## 4 Network Layer: The Main Building Block of Fixed Networks
### Five Generations of Access: From PSTN to 50G EPON
#### 4.1.2 F1g--1980's  
**LAN:** A local area network (LAN) is not only a computer network covering a small geographical region, but it also stands for a common link that connects LAN users to the global Internet. LAN has the advantage of serving many more users than PSTN; its disadvantage is the absence of a QoS guarantee. The involved protocols play a key role in both transmission efficiency and the QoS offered to the users. To concentrate on some important \"fixed\" LAN configurations, in accordance with the utilized data-link layer  
Figure 4: Most important deployed access standards over the past 50 years.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Year** & **Name** & **Standard** & **DS Rate** & **US Rate** & **Maximum Reach** \\ \hline
1875 & PSTN & - & up to 64 kb/s & - & - \\
1988 & N-ISDN & Lseries & up to 2 Mb/s & - & - \\
1988 & B-ISDN & Lseries & up to 622 Mb/s & up to 622 Mb/s & - \\
1992 & HPC & - & 40 Mb/s & 9 Mb/s & 25 km \\
1997 & DOCSIS & J.112, J.122, J.222 & 40 Mb/s & 10 Mb/s & - \\
1998 & HDSL & G991.1 & 1.5 Mb/s & 1.5 Mb/s & 4 km \\
1999 & ADSL & G992.1 & 7 Mb/s & 800 kb/s & +6 km \\
2002 & ADSL2 & G992.3 & 8 Mb/s & 1 Mb/s & 2 km \\
2003 & ADSL2+ & G992.5 & 24 Mb/s & 1 Mb/s & 1 km \\
2002 & ADSL2-RE & G992.3 & 8 Mb/s & 1 Mb/s & 7 km \\ - & SDSL & - & 1.5 Mb/s & 1.5 Mb/s & 3-6 km \\
2001 & VDSL & G993.1 & 52 Mb/s & 2.3 Mb/s & 1.5 km \\
2006 & VDSL2 & G993.2 & 200 Mb/s & 100 Mb/s & 2.2 km \\
2014 & G.Fast & G.9700, G.9701 & up to 1 Gb/s & up to 1 Gb/s & 0.5 km \\ \hline \hline \end{tabular}
\end{table}
Table 3: Details of various copper-based access standards.  
protocol, the LAN is called Ethernet LAN (IEEE 802.3), token-ring LAN (IEEE 802.5), or FDDI (Fiber Distributed Data Interface) LAN (ANSI X3T9.5) (Figure 5) [4].  
**ISDN:** In ISDN, the network access interface is called the basic rate interface (BRI) and is offered to the user over a twisted pair of copper wires. BRI consists of two \"B\" (Bearer) channels of 64 kb/s (readily aggregated to one channel of 128 kb/s) and one \"D\" (Delta or Data) channel of 16 kb/s. Users need to be within a 5.5 km distance of the local ISDN office to have a BRI-line. Although ISDN could offer to the users a higher number of B channels (e.g., six B channels, 384 kb/s, for the videophone service), ISDN was unable to support  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multirow{2}{*}{**Name**} & \multirow{2}{*}{**Standard**} & \multirow{2}{*}{**DS/US Rate**} & \multicolumn{2}{c}{**Number of**} & \multirow{2}{*}{**Maximum**} & \multirow{2}{*}{**Technology/Traffic**} & \multirow{2}{*}{**Splitting**} \\  & & & & & **\(\lambda\)s per** & & & **Radio** \\  & & & & **Direction** & & & **Mode** & **Ratio** \\ \hline
1998 & APON & G983.x & 622/155 Mb/s & 1 & 10 km & ATM & 1:32 \\
1999 & BPON & G983.x & 622/155 Mb/s & 1 & 20 km & ATM & 1:32 \\
2004 & GPON & G984.x & 2.5/1.25 Gb/s & 1 & 20 km & GEM & 1:128 \\
2004 & EPON & 802.3 ah & 1.25/1.25 Gb/s & 1 & 20 km & Ethernet & 1:128 \\
2009 & 10G-EPON & 802.3 av & 10/10 Gb/s & 1 & 40 km & Ethernet & 1:128 \\
2010 & XG-PON & G987.x & 10/2.5 Gb/s & 1 & 60 km & TWDM & 1:256 \\
2015 & NG-PON2 & G989.x & 40/40 Gb/s & up to 8 & 40 km & TWDM & 1:256 \\
2016 & XG-PON & G9807.x & 10/10 Gb/s & 1 & 60 km & TWDM & 1:256 \\
2020 & 50G-EPON & 802.3 ca & 50/50 Gb/s & up to 2 & 20 km & Ethernet & 1:128 \\
2021 & 50G-TDM-PON & G.9804.x: & 50/50,25,12.5 & 1 & 60 km & TDMA & 1:256 \\  & PON & & Gb/s & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Details of various fiber-based access standards.  
Figure 5: LAN types: Ethernet LAN, TOKEN RING LAN and FDDI LAN.  
broadband services such as a HD video service, and became obsolete with the advent of DSL systems.