• Manually
• Automatically
• Autonomously

• IP address
• Default router
• Subnet Mask
• DNS resolver
• NTP
• Domain name
• ...

• Gives best level of control
• Common method for servers
• Does not scale well
• Problematic if network environment changes
• e.g. if network renumbering is required due to a change of ISP; using hard encoded addresses
• Not consumer friendly

• Hosts can fetch settings using some protocol
• Settings are administratively configured in servers that hosts can query
• Provide a single point of administration
• Can potentially enforce policy on hosts
• Aids accountability (User logged in at time x)

• Supports stateful address assignments
• Uses a pool of IP addresses allocated to the service
• Allocates IP addresses to the clients on request
• Can provide other configuration informaion (e.g. NTP time server, local domain name, etc)

The DHCP server has to keep state (information) on which devices were allocate which IPs

All addresses assigned with a lease timer

• Uses a 4-way protocol exchange
• Client looks (broadcasts) for server on local subnet
• Server responds with DHCP OFFER
• This includes the offered IP address
• Client confirms address with DHCP REQUEST
• Server reconfirms with DHCP ACK
• Includes lease timer and any other configuration information

• The time period when the DHCP assigned address is still valid
• Tuning the lease timer is important
• Typically set to 1 hour
• When lease expires, client must renew; it may request same address again

• IPv6 formed from the 64-bit network prefix sent in a router advertisement, with a 64-bit host part appended (based on MAC/Ethernet address, or 'random' for privacy addresses)
• No server is required to hold the state of the address allocation to the internet
• There is no lease
• Instead the advertisement has a valid lifetime indicator
• You can run an IPv6 network without DHCPv6

• Managed service; administrative control
• Improved accountability; (IP x logged in at time y)
• Can give specific addresses to specific hosts
• Can give different information to hosts in the same subnet

• Doesn't require a DHCP server to be supported
• Host 'fate shares' with its router
• Gets prefix and default gateway from router
• If a DHCP server goes down, there is no way to tell the hosts to get a new address
• More efficient: can multicast Router Advertisements

• DNS is configured by zone files
• Forward and reverse DNS information
• Can be manually configured
• Can be dynamic (Dynamic DNS from hosts)
• Usually configure "friendly" names for DHCP clients
• Pre-populate reverse DNS zone file
• Gives meaningful answer to reverse lookup

• Networks self-configuring without manual intervention
• No administrative configured DHCP or DNS service
• Rely on hosts to provide the service themselves

• Particularly in ad-hoc (possibly not externally connected) network subnets
• Usually targeted to work within a signal local subnet

• A method to obtain link-local IP addresses
• Need a way to advertise and resolve host names
• Need automatic discovery of network services

• Need link-local addresses that can be used within a subnet
• Hosts need to be able to generate these
• Packets with these addresses are never forwarded by routers
• IPv4
• Use reserved range 169.254.0.0/16
• May see this if IPv4 fails to contact a DHCP server when connecting network
• IPv6
• Use standard link-local addresses under fe80::/10

• A Zeroconf host name resolution service
• Similar to unicast DNS, to resolve hostnames to IPs in small networks that don't include nameserver
• DNS query/response sent using multicast on local subnet (instead than to DNS resolver)
• If host has answer, it multicasts respond
• Up to hosts to query and respond as required

• mDNS (Apple)
• Uses .local domain
• Link-local multicast name resolution (LLMNR) (MSFT)
• Can use any domain

• Apple's local Zeroconf name resolution service
• Hosts hold their own DNS records (A, AAAA, etc)
• They join the mDNS multicast group
• Clients send mDNS requests to multicast group
• Host with matching information responds
• No requirement on an administratively controlled DNS resolved, or off-site recursion
• Restricted to local subnet - can't discover hosts in different subnets

• Well-known addresses
• DNS SRV records
• DNS-SD (used with mDNS)

• Lookup services by name in DNS
• Uses a specific DNS SRV record type
• Just another DNS record type A or AAAA
• DNS entry of format:
• _Service._protocol.Name TTL Class SRV Priority Weight Port Target
• The response indicates the service available

• Apple's service discovery solution
• Uses DNS SRV, TXT and PTR records
• Hosts offering services use multicast to announce them, or respond multicast service discovery requests

• ISO standard, promoted by UPnP Forum
• Defines addressing and service discovery
• Clients join multicast groups to announce/discover services
• Discovery gives URL from which XML service descriptions can be retreived
• Control messages
• Discovery includes actions that can be sent to a device from a control point
• Uses Simple Object Access Protocol (SOAP)
• Can control a home router (Adding NAT)