BAI513 - Protocols IP Version 6 Operation BAIST – Network Management

Objectives Neighbor Discovery Auto Configuration MTU Discovery ICMPv6 IPv6 Security IPv6 QOs IPv6 Technology Scope

Neighbor Discovery RFC 2461 Protocol built on top of ICMPv6 (RFC 2463) –Combination of IPv4 protocols (ARP, ICMP,…) Neighbor Discovery: –Determines the link-layer address of a neighbor on the same link, Duplicate Address Detection –Finds neighbor routers, Keeps track of neighbors Defines 5 ICMPv6 packet types –Router Solicitation / Router Advertisements –Neighbor Solicitation / Neighbor Advertisements –Redirect

Router Solicitation Message Formats Type = 133 Code = 0 Valid Options = Source Link-Layer Address TypeCodeChecksum Reserved Options …

Router Advertisement Message Formats Type = 134 Code = 0 TypeCodeChecksum Cur Hop LimitMO ReservedRouter Lifetime Reachable Time Retrans Timer Options…

RA Message Formats (cont.) Cur Hop Limit –Default value that should be placed in the Hop Count field of the IP header. M – “Managed Address Configuration” flag –When set, hosts use the administered (stateful) protocol for address autoconfiguration in addition to any address autoconfiguration using statless address autoconfiguration. O – “Other Stateful Configuration” flag –When set, hosts use the administered (stateful) protocol for autoconfiguration of other (non- address) information.

RA Message Formats (cont.) Router Lifetime –Lifetime associated with the default router in units of seconds. Maximun value is 18.2 hours. A value of 0 indicates that the router is not a default router. Reachable Time –The time, in seconds, that a node assumes a neighbor is reachable. Retrans Timer –The time, in milliseconds, between retransmitted Neighbor Solication messages.

RA Message Formats (cont.) Possible Options Source Link-Layer Address –link-layer address of the interface which the RA is sent. MTU –Should be sent on links that have a cariable MTU Prefix Information –Specify the prefixes that are on-link and/or are used for address autoconfiguration.

Neighbor Solication Message Format Type = 135 Code = 0 TypeCodeChecksum Reserved Target Address Options …

NS Message Formats (cont.) Target Address –IP address of the target of the solication. –MUST NOT be a multicast address. Possible Option –Sender’s source link-layer address,must not be included when source IP address is unspecified. Must be included with multicast and should be included with unicast

Neighbor Advertisement Message Format Type = 136 Code = 0 TypeCodeChecksum Reserved Target Address Options … R RSO

NA Message Formats (cont.) R – Router Flag, indicates that the sender is a router. S – Solicated Flag, indicates that the advertisement was sent in response to a NA from the destination address. O – Override Flag, indicates that the advertisement should override an existing cache entry. Target Address – MUST NOT be a multicast address Posible Options – Target Link-Layer Address

Redirect Message Format Type = 137Code = 0 TypeCodeChecksum Reserved Target Address Options … Destination Address

Redirect Message Format (cont.) Target Address –An IP address that is a better first hop to use for the ICMP destination address. Destination Address –IP address of the destination which is redirected to the target. Posible Options –Target link-layer address – should be included, if known. –Redirected Header – as much as posible of the IP packet that triggered the sending of the Redirect Message.

IPv6 and Path MTU Discovery Definitions: –link MTUa link’s maximum transmission unit, –path MTUthe minimum MTU of all the links in a path between a source and a destination Minimum link MTU for IPv6 is 1280 octets (68 octets for IPv4) –On links with MTU < 1280, link-specific fragmentation and reassembly must be used Implementations are expected to perform path MTU discovery to send packets bigger than 1280 octets: –for each dest., start by assuming MTU of first-hop link –if a packet reaches a link in which it cannot fit, will invoke ICMP “packet too big” message to source, reporting the link’s MTU; MTU is cached by source for specific destination Minimal implementation can omit path MTU discovery as long as all packets kept ≤ 1280 octets – e.g., in a boot ROM

IPv6 Auto-Configuration At boot time, an IPv6 host build a Link-Local address, then its global IPv6 address(es) from RA RA indicates SUBNET PREFIX Stateless Stateless (RFC 2462) –Host autonomously configures its own Link-Local address –Router solicitation are sent by booting nodes to request RAs for configuring the interfaces. Stateful Stateful –DHCPv6 (under definition at IETF) Renumbering Renumbering Hosts renumbering is done by modifying the RA to announce the old prefix with a short lifetime and the new prefix. Router renumbering protocol (RFC 2894), to allow domain-interior routers to learn of prefix introduction / withdrawal SUBNET PREFIX + MAC ADDRESS

Stateless Autoconfiguration Router solicitations are sent by booting nodes to request RAs for configuring the interfaces. 1 - ICMP Type = 133 (RS) Src = :: Dst = All-Routers multicast Address query= please send RA 2. RA 1. RS 2 - ICMP Type = 134 (RA) Src = Router Link-local Address Dst = All-nodes multicast address Data= options, prefix, lifetime, autoconfig flag

Duplicate Address Detection Duplicate Address Detection (DAD) (RFC 2462) uses neighbor solicitation to verify the existence of an address to be configured. ICMP type = 135 ICMP type = 135 Src = 0 (::) Dst = Solicited-node multicast of A Data = link-layer address of A Query = what is your link address? AB

ICMPv6 (RFC 2463) Similar to ICMP for IPv4 Uses an IPv6 Next Header value of 58. ICMPv6 messages are grouped into 2 general classes: error & informational message The 2 message classes are identified by the high-order bit in the ICMPv6 Type field. High-order bit value of 0 identifies an error message (values of 0 to 127) High-order bit value of 1 identifies an informational message (values of 128 to 255)

ICMPv6 Messages ICMPv6 Error Messages –1Destination Unreachable –2Packet Too Big –3Time Exceeded –4Parameter Problem ICMPv6 Informational Messages –128Echo Request –129Echo Reply TypeCodeChecksum Message Body

ICMPv6 Error Messages Destination Unreachable Message Type 1 –Code 0 – no route to destination –Code 1 – communication with destination administratively prohibited –Code 2 – not assigned –Code 3 – address unreachable –Code 4 – port unreachable

ICMPv6 Error Messages (cont.) Packet Too Big Type 2 –Code – Set to 0 by sender and ignored by receiver Time Exceeded Message Type 3 –Code 0 – hop limit exceeded in transit –Code 1 – fragment reassembly time exceeded

ICMPv6 Error Messages (cont.) Parameter Problem Message Type 4 –Code 0 – erroneous header field encountered –Code 1 – unrecognized Next Header type encountered –Code 2 – unrecognized IPv6 option encountered

ICMPv6 Informational Messages Both ICMPv6 Echo Request Messages (Type 128, Code 0) and Echo Reply Messages (Type 129, Code 0) perform as ICMPv4 Echo messages with identical fields TypeCodeChecksum IdentifierSequence Number Data …

IPv6 Security - IPSec IPSec standards apply to both IPv4 and IPv6 All implementations required to support authentication and encryption headers (“IPSec”) Authentication separate from encryption for use in situations where encryption is prohibited or prohibitively expensive Key distribution protocols are not yet defined (independent of IP v4/v6) Support for manual key configuration required

IP Quality of Service (v4 &v6) Two basic approaches developed by IETF: “Integrated Service” (int-serv) –fine-grain (per-flow), quantitative promises (e.g., x bits per second), uses RSVP signaling “Differentiated Service” (diff-serv) –coarse-grain (per-class), qualitative promises (e.g., higher priority), no explicit signaling Signaled diff-serv (RFC 2998) – uses RSVP for signaling with course-grained qualitative aggregate markings – allows for policy control without requiring per- router state overhead

IPv6 Support for Int-Serv 20-bit Flow Label field to identify specific flows needing special QoS –each source chooses its own Flow Label values; routers use Source Addr + Flow Label to identify distinct flows –Flow Label value of 0 used when no special QoS requested (the common case today) This part of IPv6 is not standardized yet, and may well change semantics in the future – flow-label-07.txt

IPv6 Support for Diff-Serv 8-bit Traffic Class field to identify specific classes of packets needing special QoS –same as new definition of IPv4 Type-of- Service byte –may be initialized by source or by router enroute; may be rewritten by routers enroute –traffic Class value of 0 used when no special QoS requested (the common case today)

IP Service IPv4 Solution IPv6 Solution DHCP IGMP/PIM/Multicast BGP IP Multicast MLD/PIM/Multicast BGP,Scope Identifier MLD/PIM/Multicast BGP,Scope Identifier Autoconfiguration Serverless, Reconfiguration, DHCP Serverless, Reconfiguration, DHCP IPv6 Technology Scope 32-bit, Network Address Translation 128-bit, Multiple Scopes 128-bit, Multiple Scopes Addressing Range Quality-of-Service Differentiated Service, Integrated Service Security IPSec Mandated, works End-to-End IPSec

Summary Neighbor Discovery Auto Configuration MTU Discovery ICMPv6 IPv6 Security IPv6 QOs IPv6 Technology Scope