IPv6 Address Provisioning
In IPv6 world there are three provisioning aspects wich are
independent of whether the IPv6 node is a Host or CE router:
•IPv6 address provisioning
•IPv6 DNS provisioning
•IPv6 Time provisioning using NTP.
IPv6 Address provisioning:
*Host IPv6 Address provisioning
*Router IPv6 Address Provisioning( Prefix Delegation)
Host IPv6 Address Provisioning
1.
Stateless Autoconfiguration(RFC2462):
IPv6-capable hosts rely on Router Advertisement (RA)
messages to obtain the information needed for
autoconfiguration. To acquire an IPv6 address, a host will
follow three steps:
a. Discover a prefix used on the link: The host can listen to
periodic RAs sent by routers on the link or it can poll for
routers with the help of Router Solicitation messages. The
prefixes information is extracted from the RA messages.
Host IPv6 Address Provisioning
Cont….
b. Generate an interface ID. To have a full IPv6 address, the host
must add an interface identifier to a prefix learned from the
routers on the link using various methods:
• Build one from the layer 2 address in the modified EUI-64
format.
• Autogenerate a random address as defined in RFC 3041.
• Acquire the interface ID via DHCPv6.
• Acquire the interface ID via IPCPv6.
• Manual configuration.
• Cryptographically generated addresses (CGAs) based on RFC
3972 through a hash that includes a public key.
Host IPv6 Address Provisioning
Cont….
c. Verify the uniqueness of the generated IPv6 address using
The Duplicate Address Detection (DAD) mechanism .
2.Statefull DHCP:
Stateful DHCP is a client/server-based mechanism that
provides managed provisioning of hosts. Its operation for IPv6
is described in RFC 3315. The disadvantage of using this
provisioning mechanism is that it requires a more complex host
implementation.Not implemented in cisco routers, Cisco
produces a product named as Cisco Network Registrar (CNR)
that does this task .
3.Stateless DHCP:
the DHCP clients don’t use the DHCP server(s) to obtain IP
address(es) information, they use the DHCP server(s) to
obtain the other useful configuration informaiton (like the
addresses of DNS servers).
Router IPv6 Address
Provisioning: Prefix Delegation
•
•
Prefix delegation (PD) is a mechanism developed to provide
automated delegation of IP address blocks. The delegation is done
from an ISP to its customer. The ISP does not require any
knowledge of the customer's internal network topology.
The DHCP-PD protocol runs between a Customer Edge (CE) and a
Provider Edge (PE) router, the CE is called a Requesting Router (RR)
and the PE router a Delegating Router (DR). The RR acts as the
DHCP client, and requests prefixes from the DR (DHCP server).
The DR injects a route into the provider's routing system for the
delegated prefix on behalf of the RR. That way, a dynamic routing
protocol between the RR and the DR is not needed; however, the
RR and the DR must be directly connected.
Router IPv6 Address
Provisioning: Prefix Delegation
cont..
IPv6 Broadband Network Access
Two IPv6 Native access architictures are prevalent:
1.
A closed model, based on L2TP and adapted to wholesaleoriented service providers
2.
An open model without L2TP
1.The closed model:(Virtualized Access Layer)
A wholesale network access provider (NAP) is not interested in
handling subscribers at layer 3. After providing broadband
access, the NAP tunnels the subscribers to an ISP for address
assignment and IP traffic forwarding. In other words, the NAP
provides the ISP with a virtual access layer.the CPE could be
IPv6 aware or couldn't.and this modeldepend on ppp.
2.Open model without L2TP:
1.PPP based model:CPE could be IPv6 aware or not.
2.Open model without PPP:the CPE could be
IPv6 Aware or not.
Customer Link Encapsulation
• To determine whether CPE should be IPv6 aware or not we
must take a look at customer link encapsulation:(for DSL-based
access) only:
1. PPPoA
2. PPPoE
3. RBE
1.PPPoA:
CPE must be IPv6 Aware
2.PPPoE:
the top CPE not IPv6 aware,and the bottom one is IPv6 aware.
3.RBE Access:the CPE not IPv6 aware
Deployment scenarios
•
The customer address allocation could be static or dynamic:
• Static: when the customer network is always numbered with the same
address prefix
• Dynamic: when the assigned address prefix changes with each
connection
• Most commonly, a /48 prefix will be delivered to every remote site with
more than one subnet. A /64 prefix will be assigned to a customer with
only one subnet or a host. As a last resort, a /128 prefix might be
assigned to individual remote PCs.
1. Single Host, there are three options:
• permanent /64 prefix is assigned to the pc using the RA from the PE
router and here there are two possibilities:
a. Upon reception of the router advertisement, the PC completes
the
64 least significant bits of the IPv6 address on its own.
b. Before reception of the router advertisement, at the IPv6CP level, an
interface identifier is given to the PC. The “Interface-Id” attribute in
the user profile is used to provide a fixed interface identifier to the
PC.
•Short-lived /64 prefix.
•Short-lived /128 prefix.
2. Connecting a Home or a Small Business:
To connect a home or small business networks to ISP the CPE
should be aware of IPv6,otherwise the solution will be as of
connecting single host with /64 prefix.
When connecting Home or a Small Business deferent issues arise:
• 1. Numbering of the PE-CPE link with global addresses (link-local
addresses can be used, but do not help network management)
• 2. Authentication of the connecting CPE
• 3. CPE prefixes database
• 4. Injection of the downstream link network and delegated
customer prefixes in the ISP routing
• 5. Delegation of a shorter than /64 prefix to the CPE router
• 6. Autoconfiguration of hosts on links attached to the CPE
router: IPv6 addresses, Internet parameters
• DHCPv6 PD is the solution to aforementioned deployment issues
3, 4, and 5. DHCPv6 PD delegates prefixes from the provider
edge router to the CPE and operates on the PE-CPE link.
• Either the provider edge router or the RADIUS database can
store the DHCPv6 PD delegated prefixes. If a local database is
maintained on the provider edge router for all the connecting
CPEs, the stored DHCP unique identifier (DUID) of the CPE
indexes the binding between a given prefix and the
corresponding CPE. In the other case, the /48 prefixes are
stored as prefix attributes in the RADIUS server along with
the other user’s attributes.
• The ISP-maintained RADIUS database performs CPE (user)
authentication. This RADIUS database contains
username/password pairs, corresponding /64 prefixes
numbering the PE-CPE link, and delegated prefixes. This
provides a solution to deployment issues 1, 2, and 3.
• Standard autoconfiguration mechanisms as well as stateless
DHCPv6 solve deployment issue 6.