| The five-layer TCP/IP model |
| 5. Application layer |
|
DHCP · DNS · FTP · Gopher · HTTP · IMAP4 · IRC · NNTP · XMPP · POP3 · SIP · SMTP · SNMP · SSH · TELNET · RPC · RTCP · RTSP · TLS · SDP · SOAP · GTP · STUN · NTP · (more) |
| 4. Transport layer |
| TCP · UDP · DCCP · SCTP · RTP · RSVP · IGMP · (more) |
| 3. Network/Internet layer |
| IP (IPv4 · IPv6) · OSPF · IS-IS · BGP · IPsec · ARP · RARP · RIP · ICMP · ICMPv6 · (more) |
| 2. Data link layer |
| 802.11 (WLAN) · 802.16 · Wi-Fi · WiMAX · ATM · DTM · Token ring · Ethernet · FDDI · Frame Relay · GPRS · EVDO · HSPA · HDLC · PPP · PPTP · L2TP · ISDN · ARCnet · (more) |
| 1. Physical layer |
| Ethernet physical layer · Modems · PLC · SONET/SDH · G.709 · Optical fiber · Coaxial cable · Twisted pair · (more) |
An interior gateway protocol (IGP) is a routing protocol that is used within an autonomous system. In contrast an exterior gateway protocol is for determining network reachability between autonomous systems (AS) and makes use of IGPs to resolve route within an AS. The interior gateway protocols can be divided into two categories: 1) Distance-vector routing protocol and 2) Link-state routing protocol.
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Types of Interior gateway protocols
Distance-vector routing protocol
They use the Bellman-Ford algorithm to calculate paths. In Distance-vector routing protocols each router does not possess information about the full network topology. It advertises its distances from other routers and receives similar advertisements from other routers. Using these routing advertisements each router populates its routing table. In the next advertisement cycle, a router advertises updated information from its routing table. This process continues until the routing tables of each router converge to stable values. This set of protocols has the disadvantage of slow convergence, however, they are usually simple to handle and are well suited for use with small networks. Some examples of distance-vector routing protocols are:
Link-state routing protocol
In the case of Link-state routing protocols, each node possesses information about the complete network topology. Each node then independently calculates the best next hop from it for every possible destination in the network using local information of the topology. The collection of best next hops forms the routing table for the node. This contrasts with distance-vector routing protocols, which work by having each node share its routing table with its neighbors. In a link-state protocol, the only information passed between the nodes is information used to construct the connectivity maps. Example of Link-state routing protocols are:
