arp mediation updates himanshu shah ciena corp andrew dolganow & neil hart alcatel/lucent eric...

ARP Mediation Updates

Himanshu Shah Ciena Corp

Andrew Dolganow & Neil Hart Alcatel/Lucent

Eric Rosen Cisco Systems Giles Heron BTVach Kompella Alcatel/Lucent Andy Malis VerizonSteven Wright AT&T Arun Vishwanathan Force10Toby Smith NetApps Shane Amante Level 3

04/21/23 IETF-74 ARP Mediation Update 3/2009 2

Updates

• IPv6 portion is re-written• Clarifying text added explaining why unicast

traffic can not flow until ARP-mediation functions have completed.

• Responded to IP Directorate review comments

• Nits fixed, references updated


IPv6<->Link Layer

• IPv6 uses extensions of ICMP to exchange IPv6 and link address information with its neighbor

• IPv6 can have more than one IPv6 addresses for a given link

• IPv6 uses –– Inverse Neighbor Discovery (IND) for Point-to-

point links such as FRL and ATM– Neighbor Discovery (ND) for multipoint links such

as Ethernet


Neighbor Discovery (ND) for Ethernet• Same as ARP, IP DA is known, DMAC is being discovered• An Ethernet based IPv6 sends ND solicitation message where –

– SMAC set to sender’s MAC address, DMAC set to all-node mulitcast– IP header set to SRC IP and DST IP set to target IP– ICMP header target IP field set to target IP address– Optional Source Link address field – set to sender’s MAC address– Could contain multiple SRC IPv6 addr set

• The receiver responds with ND advertisement message where– SMAC set to responder’s MAC address, DMAC set to requester’s MAC– IP header set to SRC IP set to responder’s IP, DST IP set to requester’s IP– ICMP header target IP field of requester’s IP, ‘soliciter’ bit set– Optional Target Link address MUST be set to responder’s MAC address

• Unsolicited ND advertisement message can be set to notify newer info– SMAC set to advertiser’s MAC– DMAC set to all-node multicast MAC– IP header set to src IP with advertiser’s IP, dst IP set to all-node-multicast IP– ICMP header target IP field set to advertiser’s IP– ‘soliciter’ bit is reset, ‘override’ bit set


Inverse Neighbor Discovery (IND)• IND is typically used for point-to-point links such as ATM and FRL

where SRC and DST Link information is known and seeking Destination IP address.

• IND solicitation has– IP header with SRC-IP set to sender’s IP and DST-IP set to all-node-

multicast IP– ICMP fields have source and target link fields set to sender and

target’s link and optional list of source IP addresses configured on that interface

• IND advertisement has– IP header with SRC-IP set to responder’s IP, DST-IP set to requester’s

IP– ICMP fields have, source and target link fields set to responder and

requester’s link address, target address list set to responder’s IP addresses configured on the interface


Scheme Overview

• Use of ICMPv6 allows use of IP PW as compared to ARP packets that are non-IP PDU

• Let ICMPv6 packets flow across IP PW• Let both PEs learn local/remote CE’s IP address

information by snooping ICMPv6 packets from local AC and PW

• In case of disparate neighbor discovery scheme, provide appropriate termination/reciprocation functions (details follow).


Both CEs are Ethernet

CE1 PE1 PE2 CE2Eth MPLS Eth

ND-Sol

Learn CE1’sLink Addr & IP

Learn CE1’s IP addr list ND-Sol

ND-Sol

ND-AdvLearn CE2’s Link & IP list

ND-Adv

ND-Adv

Learn CE2’s IP addr list

Src MAC=PE2

Src MAC=PE1

timeline


Both CEs are Ethernet but uses ND-Adv only

CE1 PE1 PE2 CE2Eth MPLS Eth

ND-Adv


Learn CE1’s IP addr list ND-Adv

ND-Adv

ND-AdvLearn CE2’s Link & IP list

ND-Adv

ND-Adv


Src MAC=PE2

Src MAC=PE1

timeline


Both CEs are point-to-point

CE1 PE1 PE2 CE2FRL MPLS FRL

IND-Sol


Learn CE1’s IP addr list IND-Sol

IND-Sol

IND-AdvLearn CE2’s Link & IP list

IND-Adv

IND-Adv


timeline

Src DLCI=PE2

Src DLCI=PE1


CE1 is Eth, CE2 is FRL (option 1)

CE1 PE1 PE2 CE2Eth MPLS FRL

ND-Sol


Learn CE1’s IP addr list ND-Sol

ND-Sol

IND-SolLearn CE2’s Link & IP list

IND-Sol

ND-Adv


timeline

Src DLCI=PE2

Src MAC=PE1

IND-AdvIND-Adv

Src DLCI=PE2

Since CE1’s IP Addr is known

Two Actions




ND-Sol Learn CE1’sLink Addr & IP


ND-SolND-Sol

IND-SolLearn CE2’s Link & IP list

IND-Sol

ND-Adv

Learn CE2’s IP addr list and discard

timeline

Src DLCI=PE2

Src MAC=PE1

IND-AdvIND-Adv

Src DLCI=PE2Two Actions

IND-SolLearn CE2’s Link & IP listIND-SolPE1 knows CE1’s

IP addr so send IND-adv on PW and ND-adv on local AC




ND-Sol


Learn CE1’s IP addr list IND-Sol

ND-Sol


IND-Adv

ND-Adv


timeline

Src DLCI=PE2

Src MAC=PE1




ND-SolLearn CE1’sLink Addr & IP Learn CE1’s

IP addr list IND-SolND-Sol


IND-AdvND-Adv


timeline

Src DLCI=PE2

Src MAC=PE1

IND-Sol


IND-Sol

Learn CE2’s IP addr list and discard


Dual Stack Support• When AC is configured to support dual stack CE, PE will

advertise IPv4 and IPv6 Address Resolution capability using IPv4 and IPv6 address list TLV in Label Mapping message

• The common denominator address resolution mechanism is adopted based on capability exchange

• If remote CE does IPv4 or IPv6 only then local PE will engage in IPv4 or IPv6 based address resolution.

• When operating in reduced scope, operator is notified using event notification, alarms, etc

• At data plane level, IP version field is used to select appropriate link header.


Conclusion

• We believe draft is ready for one more final call and then be sent for RFC approval

• The applicable IPv6 related changes from this draft will be ported to IPLS draft and will be submitted for final call

arp mediation updates himanshu shah ciena corp andrew dolganow & neil hart alcatel/lucent eric...

Documents

src ip set

srcip set

dst ip set

dstip set

senders ip

ip pwlet

destination ip

responders ip addresses