 August 2007 19:36 UTC
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To: Roland Weber <ossfwot@dubioso.net>
Subject: Re: [SWMP] Re: faster field messages
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Date: Fri, 31 Aug 2007 15:36:59 -0400
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Roland: I assumed that the IDs are valid for a session, i.e., the messages between the HELLO and the BYE. I also assume that any network element wishing to use an ID must first send a SET message establishing the mapping for that node, which can be followed by later SETF messages that use the ID. I assume that at any time a SET message may be issued to change the ID that is being used even if there have been prior SETF messages using an earlier ID. I assume that if a network element cannot formulate a legitimate ID that SET messages may be used in lieu of a SETF message. This would mean that a pre-established limit would be acceptable, if large enough to cover most situations. I believe it is an ad hoc mechanism, but I assumed it was to make the processing more efficient. I'm not sure whether the focus was on networking issues or lookup efficiency on the network elements. I assume the technique was introduced because the X3D data model has within-node names for fields. jfp Roland Weber <ossfwot@dubioso.net> wrote on 08/31/2007 12:33:37 PM: > > > > So each side gets to declare its own mapping and the other is obligated to > > keep track of that. > > What are the limits, like a maximum number of mappings, or a > maximum guaranteed lifetime of mappings? Unlimited mappings > that each peer needs to keep track of open the gate for easy > DoS attacks. Negotiated limits with each peer would not allow > a server to use the same mappings for each client. > One approach would be that a peer advertises how many mappings > it is going to use, so that the partner can decide on whether > to accept that number or cancel the connection. Another is to > define a maximum number in the protocol, like 255 or 256. That > may be too restrictive, but allowing two bytes and more than > 65000 mappings will trigger memory problems, in particular on > a server. > > >From the paper (I've read it by now) I perceived it rather > as an ad hoc technique used to shrink the size of a group of > messages in an UDP packet. In that case, the lifetime of a > mapping could be restricted to the packet. But that doesn't > map to TCP connections, or your discussion of defining the > mappings on a separate channel. > In the extreme case of ad hoc, you'd have only one mapping > which is defined at the beginning of a sequence of messages > referring to the same node, and overwritten by the next > definition. Actually, that's not even a mapping anymore, > but an implicit argument. > > cheers, > Roland > > _______________________________________________ > SWMP mailing list > SWMP@ietf.org > https://www1.ietf.org/mailman/listinfo/swmp
_______________________________________________ SWMP mailing list SWMP@ietf.org https://www1.ietf.org/mailman/listinfo/swmp
- Re: [SWMP] Re: faster field messages john_patterson
- [SWMP] My understanding so far john_patterson
- Re: [SWMP] My understanding so far Roland Weber
- Re: [SWMP] My understanding so far Jay C. Weber
- Re: [SWMP] My understanding so far john_patterson
- RE: [SWMP] My understanding so far Tony Parisi
- [SWMP] semantic layers Jay C. Weber
- [SWMP] field-creation semantics Jay C. Weber
- [SWMP] introducing RPC to an asynchronous protocol Jay C. Weber
- [SWMP] Re: semantic layers john_patterson
- [SWMP] faster field messages Jay C. Weber
- [SWMP] Re: field-creation semantics john_patterson
- [SWMP] Re: introducing RPC to an asynchronous pro… john_patterson
- RE: [SWMP] introducing RPC to an asynchronous pro… Tony Parisi
- RE: [SWMP] semantic layers Tony Parisi
- [SWMP] Re: faster field messages john_patterson
- [SWMP] Re: faster field messages Jay C. Weber
- [SWMP] Re: faster field messages john_patterson
- [SWMP] Re: faster field messages Jay C. Weber
- [SWMP] Re: faster field messages john_patterson
- RE: [SWMP] introducing RPC to an asynchronous pro… john_patterson
- RE: [SWMP] introducing RPC to an asynchronous pro… Tony Parisi
- Re: [SWMP] Re: faster field messages Roland Weber
- Re: [SWMP] My understanding so far Roland Weber
- Re: [SWMP] Re: faster field messages Roland Weber
- Re: [SWMP] My understanding so far john_patterson
- Re: [SWMP] My understanding so far Roland Weber
- Re: [SWMP] My understanding so far Jay C. Weber
- Re: [SWMP] My understanding so far Roland Weber