ETRI

멀티캐스트 신뢰전송 기술(Reliable Multicast Transport Protocols)

고석 주

sjkoh@pec.etri.re.kr

KRNET20012

목 차

Overview & History Protocols in IETF RMT WG

TRACK: Tree-based ACK ALC: Asynchronous Layered Coding NORM: NACK Oriented Reliable Multicast

ECTP in ITU-T SG7 | ISO/IEC JTC1/SC6 Enhanced Communications Transport Protocol

Concluding Remarks

KRNET20013

RMT: Overview

End-to-End Reliable Multicast Transport 멀티캐스트전송에서의 TCP 기능 제공 가정: IP Multicast in Networks

KRNET20014

RMT: Issues

Reliable Multicast Error Control (Loss Recovery) Flow and Congestion Control

» Transmission Rate Control » Congestion Avoidance

Scalability Issue in TCP-like RMT ACK/NACK Implosions RTT estimation Heterogeneous Receivers

KRNET20015

RMT: History

A lot of Researches & Development http://research.ivv.nasa.gov/RMP/ http://www.nard.net/~tmont/

IRTF RM RG (Research Group) IETF RMT WG: 1999. 3 ~

Building Block Approach: BBs & PIs One-to-Many Bulk Data Transport

ITU-T SG7 | ISO/IEC JTC1/SC6 ECTS & ECTP (X.ectp | ISO/IEC 14476)

» Enhanced Communications Transport Protocol

KRNET20016

IETF RMT WG

BB & PI approach One Size does not fit all

Building Block drafts FEC (Forward Error Correction) GRA (generic Router Assist) Congestion Control: LCC, PGM-CC, TFMCC 기타 PI-specific BBs: LCT, Tree

3 PI (Protocol Instantiations) TRACK/ALC/NORM

KRNET20017

TRACK: Overview

Base Protocols RMTP-II: Talarian Corporation

» www.talarian.com TRAM: Sun MicroSystem (Java)

» www.experimentalstuff.com (JRMS) Related BBs

Tree-Configuration: rmt-bb-tree-config-02.txt TRACK BB: rmt-bb-track-01.txt TFMCC (TCP-Friendly): will be made 기타 BBs: TRACK Security, FEC, GRA

KRNET20018

TRACK: Architecture

Tree based ACK ACK packets flow children to root via parents

KRNET20019

TRACK: Logical ACK Tree

Tree Nodes Sender (Root), Service Nodes (Parent), Receivers

Configuration Steps (automatic) Session Advertisement: Tree Information Service Node Discovery by Receiver Distance Measurement: TTL, Tree Level, ……

» Sender distance: from Sender to SN» Neighbor distance: from SN to Receiver

Selection and Bind to the best Service Node» Loop-free ACK Tree

KRNET200110

Tree Configuration: Mores

Service Node Discovery schemes ERS (Expanding Ring Search) POC (Point of Contact): like DNS Mesh: Pre-established Mesh of Service Nodes

Tree Maintenance Monitoring Parent and Children

» TRACK PI issues (?) Tree Optimization

» Continue Node Discovery and Selection» Desired (?)

KRNET200111

TRACK BB (1)

Assumptions Logical ACK Tree: Tree Configuration BB Session Announcement: out-of-band

TRACK Functionality Hierarchical Session Creation & Maintenance

» Bind, Unbind, Eject, Fault Detection/Recovery TRACK Generation

» TRACK packets: Selective ACK» Rotating algorithm: AckWindow, AckTimer» Flow Control (Receiver Window)

KRNET200112

TRACK BB (2)

TRACK Functionality (Continued) Local Recovery

» Multicast Retransmission to Children TRACK Aggregation

» Feedback aggregation on Confirmed Delivery, Flow Control, Membership, Slow Receiver

Distributed RTT calculation» Group RTT: Sender – Receivers (for congestion

control such as TFMCC) » Local RTT: Parent – Children (for local timers)

KRNET200113

TRACK PI

TRACK Protocol Instantiation Tree Configuration BB TRACK BB TCP Friendly Multicast Congestion Control BB

» Others: TRACK Security, FEC BB, GRA BB» TRACK PI draft will be made

Considerations Service Node (Repair Node)

» End Receiver or Dedicated Server (?) Tree configuration is easy and effective (?)

KRNET200114

ALC: Overview

Asynchronous Layered Coding: Features No feedback from receivers such as ACK/NACK

» Forward Error Correction: for error recovery» Multi-rate transport: for congestion control

Leading company: Digital Fountain» www.digitalfountain.com

Related BBs FEC: rmt-bb-fec-02.txt & rmt-bb-fec-info-00.txt LCT (Layered Coding Transport): rmt-bb-lct-00.txt LCC (Layered Congestion Cont.):rmt-bb-lcc-00.txt

KRNET200115

ALC: FEC BB (1)

FEC coding with Redundancy» Source Symbols: k» Transmitted Symbols: n (> k)» Redundant Symbols: n – k

Simple Parity-Check coding: n = k + 1

KRNET200116

ALC: FEC BB (2)

FEC Coding Examples Existing well-known FEC codes Patent-pending: Tornado and LT codes

FEC-based transport: Digital Fountain

KRNET200117

ALC: LCT BB

Layered Coding Transport Multiple LCT Groups

» Multiple Channels for One Source (Content)» TV Example: B&W, Color, HDTV

KRNET200118

ALC: LCC BB

Layered Congestion Control Multiple Multicast Channels (Groups)

» Different Data Rate (Different QoS) Receiver-driven Congestion Control

» All Receivers join <Base Group>» They can join other Groups, according to their

local system resources» Dynamic Join and Leave, depending on

network conditions

KRNET200119

ALC PI

ALC PI FEC: for error control LCT: Base BB for ALC PI LCC: for congestion control

Status ALC PI will be made

» Just integration of these related BBs» Optional use of Retransmission-request packets

FEC BB & LCT BB are quite stable» will be progressed as RFCs

KRNET200120

NORM: Overview

Base Protocol SRM (Scalable Reliable Multicast)

»미국학계 중심으로 연구 진행» www.aciri.org/floyd/srm.html» MBONE whiteboard application

Related BBs NORM BB: not yet made

» NACK suppression with back-off timer PGMCC: rmt-bb-pgmcc-00.txt

KRNET200121

NORM PI

NORM PI rmt-pi-norm-00.txt

» NORM BB + PGMCC BB NORM Packets

» Info, Data, NACK, ACK, Report Status: too premature

» Basic framework is not specified yet» Use of ACK/NACK: scope-creep into TRACK (?)

KRNET200122

요약: IETF RMT Protocols

TRACK PI ALC PI NORM PI

Error Control(Base Docu.)

Tree BBTRACK BB

FEC BBLCT BB

NORM BB(not yet)

CongestionControl

TFMCC(not yet)

LCC BB PGMCC BB

Additional(Optional)

FEC BBGRA BB

GRA BB (?) FEC BB (?)GRA BB (?)

Leading Player

Talarian Corporation

Digital Fountain

USA Universities

KRNET200123

ECTP: 개요

Enhanced Communication Transport Protocol ITU-T SG7 | ISO/IEC JTC1/SC6

» Project: X.ectp | ISO/IEC 14476» By Korean Contributions

Base Documents (Standards)» ECTS (ITU-T X.605 | ISO/IEC 13252)» Multi-peer Communication (ITU-T X.601)

Current ECTP Documents» ECTP-1 (14476-1): Basics + Error Control » ECTP-2 (14476-2): QoS-related features

KRNET200124

ECTP: OperationsConnection Creation

ECTPConnection

Lifetime

Multicast Data Transfer

Connection Termination

Tree-based Reliability Control

Tree Membership Maintenance

Late Join and Leave

Control Tree Creation

QoS Negotiation

QoS Monitoring

QoS Maintenance

KRNET200125

ECTP: Features

Tree-based Error Control Adopt the TRACK approach in IETF Top-down based Tree Configuration Scheme

» TRACK: Bottom-Up ECTP distinctively provides

Tight Session and Membership Management» Session Creation and Join via Sender

QoS-based Session Management» Support Resource Reservation (RSVP)» Session Monitoring/Maintenance» Rate adaptation for congestion control

KRNET200126

ECTP: 활동 현황

표준화현황/활동 ITU-T SG17 Q.8 | ISO/IEC JTC1/SC6/WG7

» ECTP-1 (14476-1): Final CD ballot processing» ECTP-1 (14476-2): CD ballot processing

IETF RMT WG» Some inputs to Tree BB and TRACK BB » Transport Session Management: 2001년 3월 IETF 회의

– draft-koh-rmt-bb-tsm-00.txt

구현/검증현황 Implementation over Linux Platform: 완료 Validation via ETRI & APAN Testbed: by 2001

KRNET200127

ECTP: Projects in 2001

ECTP 표준 규격 개발 및 검증 (by ETRI) http://ectp.etri.re.kr (or pec.etri.re.kr/ectsp) ECTP Beta version Release 예정: by 2001 Current Members: 강신각, 고석주, 박주영, 김은숙

Collaboration with Academy (in 2001) GMP 설계 및 개발: 고려대 (강현국 교수)

» Web 기반 세션 공지/등록/관리 ECTP 응용 개발: 외국어대 (홍진표교수)

» Reliable File Transfer, Real-time Streaming ECTP with RSVP: 충남대 (김대영 교수)

» ECTP QoS 제어 기능 검증

KRNET200128

Concluding Remarks

Summary RMT: 종단간 멀티캐스트 신뢰전송 서비스(기술) 표준기술 성숙: IETF and ITU-T/JTC1

Prospects and Future Directions RMT depends on Deployment of IP multicast 서비스측면에서 RMT extensions 필요

» Reliability vs. Real-time streaming»그룹관리, 세션관리, 보안/인증, 과금 등

Integration of RMT with Emerging Technology» SSM, ALM (like CDN), Xcast (SGM)