| Internet Engineering Task Force | S. Pallagatti, Ed. |
| Internet-Draft | S. Paragiri |
| Intended status: Standards Track | B. Saji |
| Expires: November 5, 2015 | Juniper Networks |
| May 4, 2015 |
BFD for VXLAN
draft-spallagatti-bfd-vxlan-00
This document describes use of Bidirectional Forwarding Detection (BFD) protocol for VXLAN . Comments on this draft should be directed to nvo3@ietf.org.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].
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"Virtual eXtensible Local Area Network (VXLAN)" has been defined in [RFC7348] that provides an encapsulation scheme which allows VM's to communicate in data centre network.
VXLAN is typically deployed in data centres on virtualized hosts, which may be spread across multiple racks. The individual racks may be parts of a different Layer 3 network or they could be in a single Layer 2 network. The VXLAN segments/overlay networks are overlaid on top of these Layer 2 or Layer 3 networks.
A VM can communicate with a VM in other host only if they are on same VXLAN. VM's are unaware of VXLAN tunnels as VXLAN tunnel terminates on VTEP (hypervisor/TOR). VETP (hypervisor/TOR) are responsible for encapsulating and decapsulating frames sent from VM's.
Since underlay is a L3 network connectivity check for these tunnels becomes important. BFD as defined in [RFC5880] can be used to monitor the VXLAN tunnels.
Main use case of BFD for VXLAN is for tunnel connectivity check. There are other use cases such as
+------------+-------------+
| Server 1 |
| |
| +----+----+ +----+----+ |
| |VM1-1 | |VM1-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| Hypervisor VTEP (IP1) |
+--------------------------+
|
|
|
| +-------------+
| | Layer 3 |
|---| Network |
| |
+-------------+
|
|
+-----------+
|
|
+------------+-------------+
| Hypervisor VTEP (IP2) |
| +----+----+ +----+----+ |
| |VM2-1 | |VM2-2 | |
| |VNI 100 | |VNI 200 | |
| | | | | |
| +---------+ +---------+ |
| Server 2 |
+--------------------------+
Consider the above diagram, where we have two servers with IP1 and IP2 and each of them are hosting two VM's. There are two VXLAN tunnels with VNI number 100 and 200. For connectivity check of these two VXLAN tunnels, BFD sessions needs to be established per tunnel. In the diagram above two BFD will be established between server 1's Hypervisor VTEP (IP1) and server2 Hypervisor VTEP(IP2). BFD session will originate from Hypervisor VTEP (IP1) and terminate at Hypervisor VTEP (IP2) and visa versa. Each BFD session on Hypervisor VTEP will be identified by its VNI in VXLAN header. No BFD packet intended to Hypervisor VTEP should be forwarded to VM's as VM's may drop this leading to false negative.
This method is also applicable VTEP which are either software or physical device.
Packet format has been defined in Section 5 of [RFC7348]. Outer IP/UDP and VXLAN header will remain same and they should be filled by sending VTEP as per [RFC7348]. Inner packet format has been defined as below for BFD packet which terminates at VETP. BFD packet MUST have a inner IP/UDP header followed by BFD payload.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
Inner IPv4 Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTL = 1 |Protocl=17(UDP)| Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Source IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner Destination Ipv4 Address = 127/8 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inner IPv6 Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | NxtHdr=17(UDP)| Hop Limit = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Inner Source IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Inner Destination IPv6 Address = +
| 0:0:0:0:0:FFFF:7F00/104 |
+ +
| |
+ +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inner UDP Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Dest Port = 3784 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
BFD packet:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Vers | Diag |Sta|P|F|C|A|D|M| Detect Mult | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Your Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Desired Min TX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min Echo RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This section describes BFD packet encapsulation while transmitting BFD packet from VTEP
Once a packet is received VTEP MUST validate packet as described in Section 4.1 of [RFC7348]. Since inner IP TTL is set to 1 packet SHOULD be consumed by VTEP and should not be forwarded further to VM. It is recommended that BFD packets should not be throttled with TTL 1. Implementation MAY have a check to relax throttling if the inner IP address is 127/8 range for IPv4 and 0:0:0:0:0:FFFF:7F00/104 for IPv6 then UDP destination port is 3784.
Demux of IP BFD packet has been defined in Section 3 of [RFC5881]. BFD demultiplexing for VXLAN is going to be different as destination IP is same for all sessions and underlay is layer 3 and may have ECMP. Source address and VNI should identify a BFD session on VTEP, initially when BFD packets are sent with with your discriminator set to 0 BFD packets MUST be demultiplexed with source address and VNI as the key. If BFD packet is received with non-zero your discriminator then BFD session should be demultiplexed only with your discriminator as the key.
Support for echo BFD is outside the scope of this document.
S-BFD can also be used for connectivity check as defined in [I-D.ietf-bfd-seamless-base]
VTEP MUST encapsulate S-BFD packet as defined in Section 5. For S-BFD however your Discriminator will be set to VNI from the VXLAN header.
VTEP MUST decapsulate S-BFD packet as defined in above section "reception of BFD packet". Reflector MUST validate if your Discriminator belongs any one of the VNI on that VTEP.
This document has no actions for IANA.
Document recommends setting of inner IP TTL to 1 which could lead to DDoS attack, implementation MUST have throttling in place. Throttling MAY be relaxed for BFD packeted based on port number.
Other than inner IP TTL set to 1 this specification does not raise any additional security issues beyond those of the specifications referred to in the list of normative references.
Authors would like to thank Jeff Hass of Juniper Networks for his reviews and feedback on this material.
| [I-D.ietf-bfd-seamless-base] | Akiya, N., Pignataro, C., Ward, D., Bhatia, M. and J. Networks, "Seamless Bidirectional Forwarding Detection (S-BFD)", Internet-Draft draft-ietf-bfd-seamless-base-04, January 2015. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC5880] | Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010. |
| [RFC5881] | Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June 2010. |
| [RFC7348] | Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger, L., Sridhar, T., Bursell, M. and C. Wright, "Virtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks", RFC 7348, August 2014. |