| Network Working Group | X. Xu |
| Internet-Draft | Huawei |
| Intended status: Standards Track | G. Shepherd |
| Expires: July 13, 2018 | Cisco |
| January 9, 2018 |
Encapsulating Non-MPLS-BIER in UDP
draft-xu-bier-non-mpls-encap-over-udp-02
Bit Index Explicit Replication (BIER) is a new multicast forwarding paradigm which doesn't require an explicit tree-building protocol nor intermediate routers to maintain any multicast state. BIER has two types of encapsulation formats: one is MPLS-BIER encapsulation, the other is non-MPLS-BIER encapsulation. This document proposes a mechanism of encapsulating non-MPLS-BIER packets over UDP tunnels.
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Bit Index Explicit Replication (BIER) [RFC8279] is a new multicast forwarding paradigm which doesn't require an explicit tree-building protocol nor intermediate routers to maintain any multicast state. As described in Section 6.9 of [RFC8279], a BFR may need to tunnel a BIER packet over a certain kind of tunnel, e.g., UDP tunnel.
[I-D.ietf-bier-mpls-encapsulation] defines two types of BIER encapsulation formats: one is MPLS-BIER encapsulation, the other is non-MPLS-BIER encapsulation. MPLS-BIER packets can be transported over UDP tunnels by using the MPLS-in-UDP encapsulation as described in [RFC7510] . This document proposes a mechanism of encapsulating non-MPLS-BIER packets over UDP tunnels.
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.
This memo makes use of the terms defined in [RFC8279]and [I-D.ietf-bier-mpls-encapsulation].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = Entropy | Dest Port = TBD1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Non-MPLS-BIER Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Non-MPLS-BIER-in-UDP Encapsulation Format
Non-MPLS-BIER-in-UDP encapsulation format is shown as follows:
UDP Length:
This Non-MPLS-BIER-in-UDP encapsulation causes non-MPLS BIER packets to be forwarded across an IP transit core via "UDP tunnels". While performing Non-MPLS-BIER-in-UDP encapsulation, an encapsulator would generate an entropy value and encode it in the Source Port field of the UDP header. The Destination Port field is set to a value (TBD1) allocated by IANA to indicate that the UDP tunnel payload is a non-MPLS-BIER packet. Transit routers, upon receiving these UDP encapsulated non-MPLS-BIER packets, could balance these packets based on the hash of the five-tuple of UDP packets. Decapsulators receiving these UDP encapsulated non-MPLS-BIER packets MUST decapsulate these packets by removing the UDP header and then forward them accordingly.
Similar to all other IP-based tunneling technologies, Non-MPLS-BIER-in-UDP encapsulation introduces overheads and reduces the effective Maximum Transmission Unit (MTU) size. Non-MPLS-BIER-in-UDP encapsulation may also impact Time-to-Live (TTL) or Hop Count (HC) and Differentiated Services (DSCP). Hence, Non-MPLS-BIER-in-UDP MUST follow the corresponding procedures defined in [RFC2003].
Encapsulators MUST NOT fragment non-MPLS-BIER packet, and when the outer IP header is IPv4, encapsulators MUST set the DF bit in the outer IPv4 header. It is strongly RECOMMENDED that IP transit core be configured to carry an MTU at least large enough to accommodate the added encapsulation headers. Meanwhile, it is strongly RECOMMENDED that Path MTU Discovery [RFC1191] [RFC1981] or Packetization Layer Path MTU Discovery (PLPMTUD) [RFC4821] is used to prevent or minimize fragmentation.
As it's explicitly stated in the Application Statements (Section 6), this Non-MPLS-BIER-in-UDP encapsulation method MUST only be used within networks that are well-managed, therefore, congestion control mechanism is not needed.
This Non-MPLS-BIER-in-UDP encapsulation technology MUST only be used within networks which are well-managed by a service provider and MUST NOT be used within the Internet. In the well-managed network, traffic is well-managed to avoid congestion and fragmentation on encapsulated packets (i.e., Non-MPLS-BIER packets) are not needed.
TBD.
One UDP destination port number indicating non-MPLS-BIER needs to be allocated by IANA:
Service Name: Non-MPLS-BIER-in-UDP Transport Protocol(s):UDP Assignee: IESG <iesg@ietf.org> Contact: IETF Chair <chair@ietf.org>. Description: Encapsulate Non-MPLS-BIER packets in UDP tunnels. Reference: This document. Port Number: TBD1 -- To be assigned by IANA.
One UDP destination port number indicating Non-MPLS-BIER with DTLS needs to be allocated by IANA:
Service Name: Non-MPLS-BIER-in-UDP-with-DTLS Transport Protocol(s): UDP Assignee: IESG <iesg@ietf.org> Contact: IETF Chair <chair@ietf.org>. Description: Encapsulate Non-MPLS-BIER packets in UDP tunnels with DTLS. Reference: This document. Port Number: TBD2 -- To be assigned by IANA.
The security problems faced with the Non-MPLS-BIER-in-UDP tunnel are exactly the same as those faced with MPLS-in-UDP tunnel [RFC7510]. In other words, the Non-MPLS-BIER-in-UDP tunnel as defined in this document by itself cannot ensure the integrity and privacy of data packets being transported through the Non-MPLS-BIER-in-UDP tunnel and cannot enable the tunnel decapsulator to authenticate the tunnel encapsulator. In the case where any of the above security issues is concerned, the Non-MPLS-BIER-in-UDP tunnel SHOULD be secured with IPsec or DTLS. IPsec was designed as a network security mechanism and therefore it resides at the network layer. As such, if the tunnel is secured with IPsec, the UDP header would not be visible to intermediate routers anymore in either IPsec tunnel or transport mode. As a result, the meaning of adopting the Non-MPLS-BIER-in-UDP tunnel as an alternative to the Non-MPLS-BIER-in-GRE or Non-MPLS-BIER-in-IP tunnel is lost. By comparison, DTLS is better suited for application security and can better preserve network and transport layer protocol information. Specifically, if DTLS is used, the destination port of the UDP header will be filled with a value (TBD2) indicating non-MPLS-BIER with DTLS and the source port can still be used as an entropy field for load-sharing purposes.
| [RFC7510] | Xu, X., Sheth, N., Yong, L., Callon, R. and D. Black, "Encapsulating MPLS in UDP", RFC 7510, DOI 10.17487/RFC7510, April 2015. |