Active networks and applications
description
Transcript of Active networks and applications
Active networks and applications
C. PHAMRESAM laboratory
December 6th, 2000
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Outline
Introduction Nowadays network technologies Active networking Application: Active Reliable Multicast Conclusions
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Outline
Introduction Nowadays network technologies Active networking Application: Active Reliable Multicast Conclusions
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The need for communication
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The way people are communicating…
Internet
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Internet milestone
1960 DoD project for a reliable, flexible network
1968 First transit node by BBN on DDP 316ARPANET was born with 4 transit nodes1969
1974 TCP/IP for internetworking
ARPANET has 200 transit nodes1983ANSNET from MERIT, MCI, IBM1990
Internet as you know it 1995
2000Internet 2, NG
??Something really fast
ATM, QoS,RVSP, DiffServ,IPv6, MPLS…
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User perspective of the Internet
from UREC, http://www.urec.fr
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What it is in reality…
from UREC, http://www.urec.fr
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Outline
Introduction Nowadays network technologies Active networking Application: Active Reliable Multicast Conclusions
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Links: the basic element for networking
Backbone links optical fibers 40 to 60 GBits/s with DWDM techniques
End-user access V.90 56KBits/s modem on twisted pair 512Kbits/s to 2MBits/s with xDSL modem 1Mbits/s to 10Mbits/s Cable-modem 64Kbits/s to 1930KBits/s ISDN access 9.6KBits/s (GSM) to 2MBits/s (UMTS)
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Routers: key elements of internetworking
Routers run routing protocols and build routing
table, receive data packets and perform
relaying, may have to consider Quality of Service
constraints for scheduling packets, are highly optimized for packet
forwarding functions.
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IP packet
IP packet
Filter Action
Forwardingtable
Routingagent
IP input processing IP output processing
IP packet
Packet scheduler
IP output processing
IP packet
Packet scheduler
General architecture of an IP router
receives input packets, sends packets to output buffers, transmits packets (with QoS?).
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Desires put on the general Internet
High-bandwidth for bandwidth-consuming applications
Ubiquity of the network access (wireless, RTC, xDSL, mobile…) for remaining connected everywhere
Quality of Service for high-quality multimedia receptio
Dynamicity, adaptability to take into account recent technologies
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Challenges for the Internet
high-speed www video-conferencing video-on-demand interactive TV programs tele-medecine high-performance computing, grids virtual reality, immersion systems distributed interactive simulations remote archival systems
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The reality…(1)
High-bandwidth accesses are not available for everybody high-bandwidth is achievable in the core
network with optical fibers and DWDM techniques but,
most end-users have an access ranging from 56Kbits/s to 2Mbits/s and,
it will be the case for many years!
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The reality…(2)
An ubiquitous network access generally implies heterogeneity and
asymmetric performances, how to take into account this
heterogeneity? The heterogeneity of bandwidth
makes QoS a difficult quest on an end-to-end basis, seems that QoS is the networking
forever Graal…
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The reality…(3)
New technologies require years to be deployed need for standardization
IPv6, MPLS new services and protocols are costly to
deploy many proprietary implementations, no
interoperability of services and new technologies
DiffServ, TagSwitching, LabelSwitching…
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Towards a better Internet…
Interoperability of systems Rapid deployment of new services,
accelerating infrastructure innovation Take into account the heterogeneity
of needs and network accesses Customization of services,
application-oriented processing features
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Towards the concept of…
Introduction Nowadays network technologies Active networking Application: Active Reliable Multicast Conclusions
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What is active networks?
Programmable nodes/routers Customized computations on packets Standardized execution environment
and programming interface No killer applications, only a different
way to offer high-value services, in an elegant manner
However, adds extra processing cost
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Motivations behind Active Networking
From the user perspective applications can specify, implement, and
deploy (on-the-fly) customized services and protocols
From the operator perspective reduce the latency/cost for new services
deployment/management From the network perspective
globally better performances by reducing the amount of traffic
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Active networks implementations
Discrete approach (operator's approach) Adds dynamic deployment features in
nodes/routers New services can be downloaded into
router's kernel Integrated approach
Adds executable code to data packets Capsule = data + code Granularity set to the packets
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DataData
The discrete approach
Separates the injection of programs from the processing of packets
active code A1
active code A2
A1A2
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The integrated approach
User packets carry code to be applied on the data part of the packet
High flexibility to define new services
data code
data datacode
data
datadata
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An active router
IP packet
IP packet
Filter Action
Forwardingtable
Routingagent
IP input processing IP output processing
IP packet
Packet scheduler
IP output processing
IP packet
Packet scheduler
some layer for executing code.Let's call it Active Layer
AL packet
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Interoperability with legacy routers
IP IP IP IP IP IP
TCP/UDP TCP/UDP TCP/UDP TCP/UDP
AL AL AL ALtraditional IP routing
APPLI APPLI
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Some open problems…
Security and integrity how to be sure that user code are safe?
Performances how to add active computation without
weeping out performances? Standardization of programming
interface How to bill the CPU time?
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Some active network applications
Customization of services Web-caching, on-the-fly compression/encryption
Filtering Auction, Distributed Interactive Simulations
Firewall Congestion control QoS Network management Reliable multicast Middleware collective operation
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Where to put active components?
In the core network? routers already have to process millions
of packets per second gigabit rates make additional processing
difficult without a dramatic slow down At the edge?
to efficiently handle heterogeneity of user accesses
to provide QoS, implement intelligent congestion avoidance mechanisms…
core networkGbits/s
wireless LAN1Mbits/s, 10MBits/s
PSTN
10Mbits/s
GSM, UMTS
visio-conferencing
ISDNxDSL
100Mbits/s
Server
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Outline
Introduction Nowadays network technologies Active networking Application: Active Reliable Multicast Conclusions
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Unicast
R
Sender Problem Sending same
data to many receivers via unicast is inefficient
Example Popular WWW
sites become serious bottlenecks
from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee
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Multicast
R
Sender Efficient one to many data distribution
from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee
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Multicast
History Long history of usage on shared medium
networks Data distribution Resource discovery: ARP, Bootp, DHCP
Ethernet Broadcast (software filtered) Multicast (hardware filtered)
Multiple LAN multicast protocols DECnet, AppleTalk, IP
from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee
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IP Multicast Introduction
Efficient one to many data distribution Tree style data distribution Packets traverse network links only once
Location independent addressing IP address per multicast group
Receiver oriented service model Applications can join and leave multicast
groups Senders do not know who is listening Similar to television model Contrasts with telephone network, ATM
from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee
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IP Multicast
Service All senders send at the same time to the same
group Receivers subscribe to any group Routers find receivers
Unreliable or reliable delivery Reserved IP addresses
224.0.0.0 to 239.255.255.255 reserved for multicast
Static addresses for popular services (e.g. SAP)
from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee
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Example: video-conferencing
from UREC, http://www.urec.fr
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video-conferencing (2)
Multicast address group 224.2.0.1
224.2.0.1
from UREC, http://www.urec.fr
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Multicast difficulties
At the routing level management of the group address (IGMP) dynamic nature of the group membership construction of the multicast tree
(pruning…) multicast packet forwarding
At the transport level reliability, loss recovery strategies flow control congestion avoidance
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Reliable multicast
What is the problem of loss recovery? feedback (ACK or NACK) implosion replies/repairs duplications adaptability to dynamic membership
changes Design goals
reduces recovery latencies reduces the feedback traffic improves recovery isolation
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Solutions
Traditional end-to-end retransmission schemes scoped retransmission with the TTL
fields receiver-based local NACK suppression
Active contributions cache of data to allow local recoveries feedback aggregation subcast
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A step toward active services: LBRM
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Active local recovery
routers perform cache of data packets repair packets are sent by routers,
when available
data1data2data3data4data5
datadatadata5
NACK4data4
data1data2data3data4data5
data1data2data3data5
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Active feedback aggregation
Routers aggregate feedback packets
NACK4
NACK4
NACK4
NACK4data4
NACK4
only one NACK is forwarded to the source
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Active subcast features
Send repair packet only to the relevant set of receivers
NACK4
NACK4
NACK4
data4
data4
data4
data4
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Active Reliable Multicast Mechanisms
Answer general questions such as is active networking beneficial for multicast? where active components should be placed? in what proportion? how fast do they need to be?
Answer specific questions such as what mechanisms (global vs local NAK
suppression, subcast facilities) for what performance?
scalabity of the proposed solutions? Design of new multicast protocols
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Network model
F active routers among N.B receivers in a local group2 kinds of receivers: linked and
free
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Benefit of global aggregation on throughput
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Benefit of the source subcast facility
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Impact of active router density
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Conclusion
Zut, j'aurais mieux fait de
rester au séminaire!!
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References
D. L. Tennehouse, J. M. Smith, W. D. Sincoskie, D. J. Wetherall, and G. J. Winden. A survey of active network research. IEEE Communications Magazine, pages 80--86, January 1997.
L. Wei, H. Lehman, S. J. Garland, and D. L. Tennenhouse. Active reliable multicast. IEEE INFOCOM'98, March 1998.
M. Maimour, C. Pham. A Throughput Analysis of Reliable Multicast Protocols in an Active Networking Environment. TR. http://resam.univ-lyon1.fr/~cpham/Paper/TR/TR01-2000.ps.gz
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Web links
ANTS http://wind.lcs.mit.edu/activeware
Tamanoir and active reliable multicast http://resam.univ-lyon1.fr
Active Networking in France http://www.loria.fr/~festor/raf/raf.html