1. Scheduling and Quality of
Services (QoS)
Advanced Telecommunication Network
(ET5187)
by
Aris Cahyadi Risdianto
23210016

2. Review Scheduling
• Scheduling and Qos : Qontrolling input to output
• Packet Classification : Same Class (FIFO/LIFO)
or Different Class (Lost/Delay Sensitive, Class)
• Queuing System : Scheduling control
• Loss Sensitive Scheduling : HoL, PBS, POB,
RED
• Buffer size : small assured delay, but loss cell
• Delay Sensitive Scheduling : Upper Bound
Method

3. Review QoS
• QoS as Technological Lever : over installed
resources or controlling traffic in the network
• QoS as Commercial Lever : sub-optimal controlling
resources = loss revenue
• QoS : performance, availability, reliability and
security (L3 QoS inspired by ATM)
• Evolution architecture : Integration IP and ATM
(Dual-Mode, I-PNNI, Ipsilon, IETF-MPLS)
• RSVP : IP Signaling Protocol, Path and
Reservation Messages
• IntServ : guaranteed and controlled-load service

4. Upper Bound Method
• Used for solving CAC (Call Admission Control)
problem
• Some assumption :
o Each arrival process satisfies with certain
business constrain
o Service time for cell/packet is deterministic and
proportional
o Scheduling rule is used to generate QoS for
class k with minimal μk ("fair" rule to prevent
blocking another class getting served)

5. Upper Bound Method (Cont.)
• Queue count is maximum difference between
inflow and outflow (λk and μk)
• If queue > 0, class served by minimal rate (μk)
• Number of queue bounded by burstinest σk
provided if λk ≤ μk
• Buffer size bounded by sum of burstinest all flows,
so loss can be guaranteed
• Maximum delay bounded by burstinest divide by
inflows, so delay can be guaranteed

6. Upper Bound Method (Cont.)
• Remarks on upper bound method :
• Zero packet loss only guaranteed for admitted
packet (satisfied with burstinest constrain), if
not packet will be lost
• Delay guaranteed are deterministic because all
stochastic assumed to be bounded or
deterministic
• Upper Bound Method more optimal than N*D/D/1
queuing for scenario where N not identical and
independent CBR resources

7. Generalized Processor Sharing (GPS)

Differ from fair policy including minimum service rate and
excess capacity allocation

Provide inherent fairness (measurable amount resource
reserved for each class based on weight

Work-conserving discipline, ideal for small amount of data
from I different jobs

8. Generalized Cμ-rules (Gcμ rules)

Powerful, dynamic scheduling rule which view QoS from
different angle such as posses delay function as monetary
cost

Founded from 3 fact in the Queuing theory:

Total workload invariant for work-conserving scheduling
rules

Class workloads “live on the faster time scale” than total
workload process

Well behaved heavy traffic limit systems, class workload
process “Converges”

Distribute total workload over different class to minimize
delay cost rate at each point

9. Generalized Cμ-rules (Gcμ rules)

With “lagrange” optimization problem, the solution defines
as mapping g intepreted as switching curve of Gcμ-rules
parameterized by scalar W

10. QoS (Quality of Services)

11. Differentiated Services (DiffServ)
• Threat each class differently on per-hop behaviour
(PHB)
• Class differentiation rather than flow differentiation
(more scalable)
• Provide QoS more natural than IntServ which inline
with Internet
• Bandwidth Broker use to managed inter-domain
resources for providing end-to-end QoS

12. Differentiated Class
• IP DSCP format:
• Two different PHB Class, except BE (Best Effort) :

Expedited Forwarding (EF) = virtual leased line or
point-to-point connection

Assured Forwarding (AF) = better best efforf

13. DS Class: Expedited Forwarding (EF)
• Absolute dedicated BW independent from other
• Guaranteed BW for providing low packet loss, low
latency and low jitter
• Implement with Priority Queue and Strict Policing
• EF behavior : departure rate EF traffic must equal
or exceeded configurable rate
• Guaranteed BW means excess traffic must be
discarded (strict policing)

14. DS Class: Assured Forwarding (AF)
• “No Free Lunch”, better service for one class,
expense of other service
• 4 Class with 3 class each based on drop
preferences
• Level forwarding assurance based on resource
allocation, load offered and drop preference
• Implement with weighted Round-robin (WRR),
Weight Fair-Queue (WFQ), and drop technology
(RED/WRED)

15. Shortcut Routing to MPLS
• Traditionally Internet routing create problem,
because size of route, per-packet lookup
burden network, bottleneck
• Solution : Eliminate L3 processing by L2
packet forwarding (Shortcut Routing)
• IP over ATM : mixed CL(connectionless)/CO
(connection oriented) for best effort traffic
• 3 Approach : flow driven, topology driven, and
Explicit shortcut

16. Layered Routing
• Top level routing by IP (OSPF), route between
nodes by ATM layer Routing (I-PNNI)
• ATM change the path based on available resources,
OSPF rediscover low weight link regularly => Hop-
by-hop path different next-hop nodes
• More vulnerable to loop, L2/L3 routing loop is
hidden at both L2/L3
• Transient loop for CO/CL environment
• I-PNNI the ultimate solution, but the standard never
finished

17. Flow Driven Shortcut
• Short messages use CL (connectionless)
because connection setup costly
• Long duration high-traffic use CO (connection-
oriented) for header efficiency
• Pareto Law : 20% flows are long and constitute
of 80% bytes
• Decision between router and switch is
complicated
• Ipsilon Switching : decision based on Ipv4
header (TCP = switch, UDP = route)

18. Topology Driven Shortcut
• Special ATM-VC setup to “shortcut” number of
router
• Integrated switch & router individually decide
to shortcut
• Sources and destination path stored in
“shortcut” forwarding table
• CO/CL forward together with QoS
differentiation
• The approach is Cisco Tag-Switching

19. Multiprotocol Label Switching
(MPLS)
• TDP (Cisco) & LDP (IETF) : signaling protocol
for routing to “shortcut” based on MPLS tag
• Support explicit routing to provide QoS
constrain routing
• Based on LDP, construct label forwarding
table (LIB), similar to ATM VPI/VCI
• Adopt label stack approach, up to 3 labels
including “push”, “pop”, and “swap”

20. Multiprotocol Label Switching
(MPLS) continue..
• Separated control and forwarding with Traffic
Engineering (TE) can mapped into label
• Flexible to form FEC to build VPN for any
other medium didn't support labelling
• Traffic Engineering : redirect, balance and
restoration the path
• “Forwarding with the clue”, the clue give next-
hop downstream router, the current router
end-up with IP lookup

21. Generalized MPLS (G-MPLS)
• Extension of MPLS for other packet switched
as IP packet
• TDM/Optical Lamda can be formed
• Redesign MPLS protocol and optical switching
without optical-electronic conversion
• Extend control plane for legacy equipment:

Simplification O&M

Efficiency and Faster

Higher Flexibility

22. Generalized MPLS (G-MPLS)
Summary
• LMP assigned to manage critical network by
mapping time slot, lambda, or port into label
• Extension to OSPF for advertising availability
of optical resources
• Enhance IP signaling RSVP to setup LSP
accross
• Scalability features such as hierarchical LSPs

23. Generalized MPLS (G-MPLS)
Example
IP Network (left) and
SDH Network (right)
Each SDH has link
capacity of 2 Mbps
Three different
configuration
originate by GMPLS
switching in the SDH
nodes

24. Reference
Piet Van Mieghem, “Data Communication Networking”,
Delft University Technology, Amsterdam, 2006.