2.8.networking-supplement

2.8.networking-supplement - 1 Supplementary Networking...

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Unformatted text preview: 1 Supplementary Networking Slides • These slides provide more detail than we covered in lecture • We don’t in general anticipate drawing upon these extra points – If/when we do, we’ll strive to explicitly cover them in lecture • But they may prove helpful in absorbing the networking background material 2 Who Does What? • Five layers – Lower three layers implemented everywhere – Top two layers implemented only at hosts Transport Network Link Physical Transport Network Link Physical Network Link Physical Application Application Host A Host B Router 3 Logical Communication • Layers interacts with peer’s corresponding layer Transport Network Link Physical Transport Network Link Physical Network Link Physical Application Application Host A Host B Router 4 Physical Communication • Communication goes down to physical network • Then from network peer to peer • Then up to relevant layer Transport Network Link Physical Transport Network Link Physical Network Link Physical Application Application Host A Host B Router 5 IP Suite: End Hosts vs. Routers HTTP TCP IP Ethernet interface HTTP TCP IP Ethernet interface IP IP Ethernet interface Ethernet interface SONET interface SONET interface host host router router HTTP message TCP segment IP packet IP packet IP packet 6 Layer Encapsulation Trans: Connection ID Net: Source/Dest Link: Src/Dest Appl: Get index.html User A User B Common case: 20 bytes TCP header + 20 bytes IP header + 14 bytes Ethernet header = 54 bytes overhead 7 The Internet Hourglass Link Physical Applications The Hourglass Model Waist There is just one network-layer protocol, IP . The “narrow waist” facilitates interoperability . SMTP HTTP NTP DNS TCP UDP IP Ethernet SONET 802.11 Transport Fiber Copper Radio (Network Layer) IP Packet Structure 4-bit Version 4-bit Header Length 8-bit Type of Service (TOS) 16-bit Total Length (Bytes) 16-bit Identification 3-bit Flags 13-bit Fragment Offset 8-bit Time to Live (TTL) 8-bit Protocol 16-bit Header Checksum 32-bit Source IP Address 32-bit Destination IP Address Options (if any) Payload IP Packet Structure 4-bit Version 4-bit Header Length 8-bit Type of Service (TOS) 16-bit Total Length (Bytes) 16-bit Identification 3-bit Flags 13-bit Fragment Offset 8-bit Time to Live (TTL) 8-bit Protocol 16-bit Header Checksum 32-bit Source IP Address 32-bit Destination IP Address Options (if any) Payload 10 IP Packet Header Fields • Version number (4 bits) – Indicates the version of the IP protocol – Necessary to know what other fields to expect – Typically “4” (for IPv4), and sometimes “6” (for IPv6) • Header length (4 bits) – Number of 32-bit words in the header – Typically “5” (for a 20-byte IPv4 header) – Can be more when IP options are used • Type-of-Service (8 bits) – Allow packets to be treated differently based on needs – E.g., low delay for audio, high bandwidth for bulk transfer IP Packet Structure 4-bit Version 4-bit Header Length 8-bit Type of Service...
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This note was uploaded on 04/14/2010 for the course CS 161 taught by Professor Wagner during the Spring '10 term at University of Central Arkansas.

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2.8.networking-supplement - 1 Supplementary Networking...

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