Advanced Communication Protocols

by Deniz Alacam

ISDN

ISDN stands for Integrated Services Digital Network -- the name for digital telephone service that works over existing copper telephone wiring. There are several types of ISDN service, but the most appropriate type for individual computer users is the ISDN Basic Rate Interface (BRI). Basic Rate ISDN divides the telephone line into 3 digital channels: 2 "B" channels and one "D" channel, each of which can be used simultaneously. The B channels are used to transmit data, at rates of 64k or 56k (depending on your telephone company). The D channel does the administrative work, such as setting up and tearing down the call and communicating with the telephone network. With two B channels, you can make two calls simultaneously.

ATM

ATM is connection oriented and is a switched based technology. Using ATM, information to be sent is segmented into fixed length cell, transported to and re-assembled at the destination. The ATM cell has a fixed length of 53 bytes. Being fixed length allows the information to be transported in a predictable manner. This predictability accommodates different traffic types on the same network.
ATM is expensive and because of its fixed small packet size, it is not adequate for larger packets. In local area, Fast Ethernet is the more promising technology. ATM's packet size is too small for IP packets.

Fast Ethernet

Fast Ethernet is a tenfold increase in Ethernet's data rate to 100Mbps. One approach was to speed up the original Ethernet system to 100-Mbps, keeping the original CSMA/CD medium access control mechanism. This approach is called 100BASE-T Fast Ethernet. Another approach presented to the committee was to create an entirely new medium access control mechanism, one based on hubs that controlled access to the medium using a "demand priority" mechanism. This new access control system transports standard Ethernet frames, but it does it with a new medium access control mechanism. This system was further extended to allow it to transport token ring frames as well. As a result, this approach is now called 100VG-AnyLAN.
Fast Ethernet (100BASE-T) will take over Ethernet's success. Many vendors provide dual-speed Ethernet interfaces that can be installed and run at either 10-Mbps or 100-Mbps automatically. This means ease of upgrade, people who already have Ethernet can upgrade their networks gradually. But since 100VG-AnyLAN uses a totally different medium access control method, there is no upgrade possibility and thus has much less chance.

MBONE

The MBONE is an outgrowth of the first two IETF "audiocast" experiments in which live audio and video were multicast from the IETF meeting site to destinations around the world. The idea is to construct a semi-permanent IP multicast testbed to carry the IETF transmissions and support continued experimentation between meetings. The MBONE is called a virtual network because it shares the same physical media -- wires, routers and other equipment -- as the Internet. The MBONE allows multicast packets to travel through routers that are set up to handle only unicast traffic. Software that utilizes the MBONE hides the multicast packets in traditional unicast packets so that unicast routers can handle the information.
MBONE will dissappear when IP multicast will be a standard.

IPv6

IPv6 is a new version of IP. IPng is designed to run well on high performance networks an at the same time is still efficient on low bandwidth networks. Changes from IPv4 to IPng

Expanded routing and addressing capabilities
increases IP address size from 32 to 128 bits.
Anycast address -- defined to identify sets of nodes where a packet sent to an anycast address is delivered to one of the nodes.
Header Format simplification-- IPng header is only twice size of IPv4 header
Improved support for options
Quality of service capabilities -- allows special handling such as "real time"
Authentication and Privacy Capabilities

IPv6 address size is unnecessarily large.

RSVP

RSVP ReServation Protocol is part of a new Internet architecture that is designed to provide multipoint communication with both real-time and best-effort service. In addition to RSVP, the architecture includes:

a multicast routing protocol that establishes the paths that data will take,
an admission control module to manage network resources, and
a packet scheduler that orders packet transmission to meet the quality of service established by admission control

RSVP carries reservation requests to the admission control module for each link of a path provided by the multicast routing protocol.

Cable modems

A cable modem is a device that allows high speed data access (for example to Internet) via a cable TV network. Speeds vary widely. In the downstream direction (from the network to the computer), speeds can be anywhere up to ~36 Mbps. (Modems this fast are not currently on the market.) Few computers will be able of connecting at such high speeds, so a more realistic number is 3-10 Mbps. In the upstream direction (from computer to network), speeds can be up to 10 Mbps. Cable modems are more complicated then their telephone counterparts. Cable modems can be part modem, part tuner, part encryption/decryption device, part bridge, part router, part SNMP agent, part Ethernet hub.
Cable modems are a good solution, they are fast and not expensive. Since the installation of ISDN is not a simple task, cable modems will be more widespread.

LANcity

LANcity products provide standard 10 Mbps Ethernet data service connection over standard 6 MHz cable TV channels at round trip distances of up to 200 miles through the cable TV headend. LANcity products are frequency agile, SNMP-network-managed, and coexist with a variety of other services that may be running on the cable TV network.

ChannelWorks

A ChannelWorks network, which can include ChannelWorks Bridges, Internet Brouters, and future ChannelWorks products; uses only one forward and one reverse 6 MHz channel.

Hybrid

The Hybrid Access System (HAS) Series 2000 provides asymmetric high speed data access to personal computer users over Cable TV or wireless broadband infrastructures. The HAS Series 2000 provides an overall throughput of 30 Mbps per 6 MHz channel and operates at 512 Kbps or 2.048 Mbps in the upstream direction.