Kurs HLN

1
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 Kommunikationssyste
me, ETH Zürich Gloriastrasse 35 CH-8092 Zürich,
Switzerland Phone [phone] 7016,
FAX [phone] E-Mail plattner stiller
_at_tik.ee.ethz.ch in cooperation with Dr. Daniel
Bauer IBM Research Division, Zürich
Laboratories Säumerstrasse 4, CH-8803 Rüschlikon,
Switzerland
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Course Outline

• Part I Introduction, Quality-of-Service,
  Internet Basics andRouting in Networks
• Part II LAN Technologies and Internetworking
• Part III Overview of Networking Technologies,
  ATM, and IP
• Part IV Carrier Technologies,Traffic
  Management, and Trends

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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

4
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.

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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
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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 -gt Intranet).
• High-speed backup systems.
• gt Need for flexibility and extensibility of
  network infrastructure
• Universal cable plants, bridges, routers, LAN
  switches
• 100 Mbit/s LAN technology as a logical step

7
Emerging Applications

• New types of applications
• Digitized analog applications E.g., video/audio
  broad-casting, 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, ...)

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Why do we need more bandwidth?

• Text and graphics based applications will
  gradually give way to distributed multimedia
  applications

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Future Developments

• Ubiquitous computers
• Virtual reality
• Distributed simulation systems
• World models or
• Battlefield simulation -gt virtual reality
• Multiparty applications
• Mobile (multimedia) systems
• Active networks

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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.

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Components of a Multimedia System
Multimedia applications
Input/output devices Camera Audio I/O
Mouse Screen
Communication Middleware
High- speed integrated services network
Multimedia Workstation Standard processor
Memory and secondary storage Special purpose
processors (optional) Graphics, audio and video
adapters Communications adapters Multimedia
operating system
Multimedia servers
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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.

• High speed network
• Basic properties high throughput, low delay, low
  delay jitter, low intrinsic error rate, and low
  loss.
• Integrated services support
• Multiple service classes,
• Quality-of-Service (QoS) guarantees,
• Facilities for the reservation of resources, and
• Implication control path separated from data
  path.

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Requirements (2)

• Multimedia applications
• User interface for controlling multimedia streams
  and applications semantics.
• Accepts Quality-of-Service requests form the
  user.
• Maps the users QoS wishes to lower level QoS
  requirements.
• Capability for requesting the quality of service
  for continuous media streams.

• Communication middleware
• Offers an easy-to-use communication service as an
  application pro-grammers interface (API).
• Accepts QoS requirements from the application.
• Maps QoS requirements to network QoS parameters
  and resource reservations.
• Manages streams between sources and sinks.

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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

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Quality-of-Service (QoS)

• What does QoS stand for?
• Quality-of-Service the grade, excellence, or
  goodness of a service in the considered case,
  communication services.
• What is QoS?
• 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)

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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.

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QoS An Example

• Different components of the communication
  architecture require distinct parameters.

Middleware
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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.

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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.

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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.

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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

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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

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Interconnection of Heterogeneous Networks
Host
Host
R
Host
Host
Host
Host
R
DECnet
R
Token Ring
Host
Host
R
Router
Host
Ethernet
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Model of a Router
Routing Agent
Management Agent
Forwarding table
IP Packets
Output Drivers
Forwardingengine
IP Packets
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IP Protocol Stack
Application layer
HTTP
DNS
FTP
Transport layer
TCP
UDP
Internet layer
IP
Routing
Phys. Network layer
Ethernet
DECnet
ATM
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Forwarding with A/B/C Address Classes

• Forwarding is based on network id
• Simple and efficient

8
32
16
0
24
Net ID
Host ID
0
A
Net ID
Host ID
10
B
Net ID
Host ID
110
C
A
B
C
A
P
A
P
A
P
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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

0 1 2 3 4 8
16 24
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Class B
10 Net ID
Host ID
Subnet
10 Net ID
Subnet ID Host ID
16 Bits
n Bits
16-n Bits
Subnet mask
Example Net 129.132.0.0, Mask 255.255.255.192
10 Bit Subnet
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Motivation for Hierarchical Routing

• Large networks (gt 10000 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.

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Hierarchical routing
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Hierarchical Routing Principles
Grouping of routes based onnetwork addresses.
C.2
C.1
C
A.2
A.1
C.3
A.2.3
A.2.5
B.2
A
B.2.4
Address Aggregation (Address Summary)
B
B.3
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Topology View of Node B.2.4
C
A
B.2.2
B.2.1
B.2.3
B.2.4
B.1
Summary Addresses (Address Prefixes)
B.3
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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

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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 Idwith intra-domainrouting significance
Address prefix used forinter-domain routing
Host Id
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Hierarchical Routing in the Internet
Intra-domainrouting
129.132./16
A
E
Inter-domain (backbone) routing
/Prefix
129.132/16 A 129.132.66/26 B 129.132.66.44/32
C 205.244/16 D
B
129.132.66./26
C
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
129.132.66.44/32
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Detailed Explanation
Sample forwarding table of backbone router
Sample destination addresses to be matched
against forwarding table
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Prefix Length Distribution in Backbone Router

• Size of backbone router forwarding table
  currently is 40000 entries
• Finding the right next hop means to find the best
  matching prefix
• Compare addresses with all prefixes in the data
  base, starting at the longest prefix length
• Slow process

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The State of the Art for Forwarding Lookups

• Patricia tries

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Trie-based Forwarding Lookup
Forwarding table 1 A 11 B 111 C 1000 D 10001
E 100011 F 1000111 G 1110111 H
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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)

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Fast Forwarding is a Difficult Problem ...

• Performance
• 10 Gbit/s throughput _at_ packet size 128 bytes -gt
  10 million packets/s -gt 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

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and was solved only recently

• M. Waldvogel, G. Varghese, J. Turner, and B.
  Plattner Scalable High Speed IP Routing
  LookupsProc. 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

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Router Architecture

• Single-CPU/Shared Bus Router

43
Router with one Card per Port
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Today Switch-based Router
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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.

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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)
• Restrictive Metrics (available bandwidth)

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Static Routing

• Routing tables configures by administrator.
• Most stable routing protocol.
• Only applicable in very small and simple networks.

Forwarding Table Node C
Dest Port Distance A 1 1 D 2 1
B 1 2 B 2 2
1
2
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Distance Vector Routing

• Distributed variant of the Bellman-Ford
  algorithm.
• Distributes reachability and metric information.

Dest. Port/Cost A A/3 C -/0 D D/1
Dest. Port/Cost A A/3 B A/4 C A/6 D A/4 C
-/0 D D/1
Dest. Port/Cost A A/3 B A/4 C
-/0 D D/1
Dest. Port/Cost A A/3 B A/4 C
-/0 A D/2 B D/3 C D/2 D D/1
Dest. Port/Cost A D/2 B D/3 C
-/0 D D/1
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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.
• Dijkstras shortest path first algorithm is
  used to calculate paths to all reachabilities.

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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.

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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).

Exterior GatewayProtocols (EGP), BGP4
52
ATM Routing Schematic Overview
Caller
Setup
Routing decision
Connect
Setup
Connect
Callee
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Signaling and Interfaces
Private NNI (B-ICI)
Public UNI
Public UNI
ILMI
Private NNI
Private UNI
NNI Network Node Interface UNI User Network
Interface ILMI Integrated Local Management
Interface B-ICI Broadband-Inter Carrier Interface
ILMI
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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.

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References

• F. Fluckiger Understanding Networked Multimedia
  Prentice Hall, London, England, 1995, ISBN
  3131909924.
• 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
  3826601718.
• 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