CIS679: DiffServ Model

1
CIS679 DiffServ Model

• Review of Last Lecture
• 2-bit DiffServ architecture

2
Review of Last Lecture

• Two Planes
• IntServ
• DiffServ
• Two types of services relative and absolute
• Basic mechanism edge-router, core-router, PHB

3
2-bit differentiated service

• Premium service (type P)
• admitted based on peak rate
• conservative, virtual wire services
• unused premium goes to best effort
• Assured service (type A)
• based on expected capacity usage profiles
• traffic unlikely to be dropped if user maintains
  profile. Out-of-profile traffic marked

4
Traffic Flows
Marking at Leaf Router
Forwarding
Company A
Metering at Border Router
Packets in premium and Assured flows have bit set
internal router
ISP
host
border router
first hop router
border router
Unmarked packet flow
Leaf Router
5
Leaf router input functionality
Marker 1
Flow 1
Marker N
Flow N
Forwarding engine
Clear A P bits
Packet classifier
Arriving packet
Best effort
Markers service class, rate, permissible burst
size
6
Marker function in routers

• Leaf routers have traffic profiles - they
  classify packets based on packet header
• If no profile present, pass as best effort
• If profile is for A
• mark in-profile packets with A, forward others
  unmarked
• If profile is for P
• delay out-of -profile packets to shape into
  profile

7
Markers to implement two different services
Drop on overflow
Packet input
Packet output
Wait for token
Set P bit
8
Output forwarding

• 2 queues P packets on higher priority queue
• Lower priority queue implements RED In or Out
  scheme (RIO)
• At border routers profile meters test marked
  flows
• drop P packets out of profile
• unmark A packets

9
Router output interface for two-bit architecture
yes
P-bit set?
High-priority Q
Packets out
no
If A-bit set incr A_cnt
Low-priority Q
If A-bit set decr A_cnt
RIO queue management
10
RED with In or Out (RIO)

• Precursor to Assured Forwarding (AF) PHB
• Similar to RED, but with two separate probability
  curves
• Has two classes, In and Out (of profile)
• Out class has lower Minthresh, so packets are
  dropped from this class first
• As avg queue length increases, in packets are
  dropped

11
RIO drop probabilities
P(drop)
1.0
MaxP
AvgLen
Minout
Minin
Maxin
Maxout
More drop probability curves (WRED)?
12
Border router input interface Profile Meters
no
Token available?
Clear A-bit
A set
token
Forwarding engine
Arriving packet
Not marked
Is packet marked?
token
P set
no
Token available?
Drop packet
13
Conclusion

• An example of relative DiffServ
• 2 bit architecture
• Premium service, Assured service
• Marker at leaf router
• Output forwarding
• Meter at border router

14
Final Review on Part 1

• Multimedia basics
• The four major steps
• Compression techniques
• Redundancy
• Classification
• JPEG
• DCT
• MPEG
• Motion prediction
• I, B and P frames, GOP
• Different units

15
Final Review on Part 2

• Better then best effort services
• Multimedia requirements to networks
• TCP
• Window control, Reliability, Flow and congestion
  control
• UDP
• Why UDP for multimedia?
• TCP friendly
• CUDP etc.
• Buffer management
• Drop-tail, RED and its variations
• HTTP and RTP
• Multicast address, routing, transport layer and
  QoS
• Anycast network-layer and application layer
  anycast

16
Final Review on Part 3

• Beyond the best effort services
• Four Principles
• Policing
• Scheduling
• Its relationship with buffer management
• RSVP
• Receiver driven and soft-state
• Integrated Service model
• Differentiated Service model