In addition to the accuracy of the biometric systems, there are other factors
that must also be considered.
These factors include the enrollment time, the throughput rate, and acceptability.
Enrollment time is the time it takes to initially "register" with a system by providing samples
of the biometric characteristic to be evaluated. An acceptable enrollment time is around two
minutes.
For example, in fingerprint systems, the actual fingerprint is stored and requires
approximately 250kb per finger for a high quality image. This level of information is required
for one-to-many searches in forensics applications on very large databases.
In finger-scan technology, a full fingerprint is not stored-the features extracted from this
fingerprint are stored using a small template that requires approximately 500 to 1000 bytes
of storage. The original fingerprint cannot be reconstructed from this template.
Updates of the enrollment information may be required because some biometric
characteristics, such as voice and signature, may change with time.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the
Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 37 & 38.

The length of time between the Issuer's receipt of a revocation request and the time the Issuer is required to revoke the certificate should bear a reasonable relationship to the amount of risk the participants are willing to assume that someone may rely on a certificate for which a proper evocation request has been given but has not yet been acted upon.
How quickly revocation requests need to be processed (and CRLs or certificate status databases need to be updated) depends upon the specific application for which the Policy Authority is rafting the Certificate Policy.
A Policy Authority should recognize that there may be risk and lost tradeoffs with respect to grace periods for revocation notices. If the Policy Authority determines that its PKI participants are willing to accept a grace period of a few hours in exchange for a lower implementation cost, the Certificate Policy may reflect that decision.

Infrared is generally considered to be more secure to eavesdropping than multidirectional radio transmissions because infrared requires direct line-of-sight paths. Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 4: Cryptography (page 173).

Explanation/Reference:
DNS relies on connectionless UDP whereas services like FTP, Telnet and SMTP rely on TCP.
Source: ROTHKE, Ben, CISSP CBK Review presentation on domain 2, August 1999.