Chapter 2. Exploring the Network Layers

Chapter Goals

This Chapter will give you an overview of networking terms and concepts of the TCP/IP protocol suite against the backdrop of Layers 14 of the Open System Interconnection (OSI) model. The following topics are covered:

• Physical LayerThe physical layer covers the mechanical and electrical properties of the physical medium with respect to copper and fiber cabling specifications, binary signaling, and encoding technologies.

• Data Link LayerThe Ethernet data link layer is used predominantly in content networking implementations. Ethernet data link layer protocols, such as Ethernet II and 802.3, are discussed.

• Network LayerThe TCP/IP network layer is composed of IP, ARP, IGMP, and ICMP. These protocols are discussed in detail in this Chapter.

• Transport LayerNumerous TCP terms and concepts are illustrated with graphic real-world examples.

• Putting It All Together with a Detailed Network TraceTo glue the numerous terms and concepts discussed in this Chapter together, a TCP/IP protocol stack trace is performed and described in detail.

In this Chapter you will learn about the lower four layers of the TCP/IP protocol suite. Although content networks operate primarily at Layers 57, Layers 14 provide the foundation of content networking technologies. The TCP/IP protocols discussed in this Chapter are related to the OSI model as outlined in Table 2-1.

Table 2-1. TCP/IP Protocols in Relation to the OSI Reference Model

OSI Model Layer	TCP/IP Protocols
Transport	TCP Three-Way Handshake Sliding Window Slow Start Congestion Avoidance Fast Retransmit and Fast Recovery Maximum Segment Size TCP over Satellite and Window Scale Option (WSOpt)
	Pragmatic General Multicast (PGM)
	User Datagram Protocol (UDP)
Data Link	Ethernet Data Link Ethernet II 802.3 Media Access Control (MAC) 802.2 Logical Link Control (LLC) Carrier Sensing Multiple Access/Collision Detection (CSMA/CD)
Network	IP Internet Control Management Protocol (ICMP) Internet Group Management Protocol (IGMP) Address Resolution Protocol (ARP) Protocol Independent Multicast (PIM)
Physical	Ethernet Media Unshielded Twisted Pair (UTP) Single Mode and Multimode Fiber
	Ethernet Signaling and Coding Manchester Encoded Signaling Multilevel Transition Level 3 (MLT-3)Signaling Non-Return to Zero (NRZ) Signaling NRZ-Inverted (NRZ-I) Signaling 4B/5B Coding 8B/10B Coding Pulse Amplitude Modulation Level 5 (PAM5)