Title: CRIO: Scaling IP Routing with the Core Router-Integrated Overlay
1CRIO Scaling IP Routing with the Core
Router-Integrated Overlay
- Xinyang Zhang Paul Francis Jia Wang
Kaoru Yoshida
2Outline
- CRIO Introduction
- CRIO Architecture
- CRIO Evaluation
- Related Works Conclusion
3CRIO Introduction
- The Scaling Problem
- CRIO Approach
- Tunneling
- Virtual Prefix
4The Scaling 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
This talk is about the static characteristics of
the scaling Validity of CRIO approach
- 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?
5CRIO Approach
- Tunneling
- Revisit old idea (1996 by Deering, original by
Bob Hinden and Robert Elz) - Decouples addressing from topology
- Virtual Prefix
- Novel approach
- Greatly shrink forwarding table
6Tunneling
Prefix TE Source
Mapping Adv. 24.1.1.0/24 TEPE2
Prefix TE Source
PE2 ---- BGP
24.1.1.0/24 ---- BGP/OSPF
24.1.1.0/24 PE2 Mapping
24.1.1.0/24 PE3 Mapping
Provider Networks
PE2
PE1
24.1.1.1
PE2
24.1.1.1
PE3
24.1.1.1
Routing Adv. 24.1.1.0/24 NHCE2
CE2
CE1
Customer Site C2 24.1.1.0/24
Customer Site C1
7Tunneling 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
8Forwarding Table Problems
- 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
9Virtual 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
Customer Site
PE1
CE2
Prefix TE Source
PE2 ---- BGP
PE3 ---- BGP
24.1.1.0/24 PE2 Mapping
24.0.0.0/8 ---- BGP
10Virtual Prefix Tradeoff
- Virtual prefixes provide a tuning knob for the
router - trade-off forwarding table size for path length
- Per-prefix basis
- Its a good trade-off to make
- Few prefixes handle most traffic
- 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
11CRIO Evaluation
- CRIO Static Analysis
- Data Collection
- Forwarding Table Content
- Virtual Prefix Placement Policy
- Simulation Results
- Global Internet
- VPN
- CRIO Dynamics
12CRIO Static Analysis
- Evaluate the static performance of CRIO by
simulation - Table Size VS. Path Length
- Simulated both Global Internet and VPN
- Simulation tool C-BGP
13Data Collection
- Global Internet
- Topology
- POP-level from RocketFuel
- 23 Tier-1 ISP, 1219 POPs, 4159 inter-POP links
- Mappings
- Derived ltprefix, TEgt mappings from RocketFuel raw
traces - Internet Traffic Matrices
- Prefix-level, across all POPs
- Use Netflow records from Tier-1 ISP backbone
- VPN
- Data is from a large VPN provider and one of its
national-sized customers
14Forwarding 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
Customer Site
PE1
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
15Virtual 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
24.1.1.0/24
PE1
Customer Site
CE2
16Results Global Internet
- Path-length vs. Table-size
- 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
Increase the percentage of shortest path
traffic by increasing of Path-Shrinking Entries
99 Traffic uses shortest path
17Results VPN
- 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
18CRIO Dynamics
- Routing Policy BGP ? Mapping tables
- Distribute mapping is simpler
- Mapping entry it is the same anywhere
- CRIO affords two benefits to BGP operation
- Fewer entries
- More stable entries
- Mapping table distribution ways
- BGP new attributes
- A separate overlay infrastructure
19CRIO Conclusion
20Conclusion
- 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
21Future 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
22 Thanks!