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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
2
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
meter
Input
classifier
marker
Shaper/
dropper
Network Architecture and Design
To interior
nodes
4
DiffServ - Traffic conditioning
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Classifier
Marks packets according to classification rules.
Meter
Checks whether the traffic falls within the negotiated
profile.
Marker
Marks traffic that falls within profile.
Shapper/Dropper
Delays and then forwards, discards, or remarks
traffic.
Network Architecture and Design
5
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
6
DiffServ - Operation
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Like leaky bucket with 2-bit designators (not just CLP setting). By
software not built into hardware.
In-profile traffic is marked:
 A-bit is set in every packet
Out-of-profile (excess) traffic is unmarked
 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
7
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
8
Problems of DiffServ
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Does not support dynamic reservations only
static.
Scalable, but provides weaker services than
IntServ (due to aggregation).
It is not yet clear what kind of guarantees can be
given to end-to-end services (how to translate
user-QoS to net-QoS?).
Missing of standardized resource management in
every node.
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Solution: Bandwidth Broker (BB)
Network Architecture and Design
9
Bandwidth Broker (BB)
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The BB performs three distinct tasks:
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Negotiation of SLAs with BBs of neighbouring domains
Translation of SLAs into one or several Traffic Control Agreements (TCAs)
for edge devices
Delivery of the TCAs to the edge routers of the administered domain
Network Architecture and Design
10
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
11
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
12
IntServ & DiffServ
Network Architecture and Design
13
Internet QoS
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Differentiated Services (DiffServ)
Multiprotocol Label Switching (MPLS)
Network Architecture and Design
14
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
15
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
16
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
18
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
19
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
20
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
21
Second Intermediate Report
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Multicast Routing (Focus on Internet Technology)
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Multicast Routing (Focus on Wireless Technologies)
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Klaoudatou
IntServ (Focus on support of IntServ over other
technologies, i.e., ATM, wireless)
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Mavrogenis
IntServ (Focus on IntServ Implementation)
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Kikilis
MBONE
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Doukas
Barbarousis
Diffserv (Focus on Diffserv Implementation)
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Ratsiatos
Network Architecture and Design
22
Second Intermediate Report
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Diffserv (Focus on support of DiffServ over other
technologies, i.e., ATM, DVB)
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Integration of IntServ and Diffserv
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Baliotis
SLAs/SLSs
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Kolovou
MPLS (Focus on Admission Control)
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Lizos
MPLS (Focus on Routing)
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Panoutsakopoulos
Rekleitis
Protocols for inter-BB communication
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Plataniwtis
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
24
Second Intermediate Report
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Report (soft and hard copy)
A related presentation (about twenty
minutes)
Usage of Greek language
Deadline: 26/04/03
Network Architecture and Design
25
End of Fourth Lecture
Network Architecture and Design
26