The document discusses using DNS service discovery (DNS-SD) to automatically configure sFlow agents. It describes how SRV and TXT records are added to a DNS zone file to provide sFlow agent configuration settings. When sFlow agents perform DNS queries, they receive responses containing the IP addresses and ports of sFlow collectors as well as sampling settings. This allows for plug-and-play configuration of many heterogeneous clients using the widely supported DNS protocol.

1. DNS Service Discovery
Automated configuration of sFlow agents

2. Configure sFlow agents

3. Configure sFlow agents
Servers

4. Configure sFlow agents
Servers Analysis tools
Listening: 10.0.0.10 UDP port 6343
Listening: 10.0.0.11 UDP port 6343

5. Configure sFlow agents
Servers metrics Analysis tools
Listening: 10.0.0.10 UDP port 6343
Listening: 10.0.0.11 UDP port 6343

6. DNS server configuration

7. DNS server configuration
monitor.inmon.com.zone file

8. DNS server configuration
monitor.inmon.com.zone file
_sflow._udp 300 SRV 0 0 6343 10.0.0.10.
_sflow._udp 300 SRV 0 0 6343 10.0.0.11.

9. DNS server configuration
monitor.inmon.com.zone file
_sflow._udp 300 SRV 0 0 6343 10.0.0.10.
_sflow._udp 300 SRV 0 0 6343 10.0.0.11.
_sflow._udp 300 TXT (
"txtvers=1"
"sampling=400"
"sampling.http=20"
"sampling.memcache=200"
"polling=20"
)

10. DNS server configuration
monitor.inmon.com.zone file
_sflow._udp 300 SRV 0 0 6343 10.0.0.10.
_sflow._udp 300 SRV 0 0 6343 10.0.0.11.
_sflow._udp 300 TXT (
"txtvers=1"
"sampling=400"
"sampling.http=20"
"sampling.memcache=200"
"polling=20"
)
Similar to MX records for configuring mail forwarding

11. DNS server configuration
monitor.inmon.com.zone file
_sflow._udp 300 SRV 0 0 6343 10.0.0.10.
_sflow._udp 300 SRV 0 0 6343 10.0.0.11.
_sflow._udp 300 TXT (
"txtvers=1"
"sampling=400"
"sampling.http=20"
"sampling.memcache=200"
"polling=20"
)
Similar to MX records for configuring mail forwarding
MX 30 aspmx5.googlemail.com.
MX 10 aspmx.l.google.com.

12. DNS server configuration
monitor.inmon.com.zone file
_sflow._udp 300 SRV 0 0 6343 10.0.0.10.
_sflow._udp 300 SRV 0 0 6343 10.0.0.11.
_sflow._udp 300 TXT (
"txtvers=1"
"sampling=400"
"sampling.http=20"
"sampling.memcache=200"
"polling=20"
)
Similar to MX records for configuring mail forwarding
MX 30 aspmx5.googlemail.com.
MX 10 aspmx.l.google.com.
TXT "v=spf1 include:_spf.google.com ~all"

13. Test SRV query
[pp@pcentos ~]$ dig SRV _sflow._udp.monitor.inmon.com

14. Test SRV query
[pp@pcentos ~]$ dig SRV _sflow._udp.monitor.inmon.com
; <<>> DiG 9.2.4 <<>> SRV _sflow._udp.monitor.inmon.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29097
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 2
;; QUESTION SECTION:
;_sflow._udp.monitor.inmon.com.! IN! SRV
;; ANSWER SECTION:
_sflow._udp.monitor.inmon.com. 300!
IN! SRV! 0 0 6343 10.0.0.10.
_sflow._udp.monitor.inmon.com. 300!
IN! SRV! 0 0 6343 10.0.0.11.
;; AUTHORITY SECTION:
monitor.inmon.com.! ! 259200! IN! NS! ns1.monitor.inmon.com.
monitor.inmon.com.! ! 259200! IN! NS! ns2.monitor.inmon.com.
;; ADDITIONAL SECTION:
ns1.monitor.inmon.com. 259200 IN A! 10.0.0.1
ns2.monitor.inmon.com. 259200 IN A! 10.1.1.1
;; Query time: 11 msec
;; SERVER: 10.0.0.1#53(10.0.0.1)
;; WHEN: Tue Feb 21 22:58:40 2012
;; MSG SIZE rcvd: 316

15. Test TXT query
[pp@pcentos ~]$ dig TXT _sflow._udp.monitor.inmon.com

16. Test TXT query
[pp@pcentos ~]$ dig TXT _sflow._udp.monitor.inmon.com
; <<>> DiG 9.2.4 <<>> TXT _sflow._udp.monitor.inmon.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 53888
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2
;; QUESTION SECTION:
;_sflow._udp.monitor.inmon.com.! IN! TXT
;; ANSWER SECTION:
_sflow._udp.monitor.inmon.com. 300!
IN! TXT! "txtvers=1" "sampling=400" "sampling.http=20"
"sampling.memcache=200" "polling=20"
;; AUTHORITY SECTION:
monitor.inmon.com.! ! 259200! IN! NS! ns1.monitor.inmon.com.
monitor.inmon.com.! ! 259200! IN! NS! ns2.monitor.inmon.com.
;; ADDITIONAL SECTION:
ns1.monitor.inmon.com. 259200 IN A! 10.0.0.1
ns2.monitor.inmon.com. 259200 IN A! 10.1.2.4
;; Query time: 3 msec
;; SERVER: 10.0.0.1#53(10.0.0.1)
;; WHEN: Tue Feb 21 23:15:39 2012
;; MSG SIZE rcvd: 253

17. Queries and responses
sFlow agent DNS server

18. Queries and responses
sFlow agent DNS server
DNS: query SRV _sflow._udp.monitor.inmon.com

19. Queries and responses
sFlow agent DNS server
DNS: query SRV _sflow._udp.monitor.inmon.com
DNS: query response SRV 0 0 6343 10.0.0.10 SRV 0 0 6343 10.0.0.11

20. Queries and responses
sFlow agent DNS server
DNS: query SRV _sflow._udp.monitor.inmon.com
DNS: query response SRV 0 0 6343 10.0.0.10 SRV 0 0 6343 10.0.0.11
DNS: query TXT _sflow._udp.monitor.inmon.com

21. Queries and responses
sFlow agent DNS server
DNS: query SRV _sflow._udp.monitor.inmon.com
DNS: query response SRV 0 0 6343 10.0.0.10 SRV 0 0 6343 10.0.0.11
DNS: query TXT _sflow._udp.monitor.inmon.com
DNS: query response TXT txtvers=1 sampling=400 ...

22. Queries and responses
sFlow agent DNS server
DNS: query SRV _sflow._udp.monitor.inmon.com
DNS: query response SRV 0 0 6343 10.0.0.10 SRV 0 0 6343 10.0.0.11
DNS: query TXT _sflow._udp.monitor.inmon.com
DNS: query response TXT txtvers=1 sampling=400 ...
DNS time to live (300 seconds)

23. Queries and responses
sFlow agent DNS server
DNS: query SRV _sflow._udp.monitor.inmon.com
DNS: query response SRV 0 0 6343 10.0.0.10 SRV 0 0 6343 10.0.0.11
DNS: query TXT _sflow._udp.monitor.inmon.com
DNS: query response TXT txtvers=1 sampling=400 ...
DNS time to live (300 seconds)
DNS: query SRV _sflow._udp.monitor.inmon.com

24. DNS-SD features

25. DNS-SD features
• Plug and play - sFlow agents are automatically configured
at server startup and can be reconfigured at any time by
changing settings on DNS server.

26. DNS-SD features
• Plug and play - sFlow agents are automatically configured
at server startup and can be reconfigured at any time by
changing settings on DNS server.
• DNS is a basic network service - client libraries exist by
default on virtually all platforms, including embedded
systems - single configuration mechanism can be applied
to Windows, Linux, hypervisors, switches, firewalls,
routers

27. DNS-SD features
• Plug and play - sFlow agents are automatically configured
at server startup and can be reconfigured at any time by
changing settings on DNS server.
• DNS is a basic network service - client libraries exist by
default on virtually all platforms, including embedded
systems - single configuration mechanism can be applied
to Windows, Linux, hypervisors, switches, firewalls,
routers
• Leverages existing DNS infrastructure for redundancy,
security, scalability, delegated control etc.

28. When to consider DNS-SD

29. When to consider DNS-SD
• Small amount of client configuration state

30. When to consider DNS-SD
• Small amount of client configuration state
• Non-homogeneous clients

31. When to consider DNS-SD
• Small amount of client configuration state
• Non-homogeneous clients
• Dynamic environment - clients added,
moved, removed. Changing server
population.

32. When to consider DNS-SD
• Small amount of client configuration state
• Non-homogeneous clients
• Dynamic environment - clients added,
moved, removed. Changing server
population.
• Large numbers of clients

33. When to consider DNS-SD
• Small amount of client configuration state
• Non-homogeneous clients
• Dynamic environment - clients added,
moved, removed. Changing server
population.
• Large numbers of clients
• Geographically dispersed clients