Segment based inter-networking to accommodate diversity at the edge

1. Segment based inter-networking to accommodate diversity at the edge DCSLAB Cho wan-hee

2. Introduction • Motivation • Many of these changes have occurred at the network edge • Diverse Internet access tech - blue-tooth ,ultra-wide-band • Edge devices - cell-phone, PDAs, sensors • Applications - content sharing , sensing app • Services supported by network - caching, mobile users

3. Segment based architecture • Diversity at the edges is going to increase in future • Goal : offer flexibility at different levels • Introduce Tapa, segment based architecture • 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

4. Segment based architecture • Transfer layer • 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 • Implements e2e application semantics over transfer layer • traditional transport protocols is already implemented within segment layer • deal with lost ADUs when TAP failures • reorder ADUs that were delivered out of order (multiple segments)

5. Tapa • illustrate the role of new layers in Tapa • forwards application data units(ADUs) rather than byte stream or packets

6. TAP • What • 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 • transport layer can also accommodate the insertion of services on the TAP • caching : Web and other type caching • typically supported at application level

7. Tapa configuration case • segments can be very diverse and customized for each environment • can bypass IP and traditional link layer • HOP for mesh access network

8. Transfer layer • 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 in-network services • ex. Catnap

9. Transfer layer • Control Plane • 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

10. Transfer layer • Data Plane • 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) • use of ADU changes the interface between transport layer and applications, compared with socket API.

11. Transport layer • support for semantic between endpoints and network • 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 end-point while TAP can serve the data in an application independent way • ex) video streaming - on mobile phone, low resolution video

12. Prototype design • assumption : TAPs are being used in typical home wireless access scenarios. • two transfer mode • pull mode : applications use “get API” to retrieve an ADU • push mode : send ADU to particular node

13. Prototype design • transfer layer • 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 • reliability ,ordering ,delegation semantics • offer caching as a part of delegation semantic.

14. Case study (Catnap) • Catnap allows a mobile client to sleep during ADU transfers by intelligently shaping when data is sent on the wireless • wired segment is the bottleneck(home wireless scenario) • implemented as a transfer service that runs at the TAP

15. Evaluation • how well support diversity • micro-benchmark to quantify Tapa overhead

16. Evaluation • segment protocols • downloade of 10MB file with different segment protocols • swift • 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.

17. Evaluation • segment protocols • multi-wan-emu toplogy • downloads 10MB file in vehicular scenario using the emulator < aggregating uplink bandwidth > < vehicular communication >

18. Evaluation • overhead • 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 < LAN > < WAN >

19. Conclusion • seperation of segment / transfer / transport Layer • offer flexibility at different levels • segment level • diverse protocols (HOP ,Bluetooth ) • transfer level • multi-path and content-centric optimization • transport level • richer semantic (Caching) • this flexibility allows diverse applications, services ,devices to be part of internet.