© 2000 b. stiller, b. plattner ethz-tik, d. bauer ibm research cm i – 1 eth zürich prof. dr....
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© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 1 ETH Zürich
Prof. Dr. Bernhard Plattner, Prof. Dr. Burkhard StillerInstitut für Technische Informatik und Kommunikationsnetze
Fachgruppe Kommunikationssysteme, ETH ZürichGloriastrasse 35
CH-8092 Zürich, Switzerland
Phone: +41 1 [632 7000 | 632 7016], FAX: +41 1 632 1035E-Mail: [ plattner | stiller ]@tik.ee.ethz.ch
in cooperation with Dr. Daniel BauerIBM Research Division, Zürich Laboratories
Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland
High Speed Networks– Technology and Applicatios –
Manno, January 9, 2001
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 2 ETH Zürich
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
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 3 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 – 4 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 – 5 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 – 6 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 – 7 ETH Zürich
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, ...)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 8 ETH Zürich
Why do we need more bandwidth?
Text and graphics based applications will gradually give way to distributed multimedia applications:
Medium Data rate of representation
Speech, telephone quality (PCM) 64 kbit/sCD quality audio 172.3 kBytes/sCompressed audio 4:1, 37'800 Hzsampling
43 kBytes/s
MPEG-1 video target rate: 1.2 Mbit/s
MPEG-2 video (digital video studiostandard quality)
target rate: 40 Mbit/s
Motion JPEG as used at ETH(Telepoly)
~8 Mbit/s for one audio/videochannel
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 9 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 – 10 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 – 11 ETH Zürich
Components of a Multimedia System
Input/output devices
• Camera• Audio I/O• Mouse• Screen
Multimedia Workstation:• Standard processor• Memory and secondary
storage• Special purpose processors
(optional)• Graphics, audio and video
adapters• Communications adapters• Multimedia operating system
Multimedia servers
High- speed
integrated services network
Multimedia applications
Communication Middleware
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 12 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.
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.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 13 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.
Communication middleware: Offers an easy-to-use
communication service as an application pro-grammer’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.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 14 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 – 15 ETH Zürich
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)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 16 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 – 17 ETH Zürich
Different components of the communication architecture require distinct parameters.
QoS – An Example
Application
Middleware
Network
OperatingSystem
User
Communication qualities:Throughput, delay, error rates, jitter
Abstract qualities:High, medium, low
Media qualities:Frames/second, synchronization
System qualities:Thread duration, priority,scheduling method
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 18 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 – 19 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 – 20 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 – 21 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 – 22 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 – 23 ETH Zürich
Interconnection of Heterogeneous Networks
HostHost
Host
HostHost
Host
Host
Host
Host
DECnet
Router
Token RingR
R
R
REthernet
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 24 ETH Zürich
Model of a Router
RoutingAgent
ManagementAgent
IPPackets
OutputDrivers
Forwarding table
Forwardingengine
IPPackets
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 25 ETH Zürich
IP Protocol Stack
Phys. Networklayer
Internetlayer
Applicationlayer
Ethernet DECnetATM
HTTP DNSFTP
IP
TCP UDPTransport
layer
Routing
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 26 ETH Zürich
Forwarding with A/B/C Address Classes
Forwarding is based on network id Simple and efficient
Net ID Host ID0
Net ID Host ID10
Net ID Host ID110
A
B
C
8 32160 24
A P
AA P
BA P
C
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 27 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
Class B 10 Net ID Host ID
Subnet 10 Net ID Subnet ID Host ID
0 1 2 3 4 8 16 24 31
16 Bits n Bits 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 – 28 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 – 29 ETH Zürich
Hierarchical routing
Routing Domain 1
Routing Domain 2
Routing Domain 3
Routing Backbone
Intra-Domain-Router
Inter-Domain-Router
Routing Domain: Anaggregate of networks
or subnetworks that usea common internal
routing protocol andcommunicate to otherrouting domains via anInter-domain routing
protocol
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 30 ETH Zürich
Hierarchical Routing Principles
Address Aggregation(Address Summary)
Grouping of routes based onnetwork addresses.
A
C
B
A.1 A.2
C.2
C.1
C.3
B.2
B.3
B.2.4
A.2.5
A.2.3
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 31 ETH Zürich
Topology View of Node B.2.4
A
C
B.3
B.2.4B.1
B.2.3
B.2.2B.2.1
Summary Addresses(Address Prefixes)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 32 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 – 33 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
Address prefix used forinter-domain routing
Host IdNetwork Id
with intra-domainrouting significance
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 34 ETH Zürich
Hierarchical Routing in the Internet
Inter-domain (backbone) routingA
B
C205.244.*/16
D129.132.66.*/26
E
Intra-domainrouting
129.132.*/16
/Prefix
129.132.66.44/32
129.132/16 ABC205.244/16D
Examples:129.132.72.15 is forwarded to A129.132.66.48 is forwarded to B129.132.66.68 is forwarded to A
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 35 ETH Zürich
Detailed Explanation
Sample forwarding table of backbone router:
Sample destination addresses to be matched against forwarding table:
Prefix (decimal) Prefix (binary) Next hop129.132/16 10000001 10000100 * A129.132.66/26 10000001 10000100 01000010 00* B129.132.66.44/32 10000001 10000100 01000010 00101100 C205.244/16 11001101 11110100 * D
Address (decimal) Address (binary) Next hop found129.132.72.15 10000001 10000100 01001000 00001111 A129.132.66.48 10000001 10000100 01000010 00110000 B129.132.66.68 10000001 10000100 01000010 01000100 A
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 37 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 – 38 ETH Zürich
Trie-based Forwarding Lookup
Forwarding table
1* A11* B111* C1000* D10001* E100011* F1000111* G1110111* H
A
B
C
H
D
E
F
G
1
1
1
1
1
1
0
0
0
0
1
1
1
Root
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 39 ETH Zürich
The State of the Art for Forwarding Lookups
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)
Patricia tries Hardware solutions - Content Addressable
Memories (CAM)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 40 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 – 41 ETH Zürich
… 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
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 42 ETH Zürich
Router Architecture
Single-CPU/Shared Bus Router
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 43 ETH Zürich
Router with one Card per Port
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 44 ETH Zürich
Today: Switch-based Router
Durchschaltenetz(switch fabric)
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
Steuerung
Paketverarbeitung
Router & Switchcontrol
Line if cards Line if cards
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 45 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 – 46 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)•
Restrictive Metrics (available bandwidth)•
)linkmetric()path(metric i
))link(metric()path(metric iMin
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 47 ETH Zürich
Static Routing
Routing tables configures by administrator. Most stable “routing protocol”. Only applicable in very small and simple networks.
C
A B
D1
2
Forwarding Table Node C
Dest Port Distance A 1 1 D 2 1 B 1 2 B 2 2
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 48 ETH Zürich
Distance Vector Routing
Distributed variant of the “Bellman-Ford” algorithm. Distributes reachability and metric information.
A
B
C
D
13
3
1
1
Dest. Port/CostA A/3C -/0D D/1
Dest. Port/CostA A/3B A/4C A/6D A/4C -/0D D/1
Dest. Port/CostA A/3B A/4C -/0D D/1
Dest. Port/CostA A/3B A/4C -/0A D/2B D/3C D/2D D/1
Dest. Port/CostA D/2B D/3C -/0D D/1
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 49 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 – 50 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 – 51 ETH Zürich
Routing in the Internet
Autonomous Systems:• Administered by a single authority.• Implements a single routing policy.• Has a unique identifier (AS number).
Interior Gateway Protocols (IGP),OSPF, RIP, ...
Exterior GatewayProtocols (EGP),BGP4
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 52 ETH Zürich
ATM Routing: Schematic Overview
Callee
Caller
Setup
Setup
Connect
Connect
Routing decision
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 53 ETH Zürich
Signaling and Interfaces
PublicATM
PrivateATM
PublicATM
PrivateATM
Private NNI(B-ICI)
PublicUNI
PrivateUNI
Public UNI
PrivateNNI
ILMI
ILMI
NNI Network Node InterfaceUNI User Network InterfaceILMI Integrated Local Management InterfaceB-ICI Broadband-Inter Carrier Interface
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research CM I – 54 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 – 55 ETH Zürich
References
• 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