Device Configuration: Infomation needed
- Address prefix
- Interface identifier
- Default gateway
- DNS server
- Hostname
- Domain name
- MTU (Maximum trasmission unit)
Device configuration: Options
- Manual
- Stateful: everything is obtained through DHCPv6
- Stateless config:
- autogen.
- addr. prefix from router
- Hybrid: Stateless DHCP
- Information other than address obtained thruogh DHCP
Device configuration: Interface identifier
- Manually config.
- DHCPv6
- Automatically generated:
- EUI48 to EUI64 mapping
- Privacy aware:
- Least significant 64 bits of IP address never change if MAC address is used.
Device Configuration: Address usage and address prefix
Usage:
- A host can have many addresses: default, privacy aware
- Can be used to accepts/initiate connetctions
- Selection of addresses may be available to user/app.
Prefix:
- Manually configured
- DHCPv6
- Automatically generated (link local)
- Through Router
Device Configuration: Router/Prefix discovery
- ICMP Router Advertisement message: sent by routers
- Solicited: routers answer host queries
- Unsolicited: routers update periodically their hosts
- Options:
- DHCP
- Information
- Prefix is on-link
- prefix can be used in auto config.
- MTU: ensures all hosts on-link use same MTU value.
- ICMP Redirect: sent by router to advise host about a best first-hop
- first hop is always on-link, irrespective of the prefix
*
- first hop is always on-link, irrespective of the prefix
Device Configuration: DAD
Duplicate Address Detection
- Probe for uniqueness of IPv6 Addr.
- Neighbor solicitiation with address being probed as target
- Sent to corresponding IPv6 solicited node multicast address
- Corresponding MAC multicast adderss
- Sent to corresponding IPv6 solicited node multicast address
- Wait for response for at least a sec, if no response the addres is valid.
Device Configuration: Stateless config w/ router and w/out
No router
- Generate link local address
- probe for its uniqueness (DAD)
- Subscribe to the corresponding IPv6 solicited node multicast adddress
- Configuring reception of mutlicast mac address
- Send ICMP Multicast listener report
- On link communication enabled
Router:
- Possibly send router solicititation
- Listen to router adv.
- Create address from advertised prefix
- Probe for uniqueness
- Subscribe to corresponding IPv6 solicidited
- Configure reception of MAC multicast
- send ICMP multicast listener report
Renumbering:
- Hosts must continue to listen to router adv. to understand if prefix is being changed.
Prefixes of global addresses assigned by the SP, if a company wants to switch SP, all the links in tn company network must change prefix. IPv6 is able to support easy renumbering for both hosts and routers:
- Edge router advertises new prefix to other routers
- Routers stop gradually to advertise old prefix and start advertising the new one (host will have two prefixes during migration)
Device Configuration: DHCP
Dynamic host configuration protocol
- Client server model
- M flag = 1 in router adv.
- Messages:
- solicit (all agents ff02::1:2)
- advertise
- request (all agents ff02::1:2)
- reply
- relelase
- reconfigure
Stateless config:
- M flag = 0
- Address autoconfigured from prefix in router adv.
- O flag = 1
- Other info configured
Device Configuration: autoconfiguration for routers
- Router renumbering
- router renumbering packets:
- they include Prefix control operations (PCOs)
- Match-prefix
- Use-prefix
- Trasposrted in ICMPv6 packets
- they include Prefix control operations (PCOs)
Device Configuration: scoped addresses
A host can have multiple interfaces, that can be connected to multiple different links.
When a host has to send a link local packet it doesn’t konw which of the multiple links is the right one, since they all have the same prefix. Since a link-local address is unique only inside their link, if the wrong interface is chosen problems may arise.
The scope is used to id the physical interface.
Network scanning and DDoS attacks
Network scanning:
- Theoretically difficult
- Tricks can be used to shrink address space
- Address harvesing: used to find addresses to be used as seeds
- Fake Router Adverisement.
DDoS:
- Attacker may use a request a large number of address for his hosts, generating lots of SYN TCP requests from unique addresses, saturating memory of server.
