Transcript **** 1 - MMLab

Segment based inter-networking to
accommodate diversity at the edge
DCSLAB Cho wan-hee
Introduction
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Motivation
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Many of these changes have occurred at the network edge
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Diverse Internet access tech
- blue-tooth ,ultra-wide-band
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Edge devices
- cell-phone, PDAs, sensors
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Applications
- content sharing , sensing app
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Services supported by network
- caching, mobile users
Segment based architecture
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Diversity at the edges is going to increase in future
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Goal : offer flexibility at different levels
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Introduce Tapa, segment based architecture
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Segment layer
corresponds to a portion of an end-to-end path that is homogeneous
best effort data delivery service to upper layer
routing, error control, congestion control service
Segment based architecture
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Transfer layer
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supports e2e data transfers over multiple segments
located on top of segments
similar to how IP supports connectivity in today’s internet
runs on Transfer Access Point(TAP)
Transport layer
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Implements e2e application semantics over transfer layer
traditional transport protocols is already implemented within
segment layer
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deal with lost ADUs when TAP failures
reorder ADUs that were delivered out of order (multiple segments)
Tapa
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illustrate the role of new layers in Tapa
forwards application data units(ADUs) rather than byte
stream or packets
TAP
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What
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glue required to combine multiple segments (ex. buffer space)
sufficient storage that facilitate relaxed synchronization
between segments and end-points
offer optimizations such as multi-path and content discovery
functions
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transport layer can also accommodate the insertion of services
on the TAP
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caching : Web and other type caching
typically supported at application level
Tapa configuration case
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segments can be very diverse and customized for each
environment
can bypass IP and traditional link layer
HOP for mesh access network
Transfer layer
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similar to IP in today’s internet
Internet routing needs to establish routes in large scale
but fairly stable
Tapa transfer layer establishes short paths(2-segments)
but path can be very volatile due to dynamic of the access
network(mobility)
IP packet forwarding is optimized for high throughput
despite large forwarding table
ADU forwarding is simple but needs to accommodate innetwork services
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ex. Catnap
Transfer layer
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Control Plane
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establish segments to set up e2e path
enable the data plane to transfer ADUs over them
globally unique “identifiers”
segment layer must be able to translate identifiers into
locators(ex. DNS for wired segments ,MAC addr for
bluetooth)
use host-name as identifiers in our prototype
needs congestion control over multi-segment path to ensure
that TAP buffers do not overflow
Transfer layer
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Data Plane
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ADU can be defined in a flexible manner based on the
requirements of the application.
(ex. whole file, chunk of file, MPEG frame in video tranfer)
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use of ADU changes the interface between transport layer and
applications, compared with socket API.
Transport layer
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support for semantic between endpoints and network
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ex) content is available in the cache of TAP
- client may not trust the TAP (open wifi)
- so client transport will request integrity check from the endpoint while TAP can serve the data in an application
independent way
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ex) video streaming
- on mobile phone, low resolution video
Prototype design
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assumption : TAPs are being used in typical home wireless
access scenarios.
two transfer mode
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pull mode : applications use “get API” to retrieve an ADU
push mode : send ADU to particular node
Prototype design
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transfer layer
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transfer ADUs and deliver them to higher
other transfer service can be used
(ex. Catnap )
once transfer layer assembles the whole ADU it sends it to the
transport layer
transport layer
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reliability ,ordering ,delegation semantics
offer caching as a part of delegation semantic.
Case study (Catnap)
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Catnap allows a mobile client to sleep during ADU
transfers by intelligently shaping when data is sent on the
wireless
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wired segment is the bottleneck(home wireless scenario)
implemented as a transfer service that runs at the TAP
Evaluation
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how well support diversity
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micro-benchmark to quantify Tapa overhead
Evaluation
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segment protocols
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downloade of 10MB file with different segment protocols
swift
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optimization of using multiple segments
scenario
multipexed different protocol segments (HOP +TCP)
different underlying tech (bluetooth + 802.11)
different ISP
We aggregate AP uplink bandwidth for efficient hand-off,
to mask failures and for aggregate throughput of multiple interfaces.
Evaluation
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segment protocols
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multi-wan-emu toplogy
downloads 10MB file in vehicular scenario using the emulator
< aggregating uplink bandwidth >
< vehicular communication >
Evaluation
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overhead
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single-wan-emu and single-lan-emu topology
Tapa-ir : push ADU , send ADU to particular node
Tapa-pull : pull ADU, pull ADU by first retrieving its id, and then
retrieving data
< WAN >
< LAN >
Conclusion
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seperation of segment / transfer / transport Layer
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segment level
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multi-path and content-centric optimization
transport level
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diverse protocols (HOP ,Bluetooth )
transfer level
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offer flexibility at different levels
richer semantic (Caching)
this flexibility allows diverse applications, services ,devices
to be part of internet.