Distributed Protocol Stacks May 2008 Beijing, China Dzmitry Kliazovich and Fabrizio Granelli University of Trento, Italy

Fabrizio Granelli November 2007 TCP/IP Layering TCP/IP protocol reference model, the de facto standard in Internet, is based on ISO/OSI layering principles  Reasons: Interoperability and Fast Deployment TCP/IP layering drove the success of Internet in 90s  Demonstrates good performance in homogeneous networks which rely on similar PHY technologies However, nowadays networks are different - Heterogeneous !!!

Fabrizio Granelli November 2007 Heterogeneity Network Heterogeneity  Devices: hand-held, mobile, sensors  Links & protocols: Wireless and Wired  Services: variety of applications, data and services  Need for rapid deployment and organization Leads to poor TCP/IP performance, due to  Strict layering  Lack of cooperation and coordination C. Barakat, E. Altman, and W. Dabbous, “On TCP performance in a heterogeneous network: a survey”, IEEE Communications Magazine, vol. 38, no. 1, January 2000, pp. 40 – 46.

Fabrizio Granelli November 2007 TCP/IP optimization in Heterogeneous Networks Cross-Layering  Allows awareness and cooperation between protocol layers  Joined, coupled design  Examples: TCP notification of non-congestion related losses Agent-Based Networking  Aims at introduction of active functionalities in the passive network core  Examples: Web-proxy, cashing proxy

Fabrizio Granelli November 2007 Our Approach Idea: Extend the idea of protocol stack modularity making it network-wide Layered Design Cross-Layering Agent-based Networking Distributed Protocol Stacks

Fabrizio Granelli November 2007 Distributed Protocol Stacks Design Details  Each functional block of the protocol stack (a protocol layer or its part) can be abstracted into a separate module and implemented at a different node in the network  Communication between host protocol stack and removed module is performed using a custom “lightweight” protocol Applications (or What is it for?)  Move protocol stack functions that generate high communication overhead into the network core behind the bottleneck link  Caution: not all the protocol stack functions can be abstracted and separated

Fabrizio Granelli November 2007 Distributed Protocol Stacks

Fabrizio Granelli November 2007 Distributed Protocol Stacks Design Procedures  Abstraction: identification and isolation of a particular function or set of functions of the protocol stack  Detachment: separation of the chosen function or a set of functions into a standalone functional block as well as its registration, transfer, and execution with “friendly” network elements (routers, switches, or gateways)  Communication between detached functional block and the host protocol stack  Execution: triggered by the host node or performed automatically by Module Running Environment (MRE) implemented by the network element

Fabrizio Granelli November 2007 Distributed Protocol Stacks Concerns  Interoperability  Incremental deployment Benefits  Protocol stack performance  Enablers for new user applications  Driven by network operator perspective Design of Distributed Protocol Stack solutions should be driven by cost/benefits analysis !!!

A Case Study

Fabrizio Granelli November G LTE background Base station File Server IP network User Terminal Bottleneck link Transport Output() Transport Network Physical ACK gen Module running environment Link Physical Link Physical TCP data TCP ACKs Link Custom protocol

Fabrizio Granelli November 2007 ARQ Proxy - Approach TCP Data PHY/LL Headers File Server Evolved Packet Core ARQ Proxy MACARQ ClientMACTCP TCP Data TCP o Access TCP header o Get IP addr, port, etc. o Generate TCP ACK & store o Compute TCP ACK identification index Generate TCP ACK Index TCP DataTCPACK TCP ACK Index HARQ ACK + TCP Index Enhanced Node B (eNB)

Dzmitry Kliazovich Sept. 11, 2007 ARQ Proxy - Benefits Reduced RTT (Round Trip Time) Fixed Host (FH) IP Network Mobile Node (MN) TCP DataTCPACK Medium Access + TCP ACK Transmission over radio channel Enhanced Node B (eNB)

Dzmitry Kliazovich Sept. 11, 2007 ARQ Proxy - Benefits End-to-end TCP semantics are maintained Fixed Host (FH) IP Network Mobile Node (MN) TCP DataTCPACKLL-ACK Enhanced Node B (eNB)

Dzmitry Kliazovich Sept. 11, 2007 ARQ Proxy - Benefits Higher channel error rates tolerance Fixed Host (FH) IP Network Mobile Node (MN) TCPACK No TCP ACK over radio channel Wired channel (BER = to ) Wireless channel (BER = to ) Enhanced Node B (eNB)

Dzmitry Kliazovich Sept. 11, 2007 ARQ Proxy - Benefits Mobility & Incremental deployment Fixed Host (FH) IP Network Mobile Node (MN) No TCP state related information is maintained ARQ Proxy ARQ Client Enhanced Node B (eNB)

Dzmitry Kliazovich Sept. 11, 2007 Current Activities and Future Work ARQ proxy material  ARQ proxy for WiFi (IEEE )  ARQ proxy for 3G LTE (Super-3G)  ARQ proxy for WiMAX (IEEE ) D. Kliazovich, F. Granelli, S. Redana and N. Riato, “Cross-Layer Error Control Optimization in 3G LTE,” IEEE Global Communications Conference (GLOBECOM), Washington, DC, U.S.A, December F. Granelli, D. Kliazovich, J. Hui, and M. Devetsikiotis, "Performance Optimization of Single- Cell Voice over WiFi Communications Using Quantitative Cross-Layering Analysis," 20th Iternational Teletraffic Congress (ITC'20), Ottawa, Canada, June Submitted for publication in Globecom 2008.

Dzmitry Kliazovich Sept. 11, 2007 Current Activities and Future Work ARQ proxy material  EU patent-pending  Proposal to 3GPP standardization group  Under consideration for next generation equipment produced by Nokia Siemens Network (NSN) D. Kliazovich, F. Granelli, S. Redana, and N. Riato, “Cross-Layer Error Recovery Optimization for 3G LTE Systems,” EP

Dzmitry Kliazovich Sept. 11, 2007 Conclusions Reallocation of protocol stack functions in the network creates an additional degree of freedom for optimization The proposed Distributed Protocol Stacks are considered for Next Generation Internet (NGI) Brings novel applications, optimal protocol stack performance, and better configurability at the expense of reduced interoperability and incremental deployment

Fabrizio Granelli November 2007 Thank you!

Fabrizio Granelli November 2007 ARQ Proxy – Packet Identification 3G LTE: Hash values WiFi: Frame Sequence Numbers PHY Header LL Header TCP data Sequence Control Address 3Address 4 Fragment Number B3B4 Bits: 412 B15 B0 Sequence Number Hybrid ARQ (HARQ-ACK) or Enhanced Node B (eNB) User Equipment (UE) HARQ ACK

Dzmitry Kliazovich Sept. 11, 2007 ARQ Proxy - Limitations TCP ACKs are not substituted:  During connection establishment and connection termination packets (identified by SIN and FIN flags)  For TCP ACK encapsulated into TCP data packet in case of bidirectional data transfer  For Duplicate TCP ACKs  TCP ACK advertising exhausted receive buffer resources (rwnd field)

Dzmitry Kliazovich Sept. 11, 2007 Evaluation: 3G LTE scenario Round Trip Time (RTT) Hash value errors

Dzmitry Kliazovich Sept. 11, 2007 WiFi: Evaluation Results Throughput performance Improvement: 20% Improvement: up to 100% VoIP and Multimedia Applications TCP file transfer, Ethernet MTU

Dzmitry Kliazovich Sept. 11, 2007 WiFi: Evaluation Results Round Trip Time (RTT) improvement Order of milliseconds

Dzmitry Kliazovich Sept. 11, 2007 WiFi: Evaluation Results High error rate tolerance