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Copyright 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.Presentation_ID.scr 1
1Presentation_ID 1999,CiscoSystems,Inc.
Introductions to ISPDesign FundamentalsIntroductions to ISP
Design Fundamentals
2Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
AgendaAgenda
Rational Behind ISP Network Design
Point of Presence Topologies
Adding Services to the Architecture
Impact of Services on the Network
3Presentation_ID 1999,CiscoSystems,Inc.
Rational Behind ISPNetwork Design
Rational Behind ISPNetwork Design
Layers upo n Layers upon Layers
upo n L ayers ...
Layers upo n Layers upon Layers
upo n L ayers ...
3Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com 4Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
The Free On-line Dictionaryof Computing
The Free On-line Dictionaryof Computing
Architecture:Design; the waycomponents fit together;
it may also be used for anycomplex system, e.g. software
architecture, networkarchitecture
5Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Network Design andArchitecture
Network Design andArchitecture
can be critical
can contribute to the successof the network
can contribute to the failure
of the network
6Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
No amount of magicknobs will save a
sloppily
designed networkPaul FergusonConsulting Engineer,
Cisco Systems
Fergusons Law ofEngineering
Fergusons Law ofEngineering
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7Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
What Is a Well-DesignedNetwork?
What Is a Well-DesignedNetwork?
One that takes into considerationsome main factors
3 Topological/protocol hierarchy
3 Redundancy
3 Addressing aggregation (IGP and BGP)
3 Scaling
3 Policy implementation (core/edge)
3 Management/maintenance/operations
3 Cost8Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
One Must Acknowledge thatOne Must Acknowledge that
Two different worlds exist
3One world revolves around privateorganizational networks and anotherconcerns the global Internet
Growth in the Internet is faster thanany other technology introduced to
the public-at-large
9Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Source: Forbes Magazine July 7th 1997
Internet
CellPhone
PC
TV
Radio
MicrowaveMicrowave
VCR
Airplane
TelephoneTelephone
Car
Electricity
Technology AdoptionTechnology Adoption
10Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
If yo u re not scared yet ,
you don t und ers tand the
prob lem!
Mike ODellChief Scientist,
UUnet
Scaling is the #1 Problem onthe Internet
Scaling is the #1 Problem onthe Internet
11Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Core Influences to ISP DesignCore Influences to ISP Design
Modular Design
Functional Design
Tiered/Hierarchical Design
Multiple Levels of Redundancy
Routing Protocol Hierarchy
Build for IP Forwarding First - thenadd services
12Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Modular DesignModular Design
Backbone linkto another PoP
Backbone linkto another PoP
Nx64customer
aggregation layer
Nx64 leased line circuit deliveryChannelised T1/E1 circuits
T1/E1 leased line circuit deliveryChannelised T3/E3 circuits
NetworkOperations
Centre
Consumer
DIALAccess
OtherISPs
Consumer Cable
andxDSL Access
Networ k
Core
ISP Services(DNS,Mail,News,
FTP,WWW)
HostedServices
NxT1/E1 customeraggregation layer
Organize the Networkinto separate andrepeatable modules
3Backbone
3POP
3Hosting Services
3 ISP Services
3Support/NOC
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13Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Functional DesignFunctional Design
One Boxcannot do everything! (no materhow hard people have tried in the past)
Each router/switch in a network has awell-defined set of functions.
The various boxes each with afunction interact with each other.
ISP Networks are a systemsapproachto design.
14Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Tiered/Hierarchical NetworkDesign
Tiered/Hierarchical NetworkDesign
Access Layer
Distribution
Layer
OtherRegions
OtherRegions
Other
Regions
Core Flat - MeshedTopologies havenot scaled.
Hierarchy is usedin network designsto scale thenetwork.
15Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Intra-POP Interconnect
Border
Backbone
Access
Multiple Levels of RedundancyMultiple Levels of Redundancy
Triple Layered POPRedundancy
3 Lower-level failures are better
3 Lower-level failures may triggerhigher-level failures
3 L2: Two of everything at
3 L3: IGP and BGP provideredundancy and load balancing
3 L4: TCP re-transmissionsrecovers during the fail-over
POP IntraconnectPOP Intraconnect
16Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Multiple Levels of RedundancyMultiple Levels of Redundancy
PoP
BackbonePeer
Networks
ResidentialAccess
LocationAccess
Objectives -
3 As little user visibility of a fault as possible
3 Minimize the impact of any fault in any part of the
network.
3 Network needs to handle L2, L3, L4, and Router
failure
17Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Hierarchy of RoutingProtocols
BGP4
and OSPF/ISIS
FDDI
Other ISPs
CustomersLocal
IXP
BGP4 Static/BGP4
BGP4
18Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
WarningWarning
Beware Block Diagram/Slideware
Design Gurus! They have gottenpeople and networks into trouble- including Cisco
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19Presentation_ID 1999,CiscoSystems,Inc.
Point of PresenceTopologies
Point of PresenceTopologies
19ISP/IXPWorkshops 1999,CiscoSystems,Inc. www.cisco.com 20Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
PoP DesignPoP Design
Core Backbone
Routers
POP
Interconnect
Medium
NeighboringPOP
NeighboringPOP
Dedicated Access PSTN/ISDN
Core 1 Core 2
SW 1 SW 2
Access 1 Access 2 NAS 1 NAS 2
External BGP Peering
21Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
45 Mb/s
HSSI
FDDI
InternetInternetBackboneBackbone
Early Internet POPArchitecture - NSPEarly Internet POPArchitecture - NSP
3Backbone trunksat 45 Mb/s
3Shared mediainterconnectwithin POP:
FDDI, Ethernet, Switched
Ethernet
3ConventionalT3 backbone
Internet router22Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
155 Mb/s
POS/ATM
XX
InternetInternetBackboneBackbone
3Backbone trunksat 155 Mb/s
Packet over SONET OC3
ATM OC3
3Switched interconnectwithin POP:
Switched FDDI/Fast Ethernet
ATM OC3
3Advanced OC3 backboneInternet router
Internet POP Architecture -96/97
Internet POP Architecture -96/97
23Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
622 Mb/s
POS/ATM
622 Mb/s ATM
1 Gb/s Ethernet
Duplex Fast E, 155/622 Mb/s ATM, or
1 Gb/s Ethernet
InternetInternetBackboneBackbone
3Backbone trunks at
622 Mb/sPacket over SONET OC12
ATM OC12
3Switched interconnect
within POP:ATM at OC3 AND OC12
Ethernet Channel
Gigabit Ethernet (early 98)
POSIP (late 98)
3Gigabit OC12 backbone
Internet router
Internet POP Architecture -97/98
Internet POP Architecture -97/98
24Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
SRP Rings - High Speedof SDH combined with fastfailover and redundancy
3High bandwidth3Reduced port counts
3Reduced complexity
3Proactive self healing
Backbone
7xxx
GSRGSR
7xxx
7xxx
7xxx
7xxx
leased l ine aggregation
Internet POP Architecture -99/01
Internet POP Architecture -99/01
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25Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Large POPs - add a 3rd layerLarge POPs - add a 3rd layer
InternetInternetBackboneBackbone
3
Problem: port density!3 Solution: buy more routers!
3 Customer routers connect toaggregation routers
Packet over SONET OC3
ATM OC3
3 Aggregation routers connect tobackbone routers
3 Scales nicely
3 X CRs to Y ARs to Z BRs
3...where X>Y>Z
3Be careful not tooversubscribe!
OC3
OC12
OC48
26Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
FDDI100Mbps
POSN x 155
SRP
2 x 622Mbpsor 2x2.5GB
Fast/Gig Ethernet100/1000Mbps
POP Interconnect SummaryPOP Interconnect Summary
27Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Key Design Principles
Interconnection forManagement, Security,and Accounting services
3Netflow Devices -
FlowCollector
3Syslog collector for all
network devices
3SNMP collector (PC BasedUNIX)
3Security Auditing Tools(NetSonar)
POS
POS & ATM for Core Backbone
GSRGSR
75077507
Customer and Services
Management
&
Accounting
28Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
ISP routing Architectures - IPISP routing Architectures - IP
IGP = EIGRP, IS-IS,or OSPF
3 a lmo s t a l wa y s IS-IS or OSPF
3 IS-IS, single level (usually L2)
3 OSPF, either single area or BB/POPareas
BGP = all routers in full mesh
3 mesh accomplished with routereflectors, confederations, actual full
mesh
All routers have all routes, so
services could go anywhere
29Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
ISP routing Architectures -IP+MPLS
ISP routing Architectures -IP+MPLS
IGP = EIGRP, IS-IS,or OSPF
3 mus t be IS-IS or OSPF to use MPLSTE
BGP = only edge routers need full routes
3 full-mesh of edge routers using
aforementioned mechanisms
3 packets are forwarded via LDP
labels, not IP destination address
Where to put your services?
3 cannot hang a cache service off of arouter that doesnt have full routes!
30Presentation_ID 1999,CiscoSystems,Inc.
Adding Services to the
Architecture
Adding Services to the
ArchitectureCause and EffectCause and Effect
3015030925_04F9_c1 1999,CiscoSystems,Inc.
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31Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Services?How many Services?
Services?How many Services?
Edge (one-time) services
Voice over IP
MPLS VPNs
CDNs
VPDNs
Managed services
DialDSLcable
Per-hop services
MPLS packet forwarding
DiffServ, other QoS
Multicast Services
Most network services are applied at the edge!
32Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Ask the Right QuestionsAsk the Right Questions
What is the value of the service?3Technical merit
3Cost savings
3Marchitecture
What is the cost of the service?
3Equipment?
3Training people to support it?
3Network buildouts/topology changes?
33Presentation_ID 1999,CiscoSystems,Inc.
Impact of Services onthe Network
Impact of Services onthe Network
3315030925_04F9_c1 1999,CiscoSystems,Inc. 34Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Who Knows?Who Knows?
What will be the impact on existing trafficloads/patterns?
Can the network deliver the performancethat your customers/applications desire?delay? jitter (delay variation)?
Make sure to add capacity as you addservices - bandwidth is a must.
35Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Deployment of New ServicesDeployment of New Services
Is more of a business decision
The technical aspect is to ensurecontinued network performance
scalability and stability
Try to keep services within your AS
3end2end control
3less likelihood of failure/flaps
36Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Deploying New ServicesDeploying New Services
Dont feed the hype fire
Look beforeyou leap!
Dont deploy new technologies andservices just for the sake of it; havevalid business and technical reasons
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37Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Deploying New ServicesDeploying New Services
Usually a Service requires a TCP/UDPtermination (I.e. TCPs three wayhandshake)
Termination should happen out side
of the pr imary f low path
Otherwise, the network is thendesigned around the single service.
38Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Deploying New ServicesDeploying New Services
CPECPE POPPOP CORECORE
MultiplePOP Services
Interconnect Leased Core
ISDN
POTS
Lease LineCable
xDSL
Access
Primary Packet Flow
Service
TerminateHere
39Presentation_ID 1999,CiscoSystems,Inc.
TransparentRedirection of a Flow
in the POP
TransparentRedirection of a Flow
in the POPFactors that went into the
design of WCCP
Factors that went into the
design of WCCP
39Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com 40Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Design Objectives for the ISPDesign Objectives for the ISP
Transparent Redirec t ionof a IP flowbased on source, destination, and/orport number.
Transparent In tegrat ion- norebuilding the POP to add this
service.
Failed open - if the service fails, itshould not effect the core IP servicenor any other services.
41Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Design Objectives for the ISPDesign Objectives for the ISP
CPECPE POPPOP CORECORE
Interconnect Leased Core
ISDN
POTS
Lease LineCable
xDSL
Access
Primary Packet Flow
WCCPService
Clusters
Not to effect the primary packet flow of thePOP - if not redirected - then is CEF/dCEFSwitched!
42Presentation_ID 1999,CiscoSystems,Inc. www.cisco.com
Design Objectives for the ISPDesign Objectives for the ISP
CPECPE POPPOP CORECORE
Interconnect Leased Core
ISDN
POTS
Lease LineCable
xDSL
Access
WCCP
ServiceClusters
Work with the multi-level L2/L3 redundancyof the ISP POP. Equal paths in the IGP +CEF leads packet asymmetry.
Input PortWCCP
Redirect
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