2.5 Compare and contrast WAN technologies

2G

1st Cell Network: Used Circuit Switched Data (CSD). CSD is somewhat similar to a dial-up modem, though no analog transmissions are involved. CSD requires a data connection to be established to the base station (incurring call charges) and is only capable of around 14.4 Kbps at best.

Metro Ethernet

A MAN based on Ethernet standards. These types of services are also more widely described as Carrier Ethernet Easily scalable-affords businesses the flexibility to match the service to their changing demands. The fact that the same protocol (Ethernet) is used on the LAN and connectivity into the public network space can make the configuration of routers, layer 3 switches, and firewalls simpler, with fewer protocol conversions required

ISDN (Integrated Services Digital Network)

A fully digital version of the local loop, standardized by the ITU. A broadband telephone line that can carry data at about five times the speed of regular telephone lines. Two channels (telephone numbers) share a single pair of wires. ISDN has been replaced by DSL.

PPPoE (PPP over Ethernet)

A means of creating PPP connections over an Ethernet link. The major benefit of PPPoE is that the end-user can just as easily establish these network connections without needing to know more than how to establish a dial-up connection, so neither the telephone company nor the ISP needs to provide any special support. Some ISPs use Point-to-Point Protocol over ATM (PPPoA) instead of PPPoE.

DSLAM (Digital Subscriber Line Access Multiplexer)

A network distribution device that aggregates individual subscriber lines into a high-capacity uplink. These high-capacity uplinks, either ATM or Gigabit Ethernet, connect subscribers to their Internet service providers (ISPs)

DMVPN (Dynamic Multipoint VPN)

A secure network that exchanges data between sites without needing to pass traffic through an organization's headquarter virtual private network (VPN) server or router. Allows IPSec-based VPNs to be set up dynamically according to traffic requirements and demand. The original concept was developed by Cisco

SIP (Session Initiation Protocol) Trunk

A service implemented on an underlying access technology, such as MPLS or Metro Ethernet. -Replaces traditional voice lines, such as ISDN PRI or a T1 leased line. -More cost-effective, allowing larger number of simultaneous calls to be made. -Limited only by the available network bandwidth and the service level purchased from the provider -Uses a customer's telephony PBX or server-based call control system (Skype) as the endpoint for the service. The IP address of the customer's phone system and the SIP trunk provider's IP address are used to set up a pathway which allows individual phone or video calls to be passed. These links are normally encrypted and secured using standard protocols like TLS. -Used to allow a private organization to make calls onto the POTS, there is the potential for hackers to exploit unsecure links to make expensive international or premium rate calls. The SIP trunk provider then charges the customer for these calls. To mitigate against this, most SIP trunk providers will provide multiple layers of authentication.

DSL (Digital Subscriber Line)

A technology for transferring data over voice-grade telephone lines. DSL uses the higher frequencies available in a copper telephone line as a communications channel. The use of a filter prevents this from contaminating voice traffic with noise. The use of advanced modulation and echo cancelling techniques enable high bandwidth, full-duplex transmissions.

Smart Jack

A termination for T-carrier wire pairs that is located at the customer demark and which functions as a connection protection and monitoring point.

ATM (Asynchronous Transfer Mode)

A transport mechanism for all types of data, including voice and video. It is standardized as part of the ITU's Broadband ISDN standard. -Uses a cell switching (or cell relay) technology. ATM cells are a small (53 byte), fixed-length packet that contains 48 bytes of data and 5 bytes of header information. -Consistent cell size reduces processing overhead during switching -Faster hardware-based switches (up to OC-192) allows for high level capacity -Small, fixed length cells make traffic more predictable, accommodates time-sensitive data easily. -Designed to make highly efficient use of available bandwidth

VDSL (Very High Bit Rate DSL)

Achieves higher bit rates than other DSL types at the expense of range. It allows for both symmetric and asymmetric modes. Asymmetric link: 300 m (1000 feet) 52 Mbps downstream and 6 Mbps upstream, Symmetric link: Supports 26 Mbps in both directions. VDSL2 also specifies a very short range (100 m/300 feet) rate of 100 Mbps (bi-directional).

PPP (Point-to-Point Protocol)

An adaptation of HDLC and forms the cornerstone of subscriber dial-up and broadband Internet access methods. Was developed for dial-up networking, but is still used over a variety of communications links, including DSL, SONET, and cellular.

DS1 (T1)

Bandwidth 1.544 Mbps Channels 24 T1 Units 1

CEPT1 (E1) *European Standard

Bandwidth 2.048 Mbps Channels 32 E1 Units 1

CEPT3 (E3)

Bandwidth 34.368 Mbps Channels 512 1E3 Units 6

DS3 (T3)

Bandwidth 44.736 Mbps Channels 672 T1 Units 28

Main drawback of DSL

Because its copper-wire technology, it suffers from attenuation. Max range of a DSL modem is typically about 3 miles (5 km), but the longer the connection, the greater the deterioration in data rate. Domestic cabling may also be relatively poor quality and pass through "noisy" environments.

Local Loop (the last mile)

Cabling from the customer premises to the local exchange. The point at which the telco's cabling enters the customer premises is referred to as the demarcation point (often shortened to demarc).

3G

Cell network: General Packet Radio Services/Enhanced Data Rates for GSM Evolution (GPRS/EDGE) is a precursor to 3G (2.5G), with GPRS offering up to about 48 Kbps and EDGE about 3-4 times that. Unlike CSD, GPRS and EDGE allow "always on" data connections, with usage billed by bandwidth consumption rather than connection time. Evolved High Speed Packet Access (HSPA+) is a 3G standard developed via several iterations from the Universal Mobile Telecommunications System (UMTS) used on GSM networks. HSPA+ nominally supports download speeds up to 168 Mbps and upload speeds up to 34 Mbps. HSPA+-based services are often marketed as 4G if the nominal data rate is better than about 20 Mbps. CDMA2000/Evolution Data Optimized (EV-DO) are the main 3G standards deployed by CDMA network providers. EV-DO can support a 3.1 Mbps downlink and 1.8 Mbps uplink

4G/LTE

Cell network: Long Term Evolution (LTE) is a converged 4G standard supported by both the GSM and CDMA network providers. LTE has a maximum downlink of 150 Mbps in theory, but no provider networks can deliver that sort of speed at the time of writing, with around 20 Mbps far more typical of real-word performance. Note: LTE uses neither TDMA nor CDMA but Orthogonal Frequency Division Multiple Access (OFDMA), which is like the technology used in Wi-Fi (and DSL). LTE Advanced (LTE-A) is intended to provide a 300 Mbps downlink, but again this aspiration is not matched by real-world performance. Current typical performance for LTE-A is around 40 Mbps According to the original specification, a 4G service was supposed to deliver 1 Gbps for stationary or slow-moving users (including pedestrians) and 100 Mbps for access from a fast-moving vehicle.

Cable Broadband

Coax for broadband access Can carry phone, voice and internet. Coax then links all the premises in a street with a Cable Modem Termination System (CMTS), which routes data traffic via the fiber backbone (typically a SONET ring) to the ISP's Point of Presence (PoP) and from there to the Internet. Cable based on the Data Over Cable Service Interface Specification (DOCSIS) supports downlink speeds of up to 38 Mbps (North America) or 50 Mbps (Europe) and uplinks of up to 27 Mbps. DOCSIS version 3 allows the use of multiplexed channels to achieve higher bandwidth.

MPLS (Multiprotocol Label Switching)

Developed by Cisco from ATM as a means of providing traffic engineering (congestion control), Class of Service (CoS), and QoS within a packet switched, rather than circuit switched, network. MPLS has subsequently been standardized by the IETF (RFC 3031). -Combines Layer 2 switching and Layer 3 routing -Create site-to-site VPNs to interconnect LANs -Traffic passing over an MPLS VPN is isolated from any other customer or public traffic. -Different sites can use any access method available (DSL, cellular, leased line, or Ethernet), and the sites can use point-to-point or multipoint topologies as required. -Provide voice and video networks with minimum service level guarantees. -Provide fast and reliable connectivity to the data centers hosting whatever cloud services are used by the enterprise. -Can apply traffic shaping policies to communications between enterprise LANs and the data center to guarantee a service level and provide link redundancy, making the connection much more reliable than one over the open Internet would be

SONET (Synchronous Optical Network)

Developed principally to provide a standard transport mechanism for the various proprietary PDH fiber optic networks that had been installed over the years. principally a Physical layer standard, defining infrastructure, line speeds, and so on Synchronous Uses TDM Offers a hierarchy of bandwidth levels based on a basic transmission rate of Synchronous Transport Signals (STS-1s)

T-carrier system/PDH

Developed to allow multiple calls to be placed on a single cable. PDH enabled voice traffic to be digitized for transport around the core network. It also enabled other types of digital data to be transported.

CSU/DSU (Channel Service Unit/Data Service Unit)

Digital leased lines use a CSU/DSU instead of the modems used for analog system A piece of equipment that connects a T-carrier leased line from the telephone company to a customer's equipment (such as a router). It performs line encoding and conditioning functions, and it often has a loopback function for testing.

SDSL (Symmetrical DSL)

Downlink and uplink are the same bandwidth rate. Primarily for business packages

Service categories Metro Ethernet (E-Line vs. E-LAN)

E-line—Establishes a point-to-point link between two sites. Multiple E-lines can be configured on a single Metro Ethernet interface, with each E-line representing a separate VLAN. E-LAN—Establishes a mesh topology between multiple sites.

Cellular Network Connections

Each base station (Cell Tower) has an effective range of up to 5 miles (8 km). The transmitter connects the phone to the mobile and PSTN networks. Transmitter coverage in many countries is now very good, except for remote rural areas. Cellular radio works in the 850 and 1900 MHz frequency bands (mostly in the Americas) and the 900 and 1800 MHz bands (rest of the world).

PDH is based on TDM (Time-Division Multiplexing)

Enables multiple circuits to be carried over the same media. The protocol assigns each circuit (or channel) a time slot. PDH is an asynchronous version of TDM, meaning that timing signals from the various components are not accurately synchronized (plesiochronous or small timing differences).

ADSL (Asymmetric DSL)

Fast downlink/Slow uplink bandwidth ADSL2+ offers downlink rates up to about 24 Mbps and uplink rates up to 1 Mbps

Satellite

Good for rural internet connections, when other options aren't available, but has severe latency problems. Delay is 4 to 5 times that of a land connection. Causes issues with real-time applications (videoconferencing, VoIP, and multi-player gaming) Consumer satellite dish VSAT (Very Small Aperture Terminal) The antenna is connected via coaxial cabling to a Digital Video Broadcast Satellite (DVB-S) modem. This can be installed in the PC as a PCI card or as an external box connected via a USB or Ethernet port. Modem modules are also available as plug-in cards for enterprise routers. While there can be latency issues, VSATs do support transmission of voice and video. VSAT networks can be connected in a point-to-point, star, or mesh network. There are also transportable terminals that are portable, but remain stationary during transmission, and mobile terminals can communicate with satellites even when they are in motion.

Frame Relay

Legacy-Replaced by MPLS and Ethernet WANs Provided data packet forwarding for services running over T-carrier lines, ISDN, or even dial-up. The advantage when used with T-carrier is that the customer can select an appropriate bandwidth level—the Committed Information Rate (CIR)—rather than having to incur the full cost of a T1 leased line. Frame Relay uses variable-length packets of up to 4096 bytes. It can encapsulate data from higher-level protocols, including TCP/IP. Provided mechanisms for the service provider to perform congestion control and maintain available bandwidth to an agreed service level, providing Quality of Service (QoS) for latency-sensitive applications, such as Voice over IP (VoIP).

ATM Switch

Makes virtual connections with other switches to provide a data path from endpoint to endpoint. Individual connections are called virtual channels (VCs).

Dail-up

Modem PPP (Point to Point Protocol) low data transfer rates and error-prone links Data rates measured in Kbps (SLOOOW)

TIA/EIA IS-95 (cdmaOne)

Phones use Code Division Multiple Access (CDMA). CDMA means that each subscriber uses a code to key the modulation of their signal and this "key" is used by the receiver to extract the subscriber's traffic from the radio channel. With CDMA, the handset is managed by the provider, not the SIM. CDMA adoption is largely restricted to the telecom providers Sprint and Verizon.

GSM (Global System for Mobile Communications)

Phones using Time Division Multiple Access (TDMA). With TDMA, each subscriber gets access to the radio channel by being allocated a time slot. GSM allows subscribers to use a subscriber identity module (SIM) card to use an unlocked handset with their chosen network provider. GSM is adopted internationally and by AT&T and T-Mobile in the US.

Dedicated/Leased Line

Provides a permanent circuit switched connection with guaranteed service levels, such as available bandwidth. Typically, a T1 (or E1) link is used to establish point-to-point links between enterprise sites.

5G

Rollout of 5G services will be relatively complex. Rather than a single large antenna serving a large wireless cell, 5G involves installing hundreds of smaller antennas, ideally with a fiber optic backhaul to the provider's access network. As well as faster mobile speeds, 5G is expected to provide fixed-wireless broadband solutions for homes and businesses, and to support IoT networks. Minimum speeds 1GBPS stationary and 100 Mbps for fast movement

SONET STS-3/OC-3

SDH STM-1 Data Rate 155.52 Mbps

SONET STS-48/OC-48

SDH STM-16 Data Rate 2.488 Gbps

SONET STS-96/OC-96

SDH STM-32 Data Rate 4.976 Gbps

SONET STS-12/OC-12

SDH STM-4 Data Rate 622.08 Mbps

SONET STS-192/OC-192

SDH STM-64 Data Rate 9.953 Gbps

VC (Virtual Channels)

Support the connection-oriented transport between endpoints and are identified by a virtual channel identifier (VCI). VCs with a common path are tied together into virtual paths (VPs) and are identified by a virtual path identifier (VPI). You can form a transmission path (TP) by combining multiple VPs. The header information identifies the transmission path required for the cell to reach its destination and allows bandwidth to be dedicated to particular data. This infrastructure means the packets arrive in order and can be quickly processed.

Local Exchange

Switches links between local access subscribers and provides transports to trunk exchanges. The local exchange is also referred to as a Class 5 office or Central Office (CO), while in the US a local telephone company is called a Local Exchange Carrier (LEC).

PRI (Primary Rate Interface) used for ISDN

T1 or E1 capacity levels (23xB or 30xB channels, depending on location in the world) and one 64 Kbps D channel. This form of ISDN is intended for larger companies.

CPE (Customer Premises Equipment)

Termination and routing equipment placed at the customer site. Some of this equipment may be owned or leased from the telco; some may be owned by the customer.

Trunk Links

These provide switching and interconnections between local exchanges within a metropolitan area or nationally and to international gateway services. Trunk offices are also referred to as Class 4 or toll offices.

BRI (Basic Rate Interface) used for ISDN

Two 64 Kbps B channels for data and one 16 Kbps D channel for link management control signals. It is sometimes called 2B+D. It is common to use one B channel for data and leave the other for voice or fax, but you can also provide a 128 Kbps connection by concatenating the two B channels. This form of ISDN is intended for SOHO use.

Ethernet over Copper

Uses digital subscriber line (DSL) variants such as SHDSL and VDSL to overcome the usual distance limitations of copper Ethernet. This does not support anything like the same speeds as LAN Ethernet (more typically 2-10 Mbps), but multiple pairs can be aggregated for higher bandwidth.

Ethernet over Fiber

Uses the 802.3 10GBASE-LR and 10GBASE-ER specifications.

Ethernet over SONET/SDH

Uses the SONET OC-192 service and encapsulates Ethernet packets in its frames. The 10GbE WAN PHY protocol uses the same wavelength and interface types (10GBASE-SW, 10GBASE-LW, and 10GBASE-EW) as the LAN PHY equivalents. Because of the different framing, it operates at a slightly slower data rate (9.95328 Gbps) than the LAN PHY version.

ATM Implementations

Widely implemented by telecommunications companies and ISPs because it provides mechanisms for traffic shaping and policing, Quality of Service (QoS), and the ability to aggregate different types of traffic. However, as the use of fiber optic cabling makes more bandwidth available, ATM becomes less efficient when transporting protocols with large frame sizes or PDUs, such as Ethernet/IP, as the small cell size means that a substantial overhead is introduced in disassembling and reassembling packets. Consequently, the market developed towards the use of native IP solutions with MPLS providing traffic shaping and QoS. ATM can make use of a variety of physical media, but in most implementations it runs over either T1/T3 links or SDH/SONET. For end customers in many parts of the world, ATM is not widely offered as a service by telecom providers anymore. It does remain supported for the organizations that have installed it already

HDLC (High-level Data Link Control)

Widely used to transfer data over a serial digital line, such as T1 or ISDN. It performs the same framing and error detection functions as Ethernet but on a point-to-point link between two routers, rather than a shared access medium.