Transcript Slide 1

Net-Centric Computing Division
Department of Computer Science
Bogor Agricultural University
KOM 312
KOMUNIKASI DATA
DAN JARINGAN KOMPUTER
ATM and Advanced Networks
Adopted from Leon-Garcia and Widjaja
Sri Wahjuni
[email protected]
AGENDA
Asynchronous Transfer Mode (ATM)
 Integrated Services (intserv)

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
RSVP
Differentiated Services (divserv)
 MPLS

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ATM NETWORK
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o Standardized by ITU-T
o End-to-end information transport using cells
o 53-byte (5+48) cell provide low delay and fine multiplexing granularity
o Support for many services through ATM Adaptation Layer
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ATM LAYERED ARCHITECTURE
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Higher Layers
Higher Layers
ATM Adaptation Layer
(AAL)
ATM Adaptation Layer
(AAL)
ATM Network Layer
ATM Network Layer
ATM Network Layer
Physical Layer
Physical Layer
Physical Layer
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USER
NETWORK
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USER
ATM LAYERED ARCHITECTURE (2)
Higher Layers
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ATM Adaptation Layer
 standard interface to higher layers
 adaptation functions
 end-to-end between end systems
 segmentation into cells and reassembly
ATM Layer
 Transfer of Cells
 Cell-Header Generation/Extraction
 VPI/VCI Translation
 Cell multiplexing/demultiplexing
 Flow and congestion control
Physical Layer
 Cell stream / bit stream conversion
 Digital transmission
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ATM Adaptation Layer
(AAL)
ATM Network Layer
Physical Layer
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AAL CONVERTS INFO INTO CELLS
Voice
AAL
A/D
s1 , s2 …
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cells
Digital voice samples
Video
A/D
Compression
…
picture
frames
Data
AAL
cells
compressed
frames
AAL
Bursty variable-length
packets
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cells
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CELL-SWITCHING – VIRTUAL CIRCUIT
Cells
Cells
Cells
Cells
Switches


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


Destination
Connection setup establishes virtual circuit by setting pointers in
tables in path across network
All cells for a connection follow the same path
Abbreviated header identifies connection
Cells queue for transmission at ATM switches & multiplexers
Fixed and Variable bit rates possible, negotiated during call set-up
Delay and loss performance negotiated prior to connection setup 7
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Source
TRAFFIC CONTRACT
During connection setup the user and the
network negotiate two sets of parameters for a
connection
 Traffic descriptor: the user specifies the traffic
that it will expect the network to transfer on its
behalf
 QoS requirements: the user specifies the type of
network performance that is required by its cells
 Traffic Contract


The user is expected to conform to traffic descriptor
The network is expected to deliver on its QoS
commitments
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
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TRAFFIC DESCRIPTORS
Peak Cell Rate: rate in cells/second that a source is
never allowed to exceed
 Sustainable Cell Rate: average cell rate produced by
the source over a long time interval
 Maximum Burst Size: maximum number of consecutive
cells that may be transmitted by a source at the peak
cell rate (PCR)
 Minimum Cell Rate: minimum average cell rate, in
cells per second, that the source is always allowed to
send
 Cell Delay Variation Tolerance: cell delay variation that
must be tolerated for in a given connection.

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QUALITY OF SERVICE PARAMETERS
Six QoS parameters are defined
 Three are intrinsic to network performance and
are not negotiated during connection setup:
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Cell error ratio: fraction of delivered cells that
contain bit errors
 Cell mis-insertion ratio: average number of
cells/second that are misdelivered
 Severely errored cell block ratio: M or more out of N
cells are lost, in error, or misdelivered
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NEGOTIABLE QOS PARAMETERS

Cell Loss Ratio (CLR): fraction of cells that are lost
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Cell Transfer Delay (CTD): negotiate “maximum delay”
Dmax: 1-a of cells have delay less than Dmax
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Determined by cell scheduling
Cell Delay Variation (CDV): Peak-to-Peak variation: Dmax-D0
probability density of cell delay

Determined by buffer priority
a
D0
Peak-to-Peak CDV
Dmax
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AGENDA
Asynchronous Transfer Mode (ATM)
 Integrated Services (intserv)

(ReSerVation Protocol) RSVP
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
Differentiated Services (divserv)
 MPLS

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INTEGRATED SERVICES (INTSERV)
Standardized by IETF
 Provides different QoS commitments : resources
(bandwidth and buffer) must be explicitly reserved
for a given data flow (using RSVP)
 Packet classifier : identify flows that are to receive a
certain level of service
 Packet scheduler : handling different packet flows in
a manner that QoS commitments are met
 Admission control : determine whether a router has
the necessary resource

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INTSERV ROUTER MODEL
Accept/reject a
flow
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Identify a
packet’s flow
Buffering to
control loss
Transmission
scheduling to
control delay
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ADMISSION CONTROL

1.
2.
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
Filter specification (filterspec) provides information
required by classifier to identify the packets in the flow
Flow specification (flowspec) describes traffic properties of
flow and QoS requirements
Traffic Specification (Tspec) describes traffic in terms of
a token bucket
Request Specification (Rspec) describes QoS in terms of
bandwidth, delay, or packet loss. Each node along path
must decide whether a flow can be accepted
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
Individual flow negotiates admission into the
network
Flow Descriptor has two parts
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CALL SETUP
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RESERVATION PROTOCOL (RSVP)
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Performs resource reservations for multipoint-multipoint
applications
 Adapts changing group membership & routes
 Unicast, a special case
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RSVP is an IP signaling protocol to setup and maintain flowspecific state in hosts and routers
Multicast-oriented
Simplex
Requests resources from sender to receiver
 Bidirectional flows require separate reservations
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Receiver-oriented
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Receivers initiate and maintain resource reservations
Soft-state at intermediate routers
Reservation valid for specified duration
 Released after timeout, unless first refreshed
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RSVP ARCHITECTURE
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Policy control determines if
application allowed to make
request
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 Admission control determines if
resources available; sets up
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
Application requests QoS
from RSVP process
RSVP prepares & sends
request messages to router
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INTSERV INVOLVES HIGH COMPLEXITY
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Number of (application) flows can become extremely large
Per-flow treatment involves high complexity
Traffic Management
Per-flow classifier
 Per-flow queueing
 Per-flow scheduling
 Hugh table sizes & high hardware complexity


Admission Control
Set up & maintenance of individual flows
 High processing load

IntServ is not scalable
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AGENDA
Asynchronous Transfer Mode (ATM)
 Integrated Services (intserv)

(ReSerVation Protocol) RSVP
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
Differentiated Services (diffserv)
 MPLS
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DIFFERENTIATED SERVICES (DIFFSERV)
Differentiated Services (DiffServ) model is designed to
be scalable and to provide QoS
 Traffic is aggregated into a limited number of classes
 Service is on aggregate-flow basis, not per individual
flow
 Each class receives a well-defined service treatment at
each DiffServ router
 No per-flow signaling
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FORWARDING PATH ARCHITECTURE
TCA
…
SLA
Notwithstanding …
H
DiffServ Domain
A
A
H
C
C
A
C
H
A

A
A

H
C = Core Router
A = Access Router
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service level, traffic profile,
marking, shaping
Access Router

H = Host
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H
Complexity at the Edge
 User negotiates Service
Level Agreement (SLA)
with service provider
 SLA includes a Traffic
Conditioning Agreement
(TCA) stipulating

classifies user packets and
marks them in DS field of IP
header as belonging to a
specific class
conditions packet stream so
it conforms to profile
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AGENDA
Asynchronous Transfer Mode (ATM)
 Integrated Services (intserv)

(ReSerVation Protocol) RSVP
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
Differentiated Services (divfferv)
 MPLS

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WHAT IS MPLS
IP
LER
IP
L1
LSR
IP
L2
LSR
IP
L3
LER
IP
Multiprotocol Label Switching (MPLS)
 Label Switching Router (LSR) : a router that supports
MPLS
 A set of protocols that enable MPLS networks
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Packets are assigned labels by edge routers (which
perform longest-prefix match)
 Packets are forwarded along a Label-Switched Path
(LSP) in the MPLS network using label switching
 LSPs can be created over multiple layer-2 links



ATM, Ethernet, PPP, frame relay
LSPs can support multiple layer-3 protocols
 IPv4, IPv6, and in others
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REFERENCES
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Garcia A.L., Widjaja A. 2004. Networks
Communication.: Fundamental Concepts and Key
Architectures 2nd ed. – Chapter 9-10. McGraw-Hill
Companies, Inc.
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