Transcript PPT

CS 414 – Multimedia Systems Design
Lecture 22 –
Multimedia Extensions to Existing IP
Protocols
Klara Nahrstedt
Spring 2011
CS 414 - Spring 2011
Outline
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Multimedia IP Extensions (Layer 3)
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Internet Multimedia Protocol Stack
APPLICATION
Media encaps
(H.264, MPEG-4)
RTSP
SIP
RSVP
Layer 5
(Session)
RTCP
RTP
KERNEL
TCP
UDP
DCCP
IP Version 4, IP Version 6
AAL3/4
AAL5
MPLS
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Layer 3
(Network)
Layer 2
(Link/MAC)
Ethernet/WiFi
ATM/Fiber Optics
Layer 4
(Transport)
Layer 3 Internet Services
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Internet Protocol (IP) – IP Version 4
 Provides
unreliable deliver of datagrams in a point-topoint fashion
 Runs on top of any Layer 2 technologies
 Supports
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IP address of 32 bits
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Different types of services (TOS)
 Precedence relation
 Services such as minimization of delay, maximization of
throughput
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Multicast
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Internet Group Management Protocol for managing groups
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New Internet Protocol - IPng
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Next Generation IP – IP Version 6
 Supports
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new features
New addressing and routing
 IP Address 128 bits
 Large hierarchical addresses, multicast addresses
More options of flow control and security
 Real-time flows
 End-to-end security
 Provider selection
Host mobility
Auto-configuration/auto-reconfiguration
Traffic Classes
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IP Packet Headers
Version Header Length
TOS
Total length
identification
Flag
Time to Live (TTL)
Fragment offset
Protocol
Header Checksum
32-bit Source IP Address
IPv4
32 bit Destination IP Address
Version
Traffic Class
Payload Length
Flow Label
Next Header
128-bit Source IP Address
128-bit Destination IP Address
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Hop limit
IPv6
QoS in Layer 3 Internet Integrated Services
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To provide network QoS in the Internet, IETF reacted by
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Development of Control (Establishment) Protocol to
reserve resources per flow
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Creating Working Group (IntServ)
Deploying Internet Integrated Services
Resource Reservation Protocol (RSVP)
Development of QoS-aware network services within IP
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Guaranteed class-of-service
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Deterministic QoS guarantees
Controlled-load class-of-service
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Statistical QoS guarantees
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Integrated Services (IntServ)
Architecture
Reservation Protocol (RSVP)
End-system
Router
Control Plane
Appl.
RSVP
daemon
Policy
control
Routing.
Admission
control
Packet
classification
RSVP
daemon
Policy
control
Admission
control
Packet
scheduler
Error
Handling
Data Plane
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Packet
scheduler
RSVP
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Provides reservation for data flows
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Flow specification is represented via
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Traffic specification, TSpec
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Request specification, Rspec
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Description of required QoS (desired flow behavior)
Is receiver-oriented and unidirectional
Uses two types of messages:
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Characteristics of the data flow
PATH messages and RSVP messages
Protocol
1.
2.
3.
Send PATH message with TSpec from Sender to Receiver(s)
Send RESV message with Rspec from Receiver(s) to Sender
Send DATA with resulting reserved QoS
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Flow Specification (1)
(Traffic Shape General Parameters)
Peak rate – highest rate at which a source
can generate traffic
 Average rate – average transmission rate
over a time interval
 Burst size – max amount of data that can
be injected into network at peak rate
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Flow Specification (2)
(in IntServ)
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Traffic described in terms of token bucket
parameters
 Token
arrival rate ‘r’
 Bucket depth ‘b’
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Amount of bits transmitted during any
interval of length t: A(t) ≤ r * t + b
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Service Requirements
(Application-specific)
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Minimum Bandwidth - min. amount of BW required by
application
Delay – can be specified as average delay or worst case
delay
 Propagation delay + Transmission delay + Queuing
delay
Delay Jitter – specifies max. difference between the
largest and smallest delays that packets experience
Loss Rate – ratio of lost packets and total packets
transmitted
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RSVP Control and Data Flow
(1) TSpec
(1) TSpec
S1
(3)
(1)
R1
(3)
(3)
D1
R2
(2) TSpec,RSpec
(2) Tspec,RSpec
(2)
(1)
(3)
(2)
(2) Tspec,RSpec
R3
R4
D2
D3
RESV messages
(3)
(1) TSpec
DATA
PATH messages
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Mixing Reservations
15MB
Mixing
S1
R1
12MB
15MB
Mixing
D1
R2
10MB
10MB
3MB
12MB
15MB
R3
D3
RESV messages
3MB
R4
D2
12MB
15MB
DATA
PATH messages
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Reservation Structures
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Resource Reservation Table
 Stores
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admitted/reserved resources
RSVP Messages
Version
Flags
Send TTL
Message Type
Reserved
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RSVP Checksum
RSVP Length
RSVP Features
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Simplex Reservation
 Reservation only in one direction (simplex flow)
Receiver Oriented
 Supports multicast communication
Routing Independent
Policy Independent
Soft State
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Reservation state has timer associated with the state
When timer expires, state is automatically deleted
RSVP periodically refreshes reservation state to maintain state
along the path
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Service Models
Describe interface between network and
its users in resource allocation architecture
 Describe what services users can ask
from network and what kind of resource
commitments the network can offer
 IntServ standard
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 Guaranteed
Service
 Controlled-load Service
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Guaranteed Service
(in IntServ)
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Provides guaranteed BW and strict bounds on endto-end queuing delay for conforming flows
Controls max. queuing delay
TSpec – describes traffic sources
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Bucket rate (‘r’) (bytes/second)
Peak rate (p) (bytes/second)
Bucket depth (b) (bytes)
Minimum policed unit (m) (bytes) – any packet with size smaller
than m will be counted as m bytes
Maximum packet size (M) (bytes) – max, packet size that can be
accepted
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Guaranteed Service (2)
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Rspec
rate (R) (bytes/second) – service rate or BW
requirement
 Slack term (S) (µsec) – extra amount of delay that a
node may add that still meets the EED (end-to-end
delay) requirement.
 Service
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This service does policing and shaping
Resources are reserved at worst case
For bursty traffic sources – low network
utilization
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Controlled Load Service
(in IntServ)
 No quantitative guarantees on delay bound or
BW
 This service model allows statistical multiplexing
– statistical guarantees
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Very high % of transmitted packets will be successfully delivered
Transit queuing delay experienced by a very high % of delivered
packets will not greatly exceed min. delay
Invocation and Policing
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Specify TSpec (average values) and do admission,
reservation, policing based on average TSpec
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IntServ (Error Handling Early Congestion Avoidance)
Avr – Average Queue Length
MaxThres – Max Queue
Length Threshold
MinThres – Min. Queue
Length Threshold
IP packet
IP packet
IP packet
IP packet
IP packet
IP packet
Input Queue
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Packet
Scheduler
IntServ (Error Handling)
Discard Algorithms
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RED: Random Early Detection
 single
FIFO queue is maintained for all packets and
packets are dropped randomly with a given probability
when the average queue length exceeds minimum
threshold (MinThresh).If max. threshold (MaxThres) is
exceeded, all packets are dropped
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WRED – Weighted RED
 Drops
packets selectively based on IP precedence
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Incoming IP packet
RED
Compute Avr
Avr < MinThres
Min < Avr < Max
Avr > MaxThres
Calculate
Packet drop probability
Low probability
High
Drop packet
Enqueue packet
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Packet Scheduling
(in IntServ)
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Isolation versus Sharing
network (e.g., telephone network) –
all flows are isolated, i.e., each connection has
dedicated resource
 Datagram-based Internet – all resources are shared
on per-packet basis without any form of isolation and
protection
IntServ requires scheduling algorithms to support delay
bounds
 Circuit-switched
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Deterministic or statistical delay bounds
Deterministic and statistical bounds reflect trade-offs between
isolation and sharing
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Packet Scheduling
(in IntServ)
 Simple Priority
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Fair queuing approach
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Allocate BW proportional to active flows based on their weights
Deadline-based schemes
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Be careful – a large volume of higher-priority packets can easily
starve lower-priority packets
Use EDF on packets
Rate-based scheduling framework
 Has
two components: regulator and scheduler
 Example: token bucket with fair queuing
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IntServ/RSVP vs DiffServ
IntServ/RSVP
BB
BB
DiffServ
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Conclusion
Improvements of existing transport
protocols such as TCP are happening to
support multimedia real-time traffic
 Improvements of existing IP protocols
such as IP are happening to support
multimedia real-time traffic
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CS 414 - Spring 2011