TCP/IP Overview

- TCP/IP Overview.
- TCP/IP Overview...1.
- TCP/IP Technology...2.
- Interior Routing Protocols...7.
- Integrated IS−IS...8.
- Exterior Routing Protocols...8.
- Cisco's TCP/IP Implementation...9.
- Routing Protocol Redistribution...10.
- Related Information...11 Cisco − TCP/IP Overview.
- Introduction TCP/IP Technology TCP.
- Routing in IP Environments Interior Routing Protocols RIP.
- Integrated IS−IS.
- Exterior Routing Protocols EGP.
- Cisco's TCP/IP Implementation Access Restrictions.
- Routing Protocol Redistribution Serverless Network Support.
- In the two decades since their invention, the heterogeneity of networks has expanded further with the.
- Figure 1 shows the TCP/IP protocol suite in relation to the OSI.
- Figure 2 shows some of the important Internet protocols and their relationship to the OSI Reference Model.
- Support for at least part of the Internet Protocol suite is available from virtually every computer vendor..
- TCP/IP Technology.
- Figure 1 TCP/IP Protocol Suite in Relation to the OSI Reference Model.
- IP is the primary Layer 3 protocol in the Internet suite.
- IP represents the heart of the Internet Protocol suite..
- Note: The term IP in the section refers to IPv4 unless otherwise stated explicitly..
- IP addresses are globally unique, 32−bit numbers assigned by the Network Information Center.
- Globally unique addresses permit IP networks anywhere in the world to communicate with each other..
- The first part designates the network address while the second part designates the host address..
- Class A networks are intended mainly for use with a few very large networks, because they provide only 8 bits for the network address field.
- Class B networks allocate 16 bits, and Class C networks allocate 24 bits for the network address field.
- In all three cases, the left most bit(s) indicate the network class.
- Subnets provide extra flexibility for the network administrator.
- For example, assume that a network has been assigned a Class A address and all the nodes on the network use a Class A address.
- (All zeros in the host field of an address specify the entire network.) The administrator can subdivide the network using subnetting.
- bits from the host portion of the address and using them as a subnet field, as depicted in Figure 4..
- If the network administrator has chosen to use 8 bits of subnetting, the second octet of a Class A IP address provides the subnet number.
- The number of bits that can be borrowed for the subnet address varies.
- To specify how many bits are used to represent the network and the subnet portion of the address, IP provides subnet masks.
- Traditionally, all subnets of the same network number used the same subnet mask.
- In other words, a network manager would choose an eight−bit mask for all subnets in the network.
- both network administrators and routing protocols.
- One of the techniques that has resulted is called Variable Length Subnet Masks (VLSM).
- On some media, such as IEEE 802 LANs, IP addresses are dynamically discovered through the use of two other members of the Internet protocol suite: Address Resolution Protocol (ARP) and Reverse Address Resolution Protocol (RARP).
- RARP uses broadcast messages to determine the network−layer address associated with a particular hardware address.
- Figure 6 shows the Internet architecture..
- Figure 6 Representation of the Internet Architecture.
- Routing protocols used with IP are dynamic in nature.
- Dynamic routing requires the software in the routing devices to calculate routes.
- Dynamic routing algorithms adapt to changes in the network and automatically select the best routes.
- In contrast with dynamic routing, static routing calls for routes to be established by the network administrator.
- Static routes do not change until the network administrator changes them..
- This sample routing table from a Cisco router shows that the first entry is interpreted as meaning "to get to network 34.1.0.0 (subnet 1 on network 34), the next stop is the node at address .
- The entire route is not known at the outset of the journey.
- Instead, at each stop, the next router hop is determined by matching the destination address within the datagram with an entry in the current node's routing table.
- Each node's involvement in the routing process consists only of forwarding packets based on internal information.
- Interior Routing Protocols.
- Interior Routing Protocols (IGPs) operate within autonomous systems.
- The following sections provide brief descriptions of several IGPs that are currently popular in TCP/IP networks.
- For additional information on these protocols, please refer to the links in the Related Information section below..
- A discussion of routing protocols within an IP environment must begin with the Routing Information Protocol (RIP).
- RIP was developed by Xerox Corporation in the early 1980s for use in Xerox Network Systems (XNS) networks.
- Today, many PC networks use routing protocols based on RIP..
- For this reason, many companies with large internetworks are migrating away from RIP to more sophisticated routing protocols..
- With the creation of the Interior Gateway Routing Protocol (IGRP) in the early 1980s, Cisco Systems was the first company to solve the problems associated with using RIP to route datagrams between interior routers..
- IGRP determines the best path through an internet by examining the bandwidth and delay of the networks between routers.
- Enhanced IGRP combines the ease of use of traditional distance vector routing protocols with the fast rerouting capabilities of the newer link state routing protocols..
- OSPF is based on work started by John McQuillan in the late 1970s and continued by Radia Perlman and Digital Equipment Corporation (DEC) in the mid−1980s.
- Autonomous systems can be divided into routing areas.
- Exterior Routing Protocols.
- The two most popular EGPs in the TCP/IP community are discussed in this section..
- This was true in the early Internet but is no longer true..
- Because of its limitations with regard to today's complex internetworks, EGP is being phased out in favor of routing protocols such as BGP..
- Like EGP, BGP is an interdomain routing protocol created for use in the Internet core routers.
- The latest revision of BGP, BGP4, was designed to handle the scaling problems of the growing Internet..
- Cisco's TCP/IP Implementation.
- In addition to IP and TCP, the Cisco TCP/IP implementation supports ARP, RARP, ICMP, Proxy ARP (in which the router acts as an ARP server on behalf of another device), Echo, Discard, and Probe (an address resolution protocol developed by Hewlett−Packard Company and used on IEEE 802.3 networks).
- Add a static route in the host pointing to a router..
- Run the ICMP Router Discovery Protocol (IRDP) in the host..
- Cisco provides many TCP/IP value−added features that enhance applications availability and reduce the total cost of internetwork ownership.
- The most important of these features are described in the following section..
- Another access list could be used to permit TCP connections from any host on a local segment to any host in the Internet but to deny all connections from the Internet into the local net except for electronic mail connections to a particular designated mail host.
- Cisco supports both the Basic and the Extended security options as described in RFC 1108 of the IP Security Option (IPSO).
- Cisco's TCP/IP implementation includes several schemes that allow foreign protocols to be tunneled through an IP network.
- The applications that use the TCP/IP protocol suite continue to evolve.
- In large networks, some routers and routing protocols are more reliable sources of routing information than others.
- Cisco IP routing software permits the reliability of information sources to be quantified by the network administrator with the administrative distance metric.
- When administrative distance is specified, the router can select between sources of routing information based on the reliability of the source.
- For example, if a router uses both IGRP and RIP, one might set the administrative distances to reflect greater confidence in the IGRP information.
- Routing Protocol Redistribution.
- Translation between two environments using different routing protocols requires that routes generated by one protocol be redistributed into the second routing protocol environment.
- Route redistribution gives a company the ability to run different routing protocols in workgroups or areas where each is particularly effective.
- Cisco permits routing protocol redistribution between any of its supported routing protocols.
- As the junction point for multiple segments, a router sees more of the complete network than most other devices.
- The current state of the routing table, including the routing protocol that derived the route, the.
- reliability of the source, the next IP address to send to, the router interface to use, whether the network is subnetted, whether the network in question is directly connected, and any routing metrics..
- The current state of the active routing protocol process, including its update interval, metric weights (if applicable), active networks for which the routing process is functioning, and routing information sources..
- The contents of the IP cache, including the destination IP address, the interface through which that destination is reached, the encapsulation method used, and the hardware address found at that destination..
- The number of intermediate hops taken as a packet traverses the network..
- The featured links are some of the most recent conversations available in this technology..
- Troubleshooting TCP/IP.
- TCP/IP Networking

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