1. Management Issues in ICMP (Internet Control Message Protocol)
Byungchul Park
DPNM Lab., CSE, POSTECH 1 1

2. Table of Contents Introduction ICMP functionalities MIB for ICMP
Security Vulnerabilities of ICMP
Redesign ‘Source Quench’ error report
Summary

3. Introduction (1/2) Unreliable IP protocol - “Best Effort”
What will happen if…
Packet can not find a router to go to final destination
TTL value goes 0
Fragmented packets can not reach to final destination in time
Network error
A host or router need some information from other hosts or routers

4. Introduction (2/2) Why the ICMP is needed?
Lacks of IP protocol’s functionality!!!
Unreliable and connectionless datagram delivery
Best-effort delivery service
Lack of error control and lack of assistance mechanisms
No error-reporting and error-correcting mechanisms
Lacks of mechanism for host and management queries
 ICMP has been designed to compensate for the above deficiencies

5. ICMP Functionalities (1/3)
ICMP Messages
Error-reporting
Query
Error reporting : report problems that a router or host may encounter when it processes an IP packet
Query message : get specific information from router or a host in order to help a host or network management.

6. ICMP Functionalities (2/3)
ICMPv4

7. ICMP Functionalities (3/3)
ICMPv6

8. What are the important things that need to be monitored and controlled?1 1

9. MIB for ICMP (1/2) Important functionalities
Error report
Query for network management
 Monitoring every ICMP message is meaningful in network management aspect
Example
Too many “source quench” message  network congestion?!
Too many “redirection” messages  ICMP attack?!

10. MIB for ICMPv6 - RFC2466 (2/2) ipv6IfIcmpInMsgs, ipv6IfIcmpInErrors,
ipv6IfIcmpInDestUnreachs,
ipv6IfIcmpInAdminProhibs,
ipv6IfIcmpInTimeExcds,
ipv6IfIcmpInParmProblems,
ipv6IfIcmpInPktTooBigs,
ipv6IfIcmpInEchos,
ipv6IfIcmpInEchoReplies,
ipv6IfIcmpInRouterSolicits,
ipv6IfIcmpInRouterAdvertisements,
ipv6IfIcmpInNeighborSolicits,
ipv6IfIcmpInNeighborAdvertisements,
ipv6IfIcmpInRedirects,
ipv6IfIcmpInGroupMembQueries,
ipv6IfIcmpInGroupMembResponses,
ipv6IfIcmpInGroupMembReductions

11.  How can we correct errors?
More Issues
Simple statistics information is not enough to manage every network problem
ICMP does not correct errors, it simply reports them.
Tracking every error message’s source host is important to correct errors
SNMP and MIB can not add additional information dynamically
 How can we correct errors?

12. What are existing problems with the protocol? Security Vulnerabilities1 1

13. Security Vulnerabilities (1/3)
Every ICMP message can be used for network attack
‘Echo’ and ‘Echo Reply’ messages
Echo requests can be used by an outsider to map our network
‘Destination Unreachable’ message
Blind connection-reset attack: Send a ‘Protocol unreachable’ message to a client with spoofed IP address
Path MTU discovery attack: Send ‘Fragmentation needed’ message to a client (c.f. PMTUD mechanism)

14. Security Vulnerabilities (2/3)
‘Source Quench’ message
ICMP Source Quench attack: attacker (probably combined with IP spoofing) sends this message in order to make a very effective DoS attack
‘Redirect’ message
Attacker sends this message to subvert the routing table
‘Time Exceeded’ message
Attacker can use traceroute to find out which hosts are the routers in our network

15. Security Vulnerabilities (3/3)
‘Time Stamp request & reply’ messages
Attacker can use this message to map our network (alternative to ping)
‘Address Mask request & reply’ messages
Attacker can use these messages to learn the topology of our network
These vulnerabilities caused by lack of authentication mechanism
Firewall is used for filtering ICMP messages (inbound/outbound)
Authentication mechanism should be integrated into ICMP

16. What are existing problems with the protocol
What are existing problems with the protocol? If you had to redesign the protocol from scratch, how would you do it differently, considering its manageability? 1 1

17. Source Quench Error (1/3)
Generated if the router or host does not have sufficient buffer space to process the request
Requests the sender to decrease the traffic rate of messages to a router or host (congestion control)

18. Source Quench Error (2/3)
Problems
A host or router will send source quench error messages responsible for every discarded packet (network overhead)
A host or router can not determine which host is responsible for network congestion
No mechanism to notify the end of congestion

19. Source Quench Error (3/3)
Redesign of Source quench error function
A host or router will send source quench error messages responsible for every discarded packet (network overhead)
Sending an error message per source host
(What will happen if the error message disappear? I don’t know!)
A host or router can not determine which host is responsible for network congestion
 Using statistics of received datagram, a host or router can determine the responsible sender
No mechanism to notify the end of congestion
 New message type (available bandwidth) is needed

20. Question? ?