Network Architecture and Design 1

Internet QoS

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 2

DiffServ - Overview

Integrated services provides QoS; but Problem of scalability

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 3

DiffServ - Overview DiffServ defines Differentiated Service Code

Point (DSCP) in 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 4

DiffServ - Operation Per Hop Behaviour (PHB)

Assured Forwarding provides low loss probability for compliant traffic.

Guarantees ordering of packets in a given AF class. Expedited Forwarding:

near constant delay/throughput Virtual Wire aggregate

Network Architecture and Design 5

DiffServ - Operation Resource allocation

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 6

DiffServ - Operation

Network Architecture and Design 7

DiffServ - Operation

classifier marker

meter

Shaper/dropper

To interiornodesInput

Network Architecture and Design 8

DiffServ - Operation

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 9

DiffServ - Operation

2-Bit Differentiated Services Architecture for the Internet Premium service

Premium service levels are specified as a desired peak bit rate for a specific flow

Assured service Best-effort service

Network Architecture and Design 10

DiffServ - Operation 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

b bits

metering in-profile traffic

out-of-profile traffic

user profile (token bucket)

set A-bit

clear A-bit

assured traffic

Network Architecture and Design 11

DiffServ - Operation In-profile traffic marked:

Set P-bit in each packet Out-of-profile traffic is delayed, and when buffer overflows it is dropped

r bps

b bits

Metering/Shaper/Set P-bit

in-profile traffic

out-of-profile traffic(delayed and dropped)

premium traffic

user profile(token bucket)

Network Architecture and Design 12

IntServ Vs DiffServ

Integrated Services

Differentiated Services

QoS guarantee Per data stream Aggregated data streams

Configuration Per session end-to end

Between domains

Duration of guarantee

Short-lived Long-term

Signaling RSVP Not yet defined

Network Architecture and Design 13

IntServ Vs DiffServ 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 14

IntServ & DiffServ

Network Architecture and Design 15

Internet QoS

Differentiated Services (DiffServ) Multiprotocol Label Switching (MPLS)

Network Architecture and Design 16

Current Situation 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 17

MPLS Overview

MPLS (Multiprotocol Label Switching) Improves the forwarding speed of a router. Introduces new capabilities for large IP

networks Introduction of many of the qualities and

attributes of switched networks to IP networks Integrates Layers 2 and 3.

Network Architecture and Design 18

MPLS Operation MPLS Components

Edge-LSR: Edge-Label Switching Router Assigns a label in an incoming IP packet

Removes the label of an incoming IP packet

LSP: Label Switching Path The path that a packet follows in an MPLS network

LSR: Label Switching Router 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 19

MPLS – Traditional IP Routing

47.1

47.247.3

IP 47.1.1.1

Dest Out

47.1 147.2 2

47.3 3

1

23

Dest Out

47.1 147.2 2

47.3 3

1

2

1

23

IP 47.1.1.1

IP 47.1.1.1IP 47.1.1.1

Dest Out

47.1 147.2 2

47.3 3

Network Architecture and Design 20

MPLS – MPLS RoutingIntfIn

LabelIn

Dest IntfOut

3 0.40 47.1 1

IntfIn

LabelIn

Dest IntfOut

LabelOut

3 0.50 47.1 1 0.40

47.1

47.247.3

1

2

31

2

1

2

3

3

IntfIn

Dest IntfOut

LabelOut

3 47.1 1 0.50

IP 47.1.1.1

IP 47.1.1.1

Network Architecture and Design 21

MPLS - Example1a. Existing routing protocols (e.g. OSPF, ISIS) establish reachability to destination networks

1b. Label Distribution Protocol (LDP) establishes label to destination network mappings.

3. Label Switches switch label packets using label swapping

4. Label Edge Router at egress removes label and delivers packet

2. Ingress Label Edge Router receives packet, performs Layer 3 value-added services, and “label” packets

Network Architecture and Design 22

MPLS Label Format IP packet is encapsulated in MPLS

header and sent down LSP

IP packet is restored at end of LSP by egress router TTL is adjusted also

…IP Packet

32-bitMPLS Header

Network Architecture and Design 23

MPLS Label format

TTLLabel CoS S

Label Class of service Stacking bit Time to live

Decrement at each LSR, or Pass through unchanged

Network Architecture and Design 24

Label Distribution Protocols

CR-LDP RSVP-TE

Network Architecture and Design 25

MPLS Fast forwarding speed Traffic Engineering

constraint-based routing explicit routing ability to compute a path at the source ability to reserve network resources and to modify link

attributes Voice/Video on IP

delay variation + QoS constraints Virtual Private Networks

controllable tunneling mechanism equivalent to a Frame Relay or ATM VC

Network Architecture and Design 26

MPLS Benefits

14

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 27

Second Intermediate Report

Integrated and Differentiated Services I. Stergiou

Group Communication, MBONE, MPLS A. Sgora

Deadline: 11/02/03

Network Architecture and Design 28

Second Intermediate Report

Structure 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 29

Second Intermediate Report

Report (soft and hard copy) A related presentation (about twenty

minutes).

Network Architecture and Design 30

End of Fourth Lecture