IPv6 and Broadband Services
LESSON 19

The Future of Networking:

• Modern communications is evolving to higher speeds and can transport all types of information.
• Real time and other high-bandwidth demanding applications are unable to run on current networks, using the current protocols.
• To move the computer industry into the next century, network hardware, software, and protocols must all be enhanced to handle these new demands.
• To support the integration of current networks and different media types, several components are needed:
  • Hardware:
    • High-speed switches and routers.
    • Fiber-optics (high-bandwidth).
  • Software:
    • Flexible, secure, and scaleable protocols.
    • Efficient routing and naming schemes.
• To handle these needs, modern protocols and hardware are being created, including:
  • Frame Relay (FR).
  • Switched Multimegabit Data Services (SMDS).
  • Broadband ISDN (B-ISDN).
  • Asynchronous Transfer Mode (ATM).
  • Synchronous Optical Network / Synchronous Digital Hierarchy (SONET/SDH)
  • Internet Protocol Next Generation (IPng).

Terminology:
Transmission Schemes

• Synchronous:
  • Signals that are sourced from the same timing reference. These have the same frequency.
• Asynchronous:
  • Sources are not limited to sending data during a set time slot (circuit switching). Signals are sourced from independent clocks.
• Data is sent asynchronously,
  Cells are sent synchronously.
• Isochronous:
  • Signals which are dependent on some uniform timing or carry their own timing information embedded as part of the signal.
• Plesiochronous:
  • Signals which are arbitrarily close in frequency to some defined precision. Not sourced from the same clock (will be skewed over time). Closeness of frequency allows a switch to cross connect or in some way process them.

Terminology:
"Fast Packet"

• Frame Relay vs. Cell Relay:
  • Share some similarities, but the performances that can be achieved, and applications which they support are different.
  • Frame Relay - is less suitable since it’s delays are more variable (due to variable size frames).
    Cell Relay - supports voice systems due to it’s consistent delay characteristics (fixed-size cells).

What is Frame Relay?

• Frame Relay is the result of:
  • Wide area networking requirements for speed.
  • LAN-WAN and LAN-LAN internetworking.
  • "bursty" data communications.
  • Natural progression beyond X.25 since transmission error rates decreased over time.
• Frame Relay is used to connect dedicated lines and X.25 to ATM, SMDS, B-ISDN and other "fast packet" technologies.

Frame Relay:
Services

• Connection-oriented service:
  • Permanent Virtual Circuits (In place).
  • Switched Virtual Circuits (Future possibility).
• High Performance:
  • Low latency.
  • High throughput.
• Logical progression:
  • Evolution from X.25 to ATM.
  • Utilizes current communications hardware (less cost).

Frame Relay:
Interface Speeds

• Range of Access Speeds:
  • 56 Kbps
  • Fractional T1 (64 - 1.544 Mbps)
  • T1 (1.544 Mbps)
• Disadvantage:
  • Does not provide as high throughput as cell-relay technologies because frames are of variable lengths and require more overhead.

Switched Multimegabit Data Services (SMDS):

• Switched Multimegabit Data Services (SMDS):
  • An emerging high-speed datagram-based public data network service developed by Bellcore.
  • Provides a connection-less delivery system for data (no voice or real-time traffic is supported).
  • It’s primary transport technology is DQDB (Distributed Queue Dual Bus).
• SMDS is struggling for market acceptance.

Broadband ISDN:

• Integrated Services Digital Network (ISDN) -
  • A set of communications standards allowing a single wire or optical fibre to carry voice, digital network services, and video.
• ISDN functions over a range of transmission speeds which are categorized in two main areas:
  • Narrowband (N-ISDN)
  • Broadband (B-ISDN)
• N-ISDN Rates:
  • DS-0 = 1 channel: 64 Kbps. (2B+D)
  • DS-1 = 24 channels: 1.544 Mbps. (23B+D)
• B-ISDN Rates:
  • T-1 (1.544 Mbps), T-3 (45 Mbps),
  • OC-3 (155 Mbps), ... ,
  • OC-192 (10 Gbps), and higher!
• B-ISDN:
  • Is a packet mode (switched) network.
  • Is the architectural framework for broadband services, which uses ATM as it’s transport mechanism.
  • Supports integrated services and new user-to-network interfaces (UNI) like ISDN.

What is ATM ?

• ATM is a cell relay technology.
• ATM, theoretically, can operate at any speed (up to extremely high speeds).
• It can support packet or circuit emulation (virtual circuits).
• Supports continuous or bursty channel traffic.
• Provides a single technology standard (desktop to desktop connectivity).
• ATM is an international standard which is actively being developed by over 300 vendors and organizations.
• It is based on packet switching technology.
• ATM’s basic transfer unit is a fixed size link-layer entity (cell = 53 octets).
• ATM provides a reliable transport from link to link since it is a connection-oriented technology.

Physical Layer:
ATM Sublayers

• Transmission Convergence Sub-Layer (TC) - ISO Level 1
  • Cell rate decoupling.
  • HEC header sequence generation / verification.
  • Cell delination.
  • Transmission frame adaptation (DS-1 / DS-3).
  • Transmission frame generation / recovery.
• DS1 (T1/E1) and DS3 (T3/E3) frame formatting schemes can be interfaced at this sublayer (ATM emulation).
  • T1 = 1.544 Mbps
  • T3 = 45 Mbps
• Physical-Medium Sublayer (PM):
  • Bit timing
  • Physical medium

Physical Layer:
SONET/SDH

• SONET (Synchronous Optical Network) and
  SDH (Synchronous Digital Hierarchy)
  • Two very similar high-speed physical transport standards commonly used with ATM.
  • Provides management features at the physical layer and can detect/correct single bit errors.
• SONET/SDH:
  • Provides an international framework for development of worldwide telecommunications transport networks, which are:
    • Flexible
    • Reliable
    • Fully manageable
    • Adaptable to growth and demand for new services.

Physical Layer:
ATM vs. SONET/SDH

• SONET/SDH includes built-in management capabilities.
• Raw ATM facilities, when used at the physical layer, do not provide any management features. They must be developed and created separately to provide the features implemented in SONET/SDH.
• Regardless of the transmission speed, SONET overhead never increases beyond 14% (static).

Data Link Layer:
ATM Layer

• ATM Layer:
  • Generic flow control.
  • Cell header generation / extraction.
  • Cell VPI/VCI translation.
  • Cell multiplexing and demultiplexing.
  • Cell loss priority bit is set if the committed information rate (CIR) is exceeded.
  • Payload type set and traffic shaping is done.

Data Link Layer:
ATM Adaptation Layer

• ATM Adaptation Layer (AAL):
  • Handling of transmission errors.
  • Handling of quantization (segmentation) effect.
  • Application flow control.
  • Timing control.
  • Handling of lost or misread cells.
  • Made up of three sublayers.

Data Link Layer:
ATM Adaptation SubLayers

• AAL Sublayers:
  • Service Specific Convergence Sublayer (SSCS)
  • Common Part Convergence Sublayer (CPCS)
  • Segmentation and Reassembly Sublayer (SAR)
• Not all AAL protocols have these sublayers. It depends upon the services they provide (most have only 2).

Why ATM ?

• ATM is scaleable:
  • speed (1.544 Mbps ... 10 Gbps)
  • size (desktop ... mainframe)
  • distance (total area networks)
• ATM is low latency.
• ATM traffic management.
• ATM works with LAN/MAN/WAN network technologies.

ATM Components:

• Physical Media:
  • Coaxial Cable
  • UTP (Class 5)
  • Fiber Optics:
    • Laser Emitting Diode
    • Photo Diode
    • Glass Silica (Fiber)

• Local Area:
  • ATM Hub
  • ATM Switches
  • ATM Network Interface Adapter Cards
• Metropolitan Area:
  • ATM Multiplexer
  • ATM Switches
  • ATM Router
• Wide Area: Public:
  • ATM Multiplexer
  • ATM (Frame Relay, SMDS) Switches
  • ATM Access Node
• Wide Area: Private:
  • ATM Concentrators
  • ATM Switches
  • ATM Gateways

ATM Network Requirements:

• Quality of Service.
• Reliability (Bit error detect/correct = SONET)
• Signaling for gigabit connections (10 Gbps)
• Signaling for network management.
  • Customer monitoring
  • Restoration
• Bandwidth on demand.
• Network services.

Internet Protocol:
Next Generation (IPng)

• The future of networking also depends upon flexible and robust communication protocols, such as IPng.
• IPng - Represents the umbrella of research and development that has gone into upgrading the Internet to a new IP protocol.
• IPng reflects many of the issues and concerns of industry vendor’s and the IAB about where the Internet is heading.

Why Should TCP/IP Change?

• New Computer and Communications Technology:
  • High speed computers are now being used as hosts and routers.
• New Applications:
  • Recent surge for multimedia applications (World Wide Web).
  • Real time traffic (video-conferencing, voice, and shared whiteboards).
• Increases in network size and load:
  • In 1994, a new host appeared on the Internet every 30 seconds.
  • More companies than all other sites.
  • Bandwidth-hungry applications (Internet Phone, WWW, infobots).
• New Policies:
  • New authorities and administrative policies (including security issues).

Internet Protocol Version 6:

• The official attempt to implement IPng features is being done through IP version 6 (IPv6).
• What happened to version 5?
  • Due to a numbering mix-up, version 5 was assigned to another protocol.
  • The IAB has decided to officially name the new IP protocol "version 6" or "ip6".

Features of IPv6:

• Preserved from IPv4:
  • Connectionless service, variable sized datagrams, and a configurable hop count (among other things).
• New or improved upon:
  • Fixed-size base header (for quicker processing).
  • Variable-length extension headers (flexible format).
  • Larger addresses (128-bit IP addresses).
  • Support for dynamic provisioning of network resources.
  • Support for future IP protocol changes.

IPv6 Base Header:

• IPv6 base header contains less information than the IPv4 header, although by default it is longer.
• Changes:
  • Alignment changed from 32-bit to 64-bit multiples.
  • Header Length field was eliminated (HLEN).
  • Total Length field is now Payload Length field.
  • Time-to-live (TTL) field is now Hop Limit.
  • Source and Destination IP addresses are now 16-octets each.
  • Fragmentation support has moved to an extension header.
  • The Service Type field was replaced by the Flow Label field.
  • The Protocol field was replaced by the Next Header field.

• Payload Length now only covers the length of the extension headers and data, not the base header.
• IPv6 supports resource reservations, where a datagram is routed over a path (flow) of intermediate routers that guarantee a specific quality of service for it.
• The Flow Label field is used for resource reservation and contains two subfields.

Two Subfields of an IPv6 Flow Label:

• T-Class (4-bits):
  • Class of datagram where:
    (0..7) = Time sensitivity range.
    (8..15) = Priority for non-flow traffic.
• Flow ID (24-bits):
  • Randomly chosen flow identifier that is used by gateways when routing IPv6 datagrams based on quality of service.

IPv6 Extension Headers:

• Similar to IPv4 options, a datagram includes extension headers for only those facilities the datagram is using.
• A sequential search is done through all the headers when processing a datagram.
• The Next Header field points to the next header or data area with the datagram.

Fragmentation and Reassembly:

• IPv6 allow reassembly at the destination, but only permits a datagram to be fragmented once during it’s trip.
• Before sending traffic, a Path MTU Discovery probe is done to determine the minimal MTU size in which the datagram will encounter over a fixed path.
• Each fragment is equipped with a base header and a small fragmentation extension header.

End-to-End Fragmentation:

• The change in fragmentation methodology was done to reduce processing overhead in routers.
• The need for MTU Discovery probes now moves IP beyond a connectionless protocol to one which requires a prior setup (of sorts).
• Dynamic route changes cannot be accommodated, so IPv6 datagrams must be "tunneled" through intermediate routers.
• Similar to IP tunneling in Multicast IP, IPv6 datagrams are encapsulated within new IPv6 (or IPv4) datagrams, which are then fragmented and routed.
• Encapsulated datagrams are extracted and routed again once they are beyond the dynamically changed route(s).

IPv6 Option Support:

• IPv6 uses separate extension headers for IP options and each must include a HLEN (header length) since they can vary in size.
• ALL IPv4 options are supported (including strict and loose source routing, etc.) as well as two new generic options.

New IPv6 Option Support:

• Hop by Hop Extension Header:
  • Accommodates any miscellaneous information for use between each pair of gateways.
• End to End Extension Header:
  • Accommodates any miscellaneous information for use solely at the source and destination nodes.

IPv6 Addressing:

• Addresses are now represented with 16-octets, providing an address space greater than 3.4x10³⁸ (2¹²⁸).
• Since IP addresses are very long, Colon Hexadecimal Notation is used to make them easier to read and write.
  104.230.140.100.255.255.255.255.0.0.17.128.150.10.255.255

• Zero compression is also used with the new notation to further shorten addresses by collapsing a string of repeated zeros:

• Colon hexadecimal notation can also incorporate the original dotted decimal notation:

IPv6 Address Types and Hierarchy:

• "IPv6 permits multiple prefixes to be assigned to a given network and allows a computer to have multiple simultaneous addresses assigned to a given interface."
• Destination addresses can be:
  • Unicast - single computer.
  • Cluster - Delivered to one computer within a specific group.
  • Multicast - Broadcasted to a specific group.
• IPv6 also provides a multilevel hierarchical address space which can:
  • Accommodate flexible addressing schemes.
  • Allow many organizations to further define subnetworks of addresses.
  • Encapsulate (represent) 48-bit Ethernet addresses.

All work was written, produced, and is copyrighted by Daniel Z. Tabor Jr.
Page created by Daniel Z. Tabor Jr. Copyright ©1995 Illusion Industries Inc.