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Mobile IPMobile IPLessons LearnedLessons Learned

The early yearsThe early years

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Who needsWho needsMobile IP anyway?Mobile IP anyway?

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A Word from the Nay SayersA Word from the Nay Sayers

• “Nomads” don’t have any problems today

• Dynamic addressing works just fine

• We don’t have enough v4 addresses as it is

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Cellular MobilityCellular Mobility

• User can handover mid flow

• Simplifies layer 2 macro mobility

• Easier to manage than dynamic address pools

• Important part of 3G standards

• Cleaner user experience

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Multiple Media NetworksMultiple Media Networks

• Cost based network selection

• Go between 802.11, cellular, satellite, etc

• Supported in Cisco’s IOS Mobile Network

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ClientsClients

Host deviceHost device ProsPros ConsCons

Terminal Terminal BasedBased

Laptops, Laptops, PDAs, etcPDAs, etc More featuresMore features Hard to deploy Hard to deploy

and manageand manage

Embedded Embedded ProxyProxy

Handset, Handset, Network Network Access pt.Access pt.

Transparent to Transparent to attached clients, attached clients, Easier to manageEasier to manage

Tied to media, Tied to media, fewer features, fewer features, less securityless security

Mobile Mobile RouterRouter

RouterRouterClients not Clients not mobile, Central mobile, Central ManagementManagement

Harder to Harder to provision and provision and deploydeploy

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InfrastructureInfrastructure

What you really need toWhat you really need toknow to keep your job.know to keep your job.

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SAM, An Engineer’s Best FriendSAM, An Engineer’s Best Friend

• Scalability – Bigger is better

• Availability – Uptime is king

• Manageability –Knowledge is power

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ScalabilityScalability

• Maximum number of users per box

• Number of users per rack

• Max Users Throughput, registration rate & memory

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Did you know…Did you know…

• …there is a significantly higher proportion of signaling traffic to user traffic required for mobility management than traditional dynamic IP routing

• That’s why we use Mobile IP. Traditional routing protocols would not scale with the quantity and frequency of mobility updates

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Registration RatesRegistration Rates

• Even with large foreign agent provinces each user may reregister every 1-2 hours

• 1 million users reregistering every 2 hours is ~140 registrations per second.

• With 200k users per HA that’s 28 registrations per second

Province – The Province – The geographic geographic area covered area covered by a single by a single foreign agent foreign agent interfaceinterface

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AAA requirementsAAA requirements

• Every registration requires a Security Association lookup

• SAs can be stored locally or in a AAA server

• How do you handle 140 queries per second per million users?

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AAA Deployment strategiesAAA Deployment strategies

ProsPros ConsCons

CentralizedCentralized Easy to manage and Easy to manage and provisionprovision

Hard to scale, Hard to scale, Latency can be a Latency can be a problemproblem

DistributedDistributed No WAN concerns No WAN concerns or latency problemsor latency problems

Hard to plan, Hard to plan, manage, deploy and manage, deploy and provisionprovision

Central + Central + CacheCache

Best of both worldsBest of both worlds Cache Management Cache Management ProblemsProblems

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Tunnel requirementsTunnel requirements

• 1 tunnel per Foreign Agent

• 1 tunnel per co-located care of address

• Tunnels can limitscalability

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AvailabilityAvailability

• Uptime is king

• 100% SYSTEM uptime is the goal

• Remember, system uptime is not box uptime

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HA AvailabilityHA Availability

• MN does not learn about HA failure until re-registration

• Bindings are stateful

• HA usually hosts a large number of subscribers

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Cisco’s HA RedundancyCisco’s HA Redundancy

• Built on HSRP

• Replicates bindings in near real time

• Transparent to Mobile Node

• Bindings AND cached Security Associationsare replicated

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ManageabilityManageability

• Fast response tooutages

• Capacity Planning

• Performance management

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RFC 2006 MIBRFC 2006 MIB

• Good fault management support

Total and per user counters for registrations and errors

• Poor capacity/performance management support

Must iterate through the binding table to count bindings

• Cisco MIB supports enhanced features

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Extracting Performance dataExtracting Performance data

• HA Registration throughput and performancehaRegistrationAccepted & haRegRepliesSent vs time

faRegRepliesRelayed & haRegRepliesSent vs time

• FA Registration throughput and performancefaRegRequestsReceived & faRegRequestsRelayed vs time

faRegRepliesRelayed & faRegRepliesRelayed vs time

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Internet DeploymentInternet Deployment

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Realities of MIP DeploymentRealities of MIP Deployment

• The Internet was designed to support Broadband and Dial-up

• Security concerns force tight network implementation

• Mobility doesn’t fit naturally

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Ingress filteringIngress filtering

• A “classic” problem in MIP

• Network designers block incoming traffic with an internal source address

• Unicast RPF is probably a more dangerous problem

• Reverse Tunnels offer a solution

HA

Internet

10.1.2.0

10.1.2.45

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Ingress filteringIngress filtering

• A “classic” problem in MIP

• Network designers block incoming traffic with an internal source address

• Unicast RPF is probably a more dangerous problem

• Reverse Tunnels offer a solution

HA

Internet

10.1.2.0

10.1.2.45

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Path MTU DiscoveryPath MTU Discovery

• Many network designers block all inbound ICMP

• Triangle routing causes problems not normally seen

• TCP Session opens, but “hangs”

• Windows support “black hole detection”

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WAP MTU length problemsWAP MTU length problems

• WAP relies on IP fragmentation

• Fragmentation occurs at WAP gateway servers MTU

• Fragments can’t be fragmented

• Gateway MTU must be <= path MTU including tunnel

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Private AddressingPrivate Addressing

• Good for “Walled Gardens”

• Large Scale NATcan be difficult

• No support for overlapping addresses in the FA

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It is worth it!It is worth it!

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Don’t WorryDon’t Worry

A Mobile IP network is just as easy to build as any IP network. There are just a few new rules.

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Sweet RewardsSweet Rewards

• Seamless IP connectivity

• Transparent user experience

• Limitless Possibilities

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Are you Ready?Are you Ready?

• There are plenty of challenging problems ahead, but the reward is great.

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Fire Away?Fire Away?

• Questions?