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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