autoconfiguracion

Protocols in Telecommunication Networks 1M.

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IPv6- Autonfiguration

Anna Calveras


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s SYLLABUS

ICMPv6 Path MTU Discovery Neighbor Discovery Multicast over IPv6 Address Autoconfiguration


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s Documentation RFC 1981. Path MTU Discovery for IP version 6 RFC 2460. Internet Protocol, Version 6 (IPv6) Specification RFC 2710. Multicast Listener Discovery (MLD) for IPv6 RFC 3315. Dynamic Host Configuration Protocol for IPv6

(DHCPv6) RFC 3810. Multicast Listener Discovery Version 2 (MLDv2) for

IPv6 RFC 4443. Internet Control Message Protocol (ICMPv6) for the

Internet Protocol Version 6 (IPv6) Specification RFC 4861. Neighbor Discovery for IP version 6 (IPv6) RFC 4862. IPv6 Stateless Address Autoconfiguration


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s Documentation Other:

RFC 2711. IPv6 Router Alert Option RFC 3590. Source Address Selection for the Multicast Listener

Discovery (MLD) Protocol RFC 3775. Mobility Support in IPv6 RFC4429. Optimistic Duplicate Address Detection (DAD) for

IPv6 RFC4541. Considerations for Internet Group Management

Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches


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ICMPV6


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s ICMPv6 ICMPv6 vs ICMPv4

Taking profit of IPv6 Messages translation

Introducing ICMPv6 and its applications Message header Basic set of messages New applications

Neighbor Discovery Multicast over IPv6 Address Autoconfiguration

Playing with ICMPV6 The ping/ping6 tool


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s ICMPv6 vs ICMPv4 Key IPv6 benefits for ICMPv6

IPv6 addresses are longer enough to Build IP addresses based on MAC addresses Define a lot of multicast groups

Broadcast is replaced by multicast Multicast link-local addresses can be defined

All host, all routers Solicited-node multicast address

Energy consumption reduced

Taking profit of IPv6 Broadcast cannot be used, only multicast is allowed Multicast can be send to an specific group of MACs


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s Remember - Nodes required addresses A host is required to recognize the following addresses as

identifying itself: One link-Local address for each interface Any additional Unicast and Anycast addresses that have been

configured for the node's interfaces (manually or automatically). The loopback address The All-Nodes multicast addresses The Solicited-Node multicast address for each of its unicast

and anycast addresses Multicast addresses of all other groups to which the node

belongs


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s Remember - Link-Local Unicast Addresses For use in a single link Used:

During automatic address configuration During neighbor discovery When no routers are present

Routers MUST NOT forward packets with these addresses as destination or source

1111111010 0 interface ID

10 bits 54 bits 64 bits

cccccc0gcccccccc ccccccccmmmmmmmm mmmmmmmmmmmmmmmm

cccccc1gcccccccc cccccccc11111111 11111110mmmmmmmm mmmmmmmmmmmmmmmm

MAC Address c: company identifier u: universal / local bitg: individual /group m: set by the manufacturer


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s Remember - Pre-Defined Multicast Addresses All Nodes Addresses:

ff01::1 All IPv6 nodes scope 1 (interface-local) ff02::1 All IPv6 nodes scope 2 (link-local)

All Routers Addresses: ff01::2 All routers in scope 1 (interface-local) ff02::2 All routers in scope 2 (link-local) ff05::2 All routers in scope 5 (site-local)

Solicited-Node Address: ff02::1:ffxx:xxxx It takes the low-order 24 bits of one address and appending

them to the prefix ff02::1:ff00/104 Ex: node with address 4037::01:800:200e:8c6c has the

solicited-node address ff02::1:ff0e:8c6c Different unicast addresses can have the same solicited-node

address


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s ICMPv6 vs ICMPv4 Understanding the change of philosophy. Some examples:

A router periodically announces its existence (Unsolicited Router Advertisement)

IPv4: destination Address = 255.255.255.255 / 224.0.0.1 IPv6: destination Address = FF02::2 Benefits:

Not a real change, just broadcast is forbidden A node A needs to know the MAC address of a node B

IPv4: ARP Request with destination address FF:FF:FF:FF:FF:FF IPv6: Neighbor Solicitation with destination the solicited-node

address derived of the unicast address of B Benefits:

Host with a different solicited-node address will discard the packet

Further benefits can be achieved with layer 2 support


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ICMPv6 vs ICMPv4 Understanding the change of philosophy. Another example:

Node B MAC address: 00-24-81-8E-BF-7F Node B link-local address: 02-24-81-FF-FE-8E-BF-7F Node B solicited-node address: FF02::1:FF-8E-BF-7F

Node A wants to know the MAC address of B A sends a Neighbor Solicitation packet with destination the solicited-

node address FF02::1:FF-8E-BF-7F The packet is embedded in a frame with destination the MAC

address corresponding to IPv6 multicast address 33-33-FF-8E-BF-7F

Multicast aware layer 2 Only NIC with this multicast address registered will pass the frame to

IP level

IGMP & MLD* Snooping Switches (RFC 4541) The frame is only forwarded to the port where node B is attached

*IPv6 multicast renames IGMP to the Multicast Listener Discovery Protocol (MLP) based on ICMPv6 messages


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s ICMPv6 vs ICMPv4 Understanding the change of philosophy. Another example:

IPv4

IPv6 + multicast promiscuous mode

IPv6 + multicast promiscuous node + MLD spoofing

A

B C D Nodes processing the frame


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ICMPv6 vs ICMPv4

Messages translationCommon ICMPv4 MessageDestination Unreachable- Network unreachable (Type 3, Code 0) Destination Unreachable-Protocol unreachable (Type 3, Code 2) Destination Unreachable-Port unreachable (Type 3, Code 3) Destination Unreachable-Fragmentation needed and DF set (Type 3, Code 4)Time Exceeded-TTL expired (Type 11, Code 0)Parameter Problem (Type 12, Code 0)Redirect (Type 5, Code 0)

ICMPv6 EquivalentDestination Unreachable-No route to destination (Type 1, Code 0)Parameter Problem-Unrecognized Next Header field (Type 4, Code 1)Destination Unreachable-Port unreachable (Type 1, Code 4)Packet Too Big (Type 2, Code 0)

Time Exceeded-Hop Limit exceeded (Type 3, Code 0)Parameter Problem (Type 4, Code 0 or 2)Neighbor Discovery Redirect message (Type 137, Code 0)


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s Introducing ICMPv6 and its applications Starting point: the role of ICMP in IPv4 networks

Basically, ICMPv4 is intended to send error and informational messages

Things have changed with IPv6: ICMPv6 is a key piece in order to achieve autoconfiguration

Neighbor reachability ( ARP) Multicast membership ( IGMP) Address autonconfigurarion (New!)

New capabilities and better performance is possible taking profit of IPv6 addressing system Link-local addresses Multicast


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s Introducing ICMPv6 and its applications RFC 4443, Internet Control Message Protocol for the

Internet Protocol Version 6 Specification Required for any IPv6 implementation

Message header Type: 0-127 Error msg /128-255 Informational msg Code: differentiates among messages of the same type Checksum : computed with IPv6 pseudo-header

Type (1 byte) Code (1 byte) Checksum (2 bytes)

Message body


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s Introducing ICMPv6 and its applications Basic set of messages

Error messages Sent by the destination node or an intermediate router, they notify

errors in forwarding or delivery Destination Unreachable Packet Too Big Time Exceeded Parameter Problem

ICMPv6 error messages are rate limited In order to conserve network banwidth Recommended method: token bucket

Average rate (msg/s) % bandwidth Burst of messages are allowed If average rate does not

exceed the overall transmission rate


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s Introducing ICMPv6 and its applications Basic set of message Error messages

Destination Unreachable (Type = 1) A packet cannot reach its destination Code:

0: No Route to Destination 1: Communications whit the Destination Administratively Prohibited 2: Beyond the Scope of Source Address 3: Address Unreachable 4: Port Unreachable 5: Source Address Failed Ingress/Egress Policy 6: Reject Route to Destination

Type=1 Code = 0-6 Checksum

Unused

Portion of discarded packet(the length of the whole ICMPv6 packet must be 1280 bytes)

1280 bytes is the minimum MTU in order to support IPv6 (RFC 2460)


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Packet Too Big (Type = 2) When a packet cannot be forwarded because the length of the

packet is bigger than the MTU of the outer link MTU: the MTU of the link that has motivated the sending of this

message

Type=2 Code = 0 Checksum

MTU

Portion of discarded packet (the length of the whole ICMPv6 packet must be 1280 bytes)


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Time Exceeded (Type = 3) Main reasons is that the hop limit field reaches the value of zero Code:

0: Hop limit exceeded in transit Hop limit decremented to zero

2: Fragment Reassembly Time Exceeded 60 seconds (RFC 2460)


Unused



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Parameter Problem (Type =4) A router discards a packet due to an error in a header or an

extensions header Code:

0: Erroneous Field Encountered 1: Unrecognized Next header Type Encountered 2: Unrecognized IPv6 Option Encountered

Pointer: Identifies the octet offset within the invoking packet where the error was detected.


Pointer



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s Introducing ICMPv6 and its applications Basic set of messages

Informational messages Provide diagnostic functions and additional host

functionality Echo Request Echo Reply

More messages are defined in others RFCs (see Neighbor Discovery and MLD)


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s Introducing ICMPv6 and its applications Basic set of message Informational messages

Echo Request (Type = 128) & Echo Reply (Type = 129) Code = 0 Identifier: to associate request & replay messages Sequence Number: messages ordering Data: optional and equal for both messages

Type=128 or 129 Code = 0 Checksum

Identifier Sequence Number

Data


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s Introducing ICMPv6 and its applications


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PATH MTU DISCOVERY


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s Path MTU Discovery Overview

Changes from IPv4 to IPv6 Description

ICMPv6 messages and options employed Procedure

Applying Path MTU Discovery An example


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s Path MTU Discovery Overview

RFC 1981 Purpose: learn the MTU of a path in order to avoid

fragmentation Changes from IPv4 to IPv6. RFC 2460:

1280 bytes is the minimum MTU in order to support IPv6 PMTU is strongly recommended

Otherwise, the packets sent will be no larger than 1280 octets Note that, fragmentation is still possible but

It is discouraged Only the source (and destination) node(s) can perform it

Using Extension header named Fragment Header Routers never fragment packets

This contributes to do not increase their process time Key point:

Example 802.15.4 networks (MTU=128 bytes)


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s Path MTU Discovery Description/Procedure

ICMP error message Packet Too Big is used

Step 1: The sender assumes the link MTU of the interface on which the traffic is being forwarded

Step 2: The sender sends IPv6 packets at the link MTU size Step 3: A router on the path unable to forward the packet sends

an ICMP Packet Too Big msg back to the sender. This msgcontains the link MTU of the link on which the forwarding failed

Step 4: The sender resets the PMTU to the value of the MTU field in the ICMPv6 Packet Too Big message


MTU



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s Path MTU Discovery Procedure (II):

Path MTU updates: If PMTU decreases

The sending host will be alerted with a ICMP Error message Packet Too Big

Discovery process is restarted

if PMTU< the MTU of the link, PMTU can increase When PMTU timer expired (10 minutes recommended)

PMTU = MTU of the link


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s Path MTU Discovery Applying Path MTU Discovery

An example

R2R1

R3

R4

MTU1=MTU6=1500 bytesMTU2=MTU3=2000 bytesMTU4=1000 bytesMTU5=2000 bytes

MTU6MTU1

MTU5

MTU4MTU2

MTU3

Host AHost B

1. A sends a packet of 1500 bytes to B (PMTU=MTU1)2. R1 forwards the packet to R23. R2 is unable to forward the packet to R34. R2 sends an ICMP msg Packet Too Big to A5. A changes its PMTU to MTU4

(PMTU==min(MTU)==MTU4)

Like PMTU wait for PMTU timer and restart => PMTU could be equal to MTU1


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NEIGHBOR DISCOVERY (ND)


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s Neighbor Discovery (ND) Overview

Changes from IPv4 to IPv6 Description

ICMPv6 messages and options employed Conceptual host data structures Procedure

Router Discovery Address Resolution Neighbor Unreachability Detection Redirect Function


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s Neighbor Discovery Overview

RFC 4861 Purpose: IPv6 nodes on the same link use ND to discover

each other's presence, to determine each other's link-layer addresses, to find routers, and to maintain reachabilityinformation about the paths to active neighbors

ND only generates link traffic Offline packets are not forwarded by routers

Packets are coded with Hop count = 255 If Hop count is 255, packet is silently discarded

Security reasons Changes from IPv4 to IPv6

ND replaces ARP! to determine link-layer address & test address

uniqueness No more ARP frames in IPv6 networks

New feature: Neighbor Unreachability Detection (NUD)


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s ICMPv6 vs ICMPv4 IPv4 to IPv6 mapping of functions

IPv4 Neighbor Function IPv6 Neighbor FunctionARP Request message Neighbor Solicitation messageARP Reply message Neighbor Advertisement msg.ARP cache Neighbor cacheGratuitous ARP Duplicate address detection (DAD)*Router Solicitation message (optional) Router Solicitation (required)*Router Advertisement message (optional) Router Advertisement (required)

Redirect message Redirect message

*Only used by Mobile IPv4


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s Neighbor Discovery Description

Option format Type: type of the option Length: The length of the option (including the type and length

fields) in units of 8 octets Value: includes specific fields of the options

Type (1 byte) Length (1 byte) Value (n bytes)


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Neighbor Discovery Description

5 new ICMPv6 informational messages Router Solicitation (Type=133, Code=0) Router Advertisement (Type=134, Code=0) Neighbor Solicitation (Type=135, Code=0) Neighbor Advertisement (Type=136, Code=0) Redirect (Type=137, Code=0)

Theses messages can include zero or more of the following options

Source/Target Link-layer Address Prefix Information

Prefixes the router is given service Redirected Header

Better route MTU Route Information


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s Neighbor Discovery Router Solicitation message

Objective: the discovery of on-link routers IPv6

From: link-local address or unspecified address (::) To: link-local scope all-routers multicast address (FF02::2)

Ethernet From: NIC MAC address To: 33-33-00-00-02


Reserved

OptionsSource Link-Layer Address option


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Neighbor Discovery Router Advertisement message

Objective: provide information related to autoconfiguration to on-link host

IPv6 From: Link-local address To:

link-local scope all-nodes multicast address (FF02::1), or unicast address of the host that has sent a Router Solicitation msg

from an unicast address

When response to router solicitation Ethernet

From: NIC router MAC address To:

33-33-00-00-01, or The unicast MAC address of the host that sent Router Solicitation

msg form an unicast address

When response to router solicitation


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s Neighbor Discovery Router Advertisement message - Fields


OptionsSource Link-Layer Address option

MTU optionPrefix Information options

Adevertisement Interval optionHome Agent Information option

Route Information options

Current Hop Limit Flags Router Lifetime

Reachable Time

Retransmission Timer


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s Multicast over IPv6 Overview

Changes from IPv4 to IPv6 Host and routers implications

Layer 2 interaction

MLD description ICMPv6 messages and options employed Procedure

Timers and counters


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Purpose: MLD (Multicast Listener Discovery) is used by an IPv6 router to discover the presence of multicast listeners on directly attached links, and to discover which multicast addresses are of interest to those neighboring nodes

Changes from IPv4 to IPv6 Multicast support is now mandatory RFC 3810: MLDv2 replaces IGMPv3

Host support - Multicast traffic reception Apps are associated to multicast groups

1 multicast group 1 IPv6 multicast address Socket is created to join the multicast group

Driver is instructed to pass to higher layers MAC address corresponding to IPv6 multicast address

MLD is used to inform local routers of this joining Also for link-local scope multicast addresses

IGMP & MLD Snooping Switches (RFC 4541) Host support - Sending multicast traffic

All hosts can sent packets to a multicast address


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Router Support - Multicast traffic reception It must place the network adapter to a special listening mode

Multicast promiscuous mode Analyzes IEEE defined Individual/Group bit (I/G)

I/G=0 Unicast I/G=1 Multicast

If (I/G==1) the frame is passed to upper layers

cccccc0gcccccccc ccccccccmmmmmmmm mmmmmmmmmmmmmmmm

c: company identifier u: universal / local bitg: individual /group m: set by the manufacturer


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Router Support - Multicast traffic forwarding Forwarding is done taking into the account the scope of the

multicast destination address If (scope > link-local)

Packets are analyzed to determine forwarding interfaces Else

Packets are processes but not forwarded

Multicast forwarding table Shows multicast groups with at least a member for a specific

multicast address on a specific link Multicast membership information is exchanged between

routers using a multicast routing protocol E.g. Protocol Independent Multicast (PIM)


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s Multicast over IPv6 Multicast MLD&IGMP snooping switches

Cisco Catalyst 3650

3Com 4800G

They support multicast L2 and L3 interaction More management so more energy consumption

Related documentation Cisco: configuring IPv6 MLD Snooping

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_35_se/configuration/guide/swv6mld.html

3Com Switch 4800G Family Command reference http://support.3com.com/documents/switches/4800G/SW4800G_Com

mand_ReferenceCMT.pdf


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s Multicast over IPv6 RFC 2710. Multicast Listener Discovery (MLD) or

MLDv1description 3 new ICMPv6 informational messages

Multicast Listener Query (Type=130) General Query / Specific Query

Multicast Listener Report (Type=131) Multicast Listener Done (Type=132)

Other particularities in IPv6 header Hop-limit=1 Hop-by-hop Options extensions header with Router Alert option

(RFC 2711) To be sure that the router process packet to multicast

addresses for which the router is not a group member

IPv6 HeaderNext Header =0

(hop-by-hop)

Hop-by-Hop Options H.Router Alert Option

Next Header=58MLD Message


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s Multicast over IPv6 Multicast Listener Discovery (MLD) description

RFC 3810. Multicast Listener Discovery Version 2 (MLDv2) for IPv6

Only two messages: A modified version of Multicast Listener Query (Type=130) A modified version of Multicast Listener Report (Type=143)

Backwards compatible Support Multicast Listener Report and Done (Type=131 and

132) Also:

Hop-limit=1 Hop-by-hop Options extensions header with Router Alert

option


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s Multicast over IPv6 MLDv2 description - Procedure

Routers send modified Multicast Listener Query 3 types of queries:

General query: There is any host interested in multicast traffic?

Multicast-address specific query: There is any host interested in traffic to this multicast

address? Multicast-address-and source specific query:

There is any host interested in traffic to this multicast address from this source?

From: link-local address of the interface of the sender To: specific multicast address queried or all-nodes multicast

address (FF01::1)


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ADDRESS AUTOCONFIGURATION


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s Address Autoconfiguration Overview of the IPv6 autoconfiguration approaches

Stateless vs stateful Changes from IPv4 to IPv6

Autoconfigured address states Based on previous seen messages

Stateless Address Autoconfiguration (new in IPv6) Description

ICMPv6 messages and options employed Procedure

Applying Stateless Address Autoconfiguration Link-local and global addresses

Stateful Address Autoconfiguration DHCPv6

Description Changes from IPv4 to IPv6


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Address Autoconfiguration Overview of the IPv6 autoconfiguration approaches

Stateless RFC 4862. IPv6 Stateless Address Autoconfiguration Purpose: To specify the steps a host takes in deciding how to autoconfigure its interfaces

in IPv6. These steps are: generating a link-local address

FE80::/64 + EUI64 derived interface generating global addresses using stateless address autoconfiguration

Using information provided by Router Advertisment join the solicited-node a multicast address

MLD (Multicast Listener Discovery) report and the DAD (Duplicate Address Detection) procedure to verify the uniqueness of the

addresses on a link Neighbor Solicitation message

Provides an alternative to DHCPv6 Autoconfiguration can be performed without any server and specific protocol support

Note that: DAD has to be performed for global and link-local addresses If global and link-local address are based on EUI64 only solicited-node multicast address

exist and then only a MLD report has to be sent


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s Address Autoconfiguration Overview of the IPv6 autoconfiguration approaches

Stateful Configuration is based on a the usage of a configuration protocol

DHCPv6 (RFC 3315)

Mixed approach is possible DHCPv6 + Router Advertisement message

Changes from IPv4 to IPv6 DHCPv6 messages are simpler than DHCPv4


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s Stateless Address Autoconfiguration RFC 4429. Optimistic Duplicate Address Detection (DAD) for

IPv6 Purpose: To minimize address configuration delays in the

successful case, to reduce disruption as far as possible in the failure case, and to remain interoperable with unmodified hosts and routers

Idea: IPv6 provide several ways to construct and unique IPv6 address

New address state Optimistic ( deprecated) When DAD is done, the address moves to Prefered


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s Stateful Address Autoconfiguration RFC3315: DHCPv6

DHCPv6 infrastructure Clients Servers Relays

UDP protocol Clients listens port 546 Servers and relays listens port 547

DHCPv6 vs DHPCv4 Messages structure simpler (see following slides)

Each action has its related message Relay interaction

All_DHCP_Relay_Agents_and_Servers address FF02::1:2


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s Stateful Address Autoconfiguration DHCPv6 message fields Client Server

Message Type Transaction ID

To group DHCPv6 messages that belongs to the same transaction Options

Message-Type Transaction ID

Options

Option-Code Option_Len

Option-Data


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s Stateful Address Autoconfiguration DHCPv6 message fields Relay Server

Message-Type

Hop-Count Link-Address

Link-Address (16 octets=2+3*4+2)

Link-Address Peer-Address

Peer-Address (16 octets=2+3*4+2)

Peer-Address Options


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Stateful Address Autoconfiguration

DHCPv6 DHCPv4 EquivalentSOLICIT DHCPDISCOVERADVERTISE DHCPOFFERREQUEST, RENEW, REBIND DHCPREQUESTREPLY DHCPACK/DHCPNAKRELEASE DHCPRELEASEINFORMATION-REQUEST DHCPINFORMDECLINE DHCPDECLINECONFIRM N/ARECONFIGURE DHCPFORCERENEWRELAY-FORW, RELAY-REPLY N/A


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s Stateful Address Autoconfiguration DHCPv6 scenarios & messages

RelayDHCP client

RelayDHCP client

DHCP server

DHCP client DHCP server

Solicit, Advertise, Request, Confirm, Renew, Rebind, Replay, Release, Decline, Reconfigure, Information-Request

Relay-Forward, Relay-Replay

autoconfiguracion

Documents

multicast addresses

icmpv6 ipv6 addresses

ipv6 specification rfc

ipv6 dhcpv6 rfc

telecommunication networks

ipv6 rfc4541

ipv6 rfc4429

ip addresses