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Relay Agent Information Option Stacking (draft-zheng-dhc-relay-agent-stacking-00) Robin Zheng IETF 76 - DHC

Outline • Objective • Problem Definition • Scenario • Proposed Solution

Objective • This contribution proposes to allow adding a “second” relay agent information option (Option 82) to a DHCP message which already has a relay agent information option

Problem Definition • RFC3046 – DHCP Relay Agent does NOT add a "second" Relay Agent Information option, when it receives a DHCP packet with a Relay Agent Information option already present from a trusted circuit • However, there are at lease two scenarios where there are multiple relay agents between DHCP client and server. Each relay agent has to add its relay agent information. – Scenario 1--Cascaded LAN access – Scenario 2--PON FTTC/B

Scenario 1--Cascaded LAN access DHCP packet F-switch-identifier C-switch-identifier eth slot/port[:vlan- eth frame/slot/port id] [:vlan-id] user1 user2 user3 Floor Aggregation switch network user4 Curb DHCP user5 switch server user6 Floor switch • This is a scenario which had been discussed in IETF 75th meeting. • As the problem is described in “draft-huang-dhc-relay-ps-00 ”, the amount of configuration information will substantially increase if only Floor switches allow to add option 82.

Scenario 2--PON FTTC/B DHCP packet ONU-identifier eth/ OLT-identifier eth/ atm slot/port[:vlan-id] atm slot/port [:vlan-id] user1 user2 AAA user3 server ONU Layer 2 network user4 splitter BNG user5 OLT user6 ONU DHCP server • In order to locate a user precisely from a DHCP message via Option 82, ONU need add a user's access loop identification on which port the user is attached, while OLT need add PON port where the ONU is attached. • DHCP Relay Agent resides in both ONU and OLT

Proposed Solution DHCP option Multiple option 82 in the end of option field • Agent Operation – The relay agent can add a “second” relay agent information option (Option 82) to a DHCP message which already has a relay agent option – The “second” relay agent information option shall be added as the last option (but before ‘End Option’ 255) – The “second” relay agent information option echoed by a server MUST be removed by the relay agent which added it when forwarding a server-to-client response back to the client

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