1. QoS Architectures for Connectionless Networks
Stewart Fallis
BT Advanced Communications Research

2. Outline Future network model A generic network model
Current architectures
ATM QoS
Integrated Services
Differentiated Services
Evolving Differentiated Services
‘Soft’ QoS
‘Hard’ QoS
Bounded Delay service
Dynamic QoS
Grade of service
Generic QoS node
Concluding comments

3. Need a Globally Accepted QoS Architecture
Generic Network Model
Core Network
Real time
Local Data
Networks
There is a distinct need for a ubiquitous QoS architecture whereby, the network is application independent.
Therefore, traditional data, mobile and real time applications can co-exist on the same communications platform which supports degrees or shades of QoS.
To propose a unified networking solution, then there must be coherence in the mechanisms employed with deliver such network functions, e.g. a generic QoS mechanism.
Mobile Networks
(real time & data)
Need a Globally Accepted QoS Architecture

4. Current QoS Architectures
ATM QoS
Delay by design
Classes: signalled via control
Integrated Services
Connection Oriented QoS
Negotiable guaranteed end-to-end
delay service
Dynamic Delay Guarantees
Zero packet loss
Heavy weight signalling protocol
Hard QoS
Requires per-flow state in routers
Pessimistic delay bound
Differentiated Services
Connectionless QoS
Small set of aggregate classes:
no per-flow information
‘Dumb’ core routers
Integrated Services:
It is connection oriented QoS
It can deliver a quantifiable, guaranteed end-to-end delay with zero packet loss
Relies on RSVP which may be too complex in it’s current implementation
It is mainly Hard QoS
Requires per-flow state in the network
the delay bound of WFQ is pessemistic
Differentiated Services:
Connectionless QoS
Uses aggregate set of classes ---> No need for per flow information
Hence the Dumb core routers
May not deliver a quantifiable low end-to-end delay bound
Static QoS approach
No feedback to users when a failure occurs
QoS maybe too soft e.g. Premium
service
No-per flow separation
Static: Subscription based
No feedback from network
when failure occurs

5. Evolving Differentiated Services
What we really need is:
Dynamic Bandwidth Allocation
Per-flow state only at edge
Signalling for hard QoS
Low delay by design not negotiation
Aggregate in core
Not soft-state
In order to provide a comprehensive QoS architecture, then there is a distinct need for the user to be able specify their QoS requirements to the underlying network.
To avoid scalability issues, the complexity should be pushed out to the edges of the network and into the hosts.
There should be some form of lightweight signalling mechanism for the Hard QoS class.
There should be no soft state in the network.
This provides an architecture that suppoprts both connectionless and connection oriented QoS
Network would support both ‘Hard’
and ‘Soft’ QoS

6. Soft QoS: Olympic Service
Ensures access to specified portion of o/p link bandwidth
Host inserts pkt
class
Gold
Profiler
Scheduling
Silver
Bronze
Random in packet drop
aggressive out packet drop
Polices pkt rate &
marks those outside negotiated rate
RIO Congestion control
(RED IN and OUT packets)
Buffer
fill
No drop
Increasing load

7. Hard QoS: Bounded Delay
Evolve Diffserv EF class
Peak rate host shaping
Limit Max Packet size
Dimensioned buffer & bandwidth
Guaranteed Delay bound +
Simple FIFO queuing
Overcomes Need For Per-Flow State

8. Hard QoS: Bounded Delay
Core Network
FIFO queuing for
BD in core routers
Host pk rate
shaping
Local Data
Networks
Complexity pushed to
network edges & hosts

9. Bounded Delay: Delay Bound
Host packetisation
delay
NW delay
Packetisation
Int-serv assumed best effort
Network delays dominant
Long timescales to
‘sort’ incoming packets
Host packetisation
delay
NW delay
Packetisation
Bounded Delay assumes high speed core
Packetisation delay dominant
FIFO queuing is sufficient

10. Dynamic QoS Lightweight signalling User initiated
Alternatively,
communication can
be via a bandwidth
broker or could
be future DNS?
Lightweight signalling
User initiated
Simple bandwidth request
Bandwidth
Request
Bandwidth request can involve only
edge nodes, or depending on how onerous,
all nodes.

11. Bounded Delay: Grade of Service
Use CAC to restrict users
Provides varying QoS from one “pool” of bandwidth C A
Low user limit
Medium user limit
High user limit

12. Generic QoS Node Current IP architecture does not support connections!
Switching engine
Signalling
Dest Address
lookup
Current IP architecture does not support connections!

13. Connection Oriented Routing
Is this not
simply MPLS?
Dest Address
lookup
Label
lookup
Signalling
Mapping
QoS
Architecture
Switching engine
CO routing does not affect the QoS Architecture

14. Conclusions Migration to control layer
QoS is application, routing independent
Common reservation method
Common signalling method
Range of QoS supported
QoS architecture not dependant on other NW functions
Work needs to be done on how and when to use these services