Network and transport layer Part1

Features of transport layer and network layer

transport layer:

1. end-to-end channel;
2. reliable communication(segmenting + ARQ)；
3. addressing of individual applications(ports)；

network layer:

1. addressing and routing of packets；
2. connecting different networks;

Addressing

address types:

1. Application layer: URL
2. Transport layer(e.g TCP): Port number (identify which application this TCP connection servers for)
3. Network layer(IP): IP address (used for identifying devices across networks)
4. Data link layer: MAC address (used for sending frames in a LAN)

address management:

1. DNS entries:
   • ICANN/Registrars manage top-level and second-level domains;
   • Network admins manage DNS for their assigned domains
2. Port numbers:
   • IANA maintains official list of port numbers;
3. IP addresses:
   • IANA and 5 RIRs allocate blocks of addresses, local registries redistribute to customers;
   • Network admins configure (static or dynamic) addresses in their assigned block;
4. MAC addresses:
   • hardware manufacturers;

each “layer 3 device” has an address

layer 3 devices includes: clients, servers and routers;

IPv4 addresses

1. 32 bits addresses
2. dotted decimal notation
3. hierarchy used for routing
4. Subnet mask: 255.255.192.0 or /26

Network classes

1. Previously used hierarchy:

   Class A: /8 (e.g. IBM, MIT, AT&T…)

   Class B: /16 (e.g. Monash)

   Class C: /24

   (the number means the digits used for network number)

IPv6

1. 128 bits
2. It’s used for easily create hierarchies, not only the amount.
3. This makes it easy to assign whole subnets

4. Address space:

   IANA+RIR(23 bits) + ISP(9 bits) + Company/Organization(16 bits) + Subnet(16 bits) + Interface ID(64 bits)(mostly the MAC address) = 128 bits;

Dynamicly configure IP address

IPv4 Dynamic Host Configuration Protocol(DHCP)

• Send broadcast to DHCP server to get an address and subnet mask
• addresses are only leased for a limited time
• Makes efficient use for limited IPv4 address space
• Much easier for admins to manage than static addresses

IPv6

DataComm Review NetworkLayer Part1

原文：http://www.cnblogs.com/sertraline/p/4570351.html