3.1 Router Module

Module Name:

sch_qsize

Purpose:

Implements the functionality required of the FCM on the Router. Is responsible for sending a representation of $p(q)$ to a Receiver when a packet is transmitted over the low-bandwidth link.

Responsibilities:

The Router module is responsible for:

• Queueing all packets which are to be sent to a receiver over the low-bandwidth link.
• Dequeuing any packets in the queue when requested by the Linux kernel QoS system.
• Piggybacking the the value of $p(q)$ based on the current queue size $q$ onto a TCP packet whenever a one is dequeued.
• Providing an interface through the /proc filesystem to get the current queue size and $p(q)$.
• Ensuring altered packets are valid TCP/IP packets as specified by reference [7], including the extensions in reference [3].
• Ensuring packets that are not valid TCP packets remain unmodified.
• Allowing the user to specify the output rate $\mu$ of the low bandwidth link. This will be specified in units of kilobits/sec.
• Allowing the user to optionally choose to specify values for some of the following constants used in the window sizing algorithm:
  1. $b$ - A constant which determines how sensitive the queue size is to the number of streams passing through it. Default value is 10.
  2. $q_{\rm min}$ - The queue size above which $p(q)$ becomes non-zero, specified in packets. Default value is 20 packets.

Collaboration:

The Router module collaborates with:

• rami_receiver (the receiver module)

SRS References:

3.1.1.1, 3.1.1.2, 3.1.1.3, 3.1.1.4, 3.1.1.5, 3.1.1.7