draft-ietf-dhc-relay-port-08.txt   draft-ietf-dhc-relay-port-09.txt 
Networking Working Group N. Shen Networking Working Group N. Shen
Internet-Draft E. Chen Internet-Draft E. Chen
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: June 1, 2018 November 28, 2017 Expires: June 2, 2018 November 29, 2017
Generalized UDP Source Port for DHCP Relay Generalized UDP Source Port for DHCP Relay
draft-ietf-dhc-relay-port-08 draft-ietf-dhc-relay-port-09
Abstract Abstract
This document proposes an extension to the DHCP protocols that allows This document proposes an extension to the DHCP protocols that allows
a relay agent to use any available source port for upstream a relay agent to use any available source port for upstream
communications, and to include a DHCP option that can be used to communications, and to include a DHCP option that can be used to
statelessly route responses back to the appropriate source port on statelessly route responses back to the appropriate source port on
downstream communications. downstream communications.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 1, 2018. This Internet-Draft will expire on June 2, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Changes to DHCP Specifications . . . . . . . . . . . . . . . 3 3. Changes to DHCP Specifications . . . . . . . . . . . . . . . 3
3.1. Changes to DHCPv4 in RFC 2131 . . . . . . . . . . . . . . 3 3.1. Additions to DHCPv4 in RFC 2131 . . . . . . . . . . . . . 3
3.2. Changes to DHCPv6 in RFC 3315 . . . . . . . . . . . . . . 4 3.2. Additions to DHCPv6 in RFC 3315 . . . . . . . . . . . . . 4
4. Relay Source Port Sub-option and Option . . . . . . . . . . . 4 4. Relay Source Port Sub-option and Option . . . . . . . . . . . 4
4.1. Source Port Sub-option for DHCPv4 . . . . . . . . . . . . 4 4.1. Source Port Sub-option for DHCPv4 . . . . . . . . . . . . 4
4.2. Relay Source Port Option for DHCPv6 . . . . . . . . . . . 5 4.2. Relay Source Port Option for DHCPv6 . . . . . . . . . . . 5
5. Relay Agent and Server Behavior . . . . . . . . . . . . . . . 6 5. Relay Agent and Server Behavior . . . . . . . . . . . . . . . 5
5.1. DHCPv4 . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. DHCPv4 . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. DHCPv6 . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. DHCPv6 . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.3. Compatibility . . . . . . . . . . . . . . . . . . . . . . 7 5.3. Compatibility . . . . . . . . . . . . . . . . . . . . . . 6
5.4. Deployment Considerations . . . . . . . . . . . . . . . . 7 5.4. Deployment Considerations . . . . . . . . . . . . . . . . 7
6. An IPv6 Cascaded Relay Example . . . . . . . . . . . . . . . 7 6. An IPv6 Cascaded Relay Example . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
10. Normative References . . . . . . . . . . . . . . . . . . . . 9 10. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
RFC 2131 [RFC2131] and RFC 3315 [RFC3315] specify the use of UDP as RFC 2131 [RFC2131] and RFC 3315 [RFC3315] specify the use of UDP as
the transport protocol for DHCP. They also define both the server the transport protocol for DHCP. They also define both the server
side and client side port numbers. The IPv4 server port is UDP side and client side port numbers. The IPv4 server port is UDP
number (67) and the client port is UDP number (68); for IPv6 the number (67) and the client port is UDP number (68); for IPv6 the
server port is (547) and the client port is (546). server port is (547) and the client port is (546).
The fixed UDP port combinations for the DHCP protocol scheme creates The fixed UDP port combinations for the DHCP protocol scheme creates
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device uses when forwarding Relay-forward Messages to this device uses when forwarding Relay-forward Messages to this
relay agent device. This UDP port is to be used by this relay agent device. This UDP port is to be used by this
relay agent device when forwarding the Relay-reply Messages relay agent device when forwarding the Relay-reply Messages
to that downstream device. to that downstream device.
Non-DHCP UDP Port: Any valid and non-zero UDP port other than port Non-DHCP UDP Port: Any valid and non-zero UDP port other than port
67 for DHCPv4 and port 547 for DHCPv6. 67 for DHCPv4 and port 547 for DHCPv6.
3. Changes to DHCP Specifications 3. Changes to DHCP Specifications
3.1. Changes to DHCPv4 in RFC 2131 3.1. Additions to DHCPv4 in RFC 2131
Section 4.1 of RFC 2131 [RFC2131] specifies that: Section 4.1 of RFC 2131 [RFC2131] specifies that:
DHCP uses UDP as its transport protocol. DHCP messages from a DHCP uses UDP as its transport protocol. DHCP messages from a
client to a server are sent to the 'DHCP server' port (67), and client to a server are sent to the 'DHCP server' port (67), and
DHCP messages from a server to a client are sent to the 'DHCP DHCP messages from a server to a client are sent to the 'DHCP
client' port (68). client' port (68).
This specification adds the following extension to the above Relay agents implementing this specification may be configured
paragraph. instead to use a source port number other than 67, and to receive
responses on that same port. This will only work when the DHCP
DHCP messages from a relay agent to a server are sent to the 'DHCP server or relay agent to which such a relay agent is forwarding
server' port (67), and the UDP source port it uses can be any messages is upgraded to support this extension.
valid UDP port available in the relay system, including the DHCP
port 67. The default port number is 67 if there is no explicit
configuration for the generalized source UDP port extension for
DHCP relay.
3.2. Changes to DHCPv6 in RFC 3315 3.2. Additions to DHCPv6 in RFC 3315
Section 5.2 of RFC 3315 [RFC3315] specifies that: Section 5.2 of RFC 3315 [RFC3315] specifies that:
Clients listen for DHCP messages on UDP port 546. Servers and Clients listen for DHCP messages on UDP port 546. Servers and
relay agents listen for DHCP messages on UDP port 547. relay agents listen for DHCP messages on UDP port 547.
This specification adds the following extension to the above Relay agents implementing this specification may be configured
paragraph. instead to use a source port number other than 547, and to receive
responses on that same port. This will only work when the DHCP
A DHCP relay agent can listen for DHCP messages from a server or server or relay agent to which such a relay agent is forwarding
another upstream relay agent device on any valid UDP port messages is upgraded to support this extension.
available in the relay system including the DHCP UDP port 547.
The default UDP port is 547 if there is no explicit configuration
for the generalized UDP source port extension for DHCP relay.
4. Relay Source Port Sub-option and Option 4. Relay Source Port Sub-option and Option
Relay agents do not maintain state. To return a message to its Relay agents do not maintain state. To return a message to its
source, the relay agent must include all the required information in source, the relay agent must include all the required information in
the Relay-Forward message. When a relay in a sequence of cascaded the Relay-Forward message. When a relay in a sequence of cascaded
relays does not use the standard source port, that source port must relays does not use the standard source port, that source port must
be included along with the source address. This option allows the be included along with the source address. This option allows the
relay agent to do so. relay agent to do so.
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5.3. Compatibility 5.3. Compatibility
Sites that need for relay agents to specify a source port will need Sites that need for relay agents to specify a source port will need
to install new DHCP server and DHCP relay agent software with this to install new DHCP server and DHCP relay agent software with this
feature. If a site installs only DHCP relay agent software with this feature. If a site installs only DHCP relay agent software with this
feature, there is no possibility that the DHCP server will be able to feature, there is no possibility that the DHCP server will be able to
communicate to the relay agent. communicate to the relay agent.
5.4. Deployment Considerations 5.4. Deployment Considerations
During deployment, it may be advisable the operator and/or user of During deployment, it is advisable the operator and/or user of the
the new DHCP relay port implementation upgrade the DHCP server first new DHCP relay port implementation upgrade the DHCP server first when
when possible, before the relay implementations are deployed. This possible, before the relay implementations are deployed. This would
would ensure that the erroneous case noted in Section 5.3 is not ensure that the erroneous case noted in Section 5.3 is not
encountered. encountered. If the upstream relay agent or server does not support
this extension, this DHCP relay port feature needs to be disabled.
When the DHCP relay port implementation is deployed, it is When the DHCP relay port implementation is deployed, the default
recommended that the configuration is setup to allow for the mode of relay agent behavior should use the DHCP UDP port, it is recommended
operation where a non-DHCP port can be used for the DHCP relay that the configuration is setup to allow for the mode of operation
agents. The recommended configuration then permits the relay agent where a non-DHCP port can be used for the DHCP relay agents.
to utilize the default DHCP UDP port, or a non-DHCP UDP port as
desired.
Although if the network uses firewall to block or allow DHCP packets Although if the network uses firewall to block or allow DHCP packets
with both static UDP source and destination port numbers, this may no with both static UDP source and destination port numbers, this may no
longer match the packets from new DHCP relay agent and server longer match the packets from new DHCP relay agent and server
software with this extension. The firewall rules need to be modified software with this extension. The firewall rules need to be modified
only to match the DHCP server side of the UDP port number, and if only to match the DHCP server side of the UDP port number, and if
necessary, IP addresses and other attributes. necessary, IP addresses and other attributes.
6. An IPv6 Cascaded Relay Example 6. An IPv6 Cascaded Relay Example
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