Transcript Document

Internet QoS
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Differentiated Services (DiffServ)
Multiprotocol Label Switching (MPLS)
Reference
Zheng Wang, Internet QoS, Architectures and
Mechanisms for QoS, ISBN 1-55860-608-4,
2001.
Network Architecture and Design
1
DiffServ - Overview
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Integrated services provides QoS; but
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Problem of scalability
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The routers have to maintain state on every
flow passing through them.
Heterogeneous networks may not be able
to provide particular QoS controls or even
RSVP.
Differentiated service (DiffServ) aims to
offer QoS to aggregated flows.
Network Architecture and Design
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DiffServ - Overview
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DiffServ defines Differentiated Service Code
Point (DSCP) in
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IPv4 TOS field,
IPv6 Traffic Class field.
All traffic in one DSCP is treated the same.
Per hop behaviour (PHB) is determined by
DSCP of packet.
Service Level Agreements concern aggregate
traffic not individual flows.
Network Architecture and Design
3
DiffServ - Operation
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Per Hop Behaviour (PHB)
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Assured Forwarding
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provides low loss probability for compliant traffic.
Guarantees ordering of packets in a given AF class.
Expedited Forwarding:
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near constant delay/throughput
Virtual Wire aggregate
Network Architecture and Design
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DiffServ - Operation
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Resource allocation
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BB: Bandwidth Broker: global view of resources
Static provisioning: may give poor service to flows
Signalling: use of RSVP to allocate resources
Network Architecture and Design
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DiffServ - Operation
Network Architecture and Design
6
DiffServ - Operation
meter
Input
classifier
marker
Shaper/
dropper
Network Architecture and Design
To interior
nodes
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DiffServ - Operation
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Classification: marks packets according to
classification rules to be specified
Metering: checks whether the traffic falls
within the negotiated profile
Marking: marks traffic that falls within profile
Conditioning: delays and then forwards,
discards, or remarks other traffic
Network Architecture and Design
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DiffServ - Operation
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2-Bit Differentiated Services
Architecture for the Internet
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Premium service
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Premium service levels are specified as a
desired peak bit rate for a specific flow
Assured service
Best-effort service
Network Architecture and Design
9
DiffServ - Operation
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In-profile traffic is marked:
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A-bit is set in every packet
Out-of-profile (excess) traffic is unmarked
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A-bit is cleared (if it was previously set) in every packet; this
traffic treated as best-effort
r bps
user profile
b bits (token bucket)
assured traffic
metering
set A-bit
in-profile traffic
clear A-bit
out-of-profile traffic
Network Architecture and Design
10
DiffServ - Operation
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In-profile traffic marked:
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Set P-bit in each packet
Out-of-profile traffic is delayed, and when buffer overflows it is
dropped
r bps
user profile
b bits (token bucket)
premium traffic
Metering/
Shaper/
Set P-bit
in-profile traffic
out-of-profile traffic
(delayed and dropped)
Network Architecture and Design
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IntServ Vs DiffServ
QoS guarantee
Configuration
Duration of
guarantee
Signaling
Integrated
Services
Per data stream
Differentiated
Services
Aggregated data
streams
Per session end- Between
to end
domains
Short-lived
Long-term
RSVP
Network Architecture and Design
Not yet defined
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IntServ Vs DiffServ
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IntServ provides fine grain control and handles
dynamic allocation of resources to flows
DiffServ provides course grain control of flows
through their aggregates
The two together can be combined to provide
scalable end to end Integrated service, using a
DiffServ region as a single element
Controlled Load can be implemented over Assured
Forwarding PHB
Guaranteed can be implemented over Expedited
Forwarding PHB
Network Architecture and Design
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IntServ & DiffServ
Network Architecture and Design
14
Internet QoS
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Differentiated Services (DiffServ)
Multiprotocol Label Switching (MPLS)
Network Architecture and Design
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Current Situation
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Geographically dispersed enterprise networks
need to be connected for transparent and
secure private IP interconnection.
Full (n^2) mesh of virtual-circuits needs for
desired guaranteed performance, or partial
meshing for low cost.
IP uses 64K size packets whereas ATM uses
53 byte-cells.
IP and circuit-switching (e.g., ATM)
technologies use different addressing
scheme.
Network Architecture and Design
16
MPLS Overview
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MPLS (Multiprotocol Label Switching)
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Improves the forwarding speed of a router.
Introduces new capabilities for large IP
networks
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Introduction of many of the qualities and
attributes of switched networks to IP networks
Integrates Layers 2 and 3.
Network Architecture and Design
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MPLS Operation
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MPLS Components
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Edge-LSR: Edge-Label Switching Router
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Assigns a label in an incoming IP packet
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Removes the label of an incoming IP packet
LSP: Label Switching Path
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The path that a packet follows in an MPLS network
LSR: Label Switching Router
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Makes forwarding decisions based SOLELY on the contents of
the label (basic advantage)
Strips off the existing label and applies a new label which tells
the next hop how to forward the packet
Network Architecture and Design
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MPLS – Traditional IP Routing
Dest
47.1
47.2
47.3
Dest
47.1
47.2
47.3
Out
1
2
3
1 47.1
1
Dest
47.1
47.2
47.3
Out
1
2
3
IP 47.1.1.1
2
IP 47.1.1.1
3
Out
1
2
3
2
IP 47.1.1.1
1
47.3
47.2
3
2
IP 47.1.1.1
Network Architecture and Design
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MPLS – MPLS Routing
Intf Label Dest Intf Label
In In
Out Out
3
0.50 47.1 1
0.40
Intf Dest Intf Label
In
Out Out 3
3
47.1 1
0.50
Label Dest Intf
In
Out
0.40 47.1 1
IP 47.1.1.1
1 47.1
3
1
1
Intf
In
3
2
2
47.3 3
47.2
2
IP 47.1.1.1
Network Architecture and Design
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MPLS - Example
1a. Existing routing protocols (e.g. OSPF, ISIS)
establish reachability to destination networks
1b. Label Distribution Protocol (LDP)
establishes label to destination
network mappings.
2. Ingress Label Edge Router
receives packet, performs Layer
3 value-added services, and
Network Architecture and Design
“label” packets
4. Label Edge Router at
egress removes label
and delivers packet
3. Label Switches
switch label packets
using label swapping
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MPLS Label Format
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IP packet is encapsulated in MPLS
header and sent down LSP
IP Packet
…
32-bit
MPLS Header
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IP packet is restored at end of LSP by egress
router
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TTL is adjusted also
Network Architecture and Design
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MPLS Label format
Label
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CoS S
TTL
Label
Class of service
Stacking bit
Time to live
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Decrement at each LSR, or
Pass through unchanged
Network Architecture and Design
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Label Distribution Protocols
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CR-LDP
RSVP-TE
Network Architecture and Design
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MPLS
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Fast forwarding speed
Traffic Engineering
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Voice/Video on IP
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constraint-based routing
explicit routing
ability to compute a path at the source
ability to reserve network resources and to modify link
attributes
delay variation + QoS constraints
Virtual Private Networks
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controllable tunneling mechanism
equivalent to a Frame Relay or ATM VC
Network Architecture and Design
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MPLS Benefits
IP over ATM
Integration
•Shared backbone for economies of scale
•Keep up with Internet growth
•Reduced complexity for lower operational
cost
•Faster time to market for IP services =>
more revenue
Traffic
Engineering
•Traffic eng. for lower trunk costs;
•Hierarchical routing for improve reliability
of core
•Shared IP/Frame backbone for economies
of scale
VPNs
•New revenue opportunity for SPs
•Scalability for lower operational costs and
faster rollout
•L2 privacy and performance for IP
Network Architecture and Design
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14
Second Intermediate Report
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Integrated and Differentiated Services
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Group Communication, MBONE, MPLS
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I. Stergiou
A. Sgora
Deadline: 11/02/03
Network Architecture and Design
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Second Intermediate Report
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Structure
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Overview of examined technology
Focus on open research points
Related to open points works - State of the
art behind open points
Your own interests - Ideas
Conclusions
References
Network Architecture and Design
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Second Intermediate Report
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Report (soft and hard copy)
A related presentation (about twenty
minutes).
Network Architecture and Design
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End of Fourth Lecture
Network Architecture and Design
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