Transcript Quality of Service in IP Networks

Lucent Worldwide Services Knowledge Seminars
Quality of
Service in IP
Networks
Sharing the Knowledge Behind the Network
Presented by:
John Railsback
Rick Blum
[email protected]
[email protected]
Background

Lucent Worldwide Services is a
provider of communications
consulting, intelligent maintenance,
and management solutions for next
generation networks

Seminar objectives



Present the major factors driving QoS
Highlight current QoS technologies
and techniques
Provide insight into the future direction
of QoS for IP networks
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QoS Research
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
Web-based industry survey
conducted September 2000

108 respondents

Represent a cross-section of
end-user organizations and
network solutions providers

Survey report available at
www.lucentnps.com/surveys
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QoS Definition
Management of available bandwidth to
deliver consistent, predictable data
(packets) over an IP-based network in
terms of:
 Latency - delay that an application
can tolerate in delivering a packet of
data
 Jitter - variation in latency
 Loss - percentage of lost data
 Throughput - amount of data carried
 Availability - network uptime
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Importance of Implementing/
Improving QoS
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The IP Network Problem

Congestion continues to plague the
Internet
• Traffic expands = or > bandwidth
• ”Best-effort" performance dictated by the very
design of the Internet Protocol (IP)

Mission critical applications, e.g., IP
Telephony and ERP, require prioritization
• Service Level Agreements (SLAs) expected
• Customer expectations increase with bandwidth
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Why QoS

Over-provisioning bandwidth not cost
effective in the long run
• Users will consume bandwidth as fast as
produced
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Need reliable data delivery
• Mission critical applications
– ERP, SAP, Financial Market data
• High bandwidth, low latency applications
– Video and audio streaming, video
conferencing, voice

Provide value-added services with SLAs
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Contributing Factors to
Importance of QoS
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QoS Technologies

Reservation
• Allocates resources on a per-flow basis
• Flows include information such as transport
protocol, source address & port, destination
address and port
– Intserv/RSVP

Prioritization
• Traffic flows are aggregated and categorized
by "class of service”
– DiffServ and IEEE 802.1p
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Integrated Services

Defined in RFCs 2205, 2206 - www.ietf.org/rfc.html
 Implemented by four components
• Signaling protocol (RSVP)
– Reserves resources and establishes paths before
transmitting data
• Admission control routine
– Determines whether a request for resources can be
granted
• Classifier
– Places packets in specific queues based on classification
result
• Packet scheduler
– Schedules the packet to meet its QoS requirements
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RSVP

Signaling protocol that can operate in
"native mode" or "encapsulated mode"
within a UDP header

Operates in tandem with either a TCP or
UDP "flow" to reserve resources among
RSVP-enabled routers

Also being used to signal QoS into DiffServ
and MPLS networks
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RSVP Request
Receiver
Re
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Pa
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1
Sender
Pa
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Mess
age
Res
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Re
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Path
Pa
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2
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1 - Traffic Specification (Tspec) in Path messagefrom Sender profiles the data flow to be sent
2 -Path message flows downstream to receiver through each router hop .
3 - Receiver receives PATH request from sender. PATH request provides return path for RESV
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message.
Differentiated Services (DiffServ)

Defined in RFCs 2474, 2475
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Creates classes of service for traffic flows
with different priorities
• Aggregates large numbers of individual
flows at the edge of the network into
small numbers of aggregated flows
through the core of the network
• Flows are marked at network edge in the
IPv4 ToS field (DS field).
• Services applied through the core
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Building Blocks of DiffServ

Packet Classifiers
• Packets sorted into queues based on values in
the DS (DiffServ) field
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Traffic Conditioning Policies
• Metering, Marking, Shaping and Policing based
on DSCP and packet header data
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Forwarding/Per Hop Behaviors
• Expedited Forwarding and Assured Forwarding

Policy Managers
• apply and communicate QoS policy
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Packet Classifiers

DiffServ Code Point (DSCP)
• Maximum of 64 classes of service
• Replaces IP TOS field
• Packets sorted into queues based on DSCP values
Source: QoS Forum
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Traffic Conditioning

Metering
• Monitors traffic patterns against traffic profiles

Marking
• DS field marks packet with specific values for
each PHB (marked by edge routers)
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Policing
• Ingress routers drop or remark traffic that does
not meet profiles and policies

Shaping
• Egress routers control forwarding rate of
packets and controls traffic flow to avoid
congestion
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Per Hop Behaviors
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Expedited Forwarding
• Guaranteed delay and jitter
(similar to ATM CBR)
– Provides a Virtual Leased
Line service
– Non-conforming policed on
ingress and shaped on
egress of Diffserv domain
– Manual provisioning or
signaling protocols
required for quantitative
guarantees.
– Typically implemented with
strict priority queuing
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Assured Forwarding (AF)
• Similar to ATM nr-VBR QoS
• Four AF classes with three
codepoints each
• AF classes not specifically
defined regarding performance
or priority between classes
– Non-conforming traffic marked
at the edge
– RED queuing most often used.
• Better then Best Effort Delivery
– Gold, Silver, Bronze services
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DiffServ Code Points for Expedited
Forwarding and Assured Forwarding
Assured
Forwarding
Low Drop
Precedence
Medium Drop
Precedence
High Drop
Precedence
Expedited
Forwarding
Class 1
Class 2
Class 3
Class 4
Class 5
001010 (AF11) 010010 (AF21) 011010 (AF31) 100010 (AF41)
001100 (AF12) 010100 (AF22) 011100 (AF32) 100100 (AF42)
001110 (AF13) 010110 (AF23) 011110 (AF33) 100110 (AF43)
101110
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IEEE 802.1p

Traffic-handling mechanism for supporting
QoS in LANs
 Allows a classification/prioritization of
differentiated services analogous to
DiffServ
 Operates at layer 2 (MAC) layer on a
switched Ethernet network
• Defines a field in the layer-2 header of “802”
packets that can carry one of eight priority
values
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IEEE 802.1p


Scope of 802.1p priority mark is limited to
the LAN. Once packets are carried off the
LAN, through a layer-3 device, the 802.1p
priority is removed.
802.1p often defined with 802.1q
• Together, define various VLAN (virtual LAN)
fields, as well as a priority field

Implemented in hardware (switches and
routers)
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Multi Protocol Label
Switching (MPLS)

More scalable mechanism for IP over ATM
than classical overlay model
• Edge routers can peer with nearby MPLS nodes
• Avoids N2 scaling issues with ATM meshed
networks

Traffic Engineering - using explicit routes
and constraint-based routing for better load
balancing.

As a tunneling mechanism to interconnect
intra-VPN sites
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MPLS Network
Legend
LSR
LSP
EdgeLSR
IGP
Domain
Cloud
LSR
LSPs provide transport for
• MPLS VPNs
• Traffic Engineered Explicit Routes
• DiffServ Aggregates
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QoS Implementation Status
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Significant Barriers to
Implementing QoS
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QoS Implementation Issues

Inter-domain and Inter-Service Provider
interoperability

Vendor interoperability
Limiting RSVP implementation in the core
Use RSVP to signal QoS to DiffServ and MPLS
network cores
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QoS support in applications
Monitoring and measuring QoS
Billing, accounting, pricing
Security and authentication
Policy management
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Biggest Challenge to
Implementing QoS
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The Bottom Line
 For Internet and WANs, DiffServ
and MPLS top candidates for
aggregated traffic flows and QoS

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DiffServ from the edge through the
core, or
DiffServ at the edge, MPLS at the
core
RSVP for signaling
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The Bottom Line
 For LANs and enterprise
networks, 802.1p is top edge QoS
mechanism using RSVP for
signaling

Microsoft supports RSVP in
Windows 2000

Microsoft APIs for application
based QoS development
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The Bottom Line
 Where do you start?
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Planning
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Design
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Determine required hardware and software
features, policy manager platforms, and
policies, perform proof of concept
Implement
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Match QoS Mechanism to Applications,
Services, Desired Traffic Types, and SLAs
Determine needed management and
accounting platforms for measuring
performance and usage
Deploy QoS mechanisms and associated
services
Operate!
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Question and Answer
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Thank You

Feedback survey
• Tell us what you think about this seminar
www.lucentnps.com/seminars/thanks.asp

Upcoming seminars
• Performance Management and Engineering,
December 13th
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For more information
• E-mail [email protected]
• Call 1-888-767-2988
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