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CRIO: Scaling IP Routing with the Core Router-Integrated Overlay. Xinyang (Joy) Zhang Paul Francis Jia Wang Kaoru Yoshida. Internet Architecture Board Routing Workshop (Oct 2006).

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crio scaling ip routing with the core router integrated overlay

CRIO:Scaling IP Routing with the Core Router-Integrated Overlay

Xinyang (Joy) Zhang Paul Francis Jia Wang Kaoru Yoshida

internet architecture board routing workshop oct 2006
Internet Architecture BoardRouting Workshop (Oct 2006)
  • It was clear at the workshop, and probably clearly evident elsewhere, that if there is a highest ranked “problem” in the routing space then it would be that of scaling the routing system
  • It appears that unbounded continued growth of the routing and forwarding system in the Internet appears to trigger off some real limitations relating to hardware design and switching centre infrastructure

---- Geoff Huston

why is scaling a problem

200K

Active BGP entries (FIB)

0

89

06

Date

Why is Scaling a Problem?
  • A glimpse of current routing system:
    • Static table size
      • Global IPv4 : ~ 200K entries
      • VPN: ~800K entries
      • And more routes are coming: IPV6, traffic-engineered, etc.
    • Routing Dynamics
      • BGP update churns
      • Persistent instabilities
      • Long convergence time (due to damping and MRAI timer)
  • Looking into the future:
    • Can we support a routing table twice (or 10 times) the size of today?
    • Can we rely on the hardware advances to alleviate the scaling pressure?
  • This talk is about the static
  • characteristics of the scaling
  • Validity of CRIO approach
crio s approach to scaling
CRIO’s Approach to Scaling
  • Tunneling
    • Revisit old idea (by Deering)
    • Decouples addressing from topology
  • Virtual Prefix
    • Novel approach
    • Greatly shrink forwarding table
crio tunneling an illustration
CRIO Tunneling: an Illustration

Prefix TE Source

Mapping Adv.

24.1.1.0/24

TE=PE2

PE2 ---- BGP

Prefix TE Source

24.1.1.0/24 PE2 Mapping

24.1.1.0/24 ---- BGP/OSPF

24.1.1.0/24 PE3 Mapping

Provider Networks

PE1

PE2

24.1.1.1

PE2

24.1.1.1

PE3

24.1.1.1

Routing Adv.

24.1.1.0/24

NH=CE2

CE1

CE2

Customer Site C2

24.1.1.0/24

Customer Site C1

crio tunneling benefits
CRIO Tunneling: Benefits
  • Separate Mapping from Routing
    • BGP only computes routes to TE prefixes
      • On the order of one thousand entries
      • Stable ISP provisioned prefixes
    • Mappings are easy to distribute
      • A mapping entry is the same no matter where it appears
    • Support multi-homing without burdening the routing system
what about router s forwarding table
What about router’s forwarding table?
  • CRIO tunneling can not shrink forwarding information
  • Forwarding table is expected to get larger
    • Since CRIO supports for fine-grained multi-homing
  • Benefits for having small forwarding tables
    • Smaller memory requirement on routers’ line cards
    • Faster transfer for forwarding table updates
crio virtual prefix an illustration
CRIO Virtual Prefix: an Illustration
  • A virtual prefix is a super-prefix that spans a large portion of the address space
  • Routers that advertise a given virtual prefix must hold the mappings for every prefix within the virtual prefix

Prefix TE Source

Routing Adv.

24.0.0.0/8

PE2 ---- BGP

24.1.1.0/24 PE2 Mapping

24.2.2.0/24 PE4 Mapping

PE3

24.1.1.1

PE2

PE2

24.1.1.1

24.1.1.0/24

24.1.1.1

PE1

Customer

Site

CE2

Prefix TE Source

PE2 ---- BGP

PE3 ---- BGP

24.0.0.0/8 ---- BGP

24.1.1.0/24 PE2 Mapping

24.2.2.0/24 PE4 Mapping

crio virtual prefix trade off
CRIO Virtual Prefix: Trade-off
  • Virtual prefixes provide a tuning knob for the router
    • trade-off forwarding table size for path length
    • Per-prefix basis
  • It’s a good trade-off to make
    • Few prefixes handle most traffic (power law)
    • Routers could shed most of their prefixes with very little overall increase in traffic volume
    • Save routers from handling large amount of mapping updates
  • Virtual Prefix is particularly suitable for VPNs
crio evaluation static analysis
CRIO Evaluation: Static Analysis
  • Evaluate the static performance of CRIO by simulation
    • Quantify table size vs. path length tradeoff
    • Simulated both Global Internet and VPN
      • Based on actual Internet topology & ISP traffic matrices
    • Simulation tool: C-BGP
crio evaluation data collection
CRIO Evaluation: Data Collection
  • Global Internet
    • Topology:
      • POP-level from RocketFuel
      • 23 Tier-1 ISP, 1219 POPs, 4159 inter-POP links
    • Mappings:
      • Derived <prefix, TE> mappings from RocketFuel raw traces
    • Internet Traffic Matrices:
      • Prefix-level, across all POP in our topology
      • Use Netflow records from Tier-1 ISP backbone
  • VPN
    • Same data is collected for VPN from a large VPN provider and one of its national-sized customers
crio evaluation forwarding table content

PE2

CRIO Evaluation: Forwarding Table Content
  • Direct Entries
  • Virtual Prefix Entries
  • “Extra” Path-Shrinking Entries

Routing Adv.

24.0.0.0/8

Prefix TE Source

PE2 ---- BGP

PE3

24.1.1.0/24 PE2 Mapping

24.1.1.0/24

PE1

Customer

Site

CE2

Prefix TE Source

Prefix TE Source

PE2 ---- BGP

24.1.1.0/24 ---- BGP

PE3 ---- BGP

24.0.0.0/8 ---- BGP

24.1.1.0/24 PE2 Mapping

crio evaluation virtual prefix placement policy

Prefix TE Source

Prefix TE Source

PE2 ---- BGP

PE2 ---- BGP

24.1.1.0/24 PE2 Mapping

24.1.1.0/24 PE2 Mapping

PE3

PE2

PE4

Prefix TE Source

Prefix TE Source

Prefix TE Source

24.1.1.0/24 ---- BGP

PE3 ---- BGP

PE4 ---- BGP

24.0.0.0/8 ---- BGP

24.0.0.0/8 ---- BGP

CRIO Evaluation: Virtual Prefix Placement Policy
  • Inter-ISP (Random)
  • Intra-ISP
  • Intra-ISP shortest customer path

Routing Adv.

24.0.0.0/8

Routing Adv.

24.0.0.0/8

Provider 2

Provider 1

PE1

24.1.1.0/24

Customer

Site

CE2

crio global internet simulation results
Path-length vs. Table-size Trade-off

Virtual Prefix does increase the path length

Average path length converges quickly as the # path-shrinking entries increases

Reduce FIB size by 3-5 times with very little path length penalty

CRIO Global Internet Simulation Results

Increase the percentage of shortest path traffic

by increasing # of Path-Shrinking Entries

99% Traffic uses shortest path

crio vpn simulation results one customer
CRIO VPN Simulation Results (One Customer)
  • Hub-Spoke nature of VPN traffic exploits the tradeoff better
  • Reduce table size by 10-20 times with very little path length penalty

Cumulative Distribution of PE Routers

PE Routers

In Hub Sites

conclusions
Conclusions
  • CRIO is a new routing architecture, aimed to provide
    • Scalable and stable core routing
      • Reduce BGP RIB by two order of magnitude
    • FIB size reduction
      • Reduce FIB by one order of magnitude for global Internet, 10-20x for VPN
future work
Future Work
  • Design and implement the mapping distribution infrastructure
  • Study the dynamics aspect of CRIO
  • Study the security aspect of CRIO
  • Explore the use of CRIO to provide traffic engineering for multi-homed site
  • Address (??) new management challenges
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