Interests

Employment history

Education

Software tools developed

Systems Expertise

Standards contributions

Patents

Professional / Academic Activities

Tutorials

Publications

Presently, I am at IBM Research, working on different aspects of SIP (Session Initiation Protocol) and 802.11 based Wireless Mesh Networks. [more information]. I am also responsible for the Advanced Networking Services micropractice for On-Demand Innovation Services (ODIS) within IBM Research. The goal of ODIS is to tap IBM researchers for solving hard customer problems.

Prior to IBM Research, I was at NEC C&C Research Labs, Princeton (May95 - Oct99). I designed the networking architecture for a high speed mobile multimedia system including an IP switching scheme ("Ipsofacto") that was a precursor to MPLS. I led an offshore development team of eight engineers  for lab trials of this system with Telia (Sweden) and Sprint. [more information]

I have participated in leading technical conferences and panels on mobile networking, including presenting tutorials to international audiences on mobile networking. I have also been active within standards bodies (IETF and ATM Forum) and have been awarded five patents on mobile and high-speed networking, with seven others currently pending.

I received my PhD in Computer Science, from Rutgers University, in 1995, and currently also hold an Adjunct Faculty position at the Wireless Information Networks Laboratory (WINLAB), Rutgers University.

My most recent information is available here.

Session Initiation Protocol (SIP) / Voice-over-IP (VoIP)

Server support for handling large SIP workloads : leading an effort to udesign and develop a set of systems-level enhancements, both at the control layer (SIP message processing) as well as media processing, for specific SIP entities such as Session Border Controllers.

SIP Benchmarking : characterize SIP workloads and develop benchmarks to capture mutliple aspects of SIP usage such as Instant Messaging, VoIP and Presence.

SIP-enabled applications : designed and implemented a client-side SIP service that allows applications to exploit SIP. Developed new application of SIP such as seamless transfer between multiple/ongoing conferences and SIP-enabled multi-player networked games. Network infrastructure blocks include coupling conference control server with a hardware media conferencing unit, SIP-enabled web servers and game servers. Also worked on suporting SIP based control for VoIP on wearable devices such as the Linux Watch.

Mobility control for dual-mode phones : Developed and prototyped a mechanism for vertical handoff support for dual-mode phones using SIP

Task Force participation (a) Research representative to SIP Technology Team study, Feb - April 2004, reporting findings to Senior VP (Technology) (b) Task force on SIP and SIMPLE , sponsored by Corporate Strategy Office. (Sept 2003) (c) Corporate Technology Team study on VoIP : Findings presented to Senior VP (Technology), Sept 2002.

VoIP over 802.11: designed an architecture for providing quality-of-service to SIP-based VoIP on 802.11 using the PCF feature of 802.11 medium access standard.

Peer-to-peer VoIP and IM : Design/implementation of a SIP based IM/VoIP for ad-hoc wireless network coupling application-layer control/data messages with wireless mesh MAC protocols.

Customer consulting : Participating in an consulting engagement for a large Canadian bank on a strategy for incoprorating SIP. Previous engagements include a e911-like service for in-building users in a campus environment using wireless-LAN based location positioning techniques and VoIP.

Mobile/ Wireless Networks

NSF ORBIT project : This is a $5.4 million joint academia/industry project for a next-generation wireless testbed. My contribution representing IBM Research includes design/implemetation of a mesh networking architecture with a peer-to-peer VoIP/IM.

Wireless Mesh Networks : Designed (a) a "wireless router" with for packet forwarding between multiple wireless interfaces combining MPLS labels with 802.11 MAC, and (b) a "multi-cellular" architecture for simultaneous transmissions in neighboring cells of a mesh network.

e911: Architected a solution for an ODIS engagement within a university for an in-building e911 solution by combining a 802.11 based position determination system with VoIP .

802.11 based Hotspot : Developed an architecture/prototype for a Public Wireless LAN system for pay-per-use Internet access at 802.11 hotspots, at multiple tiers of service.

Network Infrastructure

MPLS Based Web-switching : architected a solution for web-switching by using a MPLS switch as a reverse proxy in front of a server farm avoiding TCP terminations.

IPv6 Content Distribution Networks (CDNs) : investigated ways in which the intrinsic mobility support in IPv6 can be used for request routing in CDNs .

IPSec Validation : designed a solution for checking if a IPSec tunnel between two endhosts is working as advertised.

Storage Virtualization : architected a solution for storage virtualization by assiging virtual IP address and port numbers to disk blocks such that movement of blocks is transparent to hosts.

Previous Employment (May 95- Oct 99)

Research Staff Member, NEC C&C Research Labs , Princeton, May 95 - Oct 99

Mobile ATM : Designed and implemented the mobile  IP/ATM  protocol architecture for one of the first  25Mbps mobile broadband  networks based on wireless ATM. In addition, the core network was also designed to support non-ATM wireless access such as wLAN and GSM.  I provided a core set of ATM Forum contributions on extending  ATM signaling/routing protocols for  "mobile ATM" in the wireless ATM working group, and supervised an 100 man-month offshore development team for lab trials of this IP/ATM mobile broadband sytem with two large carriers, Telia (Jan -Aug '99) and Sprint (May - July'99).

- Press release from NEC Corporation  anouncing trials with Telia, Sweden.
- A presentation describing the overall  WATMnet system :  my contributions comprising  the network protocol architecture/implementation.
- Demonstration of  WATMnet system at  Wireless Broadband Testbeds (DEMO '98) , Oct '98
- Demonstration of Mobile ATM prototype at ACM Mobicom'96 

IP Switching : Responsible for design/implementation of Ipsofacto, an IP switching technology that was a precursor to MPLS  whose key feature was support for IP multicast.  In conjunction with  Mobile IP and RSVP,  Ipsofacto  provided an IP based protocol architecture for  the WATMnet system.  I supervised a eight-person offshore development  project  (Feb - May'99) for deployment of Ipsofacto in the above trials.

- Presentation and demonstration of MPLS multicast at MPLS' '99 Conference
- IP Switching over ATM project with GMD Fokus and trial of Ipsofacto connecting  NEC Princeton, NEC Berlin and Berkom.
- Ipsofacto was  used by NEC Europe as a solution for IP/ATM integration, in field trials  for   IthACI ,  a EU project comprising NEC Europe, Alcatel and Cisco.

Linux based switch controller : An open architecture for IP/ATM switches and  base-stations, with separation of networking software(running on an external Linux PC) from the switching hardware,  using GSMP  (Generalised Switch Management Protocol) as the control interface, thus enabling a choice of either IP or ATM protocol stacks to control a common switching  hardware.  In 1996, this was one of the earliest use of open-source software (Linux and Linux-ATM stacks), for  networking projects in industry.

Post-Doc :  Wireless Information Networks Lab (WINLAB ) , Feb-May '95
   Project : Combining Mobile IP and IP multicast

Phd   : Rutgers University, CS  1995
    Thesis :   Structuring distributed algorithms and services in networks with mobile hosts 
    ( Abstract )  (PS )

Software Tools Developed

Standards Participation

IETF (Internet Engineering Task Force)
- Overview of  IP multicast in a Multi-Protocol Label Switching (MPLS) Environment, IETF  RFC 3353 , August 2002, MPLS working group
- IP Multicast Support in MPLS Networks. Internet Draft <draft-acharya-ipsofacto-mpls-mcast-00.txt>  Presented to the MPLS working group, 43rd IETF,  March 99.
- IPSOFACTO : IP Switching Over Fast ATM Cell Transport.  Internet draft <draft-acharya-ipsw-fast-cell-00.txt>, July 1997

ATM Forum
- Integrated location management for mobile ATM :interworking with mobile telephony and mobile IP. WATM WG, ATM Forum, Sept 1997.
- Comparison of location management schemes for mobile ATM.  WATM WG, ATM Forum, Feb 1997.
- Primitives for location management and handoff in Mobile ATM Networks. Wireless ATM Working Group, ATM Forum, Aug 1996.

Patents

Patents Awarded

-Handoff control for point to multipoint connections in mobile ATM networks. US Patent 6,643,279. Nov 2003.
-System and method for transferring IP packets using fast ATM cell transport. US patent 6,343,326. Jan 2002.
-Handoff method for an ATM wireless network wherein both the switch and the mobile buffer cells and the mobile controls when the handoff will occur. US patent 6,023,461. Feb 2000.
-Handoff-control technique for wireless ATM. US patent 5,974,036. Oct 1999.
-Method for Internet Protocol switching over fast ATM cell transport. US patent 5,903,559. May 1999.

Patent applications filed

SIP/ VoIP
- SIP based VoIP MultiPlayer Network Games. Co-inventors. Filed : Feb 2004
- System and Apparatus for geographically distributed VoIP Conference Service with enhanced QoS. Filed : Oct 2003
- Eanbling collaborative applications using SIP based VoIP. Filed : Oct 2003
- Method, system and service for achieving synchronous communication responsive to dynamic status. Filed : Jan 2004
- Differentiated handling of SIP messages for VoIP call control. Filed : Nov 2003
- A method and apparatus for providing quality of service to VoIP over 802.11 wireless LANs. Filed : Nov 2003

802.11 Hotspots
- Network-layer enforcement of differentiated connectivity for public wireless internet access. Filed : Aug 2002

MPLS
- A method and apparatus for content-aware for web-switching. Filed: Oct 2001
- Network l route control. Filed : Oct 2003

Service Discovery
- Dynamis Service Discovery. Filed : Jan 2002

Internet Storage
- Virtualization of ISCSI Storage. Filed : Jan 2002

IP Security
- Validation of Network Communication Tunnels. Filed : May 2000

Professional/ academic activities

Adjunct Faculty

Visiting Professor, Wireless Information Networks Laboratory (WINLAB), Rutgers University

Conference Chair

Co-chair, Global Internet and Next Generation Networks Symposium, Globecom 2004

Technical Program Committees

- Workshop on Pervasive Wireless Networking (in conjunction with PerCom), 2005
- The 25th IEEE International Conference on Distributed Computing Systems (ICDCS), 2005
- ACM Annual International Conference on Mobile Computing and Networking (MobiCom) : 1999 , 2000 , 2001 , 2002 , 2004
- 1st IEEE International Conference on Mobile Ad-Hoc and Sensor Systems (MASS), 2004
- IE EE International Workshop on IP Operations and Management (IPOM) 2004
- 1st Working Conference on Wireless On-demand Network Systems (WONS) 2004
- IFIP Personal Wireless Communications (PWC) : 2003, 2004
- IEEE Global Communications Conference (Globecom) General Conference: 2003, 2004
- First International Workshop on Broadband Wireless Multimedia: Algorithms, Architectures and Applications (BroadWiM), 2004
- The 5th ACM Intl Workshop on Wireless Mobile Multimedia (WoWMoM) : 2002
- International Workshop on Mobile Distributed Computing (MDC) : 2003, 2004
- International Conference on E-business and Telecommunication Networks (ICETE) 2003
- The 19th IEEE International Conference on Distributed Computing Systems (ICDCS '99)

Panels

- Panel Session, ACM WoWMoM 2002 "Which wireless network technology will prevail for scalable mobile multimedia services : cellular (3G/4G) vs. WLAN?" (Foils)
-Wireless ATM. Panel Session, Nomadic '97.
- Invited Participant, Dagstuhl Seminar "Mobile Multimedia Communication - Systems and Networks" Schloss Dagstuhl International Conference and Research Center for Computer Science. May4 - 6, 1999.
- Presentation  at  Wireless Broadband Communications Workshop, Sept 1997, organised by European  Union ACTS Programme.

Session Chairs

- System Level Design Issues, IEEE Intl Conference on Pervasive Computing and Communications (PerCom), 2003.
- Multicast Routing Session, IEEE Globecom 98

NSF programs

Industry Partner, ORBIT : NSF funded $5.45 million/ 4-year project on a Testbed for Next Generation Wireless Networks and Applications. Participant in two experimental work packages :
- Ad-hoc Networking in 802.11x WLAN scenarios
- Peer-to-peer infrastructure for VoIP and IM

Panel Member , National Science Foundation (NSF) Wireless & Mobile Communications & Networking Panel, 1997, Arlington.

Phd Thesis Committee

External Member, PhD Dissertation Committee of Sudeept Bhatnagar
Thesis title : " Distributed Admission Control in Core-Stateless Networks"
Computer Science Dept, Rutgers University, April 2004

External Member, PhD Dissertation Committee of Dragos Niculescu
Thesis title : "Forwarding and Positioning problems in Ad Hoc Networks"
Computer Science Dept, Rutgers University, March 2004.

Recent Invited Talks

- SIP : What is it, and how can we leverage it for next generation networking? IBM Networking Services Global "Coffee Class". Dec, 2003.
- SIP : Tutorial, Impact and Opportunities. Pervasive Computing Infrastructure Dept. Lunch-n-learn series talk. IBM TJ Watson Research Center. Feb, 2004.
- Medium access protocols for wireless mesh networks supporting peer-to-peer VoIP and IM. A. Acharya. Invited Presentation at Rutgers WINLAB (Wireless Information Networks Laboratory), Fall 2003 Industrial Advisory Board meeting, Nov 2003. (Slides)
- Multi-hop 802.11 wireless networks. IBM TJ Watson - Seminars in Communication. A. Acharya, Nov 2002.

Tutorial Presentation

Session Initiation Protocol (SIP) : A protocol for supporting multimedia in next-generation networks. ACM Multimedia 2005. (With Archan Misra, IBM Research and Avshalom Houri, IBM)

Session Initiation Protocol (SIP): A Protocol for Managing Next Generation Networks. 13th IEEE Conference on Network Protocols (ICNP), 2005. (With Archan Misra, IBM Research and Avshalom Houri, IBM)

Session Initiation Protocol (SIP): Multimedia Signaling in Next Generation Networks. 1st Intl Conference on Communication System Software and Middleware (COMSWARE), 2006 (With A Houri, IBM)

Wireless ATM : Standards, architectures, protocols & implementation.
The 3rd Annual ACM/IEEE International Conference on Mobile Computing  and Networking ( Mobicom '97 ), Sept 1997,  Budapest.

Representative Publications

SIP / VoIP

Using Session Initiation Protocol to build Context-aware VoIP support for Multiplayer Networked Games. ACM Workshop on Network and Systems support for Games (NetGames) 2004. Also appears as IBM Research Report RC 23209.

Design and Implementation of SIP Network and Client Services for enabling Collaborative Applications. 13th Intl Conference on Computer Communication and Networks (ICCCN) 2004. Also appears as IBM Research Report RC 23148.

Unleashing the power of Wearable Devices in a SIP infrastructure. Submitted for publication.

DCMA : A Label Switching MAC for Efficient Packet Forwarding in Multi Hop Wireless Networks. Submitted for journal publication. Also appears as IBM Research Report RC 23210.

Design and Analysis of a Cooperative Medium Access scheme for High-Performance Wireless Mesh Networks. 1st International conference on Broadband Networks (BroadNets) 2004 - Broadband Wireless Networking Symposium, Oct 2004. Also appears as  IBM Research Report  RC 22528.

High Performance Architectures for IP-based Multi-hop 802.11 networks.   IEEE  Wireless Communications Magazine, Special Issue on "Merging IP and Wireless Networks", Oct 2003.  

A Label-switching Packet Forwarding Architecture for Multi-hop Wireless LANs.   Best Paper Award at  ACM WoWMoM 2002. 
Slides,  IBM Research Report  RC 22512

MACA-P : A MAC for Concurrent Transmissions in Multi-Hop Wireless Networks.  IEEE  International Conference on Pervasive Computing and Communications (Percom), March 2003. Also appears as  IBM Research Report  RC 22528

Supporting Concurrent Transmissions in Multi-hop Wireless Networks. Presentation at 2nd  NY Metro Area Networking Workshop, Columbia University, Sept 2002 :  Paper Slides

A shorter version : MACA-P: A MAC Protocol to Improve Parallelism in Multi-Hop Wireless Networks. IBM Research Report  RC 22325

Challenges in high performance data forwarding in multi-hop wireless networks. IBM Research Report  RC 22506

Multi-hop 802.11 wireless networks. Talk presented at  IBM Research Communications and Networking Reading Group, Nov 2002

ts-PWLAN : A Value-added System for Providing Tiered Wireless Services in Public Hot-spots. IEEE 2003 International Conference on Communications (ICC 2003). Also appears as  IBM Technical Report RC 22516

airConn : A framework for tiered services in public wireless LAN hot-spots. To appear in IEEE Communications. A. Acharya, C. Bisdikian,  Young-Bae Ko  and A. Misra. (Paper)

MPLS

Overview of  IP multicast in a Multi-Protocol Label Switching Environment (MPLS) Environment , IETF  RFC 3353 , August 2002, MPLS working group

Framework for IP multicast in MPLS,  April 2002, IETF MPLS working group Internet Draft

Web Switching using MPLS . Technical Focus, MPLSWorld

Native IP multicast support in MPLS.  Lecture notes in Computer Science 1736.  Also appears in 1st Intl wkshp on Networked Group Comunications, Nov '99

IPSOFACTO : IP switching over fast ATM cell transport.   Internet draft  <draft-acharya-ipsw-fast-cell-00.txt> , July '97

IPv6

Using Mobility Support for Request-Routing in IPv6 CDNs. IBM Technical Report .  7th Intl Workshop on web content caching and distribution (WCW-7 ).

MRSVP : A reservation protocol for integrated  services packet networks with mobile hosts .  ACM/Baltzer Journal of Wireless Networks, Vol. 7, Issue 1, Jan 2001

Integrated services packet networks with mobile  hosts : architecture and performance . ACM/Baltzer Journal of Wireless Networks, Vol. 5, Issue 2, Mar 1999

Rate adaptation schemes in networks with mobile hosts. The fourth annual ACM/IEEE international conference on Mobile computing and networking (Mobicom), Oct 1998. 

On accomodating mobile hosts in an integrated services packet network. IEEE Infocom '97.

A framework for delivering multicast messages in  networks with mobile hosts .  ACM Mobile Networks and Applications, Vol. 1, Issue 2, Oct 1996

IP multicast extensions for mobile internetworking.  IEEE Infocom '96.

IPSECvalidate - A Tool to Validate IPSEC Configurations.  Usenix LISA 2001 15th Systems Administration Conference, Dec '01

Mobility support for IP over wireless ATM. IEEE Communications, April '98

Mobility management in wireless ATM networks. IEEE Communications,  Nov '97

Mobile ATM : architecture, protocols  and  implementation. 2nd IEEE Intl workshop on broadband  switching systems,  Dec '97

Peer to Peer (P2P) Networking

SRIRAM - A Scalable, Resilient Autonomic Mesh.   IBM Systems Journal, Vol. 42,  No. 1, 2003.

Content Distribution Networks

MPLS   based request routing,  6th Intl Workshop on Caching and Content Distribution (WCW-6 ), June 2001

MPLS-based Web Switching , 1st New York Metro Area Networking Wkshp, March 2001

Local and wide-area server selection : techniques and challenges,  Invited talk Opensig 2000

IP Multicast

Distributed Admission Control for Heterogeneous Multicast with Bandwitdh Guarantees. 11th Intl Workshop on  Quality of Service (IWQoS 2003), June 2003. Also appears as Lecture Notes in Computer Science 2707.

IP switching over fast ATM cell transport  (IPSOFACTO) : Switching multicast flows . IEEE Globecom '97

IP Switching over fast ATM cell transport.  (IPSOFACTO) : IP multicast over wireless ATM. IEEE ICUPC '98

IP multicast extensions for mobile internetworking.  IEEE Infocom '96.

Routing and RSVP

A framework for handling route changes and aggregation in IPSOFACTO.  IEEE  Globecom '98

Designing distributed algorithms for mobile computing networks. Computer Communications 19 (1996)

Recording distributed snapshots based on causal order of message  delivery.   Information Processing Letters Vol. 44, No. 6, Dec '92

Recognition of occluded objects with heuristic search. Pattern Recognition Vol. 23, No. 6, '90

Heuristic search in restricted memory. Artificial Intelligence Vol. 41, No. 2, Dec. '89