]> Tsinghua University

Department of Computer Science, Tsinghua University Beijing 100084 China +86-10-6260-3059 yong@csnet1.cs.tsinghua.edu.cn

Tsinghua University

Department of Computer Science, Tsinghua University Beijing 100084 China +86-10-6278-5822 knight.dongjiang@gmail.com

Tsinghua University

Department of Computer Science, Tsinghua University Beijing 100084 China +86-10-6278-5822 weapon9@gmail.com

Tsinghua University

Department of Computer Science, Tsinghua University Beijing 100084 China +86-10-6278-5822 xmw@cernet.edu.cn

Aalto University

Konemiehentie 2 Espoo 02150 Finland +358-40-5954222 antti.yla-jaaski@aalto.fi

Internet Area Softwire Management Information Base MIB SMIv2 mesh This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it defines objects for managing a softwire mesh.

The softwire mesh framework is a tunneling mechanism that enables connectivity between islands of IPv4 networks across a single IPv6 backbone and vice versa. In a softwire mesh, extended Multiprotocol BGP (MP-BGP) is used to set up tunnels and advertise prefixes among Address Family Border Routers (AFBRs). This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it defines objects for managing a softwire mesh .

For a detailed overview of the documents that describe the current Internet-Standard Management Framework, please refer to section 7 of RFC 3410 . Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. MIB objects are generally accessed through the Simple Network Management Protocol (SNMP). Objects in the MIB are defined using the mechanisms defined in the Structure of Management Information (SMI). This memo specifies a MIB module that is compliant to the SMIv2, which is described in STD 58, RFC 2578 , STD 58, RFC 2579 and STD 58, RFC 2580 .

This document uses terminology from the softwire problem statement , the BGP encapsulation Subsequent Address Family Identifier (SAFI), the BGP tunnel encapsulation attribute , the softwire mesh framework , and the BGP IPsec tunnel encapsulation attribute . The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 .

The Softwire Mesh MIB provides a method to monitor the softwire mesh objects through SNMP.

The swmSupportedTunnelTable subtree provides the information about what types of tunnels can be used for softwire mesh scenarios in the AFBR. The softwire mesh framework does not mandate the use of any particular tunneling technology. Based on the BGP tunnel encapsulation attribute tunnel types introduced by RFC 5512 and RFC 5566 , the softwire mesh tunnel types include at least L2TPv3 (Layer 2 Tunneling Protocol version 3) over IP, GRE (Generic Routing Encapsulation), Transmit tunnel endpoint, IPsec in Tunnel-mode, IP in IP tunnel with IPsec Transport Mode, MPLS-in-IP tunnel with IPsec Transport Mode, and IP in IP. The detailed encapsulation information of different tunnel types (e.g., L2TPv3 Session ID, GRE Key, etc.) is not managed in the Softwire Mesh MIB.

The swmEncapsTable subtree provides softwire mesh NLRI-NH information (Network Layer Reachability Information - Next Hop) about the AFBR. It keeps the mapping between the External-IP (E-IP) prefix and the Internal-IP (I-IP) address of the next hop. The mappings determine which I-IP destination address will be used to encapsulate the received packet according to its E-IP destination address. The definitions of E-IP and I-IP are explained in Section 4.1 of RFC 5565 . The number of entries in swmEncapsTable shows how many softwire mesh tunnels are maintained in this AFBR.

This subtree provides the softwire mesh BGP neighbor information of an AFBR. It includes the address of the softwire mesh BGP peer and the kind of tunnel that the AFBR would use to communicate with this BGP peer.

This subtree provides the conformance information of MIB objects.

The Interfaces MIB defines generic managed objects for managing interfaces. Each logical interface (physical or virtual) has an ifEntry. Tunnels are handled by creating logical interfaces (ifEntry). Being a tunnel, the softwire mesh interface has an entry in the Interface MIB, as well as an entry in the IP Tunnel MIB. Those corresponding entries are indexed by ifIndex. The ifOperStatus in the ifTable represents whether the mesh function of the AFBR has been triggered. If the softwire mesh capability is negotiated during the BGP OPEN phase, the mesh function is considered to be started, and the ifOperStatus is "up". Otherwise, the ifOperStatus is "down". In the case of an IPv4-over-IPv6 softwire mesh tunnel, ifInUcastPkts counts the number of IPv6 packets that are sent to the virtual interface for decapsulation into IPv4. The ifOutUcastPkts counts the number of IPv6 packets that are generated by encapsulating IPv4 packets sent to the virtual interface. In particular, if these IPv4 packets need fragmentation, ifOutUcastPkts counts the number of packets after fragmentation. In the case of an IPv6-over-IPv4 softwire mesh tunnel, ifInUcastPkts counts the number of IPv4 packets that are delivered to the virtual interface for decapsulation into IPv6. The ifOutUcastPkts counts the number of IPv4 packets that are generated by encapsulating IPv6 packets sent down to the virtual interface. In particular, if these IPv6 packets need to be fragmented, ifOutUcastPkts counts the number of packets after fragmentation. Similar definitions apply to other counter objects in the ifTable.

The IP Tunnel MIB contains objects applicable to all IP tunnels, including softwire mesh tunnels. Meanwhile, the Softwire Mesh MIB extends the IP Tunnel MIB to further describe encapsulation-specific information. When running a point-to-multipoint tunnel, it is necessary for a softwire mesh AFBR to maintain an encapsulation table in order to perform correct "forwarding" among AFBRs. This forwarding function on an AFBR is performed by using the E-IP destination address to look up the I-IP encapsulation destination address in the encapsulation table. An AFBR also needs to know the BGP peer information of the other AFBRs, so that it can negotiate the NLRI-NH information and the tunnel parameters with them. The Softwire Mesh MIB requires the implementation of the IP Tunnel MIB. The tunnelIfEncapsMethod in the tunnelIfEntry MUST be set to softwireMesh(16), and a corresponding entry in the Softwire Mesh MIB module will be presented for the tunnelIfEntry. The tunnelIfRemoteInetAddress MUST be set to "0.0.0.0" for IPv4 or "::" for IPv6 because it is a point-to-multipoint tunnel. The tunnelIfAddressType in the tunnelIfTable represents the type of address in the corresponding tunnelIfLocalInetAddress and tunnelIfRemoteInetAddress objects. The tunnelIfAddressType is identical to swmEncapsIIPDstType in softwire mesh, which can support either IPv4-over-IPv6 or IPv6-over-IPv4. When the swmEncapsEIPDstType is IPv6 and the swmEncapsIIPDstType is IPv4, the tunnel type is IPv6-over-IPv4; when the swmEncapsEIPDstType is IPv4 and the swmEncapsIIPDstType is IPv6, the encapsulation mode is IPv4-over-IPv6.

The following MIB module IMPORTS objects from SNMPv2-SMI , SNMPv2-CONF , IF-MIB , and INET-ADDRESS-MIB .

Because this MIB module reuses the IP Tunnel MIB, the security considerations of the IP Tunnel MIB are also applicable to the Softwire Mesh MIB. There are no management objects defined in this MIB module that have a MAX-ACCESS clause of read-write and/or read-create. So, if this MIB module is implemented correctly, then there is no risk that an intruder can alter or create any management objects of this MIB module via direct SNMP SET operations. Some of the readable objects in this MIB module (i.e., objects with a MAX-ACCESS other than not-accessible) may be considered sensitive or vulnerable in some network environments. It is thus important to control even GET and/or NOTIFY access to these objects and possibly to even encrypt the values of these objects when sending them over the network via SNMP. These are the objects and their sensitivity/vulnerability: swmSupportedTunnelType, swmEncapsIIPDstType, swmEncapsIIPDst, and swmBGPNeighborTunnelType can expose the types of tunnels used within the internal network and potentially reveal the topology of the internal network. SNMP versions prior to SNMPv3 did not include adequate security. Even if the network itself is secure (for example by using IPsec), there is no control as to who on the secure network is allowed to access and GET/SET (read/change/create/delete) the objects in this MIB module. Implementations SHOULD provide the security features described by the SNMPv3 framework (see ), and implementations claiming compliance to the SNMPv3 standard MUST include full support for authentication and privacy via the User-based Security Model (USM) with the AES cipher algorithm . Implementations MAY also provide support for the Transport Security Model (TSM) in combination with a secure transport such as SSH or TLS/DTLS . Further, deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED. Instead, it is RECOMMENDED to deploy SNMPv3 and to enable cryptographic security. It is then a customer/operator responsibility to ensure that the SNMP entity giving access to an instance of this MIB module is properly configured to give access to the objects only to those principals (users) that have legitimate rights to indeed GET or SET (change/create/delete) them.

IANA has allocated the following OBJECT IDENTIFIER value and recorded it in the SMI Numbers registry in the subregistry called "SMI Network Management MGMT Codes Internet-standard MIB" under the mib-2 branch (1.3.6.1.2.1):

IANA has recorded the following IANAtunnelType Textual Convention within the IANAifType-MIB:

&rfc2119; &rfc2578; &rfc2579; &rfc2580; &rfc4001; &rfc3410;

The authors would like to thank Dave Thaler, Jean-Philippe Dionne, Qi Sun, Sheng Jiang, and Yu Fu for their valuable comments.