1. High performance recursive DNS solution
Peng Zuo

2. Agenda
Introduction to recursive resolver
Problems of the recursive resolver
SDNS-R: High-performance recursive DNS solution

3. How DNS works User opens browser, enters URL Browser now has IP
Recursive resolver
Browser sends HTTP request to web server
web server sends HTML data stream
Browser renders HTML data

4. DNS Server Types DNS Server: a server that answers DNS queries.
Functional Differences
Authoritative DNS Server
Caching DNS Server/Recursive DNS Server
Forwarding DNS Server
Relational Differences
Primary and Slave Servers
Public and Private Servers

5. Ask example server @ ns.example.cn (+ glue)
DNS Server Types
root-server
A ?
Add to cache
Ask cn server (+ glue)
Recursive Resolver
Stub
Resolver
A ?
A ?
gtld-server
Ask example ns.example.cn (+ glue)
A ?
example-server +
Properties of the recursive DNS
Maintains a cache of recently request data
Access to the entire range of DNS world
Combination of forwarding DNS and recursive DNS
Forwarding
DNS server
Recursive
DNS server

6. Agenda
Introduction to recursive resolver
Problems of the recursive resolver
SDNS-R: High-performance recursive DNS solution

7. Security Issue Various DDoS attack Cache poisoning (Kaminsky attack)
Amplification attack

8. Nxdomain flood ? ? ? ? Recursive DNS Authoritative DNS Botnet
jgalk.dsjgdgasg.cn ? ?
5jt.d5t53g.43t.net ?
53sas.kdjgsjals.com ?
325jkdngoug.cn
Recursive
DNS
Authoritative
DNS
Botnet
The recursive server
is running out of
available resource!!
randomly generated
subdomain strings
Cache

9. DNS Server Types CDNs depend on user’s DNS to direct requests
Remote DNS services break this assumption

10. Agenda
Introduction to recursive resolver
Problems of the recursive resolver
SDNS-R: High-performance recursive DNS solution

11. SDNS-R: High performance Recursive DNS
Cache
Forward
Log
RCM
New design and architecture
Support DNS view
High performance
Cache  performance is about 100 times higher than  common DNS server
Forward  performance is about 10 times higher than  common DNS server
High Performance DNS Engine
Operation System
Common DNS server
SDNS-R
Cache performance (QPS)
30,000 ~ 150,000
10,000,000
Forward performance (QPS)
5,000 ~ 15,000
50,000 + +

12. Benefits
DNSSEC traffic grows up sharply
The average traffic is up to about 4.5 times
The size of None-exist domain response message is up to about 12 times larger
Larger
Bandwidth
10,000,000 = 100 * 100,000
Internet
Reduce cost significantly
Mitigate Nxdomain flood attack
Easy to maintain
Anti-attack device
10GE
More Servers & More cabinets in IDC room
A DNS node with 10 Gb bandwidth
2 SDNS-R
100 common DNS servers ……
Higher Cost
100,000 QPS per server
10,000,000 QPS per server

13. Improvement of view function
view: A powerful and useful feature of BIND 9 that lets a name server answer a DNS query differently depending on who is asking.
Configuring a large number of DNS views uses more device memory and more processor time.
SDNS-R improves view function:
Speed up DNS view lookup
Reduce time complexity of DNS view lookup
Lower memory consumption
optimized data structure and algorithm
Expand the use of View function:
from IP to IP + domain

14. Architecture of a public DNS
Example: A public DNS consists of SDNS-R
Recursive
DNS server
Forwarding
DNS server
User in Beijing
Beijing
Public DNS
User in Shanghai
Shanghai
Hongkong
User in Hongkong
Suboptimal route
Guangzhou

15. Thanks!