Avaya Configuring IPsec Services Manuel d'utilisateur télécharger pdf (Page 29)

Overview of IPsec

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To specify the protocol criterion, you must provide the numeric value assigned to

the protocol for use over the Internet. You can specify only a single protocol value

for each policy. The protocol number is represented in the 1-byte protocol field in

an IP packet header.

For a list of protocol numbers, see Appendix E, “

Protocol Numbers.” To obtain

the most recent list of the numeric values assigned to various protocols, see the

Internet Assigned Numbers Authority (IANA) Web site at:

http://www.iana.org

The direct path to the list of legal values that you can specify for an IPsec policy

protocol criterion is:

http://www.iana.org/assignments/protocol-numbers

Security Associations

A security association (SA) is a relationship in which two peers share the

necessary information to securely protect and unprotect data. An IPsec SA is

uniquely identified by an IP destination address, security parameter index (SPI),

and security protocol identifier (for example, ESP in tunnel mode).

An IPsec policy determines which packets are handled and which IPsec security

service (for example, confidentiality) is applied to the packets. You can apply one

or more IPsec security services.

SAs themselves must be created and shared in a secure manner. To create SAs,

you can use one of two methods:

• Use the automated security negotiation process provided by the Internet Key

Exchange (IKE) protocol. (IKE is the recommended method.)

• Manually configure the sending and receiving devices with a shared secret. A

shared secret is a unique security identifier.

Automated Security Associations Using IKE

Internet Key Exchange is an automated protocol to establish security associations

over the Internet. (IKE is also referred to as the Internet Security Association Key

Management Protocol with Oakley Key Determination, or ISAKMP/Oakley.) IKE

negotiates, establishes, modifies, and deletes security associations.

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Avaya Configuring IPsec Services Manuel d'utilisateur Page 29