December 5 2008 - 11:00 PST
* CTP+LPL status review * Shepherd for TEP 124 * Plans for IP stack
* Razvan Musaloiu-E. (RM) * Mike * Omprakash Gnawali (OG) * Phil Levis (PAL) * Steve Dawson-Haggerty (SDH)
CTP + LPL
OG: tried latest versions [CTP + LPL] without success
PAL: Define without success?
OG: Can get data, duty cycle are 20-30%
RM: Varying data rate doesn't change duty cycle
OG: Good to sumarize these experiences
ETH- Good results with a few changes to LPL: keep track of wakeup time for neighbors Uhland (?) also used it with very good results. Sumarize: worked well at some point, requires tweaking LPL
SDH: This belongs in the link layer, not in CTP
RM: Did the ETH guys modify LPL?
RM: What if we buffered messages for a long time and burst packets
together to amortize the wakeup cost. <discussion about the length of receive check intervals>
SDH: it's about 15-20ms
RM: False positives, 802.11 interference, everything contributes to a ~5%
base duty cycle
PAL: so why do these modifications help?
RM: what about LPP for probing?
PAL: needs to work for lots of different network layers.
OG: LPP for deluge?
RM: <explaination of LPP>
PAL: how does broadcast work?
RM: you just need to wait for a probe interval and reply to all
RM: resilient to false positives
PAL: probe collisions?
RM: Haven't looked at that
PAL: there's no reason there shouldn't be both in the tree.
RM: it's much easier to get good performance with CTP.
PAL: John is a cc2420 maintainer, just put it in there.
OG: What is LPP not useful for?
RM: The checks in LPL can go much lower then LPP. Right now it's
about 20ms, but Prabal says it can go lower. It needs some lower level tricks to go lower.
OG: the fundamental limitation is you need to send a packet and wait
for an ack. software architecture: you need a bunch of tweaks for 30% DC. Phil: can you revive this [how to set DC] in core? There are multiple places where this is done.
TEP for shepherding
TEP123 (CTP) will be shepherded by J. Hui
TEP124 (LEEP) needs a shepherd. Maybe Alec Woo?
What about Dutchy (?) on the Double Cost paper at HotEmNets (from Emory)
OG: do you buy this "Dutchy" story? It's similar to 4bitle
Anyways, hopefully we have a shephard. [SDH: missed the name]
RM: quick comment about TEP123: last paragraph of section 2.
CTP offers some way of aggregating small packets using the intercept interface.
PAL: this is more like Jumbo ethernet frames where L3 deals with the
packing. But, CTP can't do this.
OG: this functionality really isn't in CTP.
OG: Steve will replace the current 6lowpan implementation.
SDH: We need to make some changes to the messaging layer, etc.
PAL: Can we also send AM messages? We need to have a migration path.
SDH: I __guess__ we could do that...
PAL: Will talk to core about cvs access.
RM: Can I modify tos.py?
PAL: email tinyos-devel to see if anyone depends on it.