Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Quality of Service for Remote Control in the High Energy Physics Experiments:
a Case Study
Tiziana Ferrari
INFN - CNAF
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Overview
• Quality of Service
• differentiated services architecture
• application characterization
• service definition and implementation
• future work
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Quality of Service: problem statement
• today: single service, best-effort• Service: type of “data” treatment during transmission across
the network - qualitative- quantitative (delay, instantaneous delay variation, packet loss,
throughput, MTU, congestion treatment)
• Class: set of packets to which a given service applies• Benefits:
- congestion management- differentiated allocation of expensive network resources (ISP)- application: differentiated treatment of streams according to their
requirements and priority- guarantees of congestion independent parameters (e.g. delay variation)
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Differentiated services
• Why the differentiated services (diffserv)?
- independent of layer 2 technologies
- interoperability between independent national research networks (different requirements, infrastructures, policies and management)
- traffic aggregation
- scalability
- no signalling
- QoS for networks not ATM based
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Diffserv architecture components
• DS field (1 byte) - IP header -
• packet classification
• packet scheduling
• traffic conditioning: - metering- marking- policing- shaping
DS field CU0 6 7
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Diffserv architecture: PHBs
• Per Hop Behaviours: description of the packet treatment into the network
• Standardised PHBs:
- Expedited Forwarding (low delay, low delay variation,
guaranteed bandwidth)
- Assured Forwarding (Behaviour Aggregate, 4 classes,
3 drop priorities per class)
• Experimental PHBs
• PHB class selectors: XXX000 (backward compatibility with TOS precedence)
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Diffserv architecture: network model
DS domain
DS domain
DS domainDS domain
Non-DS capabledomain
MPLS
Core domain
marking
Markingpolicing scheduling
shaping
DS domainATM
DS region
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Application characterization
Goal:
identification of the application requirements for
service definition
1 Trigger hardware remote control
2 Monitoring: quality and correctness of analysis results
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Application 1: trigger hardware remote control
VMEServer 1
...
Client 1
Client 2
Client 3
Client n
...
bottlenecks
VME
VME
Server 2
Server m
R1 R2 R3
• ROBIN • client - server, duplex exchange of data, interactive• few transactions (low bandwidth) • TCP ports and IP address of the server known• one-way delay sensitiveness• high reliability (packet loss probability, bandwidth)• burst tolerance
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Application 2: Analysis monitoring
server
...
bottleneck
• exchange of analysis results (root object)• duplex, asymmetric traffic volume• low bandwidth consumption• client - server, • TCP, IP address of server and clients known• packet loss tolerant• minimum bandwidth guarantee per client• dynamic allocation of the maximum overall capacity allocated
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Service Level Specification (SLS) - 1
• Hardware remote control:
- packet classification and marking (at the edge): if (pack(src) = (s1 || s2 || … || sm) &&
pack(dst) = (d1 || d2 || … || dn) &&
protocol = TCP && pack(port)[x, y] ) then label(pack) = max precedence
- bandwidth guarantee (through policing):max service rate = 64 Kbps * Nsrc 64 kbps: estimated rate consumed by 1 server/client
Nsrc: number of servers (upstream) of clients (downstream)if (traffic <= max && burst <= 64 kby) then
label = Expedited Forwardingelse label = best-effort
- one-way delay (through scheduling): priority queuing
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Service Level - 1: implementation
scheduling
VME
Server 1
VME
Server 2
VME...
Client 1
Client 2
Client 3
Client 4
rR
Server 8
marking
R
Rr
r
traffic, max rate R
scheduling marking
Server client:
traffic, max rate r policing
PQ
PQ
PQ
PQ
PQ
PQ
PQ
PQ PQ
PQ
PQ
PQ
PQ
Client server:
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Service Level Specification -2
• Analysis monitoring:
- server client:
* packet classification and marking (at the edge): if (pack(src) = s && pack(dst)=(d1 || d2 || … || dn) &&
protocol = TCP)
then label(pack) = PHB Assured Forwarding(AF)class
* bandwidth guarantee (through policing):max service rate per client = 256 Mbps min rate per client: 64 kbps
for each client: if (traffic <= min && burst <= 16 Kby) then label =
AF11; else if (traffic <= max) then label = AF12;
else drop(packet)
* scheduling: Weighted Fair Queuing * traffic differentiation: Weighted Random Early Discard
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Service Level Specification -2 (cont)
- Client server:
* packet classification and marking (at the edge): if (pack(src) = di && pack(dst) = s && protocol =
TCP)
then label(pack) = PHB Assured Forwarding(AF)class
* bandwidth guarantee (through policing):max service rate = 5 Mbps min rate per client: 64 kbps
for each client: if (traffic <= min && burst <= 16 Kby) then
label = AF11; else label = AF12;
if (traffic(Af12) <= max) then OK else drop(packet);
* scheduling: Weighted Fair Queuing * traffic differentiation: Weighted Random Early Discard
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Service Level -2: implementation
scheduling
Server
Client 1
Client 2
Client 3
Client 4
r
marking
R
r
r
r
traffic, max rate R
scheduling markingServer client: traffic, max rate r policing
WFQ
WFQ
WFQ
WFQ
WFQ
WFQ WFQ
WFQ
WFQ
WFQ
WFQ
Client server:
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Scheduling: PQ vs WFQPriority Queuing:
absolute precedence over any other queueone-way delay minimization
WFQ: distribution of bandwidth between queues according to the weight associated to each of them
Tiziana Ferrari Quality of Service for Remote Control in the High Energy Physics ExperimentsCHEP, 07 Feb 2000
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Future work
Fermilab
ESnetdiffserv Testbed
European diffserv testbedor ATM p-2-p link
Test site 1
Test site 1
Test site 1
...
•Testbed configuration •tuning of router configuration•validation of the EF : priority queuing, burstiness and scheduling•validation of the AF implementation: WRED configuration