Mobile Network Infrastructure Getting Started
    : GTP Protection Profile
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    Mobile Network Infrastructure Getting Started

    GTP Protection Profile

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    End-of-Life (EoL)

    GTP Protection Profile

    Use these fields to create a GTP Protection profile to define how the firewall inspects, validates, and filters GTP traffic.
    The GTP Protection profile (ObjectsSecurity ProfilesGTP Protection) enables the firewall to inspect GTP traffic. The options in the profile allow you to enable stateful inspection of GTPv1-C and GTPv2-C, enable protocol validation for GTPv1-C, GTPv2-C, and GTP-U, and enable GTP-U content inspection to scan user data within GTP-U tunnels.
    The options also allow you to filter GTP sessions based on APN, IMSI-Prefix, and RAT, and prevent end-user IP address spoofing to protect the mobile subscribers from being overbilled.
    To Configure GTP Stateful Inspection, you must attach the GTP Protection profile to a Security policy rule for a zone.
    FieldDescription
    GTP Inspection
    GTP-C
    • Select Stateful Inspection to enable the firewall to inspect GTPv1-C or GTPv2-C or both. When you enable stateful inspection, the firewall uses the source IP address, source port, destination IP address, destination port, protocol, and the Tunnel Endpoint IDs (TEID) to keep track of a GTP session. It also checks and validates the order of the different types of GTP messages that establish a GTP tunnel. The TEID uniquely identifies the GSN tunnel endpoints. The tunnels for an uplink and a downlink are separate and use a different TEID.
    • Select the Action that the firewall takes upon a validity check failure: Alert allows the traffic but generates a log; Block denies the traffic and generates a log.
    • Specify the validity checks that the firewall performs on a GTP header and the Information Elements (IE) in a payload (and to which the firewall applies the specified Action):
      • Reserved IE—Checks for the GTPv1-C or GTPv2-C messages that use reserved IE values.
      • Order of IE (GTPv1-C only)—Checks that the order of IEs in GTPv1-C messages is accurate.
      • Length of IE—Checks for the GTPv1-C or GTPv2-C messages with invalid IE length.
      • Reserved field in header—Checks for malformed packets that use invalid values or reserved values in a header.
      • Unsupported message type—Checks for unknown or incorrect message types.
    NAT for outer GTP sessions is not supported with GTP stateful inspection.
    GTP-U
    Enabling Stateful Inspection for GTPv1-C and/or GTPv2-C automatically enables GTP-U stateful inspection.
    You can specify the following validity checks for GTP-U payloads and Block or Alert upon a validity check failure:
    • Reserved IE—Checks for the GTP-U messages that use reserved IE values in the payload.
    • Order of IE—Checks that the order of the IEs in GTP-U messages is correct.
    • Length of IE—Checks for messages with invalid IE length.
    • Reserved field in header—Checks for malformed packets that use invalid values or reserved values in a header.
    • Unsupported message type—Checks for unknown or incorrect message types.
    You can also allow, block or alert on:
    • End User IP Address Spoofing—When the source IP address in a GTP-U packet from the subscriber user equipment is not the same as the IP address in the corresponding GTP-C message exchanged during tunnel set up.
    • GTP-in-GTP—A GTP message inside another GTP message. Upon detection, the firewall generates a GTP log with critical severity.
    GTP-U (cont)
    Enable GTP-U Content Inspection if you want to inspect and apply policy to the user data payload within a GTP-U packet. Inspecting GTP-U content allows you to correlate IMSI and IMEI information learned from GTP-C messages with the IP traffic encapsulated in GTP-U packets.
    You don’t need a Tunnel Content Inspection policy to perform content inspection inside GTP-U tunnels if you use a GTP Protection profile and enable GTP-U Content Inspection.
    GTP-U inner sessions do not support decryption, NAT, or policy-based forwarding (PBF).
    Filtering Options
    RAT Filtering
    By default all Radio Access Technologies (RAT) are allowed. GTP-C Create-PDP-Request and Create-Session-Request messages are filtered or allowed based on the RAT filter. You can specify whether to allow, block or alert on the following Remote Access Technologies (RAT) that the user equipment uses to access the mobile core network:
    • UTRAN
    • GERAN
    • WLAN
    • GAN
    • HSPA Evolution
    • EUTRAN
    • Virtual
    • EUTRAN-NB-IoT
    IMSI Filtering
    IMSI (International Mobile Subscriber Identity) is a unique identification associated with a subscriber in GSM, UMTS and LTE networks that is provisioned in the Subscriber Identity Module (SIM) card.
    An IMSI is usually presented as a 15-digit number (8 bytes), but can be shorter. IMSI has three parts:
    • Mobile Country Code (MCC) consisting of three digits. The MCC uniquely identifies the country of domicile of the mobile subscriber.
    • Mobile Network Code (MNC) consisting of two or three digits; 2 digits European standard or 3 digits North America standard. The MNC identifies the home PLMN of the mobile subscriber.
    • Mobile Subscriber Identification Number (MSIN) identifying the mobile subscriber within a PLMN.
    The IMSI Prefix combines the MCC and MNC and allows you to allow, block, or alert on GTP traffic from a specific PLMN. By default all IMSI are allowed.
    You can either manually enter or import a csv file with IMSI or IMSI prefixes into the firewall. The IMSI can include a wildcard, for example, 310* or 240011*. The firewall supports a maximum of 5,000 IMSI or IMSI prefixes.
    APN Filtering
    The Access Point Name (APN) is a reference to a GGSN/ PGW that a user equipment requires to connect to the internet. The APN is composed of two parts:
    • APN Network Identifier that defines the external network to which the GGSN/PGW is connected and optionally a requested service by the mobile station. This part of the APN is mandatory.
    • APN Operator Identifier that defines in which PLMN GPRS/EPS backbone the GGSN/PGW is located. This part of the APN is optional.
    By default all APNs are allowed. The APN filter allows you to allow, block, or alert on GTP traffic based on the APN value. GTP-C Create-PDP-Request and Create-Session-Request messages are filtered or allowed based on the rules defined for APN filtering.
    You can manually add or import an APN filtering list into the firewall. The value for the APN must include the network ID or the domain name of the network (for example, example.com) and, optionally, the operator ID.
    For APN filtering, the wildcard (*) allows you to match for all APN. A combination of * and other characters is not supported for wildcards. For example, internet.mnc* will be treated as regular APN and will not filter all entries that start with internet.mnc.
    The firewall supports a maximum of 1,000 APN filters.
    GTP Tunnel Limit
    Max Concurrent Tunnels Allowed per Destination
    Allows you to limit the maximum number of GTP-U tunnels to a destination IP address, for example, to the GGSN. Range: 0 to 100,000,000 tunnels.
    Alert at Max Concurrent Tunnels per Destination
    Specify the threshold at which the firewall triggers an alert when the maximum number of GTP-U tunnels to a destination has been established. A GTP log message of high severity is generated when the configured tunnel limit is reached.
    Logging Frequency
    The number of events that the firewall counts before it generates a log when the configured GTP tunnel limits are exceeded. This setting allows you to reduce the volume of messages logged. Default: 100; range: 1 to 100,000,000
    Overbilling Protection
    Select the virtual system that serves as the Gi/ SGi firewall on your firewall. The Gi/ SGi firewall inspects the mobile subscriber IP traffic traversing the Gi/ SGi interface from the PGW/ GGSN to the external PDN (packet data network) such as the internet and secures internet access for mobile subscribers.
    Overbilling can occur when a GGSN assigns a previously used IP address from the End User IP address pool to a mobile subscriber. When a malicious server on the internet continues to send packets to this IP address as it did not close the session initiated for the previous subscriber and the session is still open on the Gi Firewall. To disallow data from being delivered, whenever a GTP tunnel is deleted (detected by delete-PDP or delete-session message) or timed-out, the firewall enabled for overbilling protection notifies the Gi/ SGi firewall to delete all the sessions that belong to the subscriber from the session table. GTP Security and SGi/ Gi firewall should be configured on the same physical firewall, but can be in different virtual systems.
    In order to delete sessions based on GTP-C events, the firewall needs to have all the relevant session information and this is possible only when you manage traffic from the SGi + S11 or S5 interfaces for GTPv2 and Gi + Gn interfaces for GTPv1 in the mobile core network.
    Other Log Settings
    By default the firewall does not log allowed GTP messages. You should be selective if you enable logging of GTP Allowed Messages for troubleshooting when needed, because such logging will generate a high volume of logs. In addition to logging Allowed Messages, this tab also allows you to selectively enable logging of user location information.
    GTPv1-C Allowed Messages
    Allows you to selectively enable logging of allowed GTPv1-C messages, if you have enabled Stateful Inspection for GTPv1-C. These messages generate logs to help you troubleshoot issues as needed. By default, the firewall does not log allowed messages. The logging options for allowed GTPv1-C messages are:
    • Tunnel Management—These GTPv1-C messages are used to manage the GTP-U tunnels, which carry encapsulated IP packets and signaling messages between a given pair of network nodes such as SGSN and GGSN. Messages logged under this option are: Create PDP Context Request, Create PDP Context Response, Update PDP Context Request, Update PDP Context Response, Delete PDP Context Request, Delete PDP Context Response. The rest of the tunnel management messages are logged as Others (explained below).
    • Path Management—These GTPv1-C messages are typically sent by the GSN or Radio Network Controller (RNC) to the other GSN or RNC to find out if the peer is alive. They include messages such as Echo Request/ Response.
    • Others—These messages include location management, mobility management, RAN information management and Multimedia Broadcast Multicast Service (MBMS) messages.
    Log User Location
    Allows you to include the user location information (as area code and Cell ID) in GTP logs.
    GTPv2-C Allowed Messages
    Allows you to selectively enable logging of the allowed GTPv2-C messages, if you have enabled Stateful Inspection for GTPv2-C. These messages generate logs to help you troubleshoot issues as needed. By default, the firewall does not log allowed messages. The logging options for allowed GTPv2-C messages are:
    • Tunnel Management—These GTPv2-C messages are used to manage the GTP-U tunnels, which carry encapsulated IP packets and signaling messages between a given pair of network nodes such as the SGW and PGW. Messages logged under this option are: Create Session Request, Create Session Response, Modify Bearer Request, Modify Bearer Response, Delete Session Request, Delete Session Context Response. The rest of the tunnel management messages are logged under the option Others.
    • Path Management—These GTPv2-C messages are typically sent by a network node such as the SGW or PGW to the other PGW or SGW to find out if the peer is alive. They include messages such as Echo Request/ Response.
    • Others—These messages include mobility management and Non-3GPP access related messages.
    GTP-U Allowed Messages
    Allows you to selectively enable logging of the allowed GTP-U messages, if you have enabled Stateful Inspection for GTPv2-C and/or GTPv1-C. These messages generate logs to help you troubleshoot issues as needed.
    The logging options for allowed GTP-U messages are:
    • Tunnel Management—These are GTP-U signaling messages such as Error Indication.
    • Path Management—These GTP-U messages are sent by a network node (such as eNodeB) to another network node (such as SGW) to find out if the peer is alive. It includes messages such as Echo Request/ Response.
    • G-PDU—G-PDU (GTP-U PDU) is used for carrying user data packets within the network nodes in the mobile core network; it consists of a GTP header plus a T-PDU.
    G-PDU Packets Logged per New GTP-U Tunnel
    Enable this option to verify that the firewall is inspecting GTP-U PDUs. The firewall generates a log for the specified number of G-PDU packets in each new GTP-U tunnel. Range is 1 to 10; default is 1.
    Packet Capture
    Enable this log setting to capture a GTP packet that is any of the following types of GTP event:
    • GTP-in-GTP
    • End user IP address spoofing
    • Abnormal GTPv1-C, GTPv2-C, and GTP-U messages that have a missing mandatory Information Element (IE), invalid IE, out-of-order IE, invalid header, or unsupported message type
    • Other abnormal GTPv1-C, GTPv2-C, and GTP-U messages

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