Authentication Methods; X.509 Certificate-Based Peer Authentication - Cisco ASR 5000 Series 3G Home NodeB Administration Manual

▀ IPSec for LTE/SAE Networks
the selection criteria for packets being sent over IPSec security associations (SAs). Traffic selectors can be created on
the P-GW, S-GW, and MME for dynamic node-to-node IPSec tunnels during crypto template configuration by
specifying a range of peer IPv4 or IPV6 addresses from which to carry traffic over IPSec tunnels.
For example, consider an eNodeB with an IP address of 1.1.1.1 and an S-GW with a service address of 2.2.2.2. The S-
GW is registered to listen for IKE requests from the eNodeBs in the network using the following information:
 Local Address: 2.2.2.2
 Peer Address Network: 1.1.0.0 Mask: 255.255.0.0
 Payload ACL (Access Control List): udp host 2.2.2.2 eq 2123 1.1.0.0 0.0.255.255
When an IKE request arrives the S-GW from eNodeB address 1.1.1.1, the IPSec subsystem converts the payload ACL
to: udp host 2.2.2.2 eq 2123 host 1.1.1.1, and this payload becomes the traffic selector for the IPSec tunnel being
negotiated.
To properly accommodate control traffic between IPSec nodes, each child SA must include at least two traffic selectors:
one with a well-known port in the source address, and one with a well-known port in the destination address. Continuing
the example above, the final traffic selectors would be:
 Destination port as well-known port: udp host 2.2.2.2 1.1.0.0 0.0.255.255 eq 2123
 Source port as well-known port: udp host 2.2.2.2 eq 2123 1.1.0.0 0.0.255.255
Note that for ACL-based node-to-node IPSec tunnels, the configured crypto ACL becomes the traffic selector with no
modification.

Authentication Methods

IPSec for LTE/SAE includes the following authentication methods:
 PSK (Pre-Shared Key) Authentication: A pre-shared key is a shared secret that was previously shared between
two network nodes. IPSec for LTE/SAE supports PSK such that both IPSec nodes must be configured to use
the same shared secret.
 X.509 Certificate-based Peer Authentication: IPSec for LTE/SAE supports X.509 certificate-based peer
authentication and CA (Certificate Authority) certificate authentication as described below.

X.509 Certificate-based Peer Authentication

X.509 specifies standard formats for public key certificates, certificate revocation lists, attribute certificates, and a
certification path validation algorithm. X.509 certificates are configured on each IPSec node so that it can send the
certificate as part of its IKE_AUTH_REQ for the remote node to authenticate it. These certificates can be in PEM
(Privacy Enhanced Mail) or DER (Distinguished Encoding Rules) format, and can be fetched from a repository via
HTTP or FTP.
CA certificate authentication is used to validate the certificate that the local node receives from a remote node during an
IKE_AUTH exchange.
A maximum of sixteen certificates and sixteen CA certificates are supported per system. One certificate is supported per
service, and a maximum of four CA certificates can be bound to one crypto template.
For configuration instructions for X.509 certificate-based peer authentication, see the configuration chapter in the
administration guides for the MME, S-GW, and P-GW.
▄ Cisco ASR 5000 Series 3G Home NodeB Gateway Administration Guide
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IP Security
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