Transcript 1-Intro-QoS-Routing - ETH TIK

Manno, January 9, 2001
High Speed Networks
– Technology and Applicatios –
Prof. Dr. Bernhard Plattner, Prof. Dr. Burkhard Stiller
Institut für Technische Informatik und Kommunikationsnetze
Fachgruppe Kommunikationssysteme, ETH Zürich
Gloriastrasse 35
CH-8092 Zürich, Switzerland
Phone: +41 1 [632 7000 | 632 7016], FAX: +41 1 632 1035
E-Mail: [ plattner | stiller ]@tik.ee.ethz.ch
in cooperation with Dr. Daniel Bauer
IBM Research Division, Zürich Laboratories
Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 1
ETH Zürich
Course Outline
Part I:
Part II:
Part III:
Part IV:
Introduction, Quality-of-Service,
Internet Basics and
Routing in Networks
LAN Technologies and Internetworking
Overview of Networking Technologies,
ATM, and IP
Carrier Technologies,
Traffic Management, and Trends
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 2
ETH Zürich
Part I: Introduction, QoS, and Routing
•
•
•
Introduction
– Applications
– Multimedia Systems
Quality of Service (QoS)
– Concept and Definitions
– Example
Routing
– Internet Basics
– Switching and Forwarding
– Routers and the Big Picture
– Routing Protocols
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 3
ETH Zürich
Introduction
Why are High Speed Networks an issue?
 Increasing dependency of business processes
on availability of various computing resources
(servers, distributed applications, interpersonal
communication facilities).
 Ever increasing processing speeds of PCs,
workstations and servers.
 Technology push:
High Speed Network Technology is available.
 User pull: New distributed multimedia applications
need faster networks and new kinds of services.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 4
ETH Zürich
Traditional Applications
Client/server networking
(e.g., Novell, Windows 95/NT).
 Document exchange (directly between users or with
a server as an intermediary).
 Electronic mail services (proprietary technologies, or
vendor independent standards like X.400 or Internet
mail).

10 Mbit/s LAN technologies have generally
been sufficient for these applications
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 5
ETH Zürich
Changing Picture

Percentage of employees really using computers
has increased (cf. visions of LAN use of the 70s!)
• 20/80% rule changes to 80/20% rule.
Graphical user interfaces tend to cause more traffic
(X-Window System, UI design trends).
 Graphical visualization of information has become
popular (World Wide Web, Internet -> Intranet).
 High-speed backup systems.
> Need for flexibility and extensibility of network
infrastructure:

•
•
Universal cable plants, bridges, routers, LAN switches
100 Mbit/s LAN technology as a logical step
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 6
ETH Zürich
Emerging Applications

New types of applications:
• Digitized analog applications: E.g., video/audio broadcasting, picture phone, HDTV, conferencing, FAX
• Digital applications per se: E.g., network management,
secure messaging, virtual reality.
• Examples: Netmeeting or MBone tools (A/V conferencing)
or Marimba (Software Updates)

Distributed applications:
• Collaborative work (CSCW)
• Support for virtual enterprises
• New technolgies in education, tele-teaching for life-long
learning
• Entertainment (distributed games, Napster, Gnutella, ...)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 7
ETH Zürich
Why do we need more bandwidth?

Text and graphics based applications will gradually
give way to distributed multimedia applications:
Medium
Speech, telephone quality (PCM)
CD quality audio
Compressed audio 4:1, 37'800 Hz
sampling
MPEG-1 video
MPEG-2 video (digital video studio
standard quality)
Motion JPEG as used at ETH
(Telepoly)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 8
Data rate of representation
64 kbit/s
172.3 kBytes/s
43 kBytes/s
target rate: 1.2 Mbit/s
target rate: 40 Mbit/s
~8 Mbit/s for one audio/video
channel
ETH Zürich
Future Developments
Ubiquitous computers
 Virtual reality
 Distributed simulation systems:

• “World models” or
• Battlefield simulation -> virtual reality
Multiparty applications
 Mobile (multimedia) systems
 Active networks

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 9
ETH Zürich
Definition of a “Multimedia System”
Simple quantitative definition: A system supporting
more than one medium (text, graphics, sound,
video, tactile feelings, smell, ...).
 Qualitative definition: A system supporting a
combination of discrete and continuous media.
 Additional properties:

•
•

Independence of the various media and
Computer-supported integration of media
(programmability, controllable timing, synchronization).
High speed networks should be capable of
supporting distributed multimedia systems.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 10
ETH Zürich
Components of a Multimedia System
Multimedia applications
Input/output
devices
• Camera
• Audio I/O
• Mouse
• Screen
Communication Middleware
Multimedia Workstation:
• Standard processor
• Memory and secondary
storage
• Special purpose processors
(optional)
• Graphics, audio and video
adapters
• Communications adapters
• Multimedia operating system
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 11
Highspeed
integrated
services
network
Multimedia
servers
ETH Zürich
Requirements (1)
Multimedia workstation:
 General state of the art high
performance hardware
platform.
 Operating system with
support for continuous
media:
•
•
•
•
Soft real-time support for
timely delivery of data,
Direct paths between data
sources and sinks,
Non-real time control
functions, and
Suitable device drivers.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
High speed network:
 Basic properties: high
throughput, low delay, low
delay jitter, low intrinsic
error rate, and low loss.
 Integrated services support:
•
•
•
•
CM I – 12
Multiple service classes,
Quality-of-Service (QoS)
guarantees,
Facilities for the reservation of
resources, and
Implication: control path
separated from data path.
ETH Zürich
Requirements (2)
Multimedia applications:
 User interface for
controlling multimedia
streams and applications
semantics.
 Accepts Quality-of-Service
requests form the user.
 Maps the user’s QoS
wishes to lower level QoS
requirements.
 Capability for requesting the
quality of service for
continuous media streams.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 13
Communication middleware:
 Offers an easy-to-use
communication service as
an application programmer’s interface (API).
 Accepts QoS requirements
from the application.
 Maps QoS requirements to
network QoS parameters
and resource reservations.
 Manages streams between
sources and sinks.
ETH Zürich
Part I: Introduction, QoS, and Routing
•
•
•
Introduction
– Applications
– Multimedia Systems
Quality of Service (QoS)
– Concept and Definitions
– Example
Routing
– Switching and Forwarding
– Routers and the Big Picture
– Routing Protocols
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 14
ETH Zürich
Quality-of-Service (QoS)

What does QoS stand for?
•

What is QoS?
•
•

Quality-of-Service: the grade, excellence, or goodness of a
service; in the considered case, communication services.
A concept for qualitative and quantitative specification of
service requirements and properties,
Complemented with a set of rules and mechanisms for
aquiring requested QoS
Why QoS?
•
Basis of a „contract“ between a service user and a service
provider (e.g. in a service level agreement)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 15
ETH Zürich
Quality-of-Service

A concept to describe service requirements is
needed.
•
Examples for service characteristics comprise:
– Throughput,
– Delay,
– Jitter,
– Error rates (reliability),
– Ordered delivery,
– Multicasting, and
– Data unit size.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 16
ETH Zürich
QoS – An Example

Different components of the communication
architecture require distinct parameters.
User
Application
Middleware
Operating
System
Network
Abstract qualities:
High, medium, low
Media qualities:
Frames/second,
synchronization
Communication qualities:
Throughput, delay,
error rates, jitter
System qualities:
Thread duration, priority,
scheduling method
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 17
ETH Zürich
Types of Service

There exist two basic types of service:
•
•

Best effort service and
Guaranteed service.
Best Effort Service:
•
•
•
•
Service type that does not give any guarantees for QoS
(no commitment).
No reservation of resources within the end-system or the
network.
Often QoS cannot be monitored, as no monitoring
mechanisms are defined; adaptive applications have to do
their own monitoring.
Specification of QoS parameters is not necessary.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 18
ETH Zürich
Type-of-Service (2)

Two different guarantees are possible:
•
•

Statistical (stochastical) guarantees – weak:
– Requested QoS is provided with some (high)
probability
– Utilization of network can be maximized (multiplexing).
– Reserving resources for an “average” case necessary.
Deterministic guarantees – strong:
– Requested QoS is fully guaranteed.
– Resource reservations are required for the worst case.
ToS is sometimes called “QoS semantics” as well.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 19
ETH Zürich
Examples

For a file transfer application:
•
•

Best effort service concerning timing and delay:
– No values can be specified or reserved.
Guaranteed service (deterministic) concerning reliability:
– Bit error rate is zero for received data (retransmission).
– However, service may be aborted due to slow links.
For video transmission:
•
Statistically Guaranteed service concerning frame delay:
– p percent of delayed frames may exceed the maximum
bounded delay D.
– “Flickering” pictures (black outs) may occur due to
frames arriving late.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 20
ETH Zürich
Part I: Introduction, QoS, and Routing
•
•
•
Introduction
– Applications
– Multimedia Systems
Quality of Service (QoS)
– Concept and Definitions
– Example
Routing
– Internet Basics
– Switching and Forwarding
– Routers and the Big Picture
– Routing Protocols
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 21
ETH Zürich
Internet (IP) Technology

Key elements of the technology used in the Internet:
•
•
•
•
•
•
•
•
Internet: Network of (sub)networks
Packet switching, using datagrams
No connection-dependent state information in the network
Distributed management
Many physical subnetwork technologies
One network protocol
Two transport protocols
Infrastructure for hundreds of different distributed
applications
• Scalability: to accommodate exponential growth
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 22
ETH Zürich
Interconnection of Heterogeneous Networks
Host
Host
R
Host
Host
Host
Host
R
Token Ring
DECnet
R
Host
Host
R
Router
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Host
Ethernet
CM I – 23
ETH Zürich
Model of a Router
Routing
Agent
Management
Agent
Forwarding
table
IP
Packets
Forwarding
engine
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Output
Drivers
CM I – 24
IP
Packets
ETH Zürich
IP Protocol Stack
Application
layer
HTTP
Transport
layer
TCP
Internet
layer
Phys. Network
layer
FTP
UDP
IP
Ethernet
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
DNS
Routing
ATM
CM I – 25
DECnet
ETH Zürich
Forwarding with A/B/C Address Classes
Forwarding is based on network id
 Simple and efficient

0
8
A
0
B
10
C
110
16
Net ID
24
Host ID
Net ID
Host ID
Net ID
A
A
32
Host ID
B
P
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
A
C
P
CM I – 26
A
P
ETH Zürich
Step 1: Subnetting
Subnetting provides flexibility for network-internal
addressing of subnetworks
 Network administrators have the freedom to
structure their own A/B/C address space into a few
or many subnetworks

01234
8
16
24
Class B
10
Net ID
Subnet
10
Net ID
Subnet ID
16 Bits
n Bits
31
Host ID
Host ID
16-n Bits
Subnet mask
Example: Net 129.132.0.0, Mask 255.255.255.192 = 10 Bit Subnet
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 27
ETH Zürich
Motivation for Hierarchical Routing

Large networks (> 10’000 sub-networks) are no
longer tractable by a flat routing architecture.
• The topology database becomes very large.
• Link state packets consume a lot of the available bandwidth.
• Path computation time grows with n2.

Administration and management becomes
increasingly difficult as the network grows.
• Administration has to be centralized.
• All routers need to run the same code, which makes updating
difficult.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 28
ETH Zürich
Hierarchical routing
Routing Domain 1
Routing Domain 3
Routing Backbone
Intra-Domain-Router
Routing Domain 2
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Routing Domain: An
aggregate of networks
or subnetworks that use
a common internal
routing protocol and
communicate to other
routing domains via an
Inter-domain routing
protocol
Inter-Domain-Router
CM I – 29
ETH Zürich
Hierarchical Routing Principles
Grouping of routes based on
network addresses.
A.1
C.2
C.1
A.2
C
C.3
A.2.3
A.2.5
B.2
A
B.2.4
Address Aggregation
(Address Summary)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
B.3
CM I – 30
B
ETH Zürich
Topology View of Node B.2.4
C
A
B.2.2
B.2.1
B.2.3
Summary Addresses
(Address Prefixes)
B.2.4
B.1
B.3
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 31
ETH Zürich
Step 2: Classless Inter-Domain Routing


For efficient address allocation and routing, the distinction
between A, B and C address classes is eliminated
Address registries may
• allocate part of a A/B/C address space to a client
• allocate several “adjacent” C networks to one client




The addresses belonging to one client may be identified by
an address prefix of up to 32 bits (typical 8-30)
Inter-domain routing is done only on the prefix
Intra-domain routing is done on the local network numbers
Prefix length is not encoded into the address
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 32
ETH Zürich
Flexible Address Structure
Inter-domain (backbone) routers only need to know
and look at the address prefixes of addresses
 Intra-domain routers only look at local network Id
 Hosts Ids have subnetwork-local significance

Network Id
with intra-domain Host Id
routing significance
Address prefix used for
inter-domain routing
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 33
ETH Zürich
Hierarchical Routing in the Internet
Intra-domain
routing
E
D
129.132.*/16
Inter-domain (backbone) routing
129.132/16 A
B
C
205.244/16 D
A
/Prefix
B
129.132.66.*/26
C
205.244.*/16
Examples:
129.132.72.15 is forwarded to A
129.132.66.48 is forwarded to B
129.132.66.68 is forwarded to A
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 34
129.132.66.44/32
ETH Zürich
Detailed Explanation
Sample forwarding table of backbone router:
Prefix (decimal)
129.132/16
129.132.66/26
129.132.66.44/32
205.244/16
Prefix (binary)
10000001 10000100 *
10000001 10000100 01000010 00*
10000001 10000100 01000010 00101100
11001101 11110100 *
Next hop
A
B
C
D
Sample destination addresses to be matched against
forwarding table:
Address (decimal)
129.132.72.15
129.132.66.48
129.132.66.68
Address (binary)
10000001 10000100 01001000 00001111
10000001 10000100 01000010 00110000
10000001 10000100 01000010 01000100
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 35
Next hop found
A
B
A
ETH Zürich
The State of the Art for Forwarding Lookups

Patricia tries
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 37
ETH Zürich
Trie-based Forwarding Lookup
Root
Forwarding table
1*
11*
111*
1000*
10001*
100011*
1000111*
1110111*
A
B
C
D
E
F
G
H
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
0
0
D 1
1
0 A 1
B 1
C
0
1
1
E 1
F 1
1
H
G
CM I – 38
ETH Zürich
The State of the Art for Forwarding Lookups
Patricia tries
 Hardware solutions - Content Addressable
Memories (CAM)


Protocol based solutions (“label switching”)
• small integer labels packets that take the same
route
• label may be used as an index into forwarding table
• IP Switching, Tag Switching, ...

Caching (using CAMs for fast operation)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 39
ETH Zürich
Fast Forwarding is a Difficult Problem ...

Performance
• 10 Gbit/s throughput @ packet size 128 bytes -> 10
million packets/s -> 100 ns per packet
• Trie lookups are too slow: O(W) memory accesses in the
worst case; only a few memory lookups can be allowed

Scalability
• Trie lookups have large memory requirements, worst
case performance is linear to the prefix length

Cost
• CAM solutions are expensive
• Caching needs associative memory (CAMs) for good
performance
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 40
ETH Zürich
… and was solved only recently

M. Waldvogel, G. Varghese, J. Turner, and
B. Plattner: Scalable High Speed IP Routing
Lookups
Proc. ACM SIGCOMM '97 Conference (in:
Computer Communication Review, Volume 27,
Number 4, October 1997)
Needs 2-3 memory accesses for finding the best
matching prefix
 Achieved with a novel application of a binary search
strategy with hash tables

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 41
ETH Zürich
Router Architecture

Single-CPU/Shared Bus Router
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 42
ETH Zürich
Router with one Card per Port
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 43
ETH Zürich
Today: Switch-based Router
Line if cards
Router & Switch
control
Steuerung
Steuerung
Paketverarbeitung
Paketverarbeitung
Steuerung
Steuerung
Paketverarbeitung
Paketverarbeitung
Steuerung
Paketverarbeitung
Steuerung
Durchschaltenetz
(switch fabric)
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Line if cards
Paketverarbeitung
CM I – 44
ETH Zürich
Tasks of a Routing Protocol

Routing involves two activities:
• Determining optimal (shortest) routing paths.
• Transporting packets through an internetwork.
Routing protocols calculate optimal routing paths
based on a distributed routing algorithm.
 Path calculation is split into two tasks:

• Collecting topology information (“get a view of the
network”).
• Constructing optimal routing paths based on the collected
topology information.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 45
ETH Zürich
Link Metrics
Paths are computed based on “metrics”.
 Static Metrics

• Assigned by network administrator.
• Examples: hop-count, distance, link capacity, weight, etc.

Dynamic Metrics
• Measured or computed by routers.
• Examples: available bandwidth, current delay, etc.

Additive Metrics (hop-count, delay, weight)
• metric (path) 

metric(link i )
Restrictive Metrics (available bandwidth)
• metric (path)  Min(metric( link i ))
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 46
ETH Zürich
Static Routing
Routing tables configures by administrator.
 Most stable “routing protocol”.
 Only applicable in very small and simple networks.

A
B
Forwarding Table Node C
Dest
A
D
B
B
Port
1
2
1
2
Distance
1
1
2
2
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
1
D
C
CM I – 47
2
ETH Zürich
Distance Vector Routing
Distributed variant of the “Bellman-Ford” algorithm.
 Distributes reachability and metric information.

Dest.
A
C
B
D
C
A
D
C
B
D
C
D
Port/Cost
A/3
D/2
A/4
D/3
-/0
D/1
A/6
-/0
A/4
D/2
D/1
D/3
-/0
D/1
D/2
D/1
B
1
A
3
D
1
3
1
C
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 48
ETH Zürich
Link State Routing

Routers distribute their local view (the “link-state”) to
all other routers. The local view consists of:
•
•
•
•
Nodal information describing routers.
Link information describing links.
Reachability information describing reachable hosts.
Metric information as attributes for links and reachabilities.
Each router maintains a complete view of the
topology in the topology database.
 Dijkstra’s “shortest path first” algorithm is used to
calculate paths to all reachabilities.

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 49
ETH Zürich
Link State Routing: Pro and Con
Link state routing converges faster than distance
vector routing and thus is more scalable.
 It provides more functionality:

• Each router knows the full topology, which makes it easier
to debug.
• Powerful source routing schemes can be implemented.
Link state routing is more robust since the topology
is described with some redundancy.
 It is more complex to implement and requires more
memory, CPU power and bandwidth.

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 50
ETH Zürich
Routing in the Internet
Interior Gateway
Protocols (IGP),
OSPF, RIP, ...
Autonomous Systems:
• Administered by a single authority.
• Implements a single routing policy.
• Has a unique identifier (AS number).
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 51
Exterior Gateway
Protocols (EGP),
BGP4
ETH Zürich
ATM Routing: Schematic Overview
Caller
Setup
Routing decision
Connect
Setup
Connect
Callee
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 52
ETH Zürich
Signaling and Interfaces
Private NNI
(B-ICI)
Public
UNI
Public
ATM
Public
ATM
Public UNI
ILMI
Private
NNI
Private
ATM
Private
UNI
ILMI
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
NNI
UNI
ILMI
B-ICI
CM I – 53
Private
ATM
Network Node Interface
User Network Interface
Integrated Local Management Interface
Broadband-Inter Carrier Interface
ETH Zürich
Summary Routing Protocols
The Internet uses hierarchical routing based on
interior and exterior gateway protocols.
 OSPF, the recommended IGP, is a link state routing
protocol that uses static metrics.
 BGP is the EGP of choice. It is a path vector
protocol supporting various routing policies.
 The current IP routing protocols do not support
dynamic metrics such as available bandwidth.
 In ATM, PNNI provides hierarchical routing using link
state routing.
 PNNI supports dynamic metrics.

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 54
ETH Zürich
References
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F. Fluckiger: Understanding Networked Multimedia; Prentice
Hall, London, England, 1995, ISBN 3–13–190992–4.
K. Nahrstedt, R. Steinmetz: Multimedia: Computing,
Communications, and Applications; Prentice Hall, Upper
Saddle River, New Jersey, U.S.A., 1995, ISBN 0-13-324435-0.
B. Stiller: Quality-of-Service; International Thomson Publishing,
Bonn, Germany, 1996, ISBN 3–8266–0171–8.
G. Malkin: RIP Version 2; RFC 2453, November 1998.
J. Moy: OSPF Version 2, RFC 2328, April 1998
ATM Forum: Private Network-Network Interface Specification
1.0 (PNNI 1.0), af-pnni-0055.000, March 1996
Y. Rekhter, T. Li: A Border Gateway Protocol 4, RFC 1771,
March 1995
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM I – 55
ETH Zürich