Sequin%20Technical%20Summary

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Sequin Technical Summary

• Mauro Campanella
• INFN-GARR
• Mauro.Campanella_at_garr.it

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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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Synergy with
- A joint
and
task force on advanced networking research
http//www.dante.net/tf-ngn
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Approach to the task(end to end QoS across
multiple domains)
QoS Definition
Bottom - up Quantitative, using a minimum and
sufficient set of QoS parameters
Top - down Qualitative through users
questionnaire
QoS service(s) definition, architecture, testing
and implementation in NREN networks
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Basic components of QoS
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Intuitive definition of QoS
The network offers a QoS service when its
capable of handling selected packets in such a
way to fulfill applications requirements.
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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Users Interview
A questionnaire has been developed to asses
users needs of QoS. The questionnaire was
articulated in 26 questions in 4 sections -
geography - qualitative perception of QoS -
quantitative perception of QoS - network options
and expectation. It was sent to 20 groups of
pan-European and large users, out of which 11
responded.
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Interview results
used
outside Europe to which connectivity is needed
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Interview results (continued)
(QoS need)
QoS
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Interview results (continued)
Overall the users showed medium to low knowledge
of their QoS needs and QoS techniques, but
unanimously requested it, as a way to have a
better service from network for their work
. Present difficulties are mainly due to
congestion. Willingness to pay is proportional
to the real benefits, granularity of the service,
provisioning time and flexibility and behaviour
of Best Effort. Need for simple, fast access to
the QoS service.
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Questionnaire summary
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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QoS parameters
From users requirements and technical
considerations ?- one-way delay ?- IP packet
delay variation ?- capacity (rate) ?- one-way
packet loss. The set is common to IETF and
ITU-T. Naming and definitions are chosen to be
comply to RFC 2330 (Framework for IP Performance
metrics) and follow the ongoing IPPM IETF working
group work.
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QoS parameters sample value ranges
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QoS parameters (continued)
Memento To build a QoS service based on the
previous listed parameters, some basic
requirements on the network should be
fulfilled - physical and data link stability -
exhibit a Bit Error Rate better than 10-12 -
overall network hardware performance. The
minimum MTU size should be chosen large enough to
avoid fragmentation. Duplicate and out-of-order
packets at the physiological level (which is not
null, but very small)
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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Which QoS service
Start with the very good service and call it
Premium IP - it satisfies all the users
requests - it is the best achievable service
possible - it maps to very high priority
scheduling techniques available now - it is
similar to a virtual wire
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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(No Transcript)
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Premium IP goals
Provision QoS for the European research users in
the form of an end to end network service
offering the equivalent of a leased line. The
service has to be implemented by combining border
to border services provided by the NRENs and
networks The architecture
has to be simple, modular, scalable, adapt to
network changes easily, based on IP and
independent from the transport technology. The
implementation and Service Level Agreements have
to match the current status of hardware
availability and network topology
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QoS Protocols and Architectures Overview
Overprovisioning
Diffserv 802.1p
RSVP (aggregates) Diffserv - 802.1p
RSVP (per flow) Diffserv - 802.1p
ATM - ATM signaling
MPLS -Traffic engineering
RSVP - Intserv
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Which QoS framework to use ?
?

• Differentiated Services - RFC2475 -
• Integrated Services - RFC 1633 -
• Overprovisioning

?
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Premium IP Specification
? Differentiated Services Architecture and use
the expedited forwarding per hop behavior
(EF PHB) ? interface definition between domains
that behaves as an EF PHB ? do not starve
best effort traffic (limited percentage of link
capacity devoted to Premium IP, about 5) ?
initial provisioning structure static, no
dynamic signaling ? IETF IPPM QoS parameters
measurement framework ? QoS parameters
monitoring system is a key element
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Premium IP Specification
? minimize number of action per node ? modular
approach that allows different implementation
schemes at every hop or domain and allows
domain to join the service when ready and
do not try to solve the most general problem,
but rather develop a model that can be
implemented in parallel with the start of GÉANT,
using available tools
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IP v4
IP v6
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Simplifying the actions for each node
In principle, each node might perform an awful
lot of tasks
- admission control and classification
- scheduling
- marking
- policing
- congestion control
- shaping
- monitoring and accounting
- QoS rules propagation
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Admission control
Use the information in the IP - IP source
and destination (prefixes) as near to the
source as possible - the DSCP (or IP precedence
equivalent value) along the path - perform an
optional, suggested, admission control based on
AS source and destination at inter-domain links
(safety measure) - rules might be based on
additional parameters, as time-of-day
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Admission control (continued)
The consequences are - allowing the computation
of total requested Premium IP capacity at each
network node in the default case (and for main
backup cases too) - short access list near
users premise (few users) - simple control at
backbones (IP addresses are not propagated) -
choosing destination-aware service (next slide)
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Examining the tasks for each node
In principle, each node might perform an awful
lot of tasks
- admission control and classification
always
- scheduling
- marking
- policing
- congestion control
- shaping
- monitoring and accounting
- QoS rules propagation
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Marking
- Mark each EF legal packet at first
classification point - Use the same DSCP value on
all domains (Class selector 5 - decimal 40
RFC 2474 to have interoperability with
ToS-only capable hardware) - strongly suggested
- - valid DSCP coupled to invalid IP addresses
implies discard to allow easy debugging -
packets with other DSCP values are left
untouched Marking is mandatory at the first
classification point, remarking is optional.
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Examining the tasks for each node
- admission control and classification
always
- scheduling
- marking
- policing
Selected locations
- congestion control
- shaping
- monitoring and accounting
- QoS rules propagation
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Policing
Microflow policing should be done as close as
possible to the source according to agreed
(through SLA) Premium IP capacity. This step is
mandatory Policing will be done using a token
bucket. The depth of the token bucket will be two
MTU close to the source and increase to 5 or more
along the path if additional policing is
required It is suggested to perform only one
additional policing stage at the ingress to GÉANT
from an NREN, with a larger aggregated capacity
value than the sum of the agreements. Avoid
unwanted packet loss is the motto.
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Policing (continued)
The additional policing stage at the ingress to
GÉANT from an NREN serves the purpose of
protecting Premium IP traffic from
misconfiguration/DoS coming from a single
source. It creates virtual pipes for the
aggregated Premium flows from each NREN to each
other (when needed). The failure of one pipe
does not influence the others.
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Sample multidomain network
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Examining the tasks for each node
- admission control and classification
always
- scheduling
- marking
- policing
Selected locations
Selected locations
- congestion control
- shaping
- monitoring and accounting
- QoS rules propagation
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Scheduling
Use the highest priority queueing mechanism (PQ
or WRR). Limit total Premium capacity when
assigning service to users at about 5 of each
core link. Assigned Premium capacity can be
larger near users sites.
Suggested Premium limit
Premium traffic
Total link capacity
Best Effort traffic
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Examining the tasks for each node
- admission control and classification
always
- scheduling
- marking
- policing
Selected locations
always
Selected locations
- congestion control
- shaping
- monitoring and accounting
- QoS rules propagation
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Shaping
The compliance of the Premium user flow to the
contracted capacity is the key for the result of
the service. Shaping is intended here as
limiting the rate of transmission to a specific
value. The speed of the core link and the highest
priority in scheduling for the packets of the
Premium IP service make delay variation small
even at aggregation points. At 2.5 Gb/s the
transmission time of a 1500 bytes packet is about
5 microseconds. The consideration suggests to
start the service without enabling shaping in the
core and it shaping may be optional also at the
border, provided the sources produce a well
shaped flow.
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Shaping
The sending source is hence required to shape the
traffic it produces. Shaping inside the sending
host itself is the preferred way, shaping by the
network will in most case lead to packet losses
No Packet/Data losses
host
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Examining the tasks for each node
- admission control and classification
always
- scheduling
- marking
- policing
Selected locations
always
Selected locations
NO Done by source
not needed
- congestion control
- shaping
- monitoring and accounting
- QoS rules propagation
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Premium IP Summary
Classification (DSCP) and High priority
scheduling on all nodes
Do not police on egress Do not shape anywhere
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Summary
Innovations - interdomain behaviour
specification - end to end service level
agreement The architecture allows - different
implementation strategy in each domain -
asynchronicity in implementation - sub-domain
implementation - explicit rate limitation only
near sending source - enabling a user just adding
few lines of access control
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Example (one direction)
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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SLA/SLS Basic implementation
In the first phase the SLS negotiation will be
performed manually (no bandwidth broker). The
analytical computation of the QoS metric in a IP
based network is extremely complex and the SLA
specification will require extensive testing of
the available infrastructure. Usually only QoS
parameter ranges can be specified and assurances
as percentages of total time. There are always
two SLA, one for each direction. The contracted
values might be different (asymmetric capacity
for example)
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Fundamental concepts (continued)
The service must be defined both as an end to end
service level agreement and be accepted as a
modification in the chain of service level
agreements between all involved domains. The
SLA/SLS is in reality a chain of SLA/SLS between
neighbour domains and a final end-to-end one.
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Fundamental concepts (continued)
Users must understand the application require
ments in term of the QoS parameter, at
least the requi- rement for the maximum
sending/receiving rate of the application. There
is the need of a central database to keep up to
date track of allocate resources and check their
availability. Debugging can be assigned to just
one specific entity.
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(No Transcript)
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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Monitoring
Highly distributed measurement of QoS parameters
that can measure the end to end and single hops
performance. Use a mixture of active (in-band)
and passive methodologies In-house developed tool
for GÉANT (Taksometro)
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Methodologies

• Active
• injects measurement traffic at small capacity
• use low cost dedicated hardware like RIPE TT
  boxes, surveyor, chariot
• suitable for loss, delay, jitter
• can be implemented in key locations

• Passive
• used also for regular (BE) traffic
• known tools based on SNMP, like netflow, that
  read counters on nodes
• suitable for packet loss, policing, queue depth
• can access every node

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Per-domain measurement
Web interface
taksometro
Ripe ttm
Ripe ttm
NREN B
router
router
NREN A
router
router
NREN C
router
Ripe ttm
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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Premium IP road map
QoS Definition Deliverable D2.1 Sequin
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Premium IP status
Currently tests are running between Switzerland,
Italy, Germany and Greece. Goal is to validate
the model, measure the network performance (end
to end) and measure the effect using a
videoconferencing application based on
H.323 Premium IP is configured on GÉANT routers.
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Premium IP in progress
Fine tuning of buffering and token bucket depth
in routers. As a rule of thumb the token bucket
depth can be assumed to be 1.2 (number of
Diffserv active interfaces on router) Scalability
- the maximum amount of aggregated Premium IP
capacity the network can offer - hardware
capabilities Fast provisioning of the
service Widespread availability and tuning of
last mile (LANs)
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Agenda
- Approach to the problem - Users requirements -
Quantitative definition of QoS - Which QoS
service - Premium IP service - Service Level
Agreements - Monitoring - Premium IP status -
Other QoS services
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Other QoS services ?
- Less than Best Effort (Scavenger) Already
working in Internet2, requires queuing and
marking, not access control - Assured Forwarding
based services. Sequin could not find a
implementation scenario for NRENs The limit is
the number of hardware queues in the routers and
the hardware performance.
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References
All the deliverables, presentation and relevant
documentation can be found on the web
in http//www.dante.net/sequin and http//ww
w.dante.net/tf-ngn
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Thank youand user QoS is even tougher
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Overprovisioning
Two possible definitions - istantaneous link
load never greater than 30 - no packet losses
(weaker) It works for 99.9 of the cases, but
capacity is far from being overprovisioned all
over Europe (yet). Even many LANs have not
enough capacity. Its not perfect (yet) though...
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Tier 1 US backbone
From Casner _at_ Nanog 22
99.99 clean
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Tier 1 US backbone (continued)
From Casner _at_ Nanog 22
99.99 clean
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Overprovisioning (continued)
Deviation from 99.99 of delay variation
constant value due to - routing problems -
routing timers set-up - ARP cache timeouts -
... Its mostly instability/misbehaviour of the
software layer on routers/switches.