問52
頻出度★★★
IPv4をIPv6に置き換える効果として, 適切なものはどれか。
平成26年度 秋期 ITパスポート試験 問52
テクノロジ系ネットワーク › ネットワーク応用
This question's explanation and your answers so far.
解説
問 52
Incorrectア
An IP address is a number that uniquely identifies a communication partner on the Internet. This principle of uniqueness does not change with IPv6 either: if global IP addresses were duplicated, the destination could not be identified and a failure would occur. IPv6 is not a mechanism under which “no problem occurs even if addresses duplicate”; its essence is that it enlarges the address space so that there are enough addresses to avoid duplication.
- イ
正解 The correct answer is イ. An IPv4 address is 32 bits long, so in theory only about 4.3 billion addresses can be represented. As Internet users and devices increased rapidly, global IP addresses (addresses that can be accessed directly from the Internet) began to run out. IPv6 extends the address length to 128 bits, allowing about 3.4×10^38 addresses to be handled — so many that they will not run out in practice. Therefore the greatest effect of replacing IPv4 with IPv6 is that “the shortage of IP addresses that can be directly accessed from the Internet is resolved”, so イ is appropriate.
Incorrectウ
Whether the medium is optical fiber, metal cable (such as ADSL), or wireless is a matter of the transmission medium at the physical and data link layers, whereas IPv4 and IPv6 are network layer protocols — different layers. Optical fiber can be used while still running IPv4, and switching to IPv6 is not what makes optical fiber usable.
Incorrectエ
Communication speed is determined by factors such as the bandwidth of the line, congestion along the route, and the processing capability of the equipment; merely switching to IPv6 does not necessarily make it faster. IPv6 does reduce the processing load on routers by simplifying the header, but that is not an essential effect of the replacement in the way that “resolving the address shortage” is, nor does it guarantee faster communication.
ここがポイント
- An IPv4 address is 32 bits long (about 4.3 billion addresses) and an IPv6 address is 128 bits long (about 3.4×10^38 addresses). The greatest purpose and effect of introducing IPv6 is to resolve the exhaustion of global IP addresses.
- IPv4 and IPv6 are network layer protocols, a different layer from the transmission medium (such as optical fiber) or the line speed. The principle that an IP address must be unique on the Internet remains unchanged under IPv6 as well.
用語