Week Six Agenda• Attendance• Announcements• Review Week Five• Current Week Information• Upcoming Assignments

Review Week Five

Routing in the Enterprise Architecture

Routing in the Enterprise Architecture

Notice that RIP is not a part of an enterprise design

• It is considered to be too slow to converge

• It is not recommended for large networks

• However, it may be adequate for small networks and may exist in legacy networks.

EIGRPThe Enhanced Interior Gateway Routing Protocol (EIGRP) represents an evolution from its predecessor IGRP.

Key capabilities that distinguish EIGRP from other routing protocols include fast convergence, support for variable-length subnet mask, support for partial updates, and support for multiple network layer protocols.

EIGRPA router running EIGRP stores all its neighbors' routing tables so that it can quickly adapt to alternate routes. If no appropriate route exists, EIGRP queries its neighbors to discover an alternate route. These queries propagate until an alternate route is found.

OSPFOSPF protocol was developed due to a need in the Internet community to introduce a high functionality non-proprietary Internal Gateway Protocol (IGP) for the TCP/IP protocol family.

The OSPF protocol is based on link-state technology, which is a departure from the Bellman-Ford vector based algorithms used in traditional Internet routing protocols such as RIP. OSPF has introduced new concepts such as authentication of routing updates, Variable Length Subnet Masks (VLSM), route summarization, and so forth.

BGPThe Border Gateway Protocol (BGP) is the routing protocol used to exchange routing information across the Internet. It makes it possible for ISPs to connect to each other and for end-users to connect to more than one ISP. BGP is the only protocol that is designed to deal with a network of the Internet's size, and the only protocol that can deal well with having multiple connections to unrelated routing domains.

IP secInternet Protocol security (IPsec) is a framework of open standards for protecting communications over Internet Protocol (IP) networks through the use of cryptographic security services. IPsec supports network-level peer authentication, data origin authentication, data integrity, data confidentiality (encryption), and replay protection.

Routers One of the primary jobs of a router is to determine the best path to a given destination.

A router learns paths, or routes, from the static configuration entered by an administrator and/or dynamically from other routers, through routing protocols

Static RoutingStatic routes in the routing table

Includes: network address and subnet mask and IP address of next hop router or exit interface.

Denoted with the code S in the routing table denotes static route.

Routing tables must contain directly connected networks used to connect remote networks before static or dynamic routing can be used.

Static Routing

Dynamic RoutingDynamic Routing Protocols (DRP)are used to

add remote networks to a routing table.

DRP are used to discover networks

DRP are used to update and maintain routing tables

DRP automatically discover the network

Network discovery is the ability of a routing protocol to share information about the networks that it knows about with other routers that are also using the same routing protocol.

Dynamic Routing

Maintaining routing tables

Dynamic routing protocols are used to share routing information with other router and to maintain and update their own routing table.

Dynamic routing protocols not only make a best path determination to various networks, they will also determine a new best path if the initial path becomes unusable (or if the topology changes)

Routing TableRouters keep a routing table in RAM

A routing table is a list of the best known available routes.

Routers use this table to make decisions about how to forward a packet.

On a Cisco router the show ip route command is used to view the TCP/IP routing table.

Routing LoopsA network problem in which packets continue to be routed in an endless circle.

Network routining loops are caused by a router(s) or link(s) failure, and the notification of the downed link has not yet reached all the other routers.

Over time, normal network growth or merging of networks can result in routing loops.

Routing protocols utilize various techniques to lessen the chance of a routing loop.

Introduction to WANsA wide area network (WAN) is a computer network that covers a broad area. Typically, it is any network whose communications links cross metropolitan, regional, or national boundaries. WAN transmission facilities are generally provided by service providers (SP), such as telephone companies that charge a usage fee called, a tariff.

WAN Connection TypesConnecting LANs together over a data communications

equipment (DCE) network

Dedicated WANs utilize synchronous serial connections.

Circuit-switched WANs use telephone company networks with asynchronous serial, and ISDN.

Packet-switched WANs use a service provider with synchronous serial.

WAN Connection TypesLeased lines are typically point-to-point connections or a dedicated connection. The WAN connection path from the CPE, through the DCE switch, to the CPE of the remote site, allowing DTE to communicate at any time with no setup procedures before transmitting data. It uses synchronous serial lines up to 45 Mbps. Excellent for constant transmission data flow.

Circuit-switching sets up a line like a phone call. No data can transfer before the end-to-end connection is established. Circuit switching uses dial-up modems and ISDN. It is used for low-bandwidth data transfers.

WAN Connection TypesPacket switching is a WAN switching method that allows you to share bandwidth with other companies to save money. Packet switching is excellent for bur sty data transfers, packet switching can save you money. Frame relay and X.25 are packet-switching technologies . Speeds can range from 56Kbps to 2.048Mbps.

WAN Connection TypesTime Division Multiplexing (TDM) is a technique for assigning bandwidth on a single wire, based on pre-assigned time slots, to data from several channels. Bandwidth is allocated to each channel regardless of a station’s ability to send data.

WAN Connection Types

WAN ProtocolsPoint-to-Point Protocol (PPP) is an industry standard protocol. PPP can be used to create point-to-point links between different vendors’ equipment. It allows authentication and multilink connections and can be run over asynchronous and synchronous links.

Asynchronous Transfer Mode (ATM) was created for time sensitive traffic, providing simultaneous transmission of voice, video, and data. ATM uses cells rather than packets that are a fixed 53-bytes long.

WAN Protocols

An ATM cell consists of a 5-byte header and a 48-byte payload. The payload size of 48 bytes was chosen as described above.

ATM defines two different cell formats: NNI (Network-Network Interface) and UNI (User-Network Interface). Most ATM links use UNI cell format.

WAN ProtocolsHigh-Level Data Link Control (HDLC)

HDLC is a Data Link protocol.

Designates a method for data encapsulation on synchronous serial links

Default encapsulation for Cisco routers

Bit oriented layer protocol created by ISO.

The HDLC header carries no identification of the type of protocol being carried inside the HDLC encapsulation. Because of this, each vendor that uses HDLC has their own way of identifying the Network layer protocol, which means that each vendor’s HDLC is proprietary for their equipment.

WAN ProtocolsHDLC frames can be transmitted over synchronous or asynchronous links.

Those links have no mechanism to mark the beginning or end of a frame, so the beginning and end of each frame has to be identified. This is done by using a frame delimiter, or flag, which is a unique sequence of bits that is guaranteed not to be seen inside a frame. This sequence is '01111110', or, in hexadecimal notation, 0x7E. Each frame begins and ends with a frame delimiter. A frame delimiter at the end of a frame may also mark the start of the next frame. A sequence of 7 or more consecutive 1-bits within a frame will cause the frame to be aborted.

WAN Protocols Link Access Procedure, Balanced (LAPB)

Connection-oriented protocol at the Data Link layer

Possesses much overhead because of strict timeout and windowing techniques

LAPB is used instead of the lower-overhead HDLC if your link is very error prone

WAN Protocols Integrated Services Digital Network (ISDN)

is a service offered by telephone companies, It is a communication protocol that allows telephone networks to carry data, voice, and other digital traffic.

ISDN network is a digital communication system that is capable of producing the maximum transmission speed of 1.4Mbps. 128Kbps speed is however more common in the digital technology. It's a international standard for sending data, voice, video over regular digital telephone lines. ISDN uses UTP (unshielded twisted pair cable) for transmission.

WAN ProtocolsFrame Relay is a packet switching protocol for connecting devices on a Wide Area Network (WAN).

Frame Relay is a protocol standard for LAN internetworking which provides a fast and efficient method of transmitting information from a user device to LAN bridges and routers.

WAN ProtocolsFrame Relay networks in the U.S. support data transfer rates at T-1 (1.544Mbps ) and T-3 (45 Mbps) speeds. In fact, you can think of Frame Relay as a way of utilizing existing T-1 and T-3 lines owned by a service provider. Most telephone companies now provide Frame Relay service for customers who want connections at 56 Kbps to T-1 speeds. (In Europe, Frame Relay speeds vary from 64 Kbps to 2 Mbps.

WAN Protocols Multiprotocol Label Switching (MPLS) replaces the

hop-by-hop, individually routed packet model with a connection-oriented model that establishes ‘paths’ to destinations.  Instead of routing each packet based upon its destination address, each packet is labeled such that it can be switched along a pre-defined path.  Thus, a single destination may have multiple paths leading to it, with one path used for voice, one for video, and one for data.

MPLS integrates Layer 2 information about network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous system or ISP in order to simplify and improve IP packet exchange.

WAN Protocols Multiprotocol Label Switching (MPLS)

MPLS is a highly scalable, protocol agnostic, data-carrying mechanism. In an MPLS network, data packets are assigned labels. Packet-forwarding decisions are made solely on the contents of this label, without the need to examine the packet itself. This allows one to create end-to-end circuits across any type of transport medium, using any protocol. The primary benefit is to eliminate dependence on a particular Data Link Technology, such as ATM,frame relay, SONET or Ethernet, and eliminate the need for multiple Layer 2 networks to satisfy different types of traffic.

WAN Protocols Multiprotocol Label Switching (MPLS)

MPLS operates at an OSI Model layer that is generally considered to lie between traditional definitions of Layer 2 (Data Link Layer ) and Layer 3 (NetworkLayer ), and thus is often referred to as a "Layer 2.5" protocol. It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames.

Transmission Modes Digital transmission, is binary codes of 0 and 1.for

transmission. It is necessary to notify the receiving end of precise information such as where the data starts and how long the interval of data is.

“Synchronous”and“asynchronous”are the two modes for communicating this information, and it is necessary to confirm which mode a each end supports. With Synchronous Transmission Mode, 64 kbps is the highest available transmission speed, while 57.6 kbps is the highest for Asynchronous Transmission Mode. Drawings

Transmission ModesSynchronous signals, signals that play the role of signs are added to the top of the data to be transmitted. With these signals, computers can precisely determine the first position of the characters. This mode can transmit data accurately, making it appropriate for corporate information networks.

Synchronous Transmission Mode

0111111001101100110001Synchronous Signal Data First Char Data Second Char

01111110 01101100 11000101

Transmission ModesAsynchronous signals, instead, use a portion of the data that has arrived as a clue, the first position of the character is identified. Two bits are added to each character, a start bit for the beginning and an end bit for the end, making the transmission speed slower.

Asynchronous Transmission Mode

001101100101100010110

Start Stop Start Stop

0011011001 0110001011

Data First Char Data Second Char

Packet-Switched Network TopologiesStar topology is a LAN physical topology with endpoints on the network converging at a common central switch (known as a hub) using point-to-point links. A logical ring topology can be configurated as a physical star topology using a unidirectional closed-loop star rather than point-to-point links. That is, connections within the hub are arranged in an internal ring.

Full mesh topology is where every node has either a physical or a virtual circuit linking it to every other network node. A full mesh supplies a great deal of redundancy but is typically reserved for network backbones because of its expense.

Packet-Switched Network TopologiesPartially meshed topology is where some network nodes form a full mesh, but others are attached to only one or two nodes in the network.

Observe the WAN Transport Technology table on pages 298 and 299 in your text book.

WAN Transport TechnologiesDS0 Rate is known as the base channel bandwidth of 64Kbps. A bandwidth of 64Kbps is the bandwidth required for an uncompressed digitized phone conversation.

Standard speech less then 4KHz; analog speech is filtered at 4KHz before being sampled.

Nyquist Theorem sample at a rate at least two times the input frequency to obtain a signal that represents the true signal.

Each sample is encoded into 8 bit octets. This DS0 rate is 8KHz. Per second times 8 bits per sample, which is 64Kbps.

TechnologiesMetro Ethernet technology is based on Ethernet technology to offer the best cost-effective, high speed connectivity for MAN and WAN.

DSL technology is a high-bandwidth technology over the traditional copper lines. It is designed to work with two modems at either end of the wire. DSL is a transmission technology that is used by SPs to deliver a wide range of services to subscribers.

Asymmetric DSL (ADSL) used over short distances (less then 21meters). Most common type used. Frequency range 100KHz to 1.1Hz. ADSL allows PSTN telephone service concurrently on the same line.

TechnologiesSymmetric (SDSL) DSL allows traffic to be transmitted in both directions at the same speed over a single twisted pair. The distance served with SDSL is 10K feet or 3048.8 meters. SDSL is often referred to as single-pair DSL. SDSL is excellent for running applications like email and web servers.

Ling Reach Ethernet (LRE) is a WAN access technology which allows for greater distance than the traditional Ethernet provides.

Cable technology is another high-speed copper platform that supports both analog and digital video services over a coaxial cable.

TechnologiesCabling technology makes use channels for upstream and downstream data flow. One application channel in the coaxial cable is used to upstream signals from the modem to the Cable Modem Termination System (CMTS). The output from the CMTS is handed to either the WAN or the PSTN. A different channel is used for the downstream signals from these Internet Service Providers to the CMTS to the modem.

The CMTS converts signals from the modem to IP packets prior to handing them to the IP router for transmission across the Internet. Downstream signals are modulated for transmission across the cable to the modem.

TechnologiesInternet download bandwidth over a cable TV line is shared 27 Mbps.

Internet upstream bandwidth over the same shared cable is 2.5 Mbps.

Wireless technology electromagnetic waves carry RF signals. It is the option of some, that these waves could be harmful to humans.

Synchronous Optical Network/Digital Hierarchy (SONET/SDH) is the ANSI standard for synchronous transmission on fiber optic media. It specifies a base signal rate (OC-1) of 51.84 Mbps and a set of multiples of that rate, known as Optical Carrier levels, up to 9.5 Gbps for OC-192.

TechnologiesSONET/SDH is a circuit based technology that provided uses high speed circuits using TDM framing.

Dark fiber is a fiber optic cable(s) leased from an SP. Fiber is typically connected to a company’s own infrastructure. Dark fiber got its name after the dot-com burst. Many of the companies that had the rights to these fiber networks either went bankrupt, or, had to abandon their goals of utilizing this fiber. This resulted in hundreds of thousands of miles of “unlit” (dark) fiber. Dark fiber is optical fiber that is lying in the ground unutilized

WAN Bandwidth OptimizationCompression is used to reduce the data size to conserve transmission time.

Private AddressingWhat has happened to IPv4 addresses?

In 1981, IPv4 Protocol was published. In 1985, about 1/16 of the total IPv4 address space was in use. By mid-2001, about 2/3 of the total IPv4 address space was in use.

Since 2001, Internet service providers have been trying to conserve IP addresses. They have assigned only a subset of addresses to customers. Currently, the number of public IP addresses available is insufficient for assigning addresses for an entire network.

The answer to this problem is to assign private addresses within a network and to translate these private addresses to public addresses when Internet connectivity is required.

Public and Private ConcernsAre there public, private, or both types of addressing

required?

How many end systems will need access to the public network? This includes email, file transfer, or web browsing.

How many end systems require access to visible public network(s). This includes e-commerce, such as web servers, database servers, application servers, and public servers. These end systems require globally unambiguous IP addresses.

Where will the boundaries be between private and public IP addresses and how will they be implemented?

Private Addresses• RFC 1918 sets aside three blocks of private IP

addresses:• One (1) Class A address• Sixteen (16) Class B addresses• Two hundred and fifty six (256) Class C addresses • These addresses are for private, internal network use

only • Packets containing these addresses are not routed

over the Internet • A router should never route RFC 1918 addresses.

Typically, ISPs configure the border routers to prevent privately addressed traffic from being forwarded

Private Addressing• 172.16.0.0 –172.31.255.255: 172.16.0.0/12

• Where does the /12 come from?• 12 bits in common

172.16.0.0 –172.31.255.255: 172.16.0.0/12 Where does the /12 come from?

• 12 bits in common10101100 . 00010000 . 00000000 . 00000000 –172.16.0.010101100 . 00011111 . 11111111 . 11111111 -172.31.255.25510101100 . 0001000 00000000 . 00000000 –172.16.0.0/12

Network Address Translation (NAT)• NAT is defined by RFC 1631. It is the process of

swapping one address for another in the IP packet header.

• NAT is a mechanism for conserving registered IP addresses in large networks and simplifying IP addressing management tasks.

• In practice, NAT is used to allow hosts that are privately addressed, using RFC 1918 addresses, to access the Internet

• NAT allows many hosts on an inside network to communicate on the Internet with one valid, assigned IP address

Network Address Translation (NAT)• NAT provides a level of security for your inside

network from the outside world

NAT Terminology• Inside local IP address: The IP address assigned to a

host on the inside network. The address is typically an RFC 1918 address.

• Inside global IP address: A globally unique IP address (typically assigned by an ISP) that represents one or more inside local IP addresses to the outside world.

• Outside global IP address: The IP address assigned to a host on the outside network by its owner. The address is globally unique.

• Outside local IP address: The local IP address assigned to a host on the outside network. In most situations, this address will be identical to the outside global address of that outside device

NAT Terminology

Static IP Address Assignment• An IP address is manually assigned to a device or

host.• The network administrator configures the IP address,

default gateway, and name servers manually by entering them into a special file or files on the end system with either a graphical or text interface.

• Static address assignment is an extra burden for the administrator—especially on large-scale networks—who must configure the address on every end system in the network.

• Typically, routers, switches, servers, and printers have IP addresses statically assigned.

Dynamic IP Address Assignment• Dynamic IP addresses are automatically assigned to the

devices.• Dynamic address assignment relieves the administrator of

manually assigning an address to every network device• Instead, the administrator must set up a server to assign the

addresses. • On that server, the administrator defines the address pools and

additional parameters that should be sent to the host (default gateway, name servers, time servers, and so forth)

• On the host, the administrator enables the host to acquire the address dynamically; this is often the default.

• When IP address reconfiguration is needed, the administrator reconfigures the server, which then performs the host-renumbering task

• DHCP is the protocol used to distribute these IP addresses

Dynamic Host Configuration Protocol (DHCP)

DHCP is a superset of the BootP protocol. This means that it uses the same protocol structure as BootP, but it has enhancements added. Both of these protocols use servers that dynamically configure clients when requested. The two major enhancements are address pools and lease time.

Dynamic Host Configuration Protocol

Dynamic Host Configuration Protocol

Dynamic Host Configuration Protocol (DHCP)

A DHCP Server can provide the following to a client:• IP address• Gateway address• Subnet mask• DNS server address• Subnet mask• Router• Domain Name• Domain Name Server(s)• WINS Server(s)

Dynamic Host Configuration Protocol

DHCP Operation• A client must have DHCP configured when starting

the network membership process• The client sends a request to a server requesting an IP

configuration• Sometimes the client may suggest the IP address it

wants, such as when requesting an extension to a DHCP lease

• The client locates a DHCP server by sending a broadcast called a DHCPDISCOVER

Enterprise Network IP Address Assignments

Classless Interdomain Routing (CIDR)• CIDR is the abbreviation for “Classless

InterdomainRouting”.• CIDR is pronounced “cider”.• CIDR replaced the old process of assigning addresses

based on Class A, Class B, and Class C.

Classless Interdomain Routing (CIDR)

A method supported by classless routing protocols, such as OSPF and BGP4, based on the concept of ignoring the IP class of address, permitting route aggregation and VLSM that enable routers to combine routes in order to minimize the routing information that needs to be conveyed by the primary routers. It allows a group of IP networks to appear to other networks as a unified, larger entity. CIDR, IP addresses and their subnet masks are written as four dotted octets, followed by a forward slash and the numbering of masking bits.

Example: 192.168.45.0/24

Classless Interdomain Routing (CIDR)

• With CIDR, addresses use bit identifiers, or bit masks, instead of an address class to determine the network portion of an address

• CIDR uses the /N notation instead of subnet masks• CIDR allows for the more efficient allocation of IP

addresses• Blocks of addresses that match an organization’s

needs can be issued

Classless Interdomain Routing (CIDR)

Classless Interdomain Routing (CIDR)

172.16.0.0 255.255.0.0 = 172.16.0.0 /16

198.30.1.0 255.255.255.0 = 198.30.1.0 /24

Note that 192.168.24.0 /22 is not a Class C network, it has a subnet mask of 255.255.252.0

Classless Interdomain Routing (CIDR)

• CIDR allows routers to summarize, or aggregate, routing information

• One address with mask can represent multiple networks

• This reduces the size of routing tables• Supernetting is another term for route aggregation

CIDR and Route Aggregation

Given four Class C Networks (/24):

192.168.16.0 11000000 10101000 00010000 00000000

192.168.17.0 11000000 10101000 00010001 00000000

192.168.18.0 11000000 10101000 00010010 00000000

192.168.19.0 11000000 10101000 00010011 00000000

Identify which bits all these networks have in common. 192.168.16.0 /22 can represent all these networks. The router will look at the first 22 bits of the address to make a routing decision

CIDR and Route Aggregation

CIDR and Route Aggregation

CIDR and Route Aggregation

Importance of Hierarchical Addressing Without summarization, every small change in the

network will be propagated (spread) throughout the entire network

Importance of Hierarchical Addressing With summarization, small changes in the network aren’t propagated (spread) throughout the entire network

Benefits of Summarization

Upcoming AssignmentsAssignment 5-1, Concept Question 4 is due May 30,

2011

Assignment 4-1-2, Basic Routing and LAN Switching Configuration is due June 27, 2011

Assignment 4-1-3, Basic Network Troubleshooting is due July 25, 2011