Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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Panel on Intra-domain Routing

WIRED 2003

Workshop on Internet Routing Evolution and Design

Aman Shaikh

University of California, Santa Cruz (UCSC)

AT&T Labs - Research

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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Where are we?• OSPF, IS-IS, RIP, EIGRP (Cisco only)

– OSPF and IS-IS are reasonably well-understood• After all, just Dijkstra … (do I see a few smiles around?)

– RIP: Who’s using it?

– EIGRP• Large user-base: Cisco can tell us…

• Vendors have worked pretty hard on their implementation– Good interoperability

– Robust code

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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What’s hot right now?• Super-fast convergence

– Millisecond range?

– Mostly focused on OSPF, IS-IS• Lower the timers

• Super-efficient, super-scalable routing calculations (=

Dijkstra)

• But not at the cost of decreased stability– Use dampening for flapping elements

– Bad news is bad; good news might be good

• Will we achieve the holy-grail of supporting all kinds of services on IP networks?

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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What issues need to be addressed?• IGP usage in real-networks

• Configuration

• Trouble-shooting

• Interface with inter-domain routing

• New protocols and technologies

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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IGP Usage in Real Networks• Real networks use IGPs in variety of ways

– Have led to quite a few hacks in IGPs• Example:

– Stub areas to limit number of routes in an OSPF area

– Not-so-stubby-areas (NSSAs) to limit “all-but-some” routes into an OSPF area

– Cisco has two more options: total stubby, NSSA total stub

– Multiple protocols within a single domain• Redistribution of routes from one to another

– Redistribution of BGP routes into IGPs• Can IGPs scale?

• Need to look at enterprise networks

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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Configuration• Quite a few knobs to play with

– Hierarchical routing• Example (OSPF/IS-IS):

– Is “At most ‘n’ routers/area” a good rule?

– Do we even need areas or we can do away with them by more efficient and scalable implementations?

– Timers• session management

• routing calculation

• route-update propagation

– Weight assignment• Traffic engineering, load-balancing

• Impact on BGP

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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Trouble-shooting• Need tools for monitoring protocols

– OSPF and IS-IS are amenable to monitoring• OSPF/IS-IS monitoring products from PacketDesign

and IPSUM

• Research prototypes at AT&T and Sprint

– How to tackle EIGRP and RIP?

• Real-time analysis for early identification of problems– Often problems slowly deteriorate performance

• Post-mortem analysis

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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Interface with Inter-domain Routing• BGP uses IGPs for various things:

– Forwarding:• To select closest exit-point (hot potato routing)

• To determine the path to the exit-point

– Control-plane:• I-BGP sessions are routed over IGPs

• Is this the right interface?– Does this provide right amount of separation?

• Example: why is BGP’s notion of “close-ness” equal to IGP path cost?

Aman Shaikh WIRED Panel on Intra-domain Routing

UCSC

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New Protocols and Technologies• MPLS/LDP

– Can call them layer 2.5, but that does not mean we do not have to address…

• change in the forwarding paradigm and its impact– label-switching instead of longest-prefix match

– tunneling through provider backbones

• issues related to deployment, management, configuration, and operations

• interaction with IGPs and BGP

– Does the core become simpler or does it become even more complex?